BIOLOGICAL ATTRIBUTES OF BIO-YOGHURT VERSUS THE CONVENTIONAL ONE FED IN SPRAY DRIED FORM

The aim of this study was to evaluate the biological attributes of yoghurt cultured via different bacterial starters and fed in the spray dried form. Cow s milk was converted whether into conventional yoghurt using yoghurt starter culture (YSC) containing of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus or into bio-yoghurt using ABT-2 culture containing of Lb. acidophilus, Bifidobacterium sp. and Str. thermophilus. At the end of incubation period, yoghurts were spray dried at 160 °C. Milk powder sample was corresponding to the control. The obtained results revealed that, conventional yoghurt possessed lower lactose content, on dry basis, and higher consistency coefficient as well as yield stress than those of bio-yoghurt, which suffered also from a late development of acidity as well as acetaldehyde content, and consequently relative delayed drop of pH value versus the conventional one. Moreover, Str. thermophilus count was higher than that of Lb. delbrueckii subsp. bulgaricus, in the conventional yoghurt. ABT-2 counts seemed trends similar to those of YSC strains, where the count either of Str. thermophilus or Bifidobacterium sp. was greater than that of Lb. acidophilus. After spray drying, considerable reductions, with about a logarithmic round were occurred in all strains, but stilled conforming the figures established a minimum of 10^7/g for the starter cultures of fermented milks and a minimum of 10^6/g for specific starter bacteria for which a claim is made for a specific microorganism that has been added as a supplement. Biologically, a significant improvement in the true digestibility of milk protein was occurred by fermentation especially via ABT -2. Conversely, the biological value of protein was higher when rats fed the unfermented products (milk powder) followed by bio-yoghurt and the conventional yoghurt came in the last order. The net protein utilization figures explained that, although the fermentation lowered this criterion, the performance of ABT-2 caused significant amelioration versus that done when YSC was used. However, the growth rate of rats was enhanced and the counts of white as well as red blood cells increased by milk fermentation especifllly with ABT-2 versus YSC, although both of hemoglobin and hematocrit % were not influenced. Rats feeding on fermented milk, regardless the kind of bacterial culture were associated with significant increment in the total as well as albumin protein of blood plasma. However, the globulin level was not influenced. The ratio between them was higher in the blood plasma of rats fed on fermented milk. Rats feeding on unfermented milk led significantly to absorb mineral of Ca, P, K, Mg, Zn, Fe and Cu with levels higher than occurred in rats fed on yoghurt, especially the conventional one. Feeding rats on milk and rather fermented milk products resulted in a considerable increment in lactic acid bacteria and bifidobacterial counts in the feces. Conversely, the coliform bacterial counts were reduced in the feces of these groups. As conclusions, the ingestion of fermented milk such as yoghurt imparts some biological benefits, especially the protein digestibility and modification of the intestinal flora in order to increase the predominance of specific nonpathogenic bacteria. While, bio-yoghurt was further distinguished with better mineral bioavailability, growth rate and blood picture.