Question

1. You decide to conduct a set of experiments to examine the volatile compounds released into the air from fatty fish as they sit on ice at the grocery store as a way of examining freshness. Hand-held biosensors for specific degradation products can be used. However, for years, gas chromatography has been the standard for examining fish values. You decide to take it a step further and arrange for samples to be shipped away for analysis by GC and GCMS Why are fish with polyunsaturated fatty acids more prone to oxidative damage? How could you minimize degradation during shipping? How could you provide a control that eliminated the variable of degradation during shipping? Describe briefly a procedure for extracting the organic compounds of interest from a plug of fish muscle. a. b. c. d.

Answer 1

a)Food products with unsaturated fats are always in threat of lipid oxidation,which can result in lowering the quality of the product by generating bad odour ,taste and shorter shelf life.Fishes contain high percentage of PUFA is vulnerable to degradation by oxidation process causing production of molecules harmful to our health and poor nutrition.Lipid belongs to fish is made of long moderate amount of chain fatty acids which is of unsaturated characteristics. PUFA like eicosapentaenoic and docosahexaneoic is present abundantly in fish oil or fish products.This oxidative damage is caused by the stress the fish experience before handling and storing.The stress results in the production reactive oxygen species like peroxide,MDA and free fatty acids.The stress level can be controlled by feeding the animal with anti oxidant before handling and shipping.

b)While shipping of the product the temperature and time of storage is significant factor which has to be given attention.Higher duration of storage results in the deterioration of freshness and nutritional level of the food product.The fishes while shipping is stored in high chilling temperature(2* celcius or lower) ,so that the molecular pathways which cause oxidative damage can be maintained in inactive form.

c)By Deep chilling,salting,drying and smoking  the fish product before shipping prevent the oxidation damage .

d)Extraction technique for the production of fish oil is carried out by following process

Cooking----> Pressing------>separation of oily and watery phases ------recovery of protein rich material

Purification of the fish oil is done by fractionation,vaccum distillation,urea crystalization and conventional crystalization.