Freeze‐dried immobilized kefir culture in cider‐making

Abstract

BACKGROUNDThe aim of the present study was to evaluate the fermentation efficiency of freeze‐dried immobilized kefir culture on natural supports (apple pieces, delignified cellulosic material) in cider making at various temperatures (5–45 °C) in comparison with freeze‐dried free cells. Freeze‐dried cells were initially tested in apple juice fermentations at 30 °C, and then the freeze‐dried cultures produced with no cryoprotectants were assessed in repeated batch fermentations.RESULTSRepeated batch fermentations lasted for longer than 5 months. High malic acid conversion rates (up to 78.5%) and ethanol productivity values (up to 37.9 g L−1 day−1) were recorded for freeze‐dried immobilized cells. Polymerase chain reaction – denaturing gradient gel electrophoresis (PCR‐DGGE) analysis showed that freeze‐drying had no effect on the microbial diversity of kefir culture. Higher alcohols were significantly reduced at low fermentation temperatures. Application of principal component analysis (PCA) revealed that both the fermentation temperature and the nature of the freeze‐dried kefir culture affected significantly the minor volatiles determined by gas chromatography/mass spectrometry (GC/MS). Notably, all ciders produced were of high quality and were accepted by the tasting panel.CONCLUSIONSFreeze‐dried immobilized kefir culture on natural supports with no cryoprotectants was found to be suitable for simultaneous alcoholic and malolactic cider fermentation at various temperatures (5–45 °C). The high operational stability of the systems was confirmed and the results obtained are of great interest for the industrial sector as they could be exploited for cider, low‐alcohol cider, or ‘soft’ cider production. © 2020 Society of Chemical Industry

High-Temperature Semi-Dry and Sweet Low Alcohol Wine-Making Using Immobilized Kefir Culture

“…Free or immobilized kefir cells were evaluated regarding their fermentation efficiency in repeated batch fermentations for a period of 3 months. Wine-making at 37 • C using wet or freeze-dried immobilized kefir culture on DCM resulted in significantly (p < 0.05) lower fermentation times compared to fermentations with free cells, in accordance to our previous studies [15,16]. Ethanol concentration ranged 6.7-10.5% (v/v) and higher mean values were noted in fermentations with wet and freeze-dried cells when immobilized kefir culture on DCM was used, although not significantly.…”

“…Higher ethanol productivities [up to 55.3 g/(Ld)] were noted in fermentations with immobilized cells (both wet and freezedried) at 37 • C in comparison to free cells [19], although not significantly in all cases, but in levels similar or greater than usually noticed in industrial fermentations [19,22]. Importantly, as repeated batch fermentations proceeded, fermentation times, ethanol production and fermentation kinetic data were improved for all freeze-dried kefir cells, indicating cell adaptation [19,23,24], despite the high fermentation temperature (37 • C) [16], and a high operational stability that could be adopted by the wine sector for low alcohol wine production [2]. On the contrary, at 45 • C, significantly (p < 0.05) higher residual sugars and significantly (p < 0.05) lower conversion values were documented compared to fermentations carried out at 37 • C (especially after the first batch fermentation) [15], probably due to "yeast stress" induced by the high temperature [19,25].…”

“…Immobilized kefir cells on delignified cellulosic material (DCM), apple pieces, and grape skins have been previously successfully used in wine and cider fermentations at a wide temperature range [6,15]. Recently, freeze-dried immobilized kefir culture was assessed in low alcohol wine and cider production [8,16]. In industrial wine production, ambient temperature fermentations are very often used, but application of cooler temperatures may be advantageous to the product quality [17].…”

“…Red wines on the other hand, require higher temperature fermentation (up to 28 • C) to achieve the desirable color and tannin extraction from the grape skins [17,18]. High fermentation temperatures (>30 • C) may result in high fermentation rates, increased productivity, and reduction of production expenses [15,16,19,20], but inactivation of most industrial yeasts is, however, a major drawback [19]. Therefore, it would be of great economical and industrial interest to investigate wine-making at temperatures >30 • C in many regions worldwide, resulting in limitation of cooling systems requirement and drastic reduction of operational costs (mostly in regions with tropical climate or in many countries with hot summer periods) [6], whilst leading to novel wine products development.…”

Impact of Sugar Type Addition and Fermentation Temperature on Pomegranate Alcoholic Beverage Production and Characteristics

“…They are considered as having an impact on the complexity of aroma even at concentrations below their odor detection thresholds [51,52]. Octanoic and decanoic acids that have been identified in the PAB samples have been reported as the most abundant acids in wines and cider [17,[53][54][55]; decanoic acid was identified in lower concentrations and only in certain samples. In all cases, no significant differences were observed (p > 0.05).…”