Development of yeast and lactic acid bacteria starter cultures for application in fermented foods and probiotic production

Abstract

In Ethiopia, a wide variety of traditionally fermented foods are produced and consumed. They are well known for their nutrition and health benefits, but their production process and quality are encountered with many problems, such as short shelf life, food-borne disease outbreaks, a lack of consistency, and poor microbial and sensory quality. Therefore, the present study was aimed at developing LAB and yeast starter cultures for fermented food and probiotic production in order to address these problems. A total of 55 ersho samples were collected. A laboratory-based experimental approach was used. Phenotype and genotype characterization were used for isolate identification. Microbial count, proximate analysis, and sensory evaluation tests were used to evaluate the effect of starter cultures on bread and ergo quality production. Isolates of three yeasts (4A, 14D, and 54A) and three LAB (1A, 13E, and 55A) were screened to develop bread starters, sourdough starters, and ergo starters. In this study, 4A, 14D, 54A, 14D54A (a combination of 14D and 54A), and bakery yeast as bread starters were used to produce BY1, BY2, BY3, BY4, and control breads, respectively. Ergo starters designated as 13E, 55A, 1A13E (a combinationof1A and 13E), 1A55A (a combination of 1A and 55A), and spontaneously fermented milk were used to make EL1, EL2, EL3, EL4, and control ergo, respectively. Moreover, sourdough starters (a combination of yeast and LAB) of 4A13E, 14D55A, 54A1A, 54A13E, and bakery yeast were used to make BS1, BS2, BS3, BS4, and control breads, respectively. In comparison to the other breads (BY1, BY2, BY3, and control breads), the characteristics of the BY4 bread were enhanced most significantly. The characteristics of the BS4 bread were also higher than those of other breads (BS1, BS2, BS3, and control breads). The total coliform count (TCC), viable count (TVC), fungal count (TFC), and shelf life of BY4 bread were 0 ± 0, 2.4 ± 0.2, 1.6 ± 0.15 log cfu/g, and 6 days, respectively. BS4 bread’s TCC, TVC, TFC, and shelf life were 0 ± 0.15, 2.0 ± 0.25, 1.4 ± 0.15 log cfu/g, and 7 days, respectively, while control bread was 0 ± 0, 3.1 ± 0.15, 2.1 ± 0.15 log cfu/g, and 4 days. Hence, the shelf life of BY4 bread was increased by more than 2 days compared to control one while BS4 bread's shelf life was extended by more than 3 days compared to control. The colour, texture, taste, odour, and overall sensory mean scores of BY4 bread were 6.8± 0.89, 7.2± 0.77, 7.2± 0.77, 7.3± 0.92, and 7.3± 92, respectively. The BS4 bread’s colour, texture, taste, odour, and overall sensory mean scores were 8.6, 8.6, 6.4, 8.1, and 7.7, respectively, while control bread was 6.6± 0.68, 6.7± 0.92, 6.9± 0.85, 7.1± 0.85, and 6.9± 0.85. Therefore, the overall sensory mean scores of BY4 and BS4 breads were significantly better than control bread. The characteristics of the EL4 ergo have improved more compared with others (EL1, EL2, EL3, and control ergo). The TCC, TVC, TFC, and shelf life of the EL4 ergo were 0± 0, 4.0 ± 0.15, 2.8± 0.15 log cfu/ml, and 5 days, respectively, while the control ergo was 2.9 ± 0.10, 5.7± 0.21, 4.6 ± 0.10 log cfu/ml, and 1 day. As a result, the shelf life of the EL4 ergo was five times higher than that of the control ergo. The EL4 ergo mean scores of colour, taste, odour, and overall sensory scores were 6.8 ± 0.8, 6.7 ± 0.92, 6.4 ± 0.82, and 6.6 ± 0.94, respectively, while the control ergo was 5.7 ± 2.58, 4.2 ± 3.54, 4.5 ± 3.47, and 4.5 ± 3.12. Thus, the sensory scores of EL4 ergo were significantly higher than control ergo. The protein content of both BY4 bread (14.84%) and BS4 bread (15.52%) was higher than control bread (13.56%). Similarly, the protein content of EL4 ergo (5.1%) was higher than that of control ergo (3.9%). All the produced starters (4A, 14D, 54A, 1A, 13E, and 55A) showed high probiotic properties, such as acid resistance (> 80%) and bile salt resistance (>140%) and high cell surface hydrophobicity (> 40%). Moreover, starters have been shown to have high levels of auto-aggregation (> 40%), variable co-aggregation with pathogens (range from 42 to 72%), variable antimicrobial activity (clear halo zone range from 3 to 31 mm), and variable antibiotic resistance responses. The results indicate that ersho samples have been proven to be a reliable source of yeast isolates, such as bakery yeast and sourdough starter culture development. Ersho samples can also be used as a source of LAB for ergo starter and sourdough starter development. Furthermore, the present findings have shown that yeast and LAB starters have probiotic properties. Therefore, yeast and LAB starters are good candidates for commercial application with several desirable health benefits due to their high probiotic scores. In general, ersho can be used as a source of yeast and LAB to develop bread, ergo, and probiotic starter cultures