Browsing by Person "Alemneh, Sendeku Takele"

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    Application of two-dimensional fluorescence spectroscopy for the on-line monitoring of teff-based substrate fermentation inoculated with certain probiotic bacteria
    (2022) Alemneh, Sendeku Takele; Emire, Shimelis Admassu; Jekle, Mario; Paquet-Durand, Olivier; von Wrochem, Almut; Hitzmann, Bernd
    There is increasing demand for cereal-based probiotic fermented beverages as an alternative to dairy-based products due to their limitations. However, analyzing and monitoring the fermentation process is usually time consuming, costly, and labor intensive. This research therefore aims to apply two-dimensional (2D)-fluorescence spectroscopy coupled with partial least-squares regression (PLSR) and artificial neural networks (ANN) for the on-line quantitative analysis of cell growth and concentrations of lactic acid and glucose during the fermentation of a teff-based substrate. This substrate was inoculated with mixed strains of Lactiplantibacillus plantarum A6 (LPA6) and Lacticaseibacillus rhamnosus GG (LCGG). The fermentation was performed under two different conditions: condition 1 (7 g/100 mL substrate inoculated with 6 log cfu/mL) and condition 2 (4 g/100 mL substrate inoculated with 6 log cfu/mL). For the prediction of LPA6 and LCGG cell growth, the relative root mean square error of prediction (pRMSEP) was measured between 2.5 and 4.5%. The highest pRMSEP (4.5%) was observed for the prediction of LPA6 cell growth under condition 2 using ANN, but the lowest pRMSEP (2.5%) was observed for the prediction of LCGG cell growth under condition 1 with ANN. A slightly more accurate prediction was found with ANN under condition 1. However, under condition 2, a superior prediction was observed with PLSR as compared to ANN. Moreover, for the prediction of lactic acid concentration, the observed values of pRMSEP were 7.6 and 7.7% using PLSR and ANN, respectively. The highest error rates of 13 and 14% were observed for the prediction of glucose concentration using PLSR and ANN, respectively. Most of the predicted values had a coefficient of determination (R2) of more than 0.85. In conclusion, a 2D-fluorescence spectroscopy combined with PLSR and ANN can be used to accurately monitor LPA6 and LCGG cell counts and lactic acid concentration in the fermentation process of a teff-based substrate. The prediction of glucose concentration, however, showed a rather high error rate.
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    Effect of refrigerated storage on some physicochemical characteristics of a teff‐based fermented beverage and the viability of the fermenting Lactiplantibacillus plantarum and Lacticaseibacillus rhamnosus used
    (2022) Alemneh, Sendeku Takele; Emire, Shimelis Admassu; Jekle, Mario; Hitzmann, Bernd
    Probiotic beverages made from cereals become interesting in the recent food industries. In this contribution, a fermented teff-based probiotic beverage was produced using the whole grain teff flour and co-culture strains of Lactiplantibacillus plantarum (LPA6) and Lacticaseibacillus rhamnosus GG (LCGG). Then, the effect of 25 days of refrigerated storage on cell viability (LPA6 and LCGG), and contents of sugars, organic acids, and titratable acidity (TA), as well as pH values were examined. Furthermore, pathogenic microorganisms, hygiene indicators, and sensory tests of the beverage were analyzed. Presumptive cell counts of LPA6 and LCGG were observed to decrease throughout refrigerated storage. Glucose, lactic acid, maltose, and acetic acid contents were significantly (p < 0.05) increased over storage time. Also, pH reduction and TA increment were observed in storage time. Examined pathogenic microorganisms and hygiene indicators were not detected in the beverage. Sensory analysis of the beverage after 10 days of refrigerated storage was accepted by the panelists. Novelty Impact Statement Throughout refrigerated storage of teff-based probiotic beverage sugars and organic acids were produced. Sensory attributes of the newly produced teff-based probiotic beverage were accepted by the panelist after 10 days of refrigerated storage. The pH of the teff-based probiotic beverage became more acidic throughout 25 days of refrigerated storage.
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    Teff-based functional probiotic beverage processed with selected probiotic bacteria
    (2022) Alemneh, Sendeku Takele; Hitzmann, Bernd
    The recent consumers’ demand have moved from the primary role of food to the healthier action of biologically active food components. For this purpose, production of probiotic functional foods through a fermentation process is the current particular interest. Dairy-based products have been used for probiotics delivery since a very long time; however, due to the drawbacks associated with them such as milk lactose indigestibility, the prevalence of cholesterol related to dairy products, and allergy to milk protein are limited their further utilization for probiotics delivery. Alternatively, cereals are becoming the favorite choices to using as fermentable substrates for the growth and delivery of probiotics. Also, vegetarianisms are increasing through time because of medical reasons. Whole grain cereals are readily available with important nutrient sources of phytochemicals, and other bioactive compounds. Cereals have functioned as an encapsulation materials to improve probiotic stability and their bioactive prebiotics selectively stimulate the growth of probiotics present in the gastrointestinal tract. Particularly, teff is a gluten free and its nutritional value is attractive with high dietary fiber. Amino acids find in teff are well balanced and contains high lysine content. Teff is a good source of essential fatty acids, fiber, minerals, and phytochemicals such as polyphenols and phytates. Consequently, the first primary objective of this research was to compare the quality attributes of whole grain teff flours grown in Ethiopia and South Africa for their proximate composition (moisture, protein, ash, fat, fiber, and carbohydrate), mineral contents (calcium, zinc, and iron), profiles of eighteen amino acids, pasting and thermal properties, and functional properties (water absorption capacity, oil absorption capacity, and swelling power), falling number and color. The proximate composition was examined using the methods of the European Commission Regulation (152/2009). Atomic spectrometer, ion-exchange chromatography, Rapid Visco-Analyzer, and Differential Scanning Calorimetry were used respectively to measure minerals, amino acids, pasting, and thermal properties. Correlation of the measured attributes were analyzed by Pearson correlation and principal component analysis. Significant (p < 0.05) differences were observed in most of the measured attributes between the two teff varieties; however, several significant (p < 0.01) correlations were obtained among the measured attributes by Pearson correlation and principal component analysis. The measured contents of moisture, protein, and zinc in South African teff variety were observed higher than the one grown in Ethiopia. However, much higher calcium and iron contents were found in Ethiopian teff variety. Ethiopian teff variety had showed higher values of foam stability, water absorption capacity, oil absorption capacity, and swelling power as compared to South African teff variety. Results from thermal and pasting properties showed that onset, peak and end temperatures, trough, final, and setback viscosities, as well as peak time, pasting temperature were observed higher in case of South African teff variety. The second primary objective was to examine the suitability of teff made substrates for their potential for the growing and delivering of selected probiotic strains of Lactiplantibacillus plantarum A6 (LPA6) and Lacticaseibacillus rhamnosus GG (LCGG). Single and co-culture fermentations were performed without pH adjustment. In 24 h fermentation with single strain of LPA6, cell count was increased to 8.35 log cfu/mL. Titratable acidity (TA) and pH were measured between 0.33 and 1.4 g/L, and 6.3 and 3.9, respectively. For the investigation of optimum fermentation process variables, Nelder-Mead simplex method was applied and found the optimum values for time and inoculum respectively as 15 h and 6 log cfu/mL. Afterwards, co-culture fermentation was performed by using the optimized process variables. As a result of co-culture fermentation, glucose was progressively consumed while lactic acid and acetic acid were produced. Cell counts of LPA6 and LCGG were able to grow to 8.42 and 8.25 log cfu/mL, respectively, which are a good counts as compared to the minimum required probiotics level of 6 log cfu/mL at consumption time. Findings showed that similar pH and TA values were attained in short time during co-culture fermentation compared to single culture fermentation. Also, without any addition teff substrate was found to be suitable for the growing and delivering of the tested probiotic strains of LPA6 and LCGG. Another focus of this research was to apply two-dimensional fluorescence spectroscopy for the on-line supervision of the fermentation process of teff-based substrate inoculated with LPA6 and LCGG. The fluorescence spectra were measured by using BioView sensor. Analysis of the fermentation process by using the conventional methods such as high performance liquid chromatography for determination of glucose and lactic acid, and using agar plate count for determination of cell counts are time consuming, labor intensive and costly methods. As an alternative the application of fluorescence spectroscopy coupled with partial least square regression and artificial neural network was applied for the on-line quantitative analysis of cell counts of LPA6 and LCGG, glucose, and lactic acid. For the prediction of cell counts of LPA6 and LCGG, the percentage errors of prediction were determined in the range of 2.5-4.5 %. Also, for lactic acid prediction, the percentage error was 7.7 %; however, percentage error for glucose prediction showed a rather high error value. This part of study verified that a two-dimensional fluorescence spectroscopy combined with partial least square regression and artificial neural network can be applied during fermentation process to predict cell counts of LPA6 and LCGG, and content of lactic acid with low uncertainty. Finally, this study was focused on the effect of refrigerator storage on the physicochemical characteristics and viability of LPA6 and LCGG in a teff-based probiotic beverage. As well as a 9-point hedonic scale was applied for sensory test of the beverage. For these determinations, a teff-based probiotic beverage was produced through the fermentation of whole grain teff flour inoculated with co-culture strains of LPA6 and LCGG. Then, the beverage was stored in refrigerator (4-6 ℃) for 25 days. Samples were taking every five days including the first day of storage to quantify cell counts of LPA6 and LCGG, pH, TA, glucose, acetic acid, lactic acid, and maltose. Over the storage time, cell counts of LPA6 and LCGG were decreased from 8.45 and 8.15 log cfu/mL to 8.28 and 7.86 log cfu/mL, respectively. While cell counts were decreased during storage, their cell counts are still observed above the minimum suggested level of 6-7 log cfu/mL at the time of consumption. Lactic acid, acetic acid, glucose, and maltose as well as TA were increased with reduction of pH over the storage time. Metabolic activities observed over the storage time indicated presence of active enzymes that were produced during fermentation process. As examined the beverage, E. coli, Pseudomonas aeruginosa, coagulase-positive Staphylococci, presumptive Bacillus cereus, Salmonella spp., and Listeria monocytogenes weren’t detected. Sensory test attributes of color, appearance, aroma, and taste of the beverage were observed between 6.2 and 6.9, which are in the accepted range. Six and above average score values of the sensory test attributes are considered to be accepted by the panelists. Overall, it could be possible to say the proposed aim for the production of a teff-based probiotic functional beverage was accomplished successfully.