EFFECTS OF PRESERVATION METHODS ON THE NUTRITIONAL QUALITIES OF MILK AND SOME MILK PRODUCTS

Abstract

Proximate compostion, bacterial load and organoleptic testing of
milk products preserved through pasteurization, fermentation and chemical
treatment were determined. Unpasteurized fresh milk (UFM), Pasteurized
fresh milk (PFM), Yogurt (YGT) and chemically preserved milk (CPM)
contained 2.72, 2,74, 2.45, 2.75% crude protein, 3.51, 3.50, 3.51, 3.52%
Fat, 0.72, 0.72, 0.77, 0.68% as11 respectively, which were not significantly
differnt (P>0.05). Bacterial load recorded were 7.0 x lo7,7 . 0 ~ 1 0an~d 2.4~10
cell/ml for UFM, PFM and YGT respectively, while corresponding shelf-lives
were 2, 7, 14 days and pH were 6.5, 6.7 and 4.5. Various concentrations of
benzoic acid, sodium benzoate, sugar and comrnon salt used revealed that
0625% of sugar induced the longest shelf-life (20 days) for Yogurt stored at
4 C. Salt, benzoic acid and sodium benzoate at concentrations (0.25, 0.10,
and 0.10% induced shelf-lives of 16.14 and 16 days respectively. Significant
(P~0.05)d ifference was observed between the flavour and taste of UFM,
PFM and YGT. NQ significant (P>0.05) difference was observed betwe~n
the appearance. It can be concluded that milk can be pasteurized at 62.8 C
for 30 minutes, fermented and chemically treated at low concentrations
with no adverse effect on its chemical and nutritional qualities.