FOC Vitamin Ina copy

KIMIA HASIL PERTANIAN
P E N DA H U LU A N
Vitamins adalah zat gizi mikro essensial yang diperlukan
untuk pertumbuhan normal, pemeliharaan, dan fungsi
tubuh manusia.
VITAMIN
Vitamins function in vivo:"
(a) Co-enzim dan prekusor enzim (niacin, thiamin, riboflavin,
biotin, pantothenic acid, vitamin B6, vitamin B12, folate); !
(b) Antioksidan (ascorbic acid, carotenoid tertentu, vitamin E); !
Recommended Textbook:!
Damo daran, S., Parkin, K.L., Fennema, O.R.
Fennema’s Foo d Chemistry 4th Ed. CRC Press.!
2007.
Belitz, H.D., Grosch, W., Schieberle, P. 2009.
Chemsitry 4th Ed. Springer.
Foo d
(c) Terlibat dalam regulasi genetik (vitamins A dan D); !
(d) Fungsi khusus, seperti vit. A untuk vision, vit. C membantu
r e a k s i h i d r o x y lat i o n , v it. K m e m b a n t u k r e a k s i
carboxylation.
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Vitamin Deficiency:"
• Keku ran gan vitam in disebut hyp o vitam in o sis an d
PERANAN:
Food Chemist, Food Technologists, Food Scientists:"
avitaminosis. !
✦ Memahami bagaimana vitamin rusak dan hilang, serta
mampu mengontrolnya.!
• Disebabkan oleh konsu msi ti dak cukup, gangguan
✦ Memahami: !
• Effek kekurangan:!
serapan karena penyakit atau stress.
a) konsep perubahan kimia proses degradasi vitamin dalam
bahan pangan.!
✴ Vitamin A ==> xerophthalmia or buta malam.!
b) mekanisme reaksi, kinetika, dan termodinamika vitamin
dalam berbagai keadaan.!
✴ Niacin ==> pellagra!
✦ Menentukan kondisi dan metode pengolahan makanan,
penyimpanan, dan penanganan untuk mengoptimalkan
ketahanan vitamin.
✴ Thiamine ==> beriberi!
✴ Vitamin B12 ==> anemia!
✴ Vitamin C ==> scurvy!
✴ Vitamin K ==> coagulation darah terganggu
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Vitamin Stability:
Nutrients
Neutral
Acid
Alkali
O2
Light
Heat
Cooking
Vitamin A
Ascorbic Acid
Biotin
Carotenes
Choline
Vitamin B12
Vitamin D
Folate
Vitamin K
Pantothenic Acid
Vitamin B6
Riboflavin
Thiamin
Tocopherol
S
U
S
S
S
S
S
U
S
S
S
S
U
S
U
S
S
U
S
S
S
U
U
U
S
S
S
S
S
U
S
S
S
S
U
U
U
U
S
U
U
S
U
U
S
U
U
U
U
U
S
S
S
S
U
U
U
U
S
U
S
U
U
U
U
S
U
U
S
U
U
U
U
U
S
S
U
U
S
S
U
U
U
U
40
100
60
30
5
10
40
100
5
75
40
75
80
55
5
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VARIATION/LOSSES OF VITAMINS IN FOOD
1) Inherent Variation:"
✴ Varietas,
tahap kematangan, lokasi tumbuh, iklim,
metode pertanian, dan kondisi lingkungan.!
✴ Tabel hubungan tingkat kematangan tomat dan kadar
vitamin C.
Weeks from
Anthesis
Weight (g)
Color
2
33.4
green
3
57.2
green
7.6
4
102
green-yellow
10.9
5
146
yellow-red
20.7
6
160
red
14.6
7
168
red
6
6
Ascorbic Acid !
(mg/100g)
107
10.1
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Vitamin variation . . .
Vitamin variation . . .
3) Preliminary Treatments:"
2) Postharvest Handling:"
• Selama penanganan pascapanen, kerusakan sel dan
kantung-kantung enzim menyebabkan pelepasan enzim
oksidasi dan hidrolisis, menyebabkan perubahan struktur
kimia dan aktivitas vitamin.
• Contohnya: !
✴ Dephosphorilasi vit. B6, thiamin, atau co-enzyme
✴ Peeling dan trimming menyebabkan kehilangan vitamin,
terutama pada vitamin yang tersimpan di bawah kulit.!
✴ Penambahan Alkali untuk mempermudah peeling dapat
meningkatkan kehilangan vitamin, seperti folate,
ascorbic acid, dan thiamin.
✴ Penggilingan biji-bijian, meliputi grinding dan fraksinasi
untuk membuang bran (kulit ari/dedak) dan embrio
menyebabkan kehilangan vitamin. Karena banyak vitamin
tersimpan dalam embrio dan bran (dedak).!
flavin.!
✴ Deglycosylasi vitamin B6.!
✴ Enzim lipoxygenase mengurangi konsentrasi berbagai
✴ Adanya kontak (exposure) antara jaringan bahan pangan
yang terpotong atau rusak dengan air menyebabkan
hilangnya vitamin yang larut air akibat pencucian
(ekstraksi/leaching).
vitamin.!
✴ Ascorbic acid oxidase dapat mengurangi konsentrasi
as. askorbat
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Vitamin variation . . .
FIGURE 1
Retention of selected nutrients as a function of
deg ree of refining in production of wheat flour.
Extraction rate refers to the percentag e recovery of
flour from whole g rain during milling (redrawn by
Ref. 98).
Pag e 542
Vitamin variation . . .
4) Blanching and Thermal Processing:"
• Selama blanching, kehilangan vitamin disebabkan oleh:!
1. Leaching (wet blanching, dengan air panas atau
steam).!
2. Oxidation (dry blanching, dengan udara panas atau
mikrowave).!
• Peningkatan
vitamin.
suhu meningkatkan reaksi deg ra dasi
Pag e 543
study and
thorough review [61,vitamin
62, 72, 113]. akibat
The elevated penamanasan
temperature of thermal processing
accelerates reactions that would
• Kerusakan
tergantung
otherwisepada:!
occur more slowly at ambient temperature. Thermally induced losses of vitamins depend on the chemical nature of the
food, its chemical environment (pH, relative humidity, transition metals, other reactive compounds, concentration of dissolved
1. the
Komposisi
kimia
bahan
! and the opportunity for leaching. The nutritional
oxygen, etc.),
stabilities of the
individual
forms ofpangan.
vitamins present,
Gb. 1. Effek Fderajat
refining
IGURE 1
significance
such losses depends
on the lingkungan
degree of loss and the
importance
of the food as
a source
of the vitamin in typical
Retention
nutrients terhadap
as a function of
2.ofKomposis
kimia
bahan
pangan
(pH,
RH,
tepungof selected
gandum
diets. Although subject to considerable variation, representative data for losses of vitamins during the canning of vegetables are deg ree of refining in production of wheat flour.
retensi beberapa zat gizi
logam, O 2 terlarut, dan komponen aktif lainnya). !
Extraction rate refers to the percentag e recovery of
shown in Table 6.
Gb. 2. RetensiFIGURE
asam
askorbat
2
Retention of ascorbic acid in peas during
dalam
kacang polong pada
experimental water blanching for 10 min at various
p etemperatures
r c o b a(redrawn
a n from
b la
ching
Ref.n118.)
selama 10 menit pada
berbagai suhu.
yang dikandungnya.
3. Stabilitas masing-masing vitamin. !
flour from whole g rain during milling (redrawn by
Ref. 98).
8.6.5 Losses of Vitamins Following Processing
4. Kemungkinan leaching.
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9 subsequent storage
Compared to loss of vitamins during thermal processing,
often has a small but significant effect on vitamin
9
content. Several factors contribute to small postprocessing
losses: (a) reaction rates are relatively slow at ambient or reduced
temperature, (b) dissolved oxygen may be depleted, and (c) pH may change during processing (pH usually declines) because of
thermal effects or concentrative effects (drying or freezing), and this can have a favorable effect on the stability of vitamins such
as thiamin and ascorbic acid. For example, Figure 3 illustrates how vitamin C retention in potatoes can be affected by thermal
processing. The relative importance of leaching, chemical degradation, and the type of container (cans or pouches) is apparent
from these data.
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In reduced-moisture foods, vitamin stability is strongly influenced by water activity in addition to the other factors to be
discussed. In the absence of oxidizing lipids, water-soluble vitamins generally exhibit little degradation at water activity less than
or equal to monolayer hydration (~0.2–0.3 aw). Degradation rates increase in proportion to water activity in regions of multilayer
hydration, which reflects greater solubility of the vitamin, potential reactants and catalysts. In contrast, the influence of water
Vitamin
variation
. . .of fat-soluble vitamins and carotenoids parallels the pattern for unsaturated fats, that is, a minimum
Vitamin
activity on
the stability
rate at variation . . .
monolayer hydration and increased rates above or below this value (see Chap. 2). Substantial losses of oxidation-sensitive
vitamins can occur if foods are overdried.
TABLE 6 Typical Losses of Vitamins during canning
Product
5) Chemical and Other Food Components:"
a
Biotin
Folate
B6
Pantothenic
acid
A
Thiamin
Riboflavin
Niacin
C
0
75
64
-
43
67
55
47
54
Asparag us
Lima beans
-
62
47
72
55
83
67
64
76
Green beans
-
57
50
60
52
62
64
40
79
Beets
-
80
9
33
50
67
60
75
70
Carrots
40
59
80
54
9
67
60
33
75
Corn
63
72
0
59
32
80
58
47
58
Mushrooms
54
84
-
54
-
80
46
52
33
Green peas
78
59
69
80
30
74
64
69
67
Spinach
67
35
75
78
32
80
50
50
72
Tomatoes
55
54
-
30
0
17
25
0
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aIncludes
blanching .
Source: From various sources, compiled by Lund [87].
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✴ Koposisi kimia bahan pangan sangat mempengaruhi
2
stabilitasFIGURE
vitamin.
!
Retention of ascorbic acid in peas during
✴ Oxidizing agents merusak ascorbic acid, vitamin A,
carotenoids, dan vitamin E.
experimental water blanching for 10 min at various
temperatures (redrawn from Ref. 118.)
✴ Reducing agents seperti ascorbic dan isoascorbic
acids, serta thiol dan tetrahydrofolates meningkatkan
stabilitas vitamins, berfungsi sebagai pengikat oxygen
and free radical.!
✴ Sulfite (SO2, bisulfite, metabisulfite), digunakan
untuk anti mikroba dan menghambat enzymatic
browning, melindungi ascorbic acid.
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Vitamin variation . . .
BIOAVAILABILITY OF VITAMINS
Chemical and other . . ."
✴ Ion Sulfite bereaksi dengan thiamin, menyebabkan
thiamin inaktif.
Sulfite juga bereaksi dengan
carbonyl groups pada vitamin B6, menyebabkan vit.
B6 inaktif.!
✴ K o m p o s i s i b a h a n p a n g a n ya n g m e n ye b a b ka n
p e r u b a h a n p H ( d a r i n et ra l m e n j a d i a s a m ) ,
mempengaruhi stabilitas thiamin dan ascorbic acid. !
✴ Acidulation meningkatkan stabilitas asam askorbat
dan thiamin. Sebaliknya, senyawa alkali mengurangi
stabilitas asam askorbat, thiamin, asam pantotenat,
dan folates.
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Terminologi yang merujuk pada sejauh mana nutrisi yang
dikonsumsi diserap oleh usus, berfungsi dalam metabolisme,
atau pemanfaatannya dalam tubuh.
Factors yang mempengaruhi bioavailability of vitamins:"
(a) Komposisi bahan pangan (viscosity, sifat emulsi, dan pH)
dapat mempengaruhi waktu bahan pangan di usus.!
(b) Bentuk vitamin (misal: coenzim), mempengaruhi bentuk
aktifnya atau fungsi metabolisme.!
(c) Interaksi antara vitamin dan komponen bahan pangan
(proteins, starches, dietary fiber, lipids) yang proses
penyerapan vitamin oleh usus.
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ADDITION OF NUTRIENTS TO FOODS
CLASSIFICATION OF VITAMIN:
a) Restoration: Penambahan nutrisi pada bahan pangan untuk
mengembalikan ke kondisi (konsentrasi) awal.!
b) Fortification: Penambahan nutrisi dalam jumlah yang
cukup signifikan untuk membuat makanan menjadi sumber
nutrisi yang ditambahkan.
c) Enrichment: Penambahan nutrisi tertentu dalam jumlah
sesuai dengan standar identitas seperti yang didefinisikan
oleh US Food and Drug Administration (FDA).!
d) N ut r if icat i o n : Ist i la h g e n e r i k d i m ak s u d ka n u nt u k
mencakup setiap penambahan nutrisi makanan.
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A. Fat Soluble Vitamins;"
A (Retinol), D (Calciferol), E (Tocopherol), dan K
(Phytomenadione).!
B. Water Soluble Vitamins:"
C ( Ascorbic acid) dan B [B1 (Thiamin), B2
(Ribiflavin), B3 (Niacin), B5 (Pantothenic acid), B6
(Pyr i doxin e), B7 (Biotin), dan B12
(Cuanocobalamine)].
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2) Structure of Vit. A
VITAMIN A (RETINOL)
Pag e 546
Pag e 54
1) Vit. A: Structure and General Properties:"
• Vitamin A mengacu pada sekelompok hidrokarbon tak
jenuh yang aktif, termasuk retinol dan senyawa
terkait, serta karotenoid tertentu.!
• Vitamin A di jaringan hewan didominasi dalam bentuk
retinol atau esternya, retinal, dan asam retinoat.!
• Karotenoid merupakan jenis vitamin A dalam makanan
yang berasal dari tanaman dan hewan.
FIGURE 5
Structures and provitamin A activities of selected carotenoids.
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FIGURE 4
in foods (Table 7 and 8). Conversion to cis isomers, which can occur during
thermal
processing,
causes a" loss of vitamin A
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Structures of common retinoids.
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activity.
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bond in the intestinal mucosa to release two molecules of active
Among
the carotenoids,
-carotene exhibits the greatest
8.7.1.2retinal.
Stability
and Modes
of Degradation
pro-vitamin A activity. Carotenoids with ring hydroxylation or the presence of carbonyl group exhibit less pro-vitamin A activity
The degradation
of vitamin
A (retinoids
and vitamin
cartenoids)
generally parallels the oxidative degradation of
than -carotene if only one ring is affected, and have no activity
if both rings
are oxygenated.
Although
twoA-active
molecules
of vitamin
Factors that promote
oxidation
of unsaturated
A are potentially producted from each molecule of dietary unsaturated
-carotene,lipids.
the inefficiency
of the process
accounts
for thelipids
factenhance
that degradation of vitamin A, either by direct
oxidation or by indirect effects of free radicals. Changes in the -carotene content of cooked dehydrated carrots illustrate typica
-carotene exhibits only ~50% of the vitamin A activity exhibited by retinol, on a mass basis. Considerable variation exists
extents of degradation during processing and typical exposure to oxygen during associated handling (Table 9). It should be
among various animal species and humans with respect to the
efficiency
utilization
carotenoids
andAthe
extent
of as
absorption
noted,
however,ofthat
extendedof
storage
of vitamin
in foods
such
fortified breakfast cereal products, infant formulas, fluid
of carotenoid molecules in intact form. The in vivo antioxidative
function
attributed
to dietary is
carotenoids
absorption
of retention of added vitamin A.
milk, fortified
sucrose,
and condiments
usually not requires
highly detrimental
to the
the intact molecule [18].
Losses of vitamin A activity of retinoids and carotenoids in foods occur mainly through reactions involving the unsaturated
3) VIT. A: Sources:"
✴ Vitamin A hanya terdapat pada jaringan hewan, minyak
hati ikan, di hati mamalia, lemak susu dan kuning telur.
Karotenoid pada hewan berasal dari tumbuhan yang
dimakan oleh hewan.!
✴ Ta n a m a n t i n d a k m e m p u n ya i v ita m i n A , teta p i
mengandung karotenoid yang berfungsi sebagai provitamin A. !
✴ Karotenoid banyak terdapat dalam sayuran warna hijau
dan kuning (wortel, bayam, selada, kangkung, paprika,
dan tomat) dan dalam buah-buahan (labu, aprikot,
jeruk dan dan minyak sawit)
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KHP: Vitamin
4) VIT. A: Requirement and Bioavailability:"
• Kebutuhan harian vitamin A berasal dari:!
✴ 75% retinol (seperti ester asam lemak, terutama
palmitat retinil),!
✴ 25% β-karoten dan karotenoid lainnya (provitamin A). 6
gr β-karoten diperlukan untuk menghasilkan 1 gr retinol.
• Retinoid, retinyl acetate, dan retinyl palmitate diserap
secara efektif kecuali dalam kondisi di mana mal-absorpsi
lemak terjadi. Diet yang mengandung bahan hidrofobik
non-absorable seperti pengganti lemak tertentu dapat
berkontribusi untuk mal-absorpsi vitamin A. !
• Penye rapan karoten o i d mu n gkin te rgan g gu karena
terjadinya ikatan caroteno-protein atau terperangkap
dalam matriks sayuran yang sulit dicerna.
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Pag e 551
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presumably other carotenoids, causes a reduction or total loss of vitamin A activity regardless of the mechanisms by which free
radical initiation occurs. For retinol and retinyl esters, however, the attack of free radicals occurs at the C14 and C15 positions.
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Oxidation of -carotene involves the formation of the 5,6-epoxide, which may isomerize to the 5,8-epoxide (mutachrome).
Photochemically induced oxidation yields mutachrome as the primary degradation product. Fragmentation of -carotene to
many lower molecular weight compounds can occur especially during high-temperature treatments. Resulting volatiles can have a
significant effect on flavor. Such fragementation also occurs during oxidation of retinoids. An overview of these reactions and
other aspects of the chemical behavior of vitamin A is shown in Figure 8.
8.7.1.3 Bioavailability
Retinoids are absorbed effectively except under conditions in which malabsorption of fat occurs. Retinyl acetate and palmitate
are as effectively utilized as nonesterified retinol. Diets containing nonabsorable hydrophobic materials such as certain fat
substitutes may contribute to malab-
VITAMIN D (CALCIFEROL)
5) Vit. A: "
!
1) Vit. D: Structure and General Properties:"
Stability and
Degradation:
✴ Vitamin D adalah beberapa jenis sterol yang larut dalam
lipid, termasuk cholecalciferol (vitamin D3) dari sumber
hewan dan ergocalciferol (vitamin D2) diproduksi secara
sintetisis
✴ Cholecalciferol (vitamin D3) terbentuk dari kolesterol
dalam ku lit m elalui fotolisis 7- dehydro chole ste rol
(provitamin D3) oleh sinar ultra violet pada kulit manusia
setelah terpapar sinar matahari. Karena dalam sintesis
vivo, kebutuhan vitamin D untuk diet tergantung pada
sejauh mana paparan terhadap sinar matahari.!
✴ Ergocalciferol (Vitamin D2) adalah bentuk sintetis dari
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FIGURE 8
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Overview of vitamin A deg radation.
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vitamin D yang dibentuk dari radiasi fitosterol (sterol
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tanaman) dengan sinar UV. 24
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he requirement for dietary vitamin D will depend on the extent of exposure to sunlight. Ergocalciferol is an exclusively
rm of vitamin D that, is formed by commercial irradiation of phytosterol (a plant sterol) with UV light. Several
ed metabolites of vitamin D2 and D3 form in vivo. The 1,25-dihydroxy derivative of cholecalciferol is the main
ally active form, and it is involved in the regulation of calcium absorption and metabolism. 25-Hydroxycholecalciferol,
to cholecalciferol,
3) Vit. D: Sources:"
✴ Hampir semua bahan pangan mengandung vitamin D. "
✴ Pro-vitamin D (ergosterol dan 7-dehydrocholesterol),
terdapat pada hewan dan tanaman. "
✴ Yeast, jamur, kol, bayam, dan minyak gan du m
mengadung provitamin D2.
FIGURE 9
Structure of erg ocalciferol (vitamin D2) and cholecalciferol
(Vitamin D3).
telur, mentega, susu sapi, hati, kerang, lemak hewan,
dan kulit babi. "
✴ Sumber utama vitamin D adalah minyak ikan."
2) Vit. D: Stability and Degradation:"
Vitamin D rentan terhadap degradasi oleh oksigen dan cahaya.
Sekitar 50% dari cholecalciferol ditambahkan ke susu skim
akan rusak bila terkena paparan lampu neon terus-menerus
pada suhu 4°C selama 12 hari.
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✴ Vitamin D3 dan provitaminnya terdapat pada kuning
✴ Fortifikasi vitamin D produk susu cair menggunakan
ergocalciferol atau cholecalciferol D.
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VITAMIN E (TOCOPHEROL)
1) Vit E: Structure and General Properties:"
• Vitamin E adalah nama generik untuk tokoferol, yang
merupakan turunan dari tocol yang memiliki satu atau
lebih gugus metil pada posisi 5, 7, atau 8 pada struktur
cincin (chromanol ring).
• Bersifat antioksidan, yang memperlambat atau mencegah
oksidasi lipid. Dengan demikian, ini memberikan kontribusi
Pag e(misalnya;
554
untuk stabilisasi bahan aktif lainnya
vitamin A,
ubiquinone, hormon, dan enzim) terhadap oksidasi. !
• Vitamin E berperan dalam konversi asam arakidonat
menjadi prostaglandin dan memperlambat agregasi sel
darah.
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2) Structure of Vitamin E:
Pag e 554
FIGURE 10
Structures of tocopherols. The structures of tocotrienols are
identical to the corresponding tocopherols, except for the
presence of double bonds at positions 3', 7', and 11'.
dants; they quench free radicals by donating the phenolic H and an electron. Tocopherols are a natural constituent of all
29
30 occurring
biological membranes and are thought
to contribute to membrane stability through their antioxidant activity. Naturally
tocopherols and tocotrienols also contribute to the stability of highly unsaturated vegetable oils through this antioxidant action. In
contrast, -tocopheryl acetate added in food fortification has no antioxidant activity because the acetate ester has replaced the
phenolic hydrogen
atom. -Tocopheryl acetate does exhibit vitamin E activity and in vivo antioxidant effects as a result of
FIGURE 10
Structures of tocopherols.
The of
structures
of tocotrienols
enzymatic
cleavage
the ester.
Theareconcentration of dietary vitamin E in animals has been shown to influence the oxidative
identical to the corresponding tocopherols, except for the
presence
of
double
bonds
at
positions
3',
7',
and
11'. example, it has been shown that the susceptibility of pork muscle products to oxidation of
stability of meats after slaughter. For
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29
30
3) Vit. E: Stability and Degradation"
• Vitamin E menunjukkan stabilitas yang cukup baik dalam
ketiadaan oksigen dan pengoksidasi lipid.!
• Aplha-toco phe rol dapat be reaksi dengan ra dikal
peroxyl (atau radikal bebas lainnya) untuk membentuk
hidroperoksida dan radikal alpha-tokoferil
408
• Reaksi pemutusan (terminasi) radikal menhasilkan dimer
tokoferil yang terikat secara kovalen membentuk dimer
dan trimer. Adanya oksidasi lanjutan dan penataan ulang
d i m e r t e r s e b ut m e n g h a s i l k a n t o c o p h e r o x i d e ,
hydroquinone tokoferil, dan kuinon tokoferil.
6 Vitamins
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31
(6.3)
31
6.2.3.3 Stability, Degradation
Losses occur in vegetable oil processing into margarine and shortening. Losses are also encountered in intensive lipid autoxidation, particularly
in dehydrated or deep fried foods (Table 6.6).
Table 6.6. Tocopherol stability during deep frying
Tocopherol
total
(mg/
100 g)
Oil before deep frying
after deep frying
Oil extracted from potato chips
immediately after production
after 2 weeks storage
at room temperature
after 1 month storage
at room temperature
after 2 months storage
at room temperature
after 1 month kept at −12 ◦ C
after 2 months kept at −12 ◦ C
Oil extracted from French fries
immediately after production
after 1 month kept at −12 ◦ C
after 2 months kept at −12 ◦ C
32
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32
82
73
Loss
(%)
11
75
39
48
22
71
17
28
24
77
63
68
78
25
20
33
33
6.2.4 Phytomenadione
(Vitamin K1 Phylloquinone)
6.2.4.1 Biological Role
7′ and 11′ is R and corresponds to that of
natural phytol. Racemic vitamin K1 synthesized
from optically inactive isophytol has the same
biological activity as the natural product. Vitamin K is involved in the post-translational
synthesis of γ -carboxyglutamic acid (Gla) in
vitamin K-dependent proteins. It is reduced to the
hydroquinone form (Formula 6.4) which acts as
a cofactor in the carboxylation of glutamic acid.
Oxidative
degradation of Vit. E
In this process, it is converted to the4)
epoxide
from
which vitamin K is regenerated. Blood clotting
factors (prothrombin, proconvertin, Christmas
and Stuart factor) as well as proteins which
perform other functions belong to the group of
vitamin K-dependent proteins which bind Ca2+
ions at Gla. Deficiency of this vitamin causes
reduced prothrombin activity, hypothrombinemia
and hemorrhage.
Pag e 557
6.2.4.2 Requirement, Occurrence
The activity is given in vitamin equivalents (VE):
1 VE = 1 µg phylloquinone. The daily requirement of vitamin K1 is shown in Table 6.3. It
is covered by food (cf. Table 6.7). The bacteria
present in the large intestine form relatively high
68
amounts of K2 . However, it is uncertain whether
74 Jurusan
they
appreciably
to covering the reTeknologi
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"
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FIGURE34
11
Pag e 558
quirement.
Overview of the oxidative deg radation 34
of vitamin E. In addition to the initial
Vitamin K1 occurs primarily in green leafy veoxidation products shown, many other compounds are formed as a result
getables (spinach, cabbage, cauliflower), but liver
of further oxidation and rearrang ement.
(veal or pork) is also an excellent source (Taspecific
forms
of
vitamin
E
(e.g.,
-,
-,
-,
-tocopherols
and tocotrienols) and, thus, estimation of total vitamin E activity in a
ble 6.7).
product based on relative potencies of the specific compounds [26]. Detection can be accomplished using either ultraviolet (UV)
absorbance of fluorescence. When saponification is used to aid in the separation of lipids from vitamin E, any vitamin E ester will
be hydrolyzed to free -tocopherol. Care must be taken to prevent oxidation during extraction, saponification, and other
6.2.4.3 Stability, Degradation
preliminary treatments.
Vitamin K
The K-group vitamins are naphthoquinone Little is known about8.7.4
the reactions
of vitamin K1
derivatives which differ in their side chains. in foods. The vitamin8.7.4.1
K compounds
Structureare
anddestroyed
General Properties
The structure of vitamin K1 is shown in For- by light and alkali. They are relatively stable to
Vitamin
K
consists
of
a
mula
6.4. The configuration
at carbon atoms atmospheric oxygen and exposure to heat.group of naphthoquinones that exist with or without a terpenoid side chain in the 3-position (Fig. 13).
VITAMIN
K (PHYTOMENADIONE)
3) Vit. K Classification:"
1) Vit K, Structure and Propersties:"
Vitamin K adalah kelompok vitamin yang terdiri dari
struktur cincin methil naphthoquinone (menadione) dan
FIGURE 12
rantai alifatik yang terikat pada
3.and-tocopherol.
Reaction ofposisi
sing let oxyg en
2) Structure of Vit. K
The unsubstituted form of vitamin K is menadione, and it is of primary significance as a synthetic form of the vitamin that is used
in vitamin supplements and food fortification. Phylloquinone (vitamin K1) is a product of plant origin, while menaquinones
1.Phylloquinone (vitamin K1); Berjumlah yang relatif
(vitmain K2) of varying chain length are products of bacterial synthesis, mainly by intestinal microflora. Phylloquinones occur in
dalamincluding
sayu
ran kale,
becauliflower,
rdau n andsecabbage,
p e rtiand they
bayam,
relatively large quantitiesbe
in sar
leafy vegetables
spinach,
are present, but less
abundant, in tomatoes and
certain vegetable
oils. Vitaminkol,
K deficiency
is rare in tetapi
healthy individuals
of the widespread
kangkung,
kembang
dan kubis,
sedikitbecause
dalam
presence of phylloquinones in the diet and because microbial menoquinones are absorbed from the lower intestine. Vitamin K
tomat with
danmalabsorpminyak nabati tertentu. Hati (sapi atau
deficiency is ordinarily associated
babi) juga merupakan sumber vit. K1 yang penting!
2.Menaquinones (vitmain K2); Disintesis oleh bakteri,
terutama oleh mikroflora dalam usus.!
3. Terdapat 3 vitamin K sintetis, yaitu vitamin K3, K4, dan
K5, yang digunakan di berbagai bidang termasuk
industri makanan hewan (vitamin K3) dan untuk
menghambat pertumbuhan jamur (vitamin K5).
35
35
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FIGURE 13
Structure of various forms of
vitamin K.
36
36
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4) Vit. K, Source:
THIAMIN (VIT. B1)
1) Vit. B1, Structure and Properties:"
✴ Thiamin (Vit. B1) adalah kombinasi pyrimidine dan thiazole
yang dihubungkan dengan jembatan methylene (-CH2-).!
✴ Secara alami, thiamin dalam bentuk thiamin pyrophosphate,
thiamin monophosphate, and thiamin triphosphate.
Pag e 568
✴ Thiamin secara komersial dalam bentuk garam hydrochloride
ment of L-ascorbic acid and DHAA. The coupling of chromatographic separation with spectro-photometric, fluorometric, or
electrochemical detection makes HPLC analysis far more specific than traditional redox methods. HPLC methods have been
reported that permit the simultaneous determination of ascorbic and isoascorbic acids as well as their dehydro forms [134]. A ✴
method based on gas chromatography-mass spectrometry has been reported, but extensive sample preparation is a
disadvantage of the procedure [33].
dan mononitrate, digunakan sebagai fortifikasi pangan.!
Thiamin pyrophosphate berfungsi sebagai coenzyme berbagai
enzim alpha-keto acid dehydrogenases, alpha-keto acid
decarboxylases, phosphoketolases, and transketolases. !
✴ Kekurangan thiamin (Vitamin B1) menyebabkan enzim di atas
8.8.2 Thiamin
8.8.2.1 Structure and General Properties
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Thiamin is a substituted pyrimidine linked through a methylene bridge (-CH2-) to Fakultas
a substituted
20). Thiamin is
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Lampung
37
widely distributed in plant and animal tissues. Most naturally occurring
thiamin exists as thiamin pyrophosphate (Fig. 20), with
37
lesser amounts of nonphosphorylated thiamin, thiamin monophosphate, and thiamin triphosphate. Thiamin pyrophosphate
functions as a coenzyme of various -keto acid dehydrogenases, -keto acid decarboxylases, phosphoketolases, and
transketolases. Thiamin is commercially available as the hydrochloride and mononitrate salts, and these forms are widely used
for food fortification and as nutritional supplements (Fig. 20).
tidak berfungsi. Kekurangan yang parah menyebabkan beriberi.
38
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The thiamin molecule exhibits unusual acid-base behavior. The first pKa (~4.8) involves dissociation of the protonated pyrimidine
N1 to yield the uncharged pyrimidyl moiety of thiamin free base (Fig. 21). In the alkaline pH range another transition is observed
(apparent pKa 9.2) that corresponds to the uptake of two equivalents of base to yield the thiamin pseudobase. The pseudobase
can undergo opening of the thiazol ring to yield the thiol form of thaimin, accompanied by dissociation of a single proton. Another
characteristic of thiamin is the quaternary N of the thiazole ring, which remains cationic at all pH values. The marked pH
dependence of thiamin degradation corresponds to the pH-dependent changes in ionic form. Protonated thiamin is far more
2)
stable than free base, pseudobase, and thiol forms, which accounts for the greater stability observed in acidic media (Table 15).
Although thiamin Thiamin
is relatively stable
oxidation
and light, it is among the least stable of the vitamins when in solution at neutral or ✴
(vit.to B1)
Structures:
alkaline pH.
Thiamin (Vit. B1), Sources:"
Terdapat pada biji-bijian, seralia, umbi-umbian, ragi,
dan beberapa jenis buah-buahan.!
✴ Terdapat pula pada daging, ikan, telur, susu, dan organ
dalam hewan seperti hati, ginjal, jantung, dan otak.
FIGURE 20
Structures of various forms of thiamin. All have thiamin (vitamin B1) activity.
39
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39
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412
6 Vitamins
Pag e 572
3) Thiamin (Vit. B1), Stability and Degradation:"
• Stabiltas Thiamin dalam air sangat rendah (mudah
larut).
Stabilitasnya dipengaruhi oleh pH, suhu,
kekuatan ion, dan ion metal. !
• Thiamin yang terikat oleh enzim kurang stabil
dibandingkan dengan Thiamin bebas.!
• Thiamine menjadi inaktif dengan adanya nitrites and
sulfite, Kemungkiana disebabkan oleh reaksi antara
group amino dengan cincin pyridine.
41
drate metabolism, the requirement increases
in a carbohydrate-enriched diet. The assay of
transketolase activity in red blood cells or the
extent of transketolase reactivation on addition of
thiamine pyrophosphate can be used as indicators
for sufficient vitamin intake in the diet.
Vitamin B1 is found in many plants. It is present
in the pericarp and germ of cereals, in yeast,
vegetables (potatoes) and shelled fruit. It is abundant in pork, beef, fish, eggs and in animal organs such as liver, kidney, brain and heart. Human milk and cow’s milk contain vitamin B1 .
Whole grain bread and potatoes are important
dietary sources. Since vitamin B1 is localized in Fig. 6.2. Inactivation rate of thiamine as affected by pH
pengaruh pH terhadap
IGURE 22
pengaruh
suhu
dan Aw aGambar
the outer part Gambar
of cereal
grain Fhulls,
flour milling
Thiamine in phosphate buffer, b thiamine in wheat or
Influence of water activity and temperature on the
inaktivasi
Thiamin.
a) Thiamin
dalam
oat
flour, c thiamine
pyrophosphate
in flour
terhadap
thiamin.
with a low extraction
grade
orin tahan
rice
polishing
retention
of daya
thiamin
a dehydrated
model foodrebuffer phospat, b) Thiamin dalam
system simulating a breakfast cereal product.
move most of the vitamin
in
the
bran
(cf.
15.3.1.3
Percentag e retention values apply to an 8-month
t e p u n g o a t, c ) T h i a m i n
storag
e period.
(From
Ref.the
32.) occurand 15.3.2.2.1). Table 6.7
lists
data
on
phyrophospate
terigu.
Table
6.8. Thiaminedalam
losses in
food during storage (12
rence of thiamine.
months)
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Food
41
6.3.1.3 Stability, Degradation
Thiamine stability in aqueous solution is relatively low. It is influenced by pH (Fig. 6.2),
temperature (Table 6.8), ionic strength and metal
Apricots
Orange juice
Peas
Green beans
Tomato juice
Thiamine loss, %
1.5 ◦ C
38 ◦ C
28
0
0
24
0
65
22
32
92
40
spectrum from 420–560 nm, photolytically
cleaves ribitol from the vitamin, converting it to
lumiflavin:
6.3.2 Riboflavin (Vitamin B2 )
6.3.2.1 Biological Role
Riboflavin (Formula 6.9) is the prosthetic group
of flavine enzymes, which are of great importance in general metabolism and particularly
in
2. Ribiflavin
(Vit. B2), Sources:"
RIBOFLAVIN (VIT.
B2) of protein.
metabolism
(6.10) sayuran,
✴ Sumber utama adalah susu dan produk susu, telur,
1. Riboflavin, Structure an d
ragi, organPagdalam
hewan, seperti jantung, hati dan ginjal, dan
e 577
Properties:"
hati ikan dan telur ikan.!
TABLE 19 Distribution of Riboflavin Compounds in Fresh Human and
✴Riboflavin,
sebelumnya dikenal
Cow's Milk
sebagai vitamin B2, adalah istilah
Compound
Human milk (%)
generik
untuk kelompok
senyawa
ya
n g m e n u n j u k ka n a k38–62
t i v ita s
FA D
biologis riboflavin. Semua turunan
Riboflavin
31–51
riboflavin diberi nama generik
flavin.!
10-Hydroxyethylflavin
2–10
Trace
✴R10-Formylmethyflavin
i b o fl a v i n a d a la h k e lo
mpok
prostetik
enzim flavinTrace–0.4
e yan g
7 -Hydroxyriboflavin
penting dalam metabolisme protein.
✴ Kandungan6.3.3
riboflavin dalam urin merupakan indikator tingkat
Pyridoxine (Pyridoxal, Vitamin B )
23–46a
35–59
(Formula 6.11) or pyridoxol (R = CH2 OH),
11–19
= CHO)
pyridoxamine
(R = vitamin
✴ Terdapat pyridoxal
dua jenis(RFlavin
yang and
menghambat
aktivitas
Trace
B2,(6.9)
yaitu:!CH2 NH2 ).
0.1–0.7
8 -Hydroxyriboflavin
Trace
Trace–0.4
✴ Kekurangan
riboflavin akan menyebabkan akumulasi asam amino
aFollowing pasteurization, FAD in bulk raw milk decreases from 26 to
yang
menyebabkan penurunan aktivitas reduktase glutathione
13%, withsel
a corresponding
increase in the percentag e of riboflavin.
dalam
darah merah.
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Source:Adapted from Refs. 111 and 112.
43
6
pasokan riboflavin. Kadar riboflavin normal bila
mengandung
lebih dari 80μg riboflavin/gr kreatinin, kadar rendah bila
6.3.3.1
Biological
Role
mengandung 27-79 μg/gr, sedangkan bila nilainya kurang dari
dari 27 μg/gr individu tersebut disarankan untuk mengkonsumsi
B6 activity is exhibited by pyridoxine
suplemen Vitamin
riboflavin.
Cow's milk (%)
The metabolically active form,
1.10-Hydroxyethylflavin, produk metabolisme bakteri flavin,
dapat menghambat penyerapan riboflavin ke dalam jaringan.!
2.Lumiflavin, juga dapat bertindak sebagai penghambat.
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to very good during conventional thermal processing, handling, and preparation. Losses during storage of riboflavin in various
dehydrated food systems (breakfast cereals and model systems) are usually negligible. Rates of degradation increase measurably
at aw above the monolayer value when temperatures are above ambient [32].
The typical mechanism of degradation of riboflavin is photochemical, which yields two biologically inactive products, lumiflavin
and lumichrome (Fig. 26), and an array of free radicals [142]. Exposure of solutions of riboflavin to visible light has been used
for many years as an experimental technique to generate free radicals. Photolysis of riboflavin yields superoxide and riboflavin
radicals (R. ), and the reaction of O2 with R. provides peroxy radicals and a wide range of other products. The extent to which
photochemical degradation of riboflavin is responsible for photosensitized oxidation reactions in food has not been quantitatively
NIACIN (NICOTINAMIDE, VIT. B3)
this process
contributes significantly. Sunlight-induced off flavor in milk, which is no longer
3.determined,
Vit. B2,although
Stability
andassuredly
Degradation:"
common, is a riboflavin-mediated photochemical process. Although the mechanism of off-flavor formation has not been fully
Structure
and
Properties:"
✴determined,
Riboflavin
relatif(probably
stabilradical-mediated)
pada proses
penangan
normal.of methionine 1.
light-induced
decarboxylation
and deamination
to form
methional (CH
3S-CH
2-CH2=O is pada
at least partially
mild oxidation of milk lipids also occurs. Changes
in
packaging
and
Penyusutan
proses responsible.
tersebutConcurrent
sekitar 10︲15%.
• Niacin adalah nama generik untuk pyridine 3-carboxylic acid
commercial distribution have minimized this problem.
(nicotinic acid) dan turunannya yang mempunyai sifat yang
sama.!
✴ Kerusakan riboflavin
disebabkan oleh adanya
Photokimia.!
• Nicotinic acid amide (I), dalam bentuk nicotinamide adenine
dinucleotide (NAD+), atau dalam bentuk phosphorylated (NADP
+), berfungsi sebagai coenzymes pada reaksi dehydrogenase.
✴ Terekspos reboflavin
oleh cahaya dengan
panjang gelombang
420︲560 nm,
menghasilkan lumiflavin
dan lumichrome, yang
bersifat tidak aktif.
2. Niacin, Resources:"
• 60︲70% kebutuhan Vit. B3 berasal dari konsumsi tryptophan,
dimana 60 mg L-tryptophan sama dengan 1 mg nicotinamide.!
• Vit. B3 baik dalam bentuk nicotinic acid berasal dari daging,
hati, serealia, dan jamur.
FIGURE 26
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45 Photochemical conversion of riboflavin
45
to
lumichrome and lumiflavin.
46
Pag e 579
PANTOTHENIC ACID (VIT. B5)
1. Structure and Properties:"
• Pantothenic acid adalah vitamin yang terdiri dari beta-alanine
berikatan dengan 2,4- dihydroxy-3,3- dimethyl-butyric
(pantoic) acid.!
• Fungsi Pantothenic acid: !
1. Sebagai komponen coenzyme A.!
2. Sebagai prosthetic group pada sintesis asam lemak..!
• Pantothenic acid didalam darah dalam bentuk molekul bebas,
sedangkan dalam organ tubuh berbentuk coenzym A.!
FIGURE 27
Structures of nicotinic acid, nicotinamide, and nicotinamide
adenine dinucleotide (phosphate).
• Pantothenic acid is sangat stabil. Sekitar 10% hilang pada
pengolahan susu, sedangkan pada pemasakan sayuran sekitar
10-30% hilang karena leaching.
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e mildly acidic conditions that prevail during roasting of 47
coffee, trigonelline
demethylated
to form nicotinic acid,
47
30-fold increase in the niacin concentration and activity
of coffee.
also changes the relative concentration of certain niacin compounds through interconversion reactions [137, 138]. For
heating releases free nicotinamide from NAD and NADP during the boiling of corn. In addition, the distribution of
mpounds within a product varies as a function of variety (e.g., sweet corn vs. field corn) and stage of maturity.
ioavailability
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48
48
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component of a coenzyme A (Fig. 42) and as a covalently bound prosthetic group (without the adenosyl moiety of coenzyme A)
of acyl carrier proteins in fatty acid synthesis. Formation of a thioester derivative of coenzyme A (CoA) with organic acids
facilitates a wide variety of metabolic processes, mainly involving addition or removal of acyl groups, in an array of biosynthetic
and catabolic reactions. Pantothenic acid is essential for all living things and is distributed widely among meats, cereal grains,
eggs, milk, and many fresh vegetables.
Pantothenic acid in many foods and most biological materials is mainly in the form of coenzyme A, the majority of which exists as
thioester derivatives of a wide variety of organic acids. Although analytical data are quite limited with respect to the free and
coenzyme A forms of pantothenic acid in foods, free pantothenic acid has been found to account for only half of the total of this
vitamin in beef muscle and peas [58]. Coenzyme A is fully available as a source of pantothenic acid because it is converted to
free pantothenic acid in the small intestine by the action of alkaline phosphatase and an amidase. Intestinal absorption occurs
through a carrier-mediated absorption process.
2. Pantothenic Acid, Function:
Synthetic pantothenic acid is used in food fortification and in vitamin supplements in the
✴Kebutuhan 6︲8 mg/hari.
1. VIT. B6, Structure and Properties:"
✴ Vitamin B6 adalah nama generik untuk jenis vitamin
Konsentrasi pada darah
10︲40 μg/100 ml and
2︲7 mg/hari dibuang
lewat urin!
mempunyai aktivitas seperti pyridoxine.
✴ Bebagai jenis Vit. B6
d i b e d a k a n
b e r d a s a ka n p a d a
komponen pada
karbon posisi ke 4. !
✴Synthetic pantothenic
acid digunakan untuk
fortifikasi pangan dan
dalam bentuk calcium
pantothenate.!
✴ Pyr i doxine (PN) =
alkohol, !
✴Panthen ol, digu nakan
✴ P y r i d oxal ( P L) =
sebagai suplemen pangan
ternak.
aldehid,!
FIGURE 42
Structure of various forms of pantothenic acid.
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49
49
FIGURE 28
Structures of vitamin B6 compounds.
✴ Pyridoxamine (PM) =
amine.
of the 3-OH (pK
Jurusan Teknologi
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"
a
3.5–5.0), the pyridine system of vitamin B6 molecules
mainlyHasil
exists
in Zwitterionic
form at ne
Fakultas Pertanian Universitas Lampung
50markedly as a function
net charge on vitamin B6 compounds varies
of pH. The 4'-amino group of PM and PMP (p
50
and the 5'-phosphate ester of PLP and PMP (pKa <2.5, ~6, and ~12) also contribute to the charge of these forms
vitamin.
All chemical forms of vitamin B6 exist in foods, although the distribution varies markedly. PN glucoside exists only
products, although most plant products also contain all other forms of the vitamin. Vitamin B6 in muscle and organ
predominantly (>80%) PLP and PMP, with minor amounts of the nonphosphorylated species. Disruption of raw pl
freeze-thaw cycling or homogenization releases phosphatases and -glucosidases that can alter the forms of vitamin
compounds by catalyzing dephosphorylation and deglycosylation reactions. Similarly, disruption of animal tissues p
cooking can cause extensive dephosphorylation of PLP and PMP. PNP is a transient intermediate in vitamin B6 me
is usually a negligible component of the total vitamin B6 content. Pyridoxine (as the HCI salt) is the form of vitamin
food fortification and in nutritional supplements because of its good stability.
TABLE 21 pK a Values
of Vitamin B6
Compounds
BIOTIN (VITAMIN B7 ATAU H)
2. Vit. B6, Sources:"
• Vitamin B6 yang mengandung glycosida, seperti pyridoxal atau
pyridoxamine, merupakan bentuk Vit. B6 dalam buah, sayuran,
dan serealia.!
Pag e 600
• Pyridoxine glucoside menjadi tersedia setelah dihidrolisis oleh
beta-glucosidases di dalam usus halus.!
•
neral Properties Pyridoxal
phosphate, berfungsi sebagai coenzyme untuk
asam amino.!
oluble vitamin that enzyme
functions coenzymatically
in carboxylation and transcarboxylation reactions. The
N-biotinyl-L-lysine)
ms are free D-biotin
and biocytin ( -Pyridoxine
(Fig. 41). Biocytin functions as the
menyebabkan:!
• Kekurangan
y consists of a biotinylated lysyl residue covalently incorporated in a protein chain of various
1. inMetabolisme
protein terganggu,
seperti
sistesis
em of biotin can exist
eight possible stereoisomers,
only one of which
(D-biotin)
is the hemoglobin.!
natural,
oth free biotin and protein-bound biocytin exhibit activity when consumed in the diet. Biotin is widely
2. Koversi tryptophan menjadi nicotinic acid terhenti,
mal products, and biotin deficiency is rare in normal humans.
n
PYRIDOXINE (PYRIDOXAL, VIT. B6)
menyebabkan terakumulasainya
xanthurenic acid
Hydroxykynurenine dan
t, light, and oxygen. Extremes of high or low pH can cause degradation, possibly Jurusan
because
they
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N-C=O (amide) bond of the biotin ring system. Oxidizing conditions
such as Fakultas
exposure
to hydrogen
51
51
lfur to form biologically inactive biotin sulfoxide or sulfone. Reaction of the biotin ring carbonyl with
hough this has not been examined. Losses of biotin during food processing and subsequent storage
d summarized [12, 67, 86]. Such losses may occur by chemical degradation processes as mentioned
ree biotin. Little degradation of biotin occurs during low-moisture storage of fortified cereal products.
retained in foods.
1. Biotin, Structure and Properties:"
pK a
PM
PLP
PMP
• Biotin adalah bicyclic, vitamin larut dalam air yang berfungsi
Ionization
PN
PL
5.00
s e b a g3–OH
ai co n e zim
p a d a 4.20–4.23
r e a k s i c3.31–3.54
a r b o x y4.14
lat i3.25–3.69
on an d
Pyridinium N
8.96–8.97
8.66–8.70
7.90–8.21
8.69
8.61
transcarboxylation.!
4'-Amino g roup
10.4–10.63
ND
biotin yaitu D-biotin bebas
dan biocytin
(e-N• Dua jenis
biotinyl-L-lysine).!
5'-Phosphate ester
<2.5
terhadap panas dan oksigen, tetapi:! <2.5
pK
• Biotin stabil
6.20
5.76
pK
✴ pH terlalu
tinggi dan rendah menyebabkan kerusakan
a1
a2
karenapKmenyebabkan hidrolisis ikatan -N-C=O (amide).
!
ND
ND
a3
✴ Terekspos
oleh
hydrogen
peroxide
mengoksidasi
sulfur
Note: PN, pyridixine;
PL, pyridoxal;
PM, pyridoxamine;
PLP, pyridoxal
5' -phosphate; PMP, pyridoxamine
5' -phosphate. ND,
not determined.
membentuk
biotin
sulfoxide atau sulfone yang tidak aktif.!
Source: Ref. 123.
• Kebutuhan Biotin adalah 30-60μg/hari. Kekurangan biotin
ditunjukan oleh kadar biotin dalam urin kurang dari 5 μg
(normal: 30︲ 50μg).
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52
ng storage of human milk also has been examined [174]. The biotin concentration of the milk samples
k at ambient temperature, 1 month at 5°C, or at -20°C or lower for 1.5 years.
ods
plantarum
oods is performed by microbiological assay (usually with Lactobacillus
) or bydan
varioushewan
✴ Bahan
pangan
Biotin
nvolving avidin2.
as the
bindingAvailability:
mengandung biotin.
Dalam
tubuh manusia, dihasilkan
oleh bakteri dalam usus
halus!
✴ Pen ye ra p an
biotin
terhambat oleh konsumsi
telur mentah, terbentuk
ikatan biotin-protein avidin.
Avidin adalah tetrameric
glycoprotein pada albumin
(putih telur). !
✴ Ke k u ra n g a n b iot in
m e n ye b a b ka n : A lo p e c i a
(ra m b ut
rontok),
conjunctivities (pink eye),
dermatitis (kulit),
FIGURE 41
Structures of biotin and biocytin.
53
53
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CYANOCOBALAMIN (VIT. B12)
1. Vit B12, Structure and Properties:"
• Vitamin B12 merupakan nama untuk komponen yang
mempunyai sifat seperti cyanocobalamin.!
• These compounds are:!
✴ Corrinoids, struktur tetrapyrrole (empat pyrrrole nitrogen)
dengan ion kobal (Co) sebagai inti struktur. !
✴ Koordinat ke lima pada ion Kobal mengikat atom nitrogen
dari dimethylbenzimidazole moiety, !
✴ Position ke enam pada ion Kobal dapat mengikat 5' deoxyadenosyl group, methyl group, water, hydroxyl ion,
nitrite, ammonia atau sulfite!
• Vitamin B12 stabil pada pH 4︲6. Pada media basa atau
mengandung reducing agents, seperti ascorbic acid or SO2, vit.
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B12 cepat rusak.
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54
54
2.
Pag e 604
R = 5' -deoxyadenosyl group, a methyl group, water, a hydroxyl
ion, or other ligands such as nitrite, ammonia or sulfite
Vit. B12, Source and Availability:"
• Sekitar 20 vitamin B12 analog ditemukan di bahan pangan.
Pyrolle2
Tetapi sebagian tidak mempunyai aktivitas seperti vit. B12
dan beberapa lainnya bersifat sama dengan vit. 12, tetapi
tidak dapat diserap.!
Pyrolle1
• Vit. B12 disintesis oleh mikroba, kemudian diserap oleh
tanaman, terutama tanaman legumes (kacang-kacangan). !
Pyrolle3
Pyrolle4
• Vitam in B12 dar i hewan dalam bentuk coenzym e,
m et h y lco ba la m i n, 5 ' - d e ox ya d e n o s y lco ba la m i n, d a n
Pag e 559
aquocobalamin.
Dan disimpan dalam hati, ginjal, limpa, dan
FIGURE 43
tion syndromes or the use of
pharmacological anticoagulants. Although the use of certain fat substitutes has beenjaringan
reported to otot.
Structure of various forms of
dimethylbenzimidazole
impair vitamin K absorption, moderate
intakes
vitamin
B12. of these substitutes have no significant effect on vitamin K utilization.
quinone
of vitamin
compounds
can be reduced to theinhydroquinone
form by certain
functions coenzymatically The
in the
transferstructure
of a methyl
groupK(from
5-methyltetrahydrofolate)
methionine
synthetase,
whilereducing
5' - agents, but vitamin
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K activity
is retained.
Photochemical
degradation
can occur,
but
thecatalyzed
vitamin
isby
quite
stable to heat.
55
deoxyadenosylcobalamin serves
as the
coenzyme
in an enzymatic
rearrangement
reaction
methylmalonyl-CoA
55
mutase. Little or no naturally
occurring
cyanocobalamin
8.7.4.2
Analytical
Methods exists in foods; in fact, the original identification of vitamin B12 as
cyanocobalamin involved its formation as an artifact of the isolation procedure. Cyanocobalamin has a reddish color in the
Spectrophotometric
chemical
based
of oxidation-reduction
properties
of vitamin
crystalline state and in solution. This colorationand
may
pose a assays
limitation
in on
themeasurement
possible addition
of cyanocobalamin
to certain
foods, K lack the
specificity
required
food analysis. Various HPLC methods exist that provide satisfactory specificity and permit individual
especially light colored products
(e.g.,
white for
bread).
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56
forms of vitamin K to be measured [135].
Unlike other vitamins that are synthesized primarily in plants, cobalamins are produced only by microbial biosynthesis. Certain
8.8toWater-Soluble
Vitaminsof vitamin B12 produced by bacteria associated with root nodules, but
legumes have been reported
absorb small amounts
little enters the seeds [99] Most
8.8.1 plant-derived
Ascorbic Acidfoods are devoid of vitamin B12 unless contaminated by fecal material, such as
from fertilizer [64, 65]. The vitamin B12 in most animal tissues consists mainly of the coenzyme forms, methylcobalamin and 5' Structure
and GeneralHerbert
Properties
deoxyadenosylcobalamin, 8.8.1.1
in addition
to aquocobalamin.
[65] has classified foods according to their vitamin B12
content, as shown in Table 29.
L-Ascorbic acid (AA) (Fig. 14) is a carbohydrate-like compound whose acidic and reducing properties are contributed by the
ASCORBIC
ACID
(VIT.
C)
compound
ishave
highly
polar;
thus, it is
readilyofsoluble
in aqueous
solution activity
and insoluble
Approximately 20 naturally2,3-enediol
occurringmoiety.
analogsThis
of vitamin
B12
been
identified.
Some
these have
no biological
in in less nonpolar
solvents.
AApartial
is acidic
in character
as but
a result
of ionization
the C-3 hydroxyl group (pKa1 = 4.04 at 25°C). A second
mammals, while others exhibit
at least
vitamin
activity
are often
poorly of
absorbed.
Vit. C, Source and Availability:"
ionization, dissociation of the C-2 hydroxyl, is much less favorable (pKa2=11.4). Two-electron oxidation and hydrogen
1. Structure
andconvert
Properties:"
dissociation
L-ascorbic acid to L-dehydroascorbic acid (DHAA).
8.8.9.2 Stability
and Modes
of Degradation
Ascorbic
acid ( AA)
adalah
Under most✴
conditions
of food processing,
preservation,
and storage, there is little nutritionally significant loss of vitamin B12.
Cyanocobalaminkadded
o m to
p breakfast
o n e ncereal sproducts
e p e has
r tbeen
i reported to undergo an average loss of 17% during processing,
with an additional 17% loss during storage for 12 months at ambient temperature [125]. In studies of the processing of fluid
karbohi drat dimana sifat
milk, 96% mean retention has been observed during high-temperature, short-time (HTST) pasteurization, and similar retention
asam
reduksi
berasal
(>90%) was found
in milk dan
processed
using various
modes of ultra-high-temperature (UHT) processing [45]. Although
dari
2,3-enediol.!
refrigerated storage
of milk
has little impact on vitamin B12 retention, storage of UHT-processed milk at ambient temperature
for up to 90 days causes progressive losses that can approach 50% of the initial vitamin B12
✴ AA sangat polar sehingga
• Vitamin C terdapat pada sel tumbuhan dan hewan, dalam
bentuk molekul bebas dan berikatan dengan protein.!
• Vitamin C banyak terdapat pada strawberries, parsley,
oranges, peterseli, jeruk, lemon (di kulit lebih banyak dari
pada dalam pulp), berbagai kubis, dan kentang.!
• Kebutuhan harian adalah 60-150 ug/hari. Indikator
mudah larut dalam air dan
tidak larut dalam pelarut
non polar.!
kekurangan vit. C adalah bila kadar AA dalam plasma darah
kurang dari 0,65 mg AA/100 ml plasma.
✴ O k s i d a s i m e n g u b a h Lascorbic acid menjadi Ldehydroascorbic acid (DHAA).
57
57
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FIGURE
14 Universitas Lampung
Fakultas
Pertanian
Structures of L-ascorbic acid and
L-dehydroascorbic acid and their isomeric
forms. (Asterisk indicates vitamin C
activity.)
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58
Pag e 566
6.3 Water-Soluble Vitamins
Vit. C, Function:"
• AA digunakan sebagai bahan makanan/aditif karena
sebagai pereduksi dan antioksidan.!
• AA efektif menghambat browning enzimatis
mengurangi produk ortho-quinone.!
Diketogulonic acid degradation products, xy- juices and dried fruits. The intermediates that
losone and 4-deoxypentosone (Formula 6.21), are have been identified are scorbamic acid (I in
FIGURE 18
then converted
into ethylglyoxal,
various reduc- Formula 6.22), which is produced by Strecker
Participation of dehydroascorbic acid in the Strecker deg radation
tonesVit.
(cf. 4.2.4.3.1),
furfural
furancarboxylic
degradation with an amino acid, and a red
C, Stability
and
Dengadation:"
reaction. and
acid.
pigment (II). A wealth of data is available on
water to act as a solvent for reactants and catalysts. The presence of certain sugars (ketoses) can increase the rate of anaerobic
ascorbic
acidsome
losses
during preservation,
storage
cincin
Lactone
menyebabkan
kerusakan
Vit. C.!
degradation. Sucrose has a similar effectPembukaan
at low pH, consistent with
its pH-dependent
generation of
fructose.
In contrast,
bersifat
sugars and sugar alcohols exert a protective effect against the oxidative degradation of AA, possibly byand
binding
metal ions andof food. Tables 6.1 and 6.2 and
processing
reducing their catalytic potency. The significance of these observations to actual foods remains to be determined.
and Polimerisasi
6.4 present severaldan
examples.
Degradasi AA disebabkan Figs.
oleh:6.3(a)
(b)
Ascorbic lurus
acid degradation
is oftendengan
used as
8.8.1.3 Functions of Ascorbic Acid in Foods
fragmentasi menghasilkan rantai
atau ring
a general indicator of changes occurring in food.
dengan
In addition to its function as an essential nutrient, AA is widely used as a food ingredient/additive because of its reducing and
•
•
panjang rantai kurang dari 6 karbon.
antioxidative properties. As discussed elsewhere in this book, AA effectively inhibits enzymatic browning by reducing orthoquinone products. Other functions include (a) reductive action in dough conditioners, (b) protection of certain oxidizable com-
• Fungsi AA lainnya adalah (a) melindungi komponen yang mudah
teroksidasi (misalnya, folates), dengan cara mengikat radikal
bebas dan oksigen, (b) pelembut adonan, (c) penghambat
pembentukan nitrosamine dalam daging, dan (d) mengikat ion
logam.!
• Kekurangan Vit. C menyebabkan Scurvy (gusi membusuk).
59
59
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(6.21)
In the presence of amino acids, ascorbic acid, dehydroascorbic acid and their degradation products might be changed further by entering into
Maillard-type browning reactions (cf. 4.2.4.4).
An example is the reaction of dehydroascorbic
acid with amino compounds
to give pigments,
FIGURE 19
Deg radation
acid as a browning
function of storagin
e
which can
causeof ascorbic
unwanted
citrus
temperature and water activity in dehydrated model
food systems simulating breakfast cereal products.
Data (means ±SD) are expressed as apparent
first-order rate constants for the loss of total
ascorbic acid (AA + DHAA). (Data from Ref. 77).
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Fig. 6.3. Ascorbic acid
lossesPertanian
as a result
of cooking
of
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cabbage (according to Plank, 1966)
60