Effect Of Thermization And Storage On The Nutritionalproperties And Shelf-Stability Of Yoghurt From Blends Of Cow Milk And Coconut Milk

ABSTRACT

Yoghurts were produced by blending reconstituted powdered cow milk (100 g of powdered

cow milk (CM) : 0.5 litres of water) with 25 % and 50 % coconut milk (CCM) and a control

(100 % cow milk) before fermentation. After fermentation for 16 h at room temperature, the

yoghurts were subjected to two heat treatments (thermization) namely, 75 0C thermization

and 80 0C thermization and a control (unthermized). The proximate, physicochemical,

vitamin and microbiological quality of yoghurt samples were investigated during storage at

room temperature for 5 weeks. The results obtained, revealed that in each of the three

formulations of yoghurt, proximate composition, titratable acidity (TTA), total solids, free

fatty acids (FFA), viscosity, microbial load and vitamins decreased as the temperature of

thermization increased. The pH and moisture increased from 4.30 and 82.36 %, respectively

with increase in thermization temperature to 4.59 and 83.39 %, respectively. Yoghurts

samples from 50 % cow milk (CM) + 50 % coconut milk (CCM) had the highest moisture

content (83.39 %) and lowest total solid content (17.84 %) compared to 82.98 % and 18.16

%, respectively from 75 % cow milk (CM) + 25 % coconut milk (CCM) and 82.92 % and

18.28 %, respectively from 100 % cow milk (CM). Titratable acidity increased significantly

(p < 0.05) with increase in percentage coconut milk ( 0.77 for 100 % cow milk (CM), 0.82 for

75 % cow milk (CM) + 25 % coconut milk (CCM) and 0.87 for 50 % cow milk (CM) + 50 %

coconut milk (CCM)). There was significant (p < 0.05) decrease in pH as the percent coconut

milk increased (4.48 for 100 % cow milk (CM), 4.40 for 75 % cow milk (CM) + 25 %

coconut milk (CCM) and 4.30 for 50 % cow milk (CM) + 50 % coconut milk (CCM)). The

highest viscosity of 282.59 ± 2.46 cPs was obtained for unthermized 100 % cow milk which

also had the highest protein content of 3.84 ± 0.11 %. Free fatty acid increased significantly

(p < 0.05) with increase in percent coconut milk and during storage. B-complex vitamins (B1,

B2 and B3) increased significantly (p