Development and evaluation of vitamin A and iron fortified milk.

Milk is centrally processed, widely distributed and regularly consumed by all sections of the society. Milk is a poor source of iron (0.2 mg/kg) and reduction in fat content of milk leads to removal of major portion of fat soluble vitamins including vitamin A. Fortification of such milk with iron and vitamin A can help to eliminate the deficiency of these nutrients in target population. Two iron salts (ferric pyrophosphate soluble and ferrous gluconate hydrate) and vitamin A acetate were selected after screening of nine iron salts and two vitamin A esters for fortification of toned milk (cow milk:buffalo milk 1:1) on the basis of sensory analysis, pH, acidity and TBA value. The level of fortification selected was 15, 20 and 25 ppm iron for FPP soluble/FG hydrate and 2500 IU/L for vitamin A acetate. Liposomes of ferrous sulphate were prepared using egg lecithin as wall material. Flavoured milk (fortified@5, 10 and 15 ppm iron) was prepared using liposomes and sensory acceptability of fortified milk (@5 ppm) was comparable to control. However, higher level of fortification led to pronounced flavour defects in milk, hence, liposomes were not considered for further experiments. The fortified milk (FPP soluble and FG hydrate@25 ppm iron) had comparable heat stability with that of control milk. There were slight changes in pH, acidity and TBA value of fortified milk (vitamin A+iron), however, there was no detrimental effect on milk system. During different processing treatments, loss of vitamin A was more in case of iron fortified milk. However, added vitamin A was found to be more stable than native vitamin A. No effect of processing treatments was observed on the stability of iron in milk. There was non significant effect of vitamin A and iron fortification on curd tension, rennet coagulation time, viscosity, colour profile and alcohol stability of milk. During storage, fortified milk had lesser oxidative stability compared to control milk. Major portion of the added iron was bound to casein compared to whey. Ultracentrifugation of milk revealed that 88-90% of both natural and added iron was retained in colloidal phase of milk. There was no effect of fortification on electrophoretic behaviour of milk proteins. Maillard browning was more in boiled and sterilised milk compared to pasteurised milk; HMF and furosine content were higher in iron fortified milk compared to control milk. Sensory acceptability, curd tension, viscosity and oxidative stability of control and fortified milk were significantly affected by the fat content. Sensory, physico-chemical and microbiological properties of dahi and yoghurt prepared from fortified milks were comparable with their control counterparts. In vitro digestibility of the added nutrients was comparable to those inherently present in milk. FPP soluble was selected for conducting animal trials due to the fact that it caused lesser changes in milk system compared to FG hydrate. In vivo results revealed that vitamin A+iron fortified milk improved iron and vitamin A status of experimental animals; vitamin A enhanced the absorption of iron and vice versa (biological indices, haemoglobin repletion, plasma ferritin, plasma transferrin and liver status of vitamin A and iron). The effects were more pronounced in anaemic rats compared to control rats. The optimum fortification level in milk was 25 ppm iron (FPP soluble) and 2500 IU/L vitamin A acetate. A 250 ml serving of the fortified milk will provide ∼30-35% of iron and vitamin A requirement on daily basis.