Freezing Technology

3.4.4. Methods of using antioxidants

1. Dip treatment prior to freezing
2. In glaze water

Water soluble antioxidants can be easily dissolved in water and can be directly used. However, oil soluble antioxidants are first emulsified in small quantity of oil in water type and used. When gallates are used there should be no contact with Fe⁺⁺ and pro oxidant metal ions may be bound by chelating agents and make them unavailable in oxidation reactions. Nitric acid, phosphoric acid, sodium phosphate citrates, tartarates and ethylene diamine tetra acetic acid (EDTA) are some of the important chelating agents. These may be used separately or along with anti oxidants.

Commonly used antioxidants

Antioxidants are of 2 types 1) Water soluble and 2) Oil soluble.

Antioxidants used in fish processing are as follows

	Compound	Nature	Max. Percentage used
1)	BHA	Oil	0.02
2)	Salts of gallic acid
	a) Propyl gallate	Water	0.01
	b) Octyl gallate	Oil	0.01
	c)Do decyl gallute	Oil	0.01
3)	Nor-dihydrogui acetic acid	Oil	0.01
4)	Ascorbic acid	Water	0.25-2
5)	Sodium ascorbate	Water	0.25-2
6)	Sodium sulphide	Water	0.25-2
7)	Tocopherols	Oil	0.03
8)	Amino acids (cystine, histidine, tryptophan)	Water	0.03
9)	Synergist (citric acid,sorbitol)	Water	0.03

           

 As antioxidants break the chain of free radical formation, oxidation is prevented. However, this is easy in the case of almost pure oils but in the case of fish it is quite difficult because the action of antioxidant depend on several factors such as

1. Property of oil in the tissues.
2. Penetration of antioxidants into tissues .
3. Presence of Pro-oxidant materials.

Therefore some antioxidants are effective only against certain species of fish. Some problems associated with the use of antioxidants in fish are

1. Determination of an antioxidant for a particular species of fish.
2. Medium and method of application of the antioxidant.