Microbiological and physiochemical Study on Bifidobacterium infantis 20088 Fermented Peanut Milk and Rice Milk and their Blends

Abstract

This study was carried out to develop probiotic fermented beverages. The commercial strain Bifidobacterium infantis 20088 was used. The growth of the strain and its related physiochemical changes during fermentation was evaluated. The strain survival during refrigeration storage was also examined. In addition the chemical composition of different fermented beverages at initial and maximum growth of the strain were also determined. Growth media were formulated from reconstituted skim milk, pure peanut milk, rice milk in addition to three different blends based on peanut milk prepared by partial substitution of 15% (A), 30% (B), 45% (C) with rice milk .peanut contains high levels of fat, fiber and protein. Moreover levels of carbohydrates were high in rice. Roasting of peanut also increased fat, proteins, fiber and ash in ratio of 0.71, 1.41, 0.32, 0.2 and 0.62% respectively. While decrease carbohydrate (1.73%) as compared to raw peanut (4.65%). The results obtained on B. infantis 20088 viable count revealed significant (P < 0.05) increases by extended fermentation period in all type of formulated beverages, as compared to strain level at beginning of fermentation. The rate of B. infantis 20088 increases in different fermented beverages were 3.71, 3.01,2.95, 2.16,2.00, and 1.93 in fermented peanut milk, blend ( B),blend( A), skim milk ,blend(C) and rice milk respectively. In spite of declining in viable count of B. infantis 20088 in all types of fermented beverages at 48h fermentation , the count still above the number required to presence in probiotic food which is at least 6 log CFU/ml fermented products. Except fermented beverage blend C (5.89) and rice milk (5.78 CFU/ml) strain viable count dose not fulfill propiotic requirement in food. During fermentation process with strain B. infantis 20088 there were significant (P<0.05) decrease in pH levels in all type of beverages by extended fermentation period to 36h .The decreases in pH were due to increased acids production during fermentation process as a result of fermenting sugar by B. infantis 20088 .TSS levels decrease in all types of fermented beverages. The rates of TSS decreases at maximum growth were 0.8, 1.1, 0.5, 1.05 and 1.25 in fermented peanut milk, rice milk, followed by the blend (A),blend (B) and blend (C) respectively . Sugar also decrease in all fermented beverages with extended fermentation period to 48 h. The rates of sugar reduction at maximum growth of strain B. infantis 20088 were 0.4, 0.31, 0.28, 0.29 ,and 0.31 in fermented peanut milk, rice milk, blend (A),blend(B) and blend (C) respectively. During the fermentation of the fermented beverages there were no significant (p>0.05) changes in compound of beverages. Fermentation of peanut milk increase in moisture, portion, ash and fiber while decrease in fat, carbohydrate and total solid in peanut milk .On the other hand during refrigeration storage of different formulated beverages. There were significant (p<0.05) reduction in B. infantis 20088 viable count in all fermented beverages .The rate of reduction in the first week of the refrigeration storage were 1.05, 1.1, 1.28 , 1.17, 0.97 and 0.27 CFU /ml in the fermented peanut milk , rice milk , blend(A) ,blend(B), blend(C) and skim milk respectively. Hopefully, the final viable count of B. infantis 20088 in fermented, peanut milk, skim milk , blend (A) and blend(B) was above the minimum number required to presence in probiotic to exert health benefits upon consumption. During two weeks refrigeration there were significant reductions in B. infantis 20088 in all types of fermented beverages , except fermented peanut milk, skim milk and blend(A) . Therefore they are suitable carrier to deliver B. infantis 20088 to consumer at the same time the fermented beverages provide other essential nutrients such as protein, fat, minerals and fiber.