Effect of Oat Flour Addition on the Physico-chemical and Microbiological Quality of Probiotic Bio-yoghurt
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Date
2013-07
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Addis Ababa University
Abstract
This research was conducted with the aim of studying the effect of oat flour addition on the
physico-chemical and microbiological quality of probiotic low fat bio-yoghurts. The low fat bioyoghurts
were prepared through mixing of liquid skimmed milk with oat flour, starter culture,
corn starch stabilizer, skimmed milk powder and sugar according to the basic formulation for
bio-yoghurt production. The effect of mixing of oat flour (8%, 12 % and 16%) and storage days
(7days, 14 days and 21days) on physico-chemical properties, microbiological qualities,
proximate composition, and sensory qualities of the low fat bio-yoghurt has been studied. The
oat flour (Avena sativa) variety had a nutritional composition of 5.62% moisture, 16.94%
protein, 6.12% fat, 1.82% ash, 4.94% crude fiber and 64.65% carbohydrate, and the skimmed
milk contained 0.31% fat, 3.51% protein and 0.86% ash. After fermentation, the proximate
composition of the control bio-yoghurt, and the 8% Oat flour,12% and 16% Oat flour added bioyoghurts
was; moisture (86.66%, 76.01%, 72.82% and 66.09%), crude protein (3.05%, 6.30%,
10.29% and 7.30%), crude fat (0.30%, 1.21%, 3.72% and 4.77%), crude fiber (0%, 4.03%,
4.80% and 4.97%) and ash (0.61%, 0.99%, 1.31% and 1.30%); respectively. The physicochemical
results of the control bio-yoghurt and 16% oat flour added bio-yoghurts was; pH (4.49
and 4.55), syneresis (8.31% and 3.2%), TA (0.87% and 0.62%), App. Viscosity (0.66 pa.s and
0.83 pa.s) and proteolysis (0.34 and 0.48); respectively.
Addition of corn starch stabilizer had reduced the effect of spontaneous whey separation which,
was more significant (p<0.05) during higher amounts but because of other quality factors 2%
was selected for processing of low fat bio-yoghurts. Aerobic plate count was found to be the
predominant micro flora count of the final products and reached more than 8.3 log cfu/g. The
sensory assessment result of the low fat bio-yoghurt was relatively acceptable by panelists in
decreasing order of oat flour composition percentage comparing to that of the control. However,
the most acceptable color, mouth feel, appearance, flavor and the highly preferred was the
control low fat bio-yoghurt followed by samples blended with 8% and 12 % oat flour. In general,
the low fat bio-yoghurt processed by mixing of partially skimmed milk with 8%, 12% and 16%
oat flour and stored for 21 days gave promising results. Thus, it is possible to produce low fat
bio- yogurts by incorporating oat flour to skimmed milk with additional ingredients and at a 42oc
for 4-6 hr., fermentation temperature and time.
Key words: Bio-yoghurt, Law fat, Oat flour, Probiotic
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Keywords
Bio-Yoghurt, Law Fat, Oat Flour, Probiotic