Abstract
This study aims to determine the yoghurt production potential of lactic acid bacteria isolated from legumes seeds (lentils, beans, cowpea, and broad beans) and examine the effects of alginate capsules of selected starter cultures with high yoghurt production potential on the physicochemical properties, sensory properties of yoghurt, and bacterial viability during storage time at 4°C. The exopolysaccharide (EPS), proteolytic activity, and acidification properties of eight different isolates were determined, and sixteen different yoghurt combinations prepared. The samples showed similar physicochemical (pH, titratable acidity, dry matter, and whey separation), bacterial count, and sensory results in comparison with the commercial yoghurt used as a control sample. The acidity and pH of the yoghurt samples were significantly affected by the storage time. Total solids of yoghurt samples generally tend to decrease and syneresis of yoghurt samples also differed for each starter culture combination during the storage time. The total count of lactic acid bacteria during the storage time was higher than 107 CFU/g. The sensory analysis results of bacterial combinations are significantly different ( p < 0.05 ). Results indicated that isolated starter cultures have potential as commercial starters to improve the quality of yoghurt. Selected starter cultures with yoghurt production potential were encapsulated. Lactic acid bacteria with encapsulation efficiency of 86,3 ± 0,2 and 82,26 ± 0,79 were selected for yoghurt production. The physicochemical properties of the yoghurt with free and encapsulated starter culture were significantly different during the storage time. The reduction (∼0,5 log cfu/g) in the numbers of free and encapsulated starter cultures is over during the storage time ( p < 0.05 ). The acceptability of yoghurt containing encapsulated bacteria was lower than the yoghurt containing free bacteria by the panelists. Consequently, it was determined that alginate capsules increased bacterial viability, but the sensory properties of yoghurt were affected adversely. The LAB isolated form legumes can be introduced to the national microbial collection.
Highlights
Lactic acid bacteria (LAB) are Gram-positive bacteria that is rod- or coccus-shaped that can produce lactic acid as the primary end product through heterofermentative or homofermentative metabolism
Hull [22] method was used to determine the proteolytic activities of the isolates. 1% from the activated cultures was inoculated into 10 mL skim milk, and samples were inoculated for 24 h at 28°C. 5 mL of active culture was mixed with 1 mL distilled water and 10 mL 0.72 N Trichloroacetic acid (TCA) for 10 minutes. 5 mL of filtrate was placed in a 50 mL flask, and 10 mL of Na2CO3Na4P2O7 solution was added and mixed. 3 mL of phenol reagent was added to the samples to obtain blue color. e samples were centrifuged at 5000 rpm for 15 minutes (Hettich Zentrifugen, Mikro 22R, Deutschland). e absorbance (OD) of the supernatants was measured at 650 nm in a spectrophotometer
EPS production for S. thermophilus and L. bulgaricus strains are 74–266 mg/L and 299–357 mg/L, respectively. e highest EPS production belongs to strain of S. thermophilus coded Cow Pea-coc (CPC) (266 mg/mL). e highest EPS production belongs to the strain of L.bulgaricus coded Broad bean-bac (BBB) (356 mg/mL) and BB (357 mg/mL). e range of S. thermophilus EPS is parallel to the study of Han et al [32]. e range of L. bulgaricus EPS value is higher than the values for the studies Kılınç and Gezginç [33]
Summary
Lactic acid bacteria (LAB) are Gram-positive bacteria that is rod- or coccus-shaped that can produce lactic acid as the primary end product through heterofermentative or homofermentative metabolism. Ese properties have recently been considered as an important factor for yoghurt starter selection [6, 7] Both species are Journal of Chemistry homofermentative, converting lactose into lactic acid [8] and producing volatile flavour compounds, such as diacetyl and acetaldehyde [9]. Starter culture production gains importance for the dairy industry to produce yoghurt with the desired quality and sensory properties. E aim of the present study is to investigate the yoghurt production potential of LAB isolated from leguminous seeds, which are natural products using EPS, proteolytic, and acidification activity, and determine the effects of microencapsulated starter cultures on the yoghurt properties regarding pH, titratable acidity, dry matter, syneresis, bacterial count, and sensory characteristics
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