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Pomelo fruit juice is concentrated using two different techniques, i.e. block freeze concentration (BFC) and thermal concentration (TC), and both concentrates were spray dried separately to observe the effects of two different concentration techniques on the physicochemical properties of the spray dried powder. BFC juice had comparatively better values of retention of acidity, colour, vitamin C, DPPH● scavenging activity, total phenolic content (TPC), and total sugar content than TC juice. The powder obtained from the combination of BFC and spray drying had better retention of vitamin C (121.17 mg/100 g), colour, and exhibited higher DPPH● scavenging activity than TC spray dried powder. The physical parameters including solubility index, bulk density, and hygroscopicity were significantly higher in BFC spray dried powder. BFC was observed as an efficient concentration technique in comparison to TC as a pretreatment to produce spray dried powder with a better retention of bioactive components and powder flow properties.
Abstract
In the study, four potent Lactobacillus cultures of L. rhamnosus K4E, L. plantarum RD7, L. fermentum K7, and L. fermentum K16 were considered for the production of B-vitamins, organic acids and biotransformation of soy isoflavones. L. plantarum RD7 showed the highest B2 production (0.84 μg mL−1) after 36 h, while L. fermentum K16 exhibited maximum B12 production (0.084 μg mL−1) after 12 h. L. rhamnosus K4E produced 0.24 μg mL−1 of folate after 12 h. Highest production of lactate (16.43 μg mL−1) and acetate (5.86 μg mL−1) was reported by L. rhamnosus K4E. L. plantarum RD7 showed maximum butyrate (0.253 μg mL−1) production compared to the other cultures. The highest bioconversion of soy aglycones was reported by L. rhamnosus K4E with 55.43% for daidzein and 72.30% for genistein, during soymilk fermentation. These potent cultures have a potential to be used as functional starter cultures for the production of functional fermented soy foods.
Present study demonstrated the isolation of most promising β-galactosidase producing bacterial strain SB from soil. Morphological, biochemical, and 16s rRNA sequence analysis identified the bacterial strain as Arthrobacter oxydans. Several chemicals, including SDS, Triton X-100, Tween 20, isoamyl alcohol, and toluene-acetone mixture, were applied for extraction of intracellular β-galactosidase from the bacterial strain Arthrobacter oxydans. Among these, Tween 20 was recorded to be most effective. Role of pH, temperature, and shaker speed on production of β-galactosidase was evaluated using Box-Behnken design of response surface methodology. According to Box-Behnken analysis, optimum production of β-galactosidase (21.38 U (mg–1 protein)) is predicted at pH 6.76, temperature 36.1 °C, and shaker speed 121.37 r.p.m. The parameters are validated with the nearest value.
