Rare fruits as a source of nutrient rich fermented products (original) (raw)
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EFFECT of DRYING TYPE and DRYING CONDITIONS OVER FERMENTATIVE ABILITY of BREWER'S YEAST
Journal of Food Process Engineering, 2003
In this work the growth and glucose consumption as well as alcohol production kinetics offresh and rehydrated brewer's yeast were evaluated. Dried yeast was obtained by fluidized bed and spray drying. Based on fermentation trials, there was no difference between the number of viable cells determined at the end of the stationary phase, however diflerences in growth velocity between the dehydrated yeast and the fresh yeast cream were found. Regarding alcohol production, no differences were found in most of the treatments (F2. F3, F4*, A I , A2, A3 and A4) with respect to the fresh yeast. The brewery dried yeast with an efticient viability and fennentative ability can be stored at least 4 months and used when required. Therefore the need of conventional propagation and fresh yeast transport may be eliminated. ' Author to whom all correspondence shall be addressed. Dra. Guadalupe Rodriguez Jimenes. M.A. de Quevedo 2779, Col. Formando Hogar. Veracruz. Ver., C.P. 91850. Mexico. TEL: (52) 29 34 14 69; FAX: (52) 29 34 57 01; EMAIL lupitaj@itver.edu.mx Journal of Food Process Engineering 26 (2003) 135-147. All Righrs Reserved. '
Effect of Rehydration on Dry Wine Yeast Activity
American Journal of Enology and Viticulture
The effects of rehydration media and temperature on resulting fermentation activity were studied for nine commercial and experimental active dry wine yeasts. Water and grape juice were used as rehydration media at temperatures from 20 to 45°C. Fermentation activity was measured by gas production from grape juice according to a previously published method. The loss of cell constituents on rehydration was also measured and related to the physical form of the samples. The optimal rehydration temperature was found to be about 38 to 40°C for all samples in either grape juice or water. The results indicate that although all the active dry wine yeasts may be added directly to must at cellar temperatures, fermentation activity is improved by the specified prior rehydration. The greater loss of cell constituents on low temperature rehydration was suggested as an explanation of the observed activity effects.
Journal of the Institute of Brewing, 2014
The effect of five additives on the rehydration process of three commercial Saccharomyces cerevisiae wine strains, in the form of active dry yeast, was tested using the approach of design of experiments. The response to additives was monitored by observing the viability, measured using fluorescence methodology at the end of the rehydration experiments, and fermentative performance, focusing attention on the first phase of fermentation, assessed based on ethanol production and the total number of cells after 48 h from the time of inoculation in synthetic must. The results showed a correlation between viability and the presence of magnesium in the rehydration medium. However, improvement in viability was not associated with better fermentation performance, which was not affected or in some cases significantly reduced. Among the additives examined, only rehydration with inactive dry yeast and ammonium showed a positive effect on the subsequent fermentations, but not for all of the strains tested. In general, considering all of the additives tested, no relationship was found between viability at the end of rehydration and fermentation performance. These findings suggest that the viability of the rehydrated yeast cells may not be a good index of fitness in the subsequent fermentation.
Vitality enhancement of the rehydrated active dry wine yeast
International Journal of Food Microbiology, 2008
In winemaking, spontaneous grape must fermentations have been replaced by inoculation of commercial active dry wine yeast (ADWY). Yeast rehydration is the key to avoiding stuck and sluggish fermentations. Despite the importance of this step, not enough is known about what this process implies for winemaking as a whole or about what kind of practices could help to improve it. The main aim of this study is to determine the best yeast rehydration conditions for ensuring good cell viability and vitality before inoculation into the must. The experimental rehydration media in this study can be divided into four groups: carbon and nitrogen compounds, metallic ions, oxidant and antioxidant agents, and membrane fluidity agents. We studied the biochemical and biophysical behaviour of ADWY after rehydration in the various media under oenological conditions, i.e. incubation at 37°C for 30 min. The viability of rehydrated yeast cells was evaluated by plating, and assessed by fluorescence microscopy and flow cytometry. The vitality of rehydrated cells was estimated by indirect impedance. The rehydrating solution complemented with magnesium provided the best vitality rate because the time taken to reach the activity threshold was cut by two thirds. This improvement was also illustrated by the less time needed to stop the leakage of intracellular compounds during the rehydration process.
Determination of fermentative properties of yeast strains isolated from spoilt fruits and beverages
Scientific Journal of Microbiology
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Efficient methods of post harvest handling, preservation and value addition are critical for minimizing high losses in the post harvest chain of fruits. The goal of this study was to address this problem by employing yeast fermentation technology to produce a more stable, value added product from mangoes. The design of the study involved determination of the fermentative capabilities of a selected yeast strain on the quality characteristics of mango wine obtained from two selected mango cultivars (improved and wild) with and without peels. The response variables monitored in the must and wine included total soluble solids (TSS), pH and total acidity (TA), microbial populations (aerophilic mesophiles, yeasts and Acetic acid Bacteria), and alcohol content. Volatile compounds development was also monitored using GC-FID procedures. Descriptive and hedonic sensory evaluations were carried out on the mango wine obtained from all treatments. The effects of mango peels in must fermentation ...
Production of alcohol by yeast isolated from apple, orange and banana
The purpose of this study was to isolate wild yeast strains present in different fruits (apple, orange and banana) and to determine the yeast growth and the amount of alcohol production at various glucose concentrations. Three fruits namely apple, banana and orange were selected as natural sources for yeast isolation. Medium used for isolation of yeast from fruits was consisting of 50 glucose, 3 malt extract, 3 yeast extract, 5 peptone and 15g/L agar. For fermentation MGYP medium used with different glucose concentrations of 5, 10, 30, 50 and 70g/L. Inocula were prepared by loop transfers from stock slants to 50 mL of the 20 percent medium in 500-mL Erlenmeyer flasks. The results showed that with higher concentration of glucose (30g/L) higher amount of alcohol (0.22g/100mL) was produced. Similarly, the yeast isolated from apple showed maximum yeast biomass (0.38g/100mL) at 70g/L glucose concentration and minimum on 50g/L (0.03g/100mL) glucose concentration. In conclusion, the wild yeast produce higher ethanol amount in case of banana fruits.
We studied the effect of continuous fermentation of high-sugar fruit must (containing about 320 g/L of total sugars) on the viability and morphology of yeast cells. The process was carried out for 2.5 months in a 4-column bioreactor at 22 °C, using the Saccharomyces bayanus S.o./1AD wine yeast strain, which was immobilized on cubes of white foam glass. During the time of continuous fermentation, the apple wine contained 11.4–16.8 % (by vol-ume) of alcohol and a total sugar concentration of 49.2–115.4 g/L. Yeast cells isolated from the carrier at the end of continuous fermentation were bigger than the cells before immo-bilization and were characterized by various shapes, e.g. they were elongated, large and round or pear-shaped. Some cells were connected to other cells in the form of aggregates. Some yeast cells from the second, third and fourth columns showed a substantial number of wrinkles or folds. Moreover, it was observed that yeast from the carrier in the first co-lumn was char...
Fermentation Capacity of Yeasts Using Mango (Mangifera indica Linn.) as Substrate
The goal of this study was to address the problem of large post harvest losses of mangoes by employing yeast fermentation technology to produce a more stable, value-added product in this case fruit wine. The design of the study involved determination of the fermentative capabilities of four commercial yeast types on musts obtained from an improved (Keitt) mango cultivar that is popularly cultivated in some parts of Ghana for export. The characteristics of the mango musts that were monitored included total soluble solids (TSS), pH and total acidity (TA), microbial populations (aerophilic mesophiles, yeasts and Acetic acid Bacteria), alcohol content and colour over the course of the fermentations. Descriptive and hedonic sensory evaluation was carried out on the ferments obtained from all treatments. Results showed that two of the yeast types namely; Red Star Pasteur and Red Star Montrachet displayed superior fermentation characteristics and produced mango wines that were acceptable b...