Bài giảng Phụ gia thực phẩm - Chương 5: Antioxidants - Huỳnh Tiến Đạt

PART 2 FOOD ADDITIVES CONTRIBUTING TO IMPROVE THE SHELF-LIFE Chương 5: ANTIOXIDANTS Group 4: Antioxidant A food additive, which prolongs the shelf-life of foods by protecting against deterioration caused by oxidation.  antibrowning agent  antioxidant  antioxidant synergist 1. Các chất chống nâu hóa Nâu hóa là vấn đề • Thực phẩm nguồn gốc thực vật có thể bị biến đổi hóa học trong quá trình: sau thu hoạch, chế biến, hoặc lưu trữ, Các phản ứng biến đổi màu (nâu hóa) được chia thành 2 loại: 1. Nâu hóa do enzyme 2. Nâu hóa không do enzyme. Ví dụ: - Nâu hóa trong quá trình cắt rau quả tươi và tiếp xúc không khí? - Nâu hóa trong quá trình thanh trùng nước quả? Nâu hóa do enzyme là kết quả của: - Oxy hóa các hợp chất polyphenols chuyển thành quinones, - Được xúc tác bởi các enzyme polyphenol oxidase: • PPO • Tyrosinasa • o-diphenol oxidase • catechol oxidase - Các phản ứng tiếp tục diễn ra và polymer hóa các quinones. Kiểm soát nâu hóa do enzyme: 1. Sử dụng phương pháp chần, 2. Acid hóa; ứng dụng sulfites 3. or sử dụng các chất thay thế sulfites như: – ascorbic acid – cysteine. Các chất thay thế này hiệu quả kém hơn so với sulfites Chemistry of browning reactions in foods Chemistry of browning reactions in foods • The optimum pH for PPO activity is between 5 and 7 • PPO is relatively heat labile • and PPO-catalyzed reactions can be inhibited by: acids phenolic acids, sulfites ascorbic acid Sulfites • Sulfite may be applied as:  E220 Sulphur dioxide  E221 Sodium sulphite  E222 Sodium bisulphite,  E223 Sodium metabisulphite  E224 Potassium metabisulphite  E225 Potassium sulphite  E226 Calcium sulphite  E227 Calcium hydrogen sulphite,  E228 Potassium bisulphite • Sulfite có nhiều dạng tồn tại ở dạng nào tùy thuộc vào bản chất của thực phẩm • Do đó nhiều chất tương đồng của sulfite được phát triển để giải quyết vấn đề công nghệ. E220 (sulphur dioxide) được sử dụng xử lý xông quả chống hóa nâu. Ngoài ra nó cũng có thể sử dụng điều chỉnh độ acid và chất bảo quản vi sinh E223 và E224 đặc biệt rất bền khi lưu trữ do đó sử dụng trong các kho bảo quản là phù hợp. E226 rất tan ít trong nước nên sử dụng được khi yếu tố hòa tan không phải ưu tiên hàng đầu Quá trình oxy hóa (oxidation) • Oxidation là một phản ứng hóa học chuyển các electron hoặc hydrogen từ một cơ chất sang chất oxy hóa. • Phản ứng oxy hóa tạo ra các gốc tự do (free radicals). Sau đó, các gốc tự do này sẽ tạo ra phản ứng oxy hóa dây chuyền. Oxidation ôi hóa (rancidity), mất mùi vị, mất màu sắc mất giá trị dinh dưỡng. Oxy hóa làm biến đổi thực phẩm: Oxidation Mức độ oxy hóa phụ thuộc vào: 1. Tồn tại các chất oxy hóa tự nhiên trong thực phẩm, 2. Có mặt của oxy, 3. độ nhạy của cơ chất đối với phản ứng oxy hóa, 4. nhiệt độ và ánh sáng, ANTIOXIDANTS AH A• AA AX ROO• R• RO• ROOH RH ROH ANTIOXIDANTS STABLISED RADICALS NON RADICALS PEROXIDE AND FREE RADICALS Ascorbic Acid Ascorbyl Palmitate Ascorbyl Stearate Calcium Ascorbate Mixed Tocopherols Concentrate Tocopherol, Alpha- Propyl Gallate Tertiary Butylhydroquinone Guaiac Resin Butylated Hydroxyanisole Butylated Hydroxytoluene ANTIOXIDANTS • Ascorbic acid, tocopherols, gallic acid, BHA and BHT • Often a combination of two or more antioxidants is more effective than any one used simply because of their synergistic effects. • The presence of other agents, such as citric acid, may also have a synergistic effect, by reducing the availability of metallic ions that may catalyse oxidation reactions. . ANTIOXIDANTS • The use of the powerful synthetic antioxidants BHA, BHT and the gallic acid is very restricted. • Tocopherols, which can be either natural or synthetic, are less restricted but are less effective in the protection of processed foods. • Antioxidants cannot restore oxidized food; they can only retard the oxidation process. • The most effective use of antioxidants is therefore in the fats and oils used in the manufacturing process. SAFE Low concentration required (0.01- 0.02%) Distribute at interfaces  Highly hydrophobic  In contact with air Stable in processing conditions ANTIOXIDANTS ANTIOXIDANTS • Regulated differently country by country • Many antioxidant but few approved by: Joint FAO/WHO Expert Committee on Food Additives (JECFA) European Community’s Scientific Committee for Food (SCF) ADI (mg/kg bw) propyl gallate 0–2.5 BHA 0–0.5 BHT 0–0.125 TBHQ 0–0.2 tocopherols 0.15–2.0 gum guaiac 0–2.5 ethoxyquin 0–0.06 phosphates 0–70.0 EDTA 2.5 tartaric acid 0–30.0 citric acid not limited lecithin not limited ascorbic acid not limited sulphites (as sulphur dioxide) 0–0.7 ascorbyl palmitate or ascorbyl 0–1.25 stearate (or the sum of both) OOHOH H – C – OH O H2C–OH H ASCORBIC ACID INS 300 Chemical names: L-Ascorbic acid, ascorbic acid, 2,3-didehydro-L- threo-hexono-1,4-lactone, 3-keto-L-gulofuranolactone DESCRIPTION: White to slightly yellow, odourless crystalline powder; melting point about 190oC with decomposition SOLUBILITY: Freely soluble in water; sparingly soluble in ethanol; insoluble in ether LOSS ON DRYING pH : 2.4 - 2.8 MAX LEVEL: GMP (In accordance with good manufacturing practices; or sufficient for purpose; or quantity not greater than required) ADI: for ascorbic acid and its Ca, K and Na salts, of 0-15 mg/kg OOHOH H – C – OH O H2C–O–C–(CH2)16 – CH3 O H Ascorbic acid + palmitic acid = Ascorbyl palmitate (Vit C ester) E305 Chemical names: ▪ Ascorbyl stearate; ▪ L-ascorbyl stearate; ▪ 2,3-didehydro-L-threo-hexono-1,4-lactone-6-stearate; ▪ 6-stearoyl-3-keto-L-gulofuranolactone Chemical formula: C24H42O7 Description: White or yellowish-white solid, with a citrus-like odour Functional use: Antioxidant Solubility: Very slightly soluble in water; freely soluble in ethanol Melting range: 107 o - 117o Max level: 5.000mg/Kg ADI: 0 – 1,25 mg/Kg OOHOH H – C – OH O H2C–O–C–(CH2)14 – CH3 O H Ascorbic acid + stearic acid = Ascorbyl stearate (Vit C ester) E304 Chemical names: ▪ Ascorbyl palmitate; ▪ L-ascorbyl palmitate; ▪ 2,3-didehydro-L-threo-hexono-1,4-lactone-6-palmitate; ▪ 6-palmitoyl-3-keto-L-gulofuranolactone Chemical formula : C22H38O7 Description : White or yellowish-white solid, with a citrus-like odour Functional use : Antioxidant Solubility : Very slightly soluble in water; soluble in ethanol Melting point : 116o Max level : 5.000mg/Kg ADI : 0 – 1,25mg/Kg E310 Propyl gallate, E311 Octyl gallate, E312 Dodecyl gallate They are fat-soluble and are added to fats and oils to delay or prevent rancidity E310 Propyl gallate, E311 Octyl gallate, E312 Dodecyl gallate Benefits • Propyl gallate is synergistic with other antioxidants, such as BHA and BHT. • It is particularly effective with polyunsaturated fats. • The antioxidant activity is maintained when the fat is blended with other ingredients in a final foodstuff. • The longer chain length of the octyl and dodecyl gallates gives advantages over propyl gallate in terms of:  greater solubility in fats  and greater stability. E310 Propyl gallate, E311 Octyl gallate, E312 Dodecyl gallate Limitations The gallates are fat-soluble, but need to be dissolved in a small quantity of hot fat first before being diluted with the rest of the fat OH C(CH3)3 O–CH3 BUTYLATED HYDROXYANISOLE (BHA) ISN 320 OH C(CH3)3 O–CH3 Chemical names : 3-Tertiary-butyl-4-hydroxyanisole, a mixture of 3- and 2-tertiary- butyl-4-hydroxyanisole DESCRIPTION : White or slightly yellow crystals or waxy solid, with a faint characteristic odour SOLUBILITY : Insoluble in water; freely soluble in ethanol and propane-1,2-diol MAX LEVEL : 200mg/Kg ADI : 0 – 0,5 mg/Kg BUTYLATED HYDROXYANISOLE (BHA) ISN 320 Function in Food • Butylated hydroxyanisole is an antioxidant and is added to delay or prevent rancidity in fats and oils in foodstuffs. • It is insoluble in water and is best suitable to foods with a high fat content. • BHA is often used in combination with other antioxidants such as BHT to give a synergistic effect. BUTYLATED HYDROXYANISOLE (BHA) ISN 320 Benefits BHA is stable to heat and mildly alkaline conditions, giving it a property that makes BHA particularly suitable in baked and fried foods Limitations BHA is a very effective antioxidant for animal fats, but its effect is less marked in vegetable oils that are being stored at ambient temperatures. OH (H3C)3C C(CH3)3 O–CH3 BUTYLATED HYDROXYTOLUENE (BHT) ISN 321 Chemical names: 2,6-Ditertiary-butyl-p-cresol, 4-methyl-2,6-ditertiary-butyl-phenol DESCRIPTION: White, crystalline or flaked solid, odourless or having a characteristic faint aromatic odour SOLUBILITY: Insoluble in water and propane-1,2-diol; freely soluble in ethanol MELTING POINT: 69 – 72oC MAX LEVEL: 100mg/Kg ADI: 0 – 0,3 mg/Kg BUTYLATED HYDROXYTOLUENE (BHT) ISN 321 Function in Food • Butylated hydroxytoluene is an antioxidant and is added to delay or prevent rancidity in fats and oils in foodstuffs. • It is insoluble in water and is best suitable to foods with a high fat content. • BHT is often used in combination with other antioxidants, such as BHA, to give a synergistic effect. BUTYLATED HYDROXYTOLUENE (BHT) ISN 321 Limitations BHT is more steam-volatile than BHA, and this makes it unsuitable for use on its own in frying oils, particularly where high-moisture foods are being fried. ANTIOXIDANT Chelating agent (sequestrant) METAL IONS STABLILSED COMPLEX EDTA (Ethylene Diamine Tetra Acetate) Calcium Disodium Ethylene Diamine Tetra Acetate Disodium Ethylene Diamine Tetra Acetate Polyphosphates Ortho- , Pyro-phosphoric acid Isopropyl citrate CALCIUM DISODIUM ETHYLENE DIAMINE TETRA ACETATE INS 385 Ca++NCH2CH2N CH2–COO – 2Na+ , CH2–COO – –OOC–H2C –OOC–H2C SYNONYMS : Calcium disodium EDTA Chemical names: N,N'-1,2-Ethanediylbis[N-(carboxymethyl)-glycinate](4-)-N,N',O,O',ON,ON]calciate(2-) disodium; Calcium disodium ethylenediaminetetraacetate; Calcium disodium (ethylene-dinitrilo)- tetraacetate. DESCRIPTION: White, odourless crystalline granules or a white to nearly white powder; slightly hygroscopic FUNCTIONAL USES : Sequestrant, preservative SOLUBILITY: Freely soluble in water, practically insoluble in ethanol. pH : 6.5 - 7.5 MAX LEVEL : beverages : 25 – 35mg/Kg, fish : 50, fruits vegetables products 100 – 200, dried vegetables 600 – 800 ADI : 0-2.5 mg/kg DISODIUM ETHYLENE DIAMINE TETRA ACETATE INS 386 NCH2CH2N CH2–COO – 2Na+ CH2–COO – –OOC–H2C –OOC–H2C SYNONYMS : Disodium EDTA, disodium edetate Chemical names : Disodium salt of N,N'-1,2-Ethanediylbis[N-(carboxymethyl)glycine]; disodium dihydrogen ethylenediaminetetraacetate; disodium dihydrogen (ethylene- dinitrilo)-tetraacetate DESCRIPTION: White, odourless crystalline granules or a white to nearly white powder FUNCTIONAL USES : Sequestrant, antioxidant synergist, preservative SOLUBILITY : Freely soluble in water, practically insoluble in ethanol. pH : 4.3 – 4.7 MAX LEVEL : beverages : 25 – 35mg/Kg, fish : 50, fruits vegetables products 100 – 200, dried vegetables 600 – 800 ADI : 0-2.5 mg/kg SODIUM POLYPHOSPHATES INS 452 O P O O– O– O P O– O– O P O O– O– O P O O– O P O– O– O P O O– O– O P O O– O P O– O– n pH changing from 3-9 Chemical names : Sodium tetrapolyphosphate, sodium hexametaphosphate, sodium polyphosphate DESCRIPTION : Colourless or white, transparent platelets, granules, or powders FUNCTIONAL USES : Emulsifier, sequestrant, texturizer SOLUBILITY : Very soluble in water MAX LEVEL : 0.6 – 1.0 % MTDI (Maximum Tolerable Daily Intake): 70 mg/kg SODIUM POLYPHOSPHATES INS 452 PENTASODIUM TRIPHOSPHATE INS 451 NaO P O O NaO P O O NaO P O ONa NaO SYNONYMS : Pentasodium tripolyphosphate, Sodium triphosphate, Sodium tripolyphosphate, Triphosphate Chemical names : Pentasodium triphosphate, pentasodium tripolyphosphate DESCRIPTION : White, slightly hygroscopic granules or powder FUNCTIONAL USES: Sequestrant, texturizer SOLUBILITY : Freely soluble in water; insoluble in ethanol pH : 9.1 - 10.1 MAX LEVEL : 0.6 – 1.0 % No ADI was established, MTDI : 70 mg/kg ISOPROPYL CITRATE INS 384 Chemical names : Citric acid mixed ester of 2-propanol. FUNCTIONAL USES : Antioxidant, sequestrant SOLUBILITY : Soluble in water and ethanol MAX LEVEL : 200mg/Kg ADI : 0-14 mg/kg HO CH CH2 – COOR CH2 – COOR COOR R isopropyl or hydrogen Antioxidative factor (AF) = IA/I0 AF values of some antioxidants (0.02%) in refined lard Antioxidant AF Antioxidant AF d--tocopherol d--tocopherol BHA BHT 5 12 9.5 6 Octyl gallate Ascorbyl palmitate BHA+BHT (0.01%+0.01%) 6 4 12