Flavoured sterilized milk enriched with alpha linolenic acid: physico-chemical properties and evaluation of storage stability

Milk is often referred as a complete food, but it lacks certain essential fatty acids like omega-3 fatty acids. Omega-3 fatty acids have been associated with reduced risk of several health diseases. Milk is being widely consumed throughout the masses; it would serve as an ideal vehicle for omega-3 fatty acid fortification. Flaxseed oil is one of the richest vegetarian sources of omega-3 fatty acids. However, due to high susceptibility to oxidation, the use of flaxseed oil is limited in food and dairy products. But this problem can be overcome by encapsulating flaxseed oil where a protective coat is formed on oil droplets. In the present study microencapsulated flaxseed oil was used to fortify milk. The selected microcapsule was used to fortify milk with the aim of providing 25 and 50% RDA of alpha linolenic acid in the milk. Based upon better sensory acceptability, 25% RDA level was selected for further study. Upon addition of flaxseed microcapsules, the sterilized flavoured milk samples were analysed for physico-chemical, sensory and compositional parameters. The samples were also evaluated for storage stability for 28 days. The pH and viscosity of the fortified flavoured milk samples differ significantly (p <0.05) from the control. There was no yeast and mould, coliform count in the samples during storage. Also, the total bacterial count was within the permissible limits for fortified sterilized milk. During storage, the seven, fourteen and twenty-one days of storage depicted non-significant difference (p>0.05) in the flavour score of fortified and control sterilised milk samples. But on 28th day of storage there is significant (p<0.05) difference in sensory score of taste and mouthfeel; however, it was still in the acceptable range. The moisture, fat, protein, ash and total carbohydrates for fortified sterilized milk were 87.30, 3.42, 3.57, 0.85, 4.85%, respectively. Therefore, it can be concluded that the milk can be successfully fortified with alpha linolenic acid fatty acids using the modified starch and soy protein isolate based flaxseed oil microencapsulated powder showed excellent storage stability. The flavoured milk thus developed would provide 0.612 g of ALA in one serving.