Preservatives
According to FSSAI "Preservative" means a substance which when added to food, is capable of inhibiting, retarding or arresting the process of fermentation, acidification or other decomposition of food.
Chemical Food Preservatives
are those substances which are added in very low quantities (up to 0.2%) and which do not alter the organoleptic and physico-chemical properties of the foods at or only very little (FAO).
Classification of Preservatives
Preservatives are divided into following two classes:
Class I preservative
The preservatives under this class are generally regarded as safe (GRAS) for human consumption. These preservatives are normally consumed daily and there is no quantity-wise or product-wise restriction on their use. The following preservatives are classified as class I preservatives and these preservatives are usually used in the preservation of fruits and vegetables-
Common salt
Sugar
Dextrose
Glucose Syrup
Spices
Vinegar or acetic acid
Honey
Edible vegetable oils
Addition of Class I preservatives in any food is not restricted, unless otherwise provided in the FSSAI regulations. Provided that the article of food to which a Class I preservative has been added conforms to the specifications laid down in Chapter 2 of FSSAI regulations.
Class II preservatives
The class-II preservatives are not generally regarded as safe and may be used in certain food products only in restricted quantity. There is quantity wise and product wise restriction on their use by the law because these chemicals are not very safe for human consumption. The name of class-II
preservatives their quantity and the products in which they may be used are enlisted in the FSSAI regulations. The class II preservatives are-
Benzoic acid including salts thereof,
Sulphurous acid including salts thereof,
Nitrates or Nitrites of Sodium or Potassium in respect of food like ham, pickled meat,
Sorbic acid including its sodium, potassium and calcium salts, propionates of calcium or sodium, lactic acid, and acid calcium phosphate.
Nisin
Sodium and calcium propionate.
Methyl or propyl Parahydroxy-Benzoate.
Propionic acid, including esters or salt thereof,
Sodium diacetate, and
Sodium, potassium and calcium salts of lactic acid.
The Use of more than one Class II preservative is prohibited under law. The Acceptable Daily Intakes (ADI) of class-II preservatives are presented in Table-1
Table-1: Acceptable Daily Intakes (ADI) of important class-II preservatives
Important class-II preservatives ADI (mg/kg body weight)
Benzoic acid and its Na/K salts expressed as benzoic acid 0 to 5
Sulphurous acid (H2So3) and its salts calculated as So2 0 to 0.7
Sodium or potassium nitrites calculated as sodium nitrite 0 to 0.2
Sodium or potassium nitrites calculated as nitrate 0 to 5
Sorbic acid and its Ca/K/Na salts expressed as sorbic acid 0 to 25
The two class II preservatives which are most used in the preservation of fruits and
Benzoic acid including salts thereof (Sodium Benzoate)
Sodium benzoate (C6H5COONa ) is a sodium salt of benzoic acid (C6H5COOH) which can be produced by reacting sodium hydroxide with benzoic acid. The food grade sodium benzoate is white, odour less, amorphous powder, flakes or granules and conforms to IS: 4447-1994 of Bureau of Indian standard. As food additive, sodium benzoate has E number E211. The solubility of the sodium benzoate is temperature dependent and its solubility increases from 62.8g/100 ml water at 00C to 74.2g/100ml water at 1000C. The sodium benzoate should be of food grade otherwise impurities may import bad benzene smell in the products. It is slightly hygroscopic, but moisture absorption does not alter its quality in any way. Sodium benzoate produces benzoic acid in the acidic medium of foods and benzoic acid acts as preservative but instead of benzoic acid sodium benzoate is added as food preservative because sodium benzoate solubility is more in water than benzoic acid. The 1g sodium benzoate is soluble only in 2 ml water whereas 1g benzoic acid requires 350 ml water. The food grade benzoic acid is white flakes or crystal with faint characteristic odour and it should conform to IS: 4448-1994 of Bureau of Indian Standard. Benzoic acid is the active ingredient in sodium benzoate and 1g of sodium benzoate produces 0.85 g benzoic acid when added in the processed fruits and vegetable products thus 1g benzoic acid is equal to 1.2g sodium benzoate. Parohydroxy benzoic acid is widely distributed in plant tissues and is a normal constituent of wine. Benzoic acid is also present naturally in cranberries (Vaccinium oxycoccos orOxycoccus palustris), prunes (Prunus domestica), greengage plum (Prunus domestica ssp. italica var. claudiana), cinnamon (Cinnamomum zeylanicum), clove (Syzygium aromaticum), apple (Malus domestica), red raspberry (Rubus idaeus) and black raspberry (Rubus occidentalis).
Table-2: Upper limit of benzoic acid in fruit and vegetable products as per FSSAI
Processed fruit and vegetable products Maxi. Benzoic acid (ppm)
Jam, marmalade, preserve canned cherry and fruit jelly 200
Nonalcoholic wines, squashes, crushes, fruit syrups,
cordials, fruit juices and barley water or
to be used after dilution 600
Ready to serve beverages 120
Pickles and chutneys made from fruits or vegetables 250
Tomato and other sauces, Tomato puree and paste 750
Syrups and sharbats 600
The antimicrobial action of sodium benzoate is due to undissociated portion of benzoic acid that plays role in preservation. The foods should be acidic for better action of this preservative because the pH of the food decides the dissociation of benzoic acid and thereby efficiency of sodium benzoate. Sodium benzoate is more efficient at lower pH and its antimicrobial action is excellent at 2 to 4 pH and is not very effective above 5 pH whereas esters of benzoic acid are more effective in microbial inhibition than benzoic acid and can be used in foods of a wide range of pH. Sodium benzoate is most suitable for foods and beverages having pH below 4.5. It is best for pickle preservation because vinegar used in pickle making and lactic acid produced during pickling lowers the pH. Sodium benzoate inhibits or kills microorganisms by interfering with the permeability of microbial cell membrane and is more effective against yeast and moulds than bacteria. In some bacteria nutritional starvation of microorganism is caused by inhibition of membrane transport of amino acids. It reduces intercellular pH in E. coli and thereby microorganism starved to death. Sodium benzoate and sodium chloride have considerable synergistic effect. Benzoic acid may be used in the preservation of fruit and vegetable juices, fruit pulp, beverages, squashes, crushes, fruit syrups, jam, marmalade, chutney, tomato sauce, puree, pastes and pickles. It is also recommended to preserve beverages containing natural anthocyanin colour because contrary to KMS it does not bleach the anthocyanin colour of the beverages. The International programme on chemical safety found no adverse effect in humans at dose of 647-825 mg/kg of body weight per day. Sodium benzoate has no cumulative effect and it excretes in urine in the form of hippuric acid within a short time. The benzoate in excess of 0.1% may import a disagreeable ‘peppery’ or burning taste to fruit juices.
Sulphurous acid including salts thereof (Potassium metabisulfite)
Sulphurous acid (H2So3) is an unstable acid produced when So2 dissolves in the water. It is used as food preservative and as bleaching agent. Sulphur dioxide is colorless, suffocating, pungent smelling, non-inflammable gas. It is readily soluble in water (85g/100 ml at 250C) and has been used for many centuries as a fumigant and specially as wine preservatives. Sulphur dioxide is used as a gas or in the form of its sulfite, bisulfite and metabisulfite salts which are powders. Metabisulfite salts are more stable to oxidation than bisuphites, which in turn show greater stability than sulphites. The most effective pH range of Sulphur dioxide is 2.5 to 5.0 and is added to foods for its antimicrobial effects, antioxidant properties and to prevent enzymatic and non-enzymatic browning.
Potassium metabisulfite (K2S2O5 or K2O5S2) , also know as Potassium pyrosulfite is a white crystal powder with pungent Sulphur odor ; is most common forms used in fruits and vegetables preservation. The molecular weight of potassium metabisulfite is 222.32g/mol and solubility in water is 450g/l at 200C. The food grade potassium metabisulfite is also known as E224. One molecule of Potassium metabisulfite(222g) yields 2 molecules of Sulphur dioxide(128g) or potassium metabisulfite (KMS) releases 57.7% Sulphur dioxide [(128/222)/100=57.7%], therefor 1.75 factor is used in the calculation of potassium metabisulfite quantity in gram to be added in the foods. The KMS amount can be calculated for know quantity of processed products with following formulae-
KMS in g = (So2 in ppm x beverage in l x 1.75)/1000
The potassium metabisulfite is used to preserve a variety of foods like wines, fruit juices, pickles, syrups, dehydrated/dried fruits and vegetables and semi processed foods like fruits pulp.
Table-3: Upper limit of Sulphur dioxide in fruit and vegetable products as per FSSAI
Processed fruit and vegetable products Maxi. Sulphur dioxide (ppm)
Jam, marmalade, pre serve canned cherry and fruit jelly 40
Nonalcoholic wines, squashes, crushes, fruit syrups, cordials, fruit juices and barley water or to be used after dilution 350
Ready to serve beverages, beer 70
Pickles and chutneys made from fruits or vegetables 100
Fruit juice concentrate 1500
Syrups and sharbats 350
Dried apricots, peaches, apples, pears and other fruits 2000
Raisins and Sultanas 750
Fruit and fruit pulp not otherwise specified in the schedule 350
Fruits, vegetables , flakes, powder, figs 600
Bibliography
Menon, K.K.G. (1981). Food Additives. Indian Food Packer, 35(3): 2-9.
Perera, C.O. and Perera, A.D. (2019). Technology of Processing oh Horticultural Crops, In: Myer K. (ed.), Handbook of Farm, Dairy and Food Machinery Engineering, 299-351. London: Academic Press.
Ranganna, S. and Padival Rajni A. (1981). Chemical preservatives and anti-oxidants. India Food Packer, 35(3):30-45.
Shah, V.K. (2003). Chemical preservation of foods. Beverage & Food World, 30(7):15-20.
Sukhthankar, D.Y. (2001).Anti-microbial spectrum of benzoic acid and sodium benzoate. Beverage & Food world, 28(5).20.
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