Biokimia Bahan Makanan (KI-5261)

Pokok Bahasan 1. Peraturan/perundangan untuk Obat & Bahan Pangan (1) 2. Nutrisi & Sifat Fisikokimia komponen utama Bahan pangan: (4-5) 3. Pengolahan & Pengawetan Bahan Pangan (2-3) 4. Pembusukan & Penyakit yang dibawa melalui Pangan (2-3)

Mikronutrien: Vitamin Vitamin merupakan senyawa organik yang tidak dapat disintesis tubuh tapi sangat dibutuhkan kehadirannya, meskipun dalam jumlah yang sangat kecil. Fungsi metabolik: Koenzim Terlilbat dalam proses transfer energi Diperlukan utk keutuhan membran

Penggolongan Vitamin- berdasarkan kelarutannya Vitamain yang larut dalam air:  mengandung atom yang elektronegatif  dipol (polar) C, golongan vit B Vitamin yang larut dalam lemak :  tidak mengandung atom yang elektronegatif  non polar A, D, E, K

Vit. C: Asam askorbat Sturktur: suatu poly-ol Gugus Hydroxyl melekat pada karbon etilenat (suatu stuktur enediol ) dengan pKa= 4.1) dan satu atom khiral* L-isomer merupakan bentuk yang ada di alam. D-isomer : asam erythorbat  tidak ada aktivitas biologis Exists as a unsaturated lactone in solution Alkene and carbonyl groups are conjugated Enediol group produces reducing characteristic of ascorbic acid D-isomer is called erythorbic acid:  no biological activity

Vit C, lanjutan

Kandungan Vit C pada berbagai buah-buahan [Vit C] mg/100 g Blackcurrent 200 Paw paw 80 Strawberry 60 Citrus 50 Mango 30 Banana 20 Apple 5

Kandungan Vit C pada sayuran Sayuran Kandungan (mg/100 g) Parsley 150 Capsicum 130 Broccoli 100 Brussel sprouts 100 Cauliflower 70 Cabbage 60 Potatoes 30 Peas 25

Keaktifan & kestabilan Paling tidak stabil Proses pencoklatan enzimatis pada buah & sayuran dapat mengoksidasi as askorbat Yang berperan dalam hal ini adalah senyawa-senyawa quinone L-dehydroascorbic acid dioksidasi lebih lanjut menjadi asam diketo-L-gulonat nonreversible delactonization Kestabilan: rentan thd: T, [garam] [gula], pH, Oxygen, Enzim (ascorbic oxidase, phenolase, cyt. Oxidase, peroxidase), katallis logam L-ascorbic acid is readily and reversibly oxidized to L-dehydroascorbic acid:  activity reduced to 80% on oxidation Kestabilan: Destruction of Vitamin C on Storage Increased by: 1. Action of metals eg. copper and iron 2. Action of enzymes particularly those containing Cu and Fe in their prosthetic group (cofactor) eg. ascorbic oxidase eg. phenolase eg. cytochrome oxidase eg. Peroxidase Enzymes do not act in intact fruits because of physical separation of enzyme and substrate rot or senescence leads to cellular disorganization and initiates decomposition Enzymic damage is inhibited: in vegetables by blanching and in fruit by pasteurisation, deaeration, and low temperature storage

Kelompok Vitamin B Riboflavin Vitamin B6 Niacin Folic Acid Pantothenic Acid Biotin

Vit. B1 : Tiamin Struktur Secara alami tiamin ditemukan sebagai: Ester antara gugus dengan asam difosfat menghasilkan difosfat, thiamine pyrophosphate (TPP) Sturktur: 2 basic nitrogens primary amino group (-NH2) quaternary ammonium group Salt formation common with organic acids inorganic acids In solution thiamine exist in different forms according to the pH

1980. A kid in Uganda about to die of hunger, and a missionaire.

Sumber tiamin (mg/100 g) Beef up to 0.6 Pork up to 1.0 Peas 0.36 Egg 0.11 Potatoes 0.10 Milk 0.03 Wheat flour: wholemeal 0.36-0.5 % extraction 0.3-0.4 73% extraction 0.07-0.1 Rice: whole rice 0.5 polished rice 0.03 rice bran 2.3

Kestabilan Vit B1 Cahaya dan keadaan asam pada bahan pangan tidak mempengaruhi kadar e.g. heating to 120 C at pH 3.5 or below Stabil pada suhu kamar dengan aktivitas air yang rendah Degradasi tiamin pada ikan & crustacean  haeme proteins nonenzymic catalyst Tannins & hypochlorit Stabilitas: Thiamine is postharvest unstable in fish and crustaceans Such thiamine degradation thought to be due to thermal stable haeme proteins they act as nonenzymic catalysts of thiamine degradation Tannins inactivate thiamine in water Chlorine (as hypochlorite) in water leads to rapid degradation of thiamine

Vitamin Yang larut dalam Lemak : Vit A Yang terdapat di mamalia: Retinol, Retinal, asam retinoat Retinol Thermal processing  trans-cis Structure of Retinol Primary alcohol derivative Four isoprene units (C=C) all trans C=C One intact nonoxygenated β-ionone Nonpolar and lipophylic Carotenoids One intact unsubstituted (nonoxygenated) β-ionone ring Conjugated double bond systems absorption in the visible spectrum produces a yellow-orange colour All trans structure for C=C system highest activity Conversion to cis isomers reduces activity occurs during thermal processing

Vitamin A lainnya

Skema proses eksitasi visual Khromoprotein gelap terang opsin 11-cis Retinal All-trans-Retinal 11-cis-Retinol all-trans-Retinol

Provit. A b-Carrotene Kebutuhan harian: 1.5-1.8 mg sebagai: 75% retinyl palmitate 25% b-Carrotene (6 g~1g retinol) Location of Vitamin A Compounds in Foods Retinoids and provitamin A carotenoids associate with lipid constituents, organelles and protein carriers in foods Also found with lipid droplets or micelles dispersed in an aqueous solution eg. occur in fat globules in milk eg. associated with dispersed oils in orange juice

Air