Description:
The derivatization of thiamin vitamers to their respective thiochrome by ferricyanide to facilitate fluorescence detection following separation by HPLC provides a powerful analytical tool. However the polyphenolic compounds in red wine readily interact with ferricyanide, reducing the effectiveness of ferricyanide oxidation in the derivatization of thiamin. We describe a method to facilitate the removal of polyphenolic compounds that interfere with the ferricyanide derivatization of thiamin. Polyvinylpolypyrrolidone afforded the total removal of phenolic compounds from red wines and allowed a spike recovery of thiamin vitamers (101% for thiamin; 104% for TMP; and 100% for TDP) in a wide range of red wines. This research found that Merlot styles of red wine contained the highest concentration of total thiamin (29.01 ng/mL) while Pinot Noir wines contained the lowest total concentration (8.27 ng/mL).
Description:
The ability of small quantities of added acetaldehyde to stimulate growth in environmentally-stressed cultures of Saccharomyces cerevisiae was examined over a broad range of stress conditions. Acetaldehyde addition substantially reduced the lag phase of cultures suddenly inoculated into medium containing inhibitory quantities of low M.W. alcohols and higher fatty acids. For ethanol-stressed cultures, acetaldehyde was effective whether added initially or during fermentation. The effects of acetaldehyde were not universal, only minor stimulation being observed for cultures exposed to heat shock, or experiencing changes in cultivation temperature or pH, despite the occurrence of long lag phases under these conditions. Acetaldehyde strongly inhibited the growth of osmotically-shocked cultures, in contrast to the effects of small quantities of ethanol. The beneficial effects of acetaldehyde appear to be largely confined to cultures exposed to chemical stress especially by agents which disturb membrane structure or function. Acetaldehyde addition has potential practical application in overcoming inhibition in such fermentations. [Copyright 2002 Elsevier]
Description:
The ability of added acetaldehyde to stimulate growth in ethanol-stressed Saccharomyces cerevisiae while grown on non-fermentable substrates (ethanol, glycerol) is reported. The addition of acetaldehyde to ethanol-stressed yeast grown on either ethanol or glycerol led to a significant decrease in lag time of 67 and 45%, respectively (p = 0.000) and an increase in the specific growth rate (0.008-0.038/h and 0.060-0.074/h, respectively). The stimulatory effect of acetaldehyde could be mimicked by the addition of propionaldehyde. Results, following metabolic tracing of the added stimulants, question the previously held notion that the acetaldehyde effect in S. cerevisiae is fully redox related.
Description:
Beer is a beverage that is produced in a multistage process, where some stages of that process are intentionally influenced by microorganisms, while at other stages of the production process microorganisms are actively discouraged. Most of the intentional microbial activity is facilitated by yeast; however bacteria also play an influential role in beer production. This paper will describe the beneficial role of bacteria in the beer production process (the Good), but will also pay due attention to the negative influences bacteria might have on the quality of beer as a commodity (the Bad), and the properties of beer that have given it the status of an inherently safe food for human consumption with regards to disease-causing bacteria (the Ugly). Copyright (C) 2013 The Institute of Brewing & Distilling
Description:
A series of physical and chemical changes occur as olives mature on the tree, and these changes are important for the production of oil and table olives. The aim of this study was to increase the understanding of the maturation process of Gordal Sevillana olives, to optimize harvest timing, and to determine the most appropriate harvesting and post-harvesting processing methods. During maturation, the olive size, flesh/pit ratio, and oil content increased, with a maximum oil content of 72 g kg(-1) (wet weight). Changes in the fatty acid composition are reported. Levels of both total sugars and total phenolic compounds slightly decreased over the maturation period; however, we observed that these compounds were continually being synthesized until full black maturity. The optimal harvest time for the production of Gordal Sevillana as Spanish-style green olives occurred immediately prior to the color change from green to turning color, at which point the sugar levels and flesh/p! it ratio were at maximum levels.