Amino Acids, Solubility, Bulk Density and Water Holding Capacity of Novel Freeze-Dried Cow’s Skimmed Milk Fermented with Potential Probiotic Lactobacillus plantarum Bu-Eg5 and Lactobacillus rhamnosus Bu-Eg6

Abstract

Lactobacillus plantarum Bu-Eg5 and Lactobacillus rhamnosus Bu-Eg6 showed a potential probiotic role in vivo and in vitro in a preliminary unpublished work. This study demonstrated that Lactobacillus plantarum Bu-Eg5 and Lactobacillus rhamnosus Bu-Eg6 mediated modifications of the physicochemical properties of fermented skimmed cow’s milk. Skim milk was inoculated with 1% (w/v) of Lactobacillus plantarum Bu-Eg5 (T1), 1% (w/v) of Lactobacillus rhamnosus Bu-Eg6 (T2) and 1% (w/v) of 1:1 Lactobacillus plantarum Bu-Eg5 and Lactobacillus rhamnosus Bu-Eg6 (T3). After that, fresh skimmed milk control (C), T1, T2, and T3 were freeze-dried (Zirbus Technology model: VaCo 5-D, S/N: COM98754, Germany). The resulting freeze-dried fresh and fermented milks powders were evaluated for their solubility index, bulk density and water holding capacity (WHC). The amino acids compositions of the freeze-dried treatments were analyzed using High Performance Amino Acid Analyzer (Biochrom 30). The microbiological quality of freeze-dried fresh and fermented milks powders was measured by enumerating lactic acid bacteria, yeast & mould and coliform bacteria. The total protein content of fresh freeze-dried skimmed milk (38.69%) was higher than that of fermented freeze-dried skimmed milk powders. The bulk density was 16.67 g/mL for all treatments. The solubility of fresh freeze-dried skimmed milk was the highest (100%), followed by the other treatments (78.95%). The WHC of fresh freeze-dried skimmed milks (11.16%) was lower than the other samples. The highest total essential amino acids were observed in fresh freeze-dried skimmed milk sample (17.26%) followed by the freeze-dried skimmed milk fermented with Lactobacillus plantarum Bu-Eg5 (16.22%) while the lowest recorded in the freeze-dried skimmed milk sample fermented with 1:1 Lactobacillus plantarum Bu-Eg5 and Lactobacillus rhamnosus Bu-Eg6 (12.87%), there was a very low bacterial count in the control treatment (1.09 log CFU/ml). Yeast & mould and coliforms were not detected in all samples.

Keywords

• Lactobacillus
• Freeze-drying
• Skim milk
• Amino acids
• Solubility index
• Bulk density