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:
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:
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:
Traditional methods of naturally black olive production employ a series of static washings prior to fermentation. This work investigates the static washings and the effects they have on the subsequent spontaneous fermentation of Kalamata olives. Significant quantities of organic carbonaceous material, including phenolic compounds, were removed during the static washings. The rate of removal peaked after four static washings, and then declined. Bacteria (including lactic acid bacteria) and yeast were found to be present in high numbers throughout the static washings. An increase in the number of static washings resulted in the removal of inhibitory phenolic compounds. This led to a reduction in the lag phase and an increase in the specific growth rate for both the yeast and lactic acid bacteria during the subsequent spontaneous fermentations. However, an increased incidence of spoilage moulds was observed in the fermentations when the olives underwent thirteen static washings.
Description:
Traditional methods of naturally black olive production employ a series of static washings prior to fermentation. This work investigates the static washings and the effects they have on the subsequent spontaneous fermentation of Kalamata olives. Significant quantities of organic carbonaceous material, including phenolic compounds, were removed during the static washings. The rate of removal peaked after four static washings, and then declined. Bacteria (including lactic acid bacteria) and yeast were found to be present in high numbers throughout the static washings. An increase in the number of static washings resulted in the removal of inhibitory phenolic compounds. This led to a reduction in the lag phase and an increase in the specific growth rate for both the yeast and lactic acid bacteria during the subsequent spontaneous fermentations. However, an increased incidence of spoilage moulds was observed in the fermentations when the olives underwent thirteen static washings.
Description:
A total of 1280 banknotes were obtained from food outlets in 10 different countries (Australia, Burkina Faso, China, Ireland, the Netherlands, New Zealand, Nigeria, Mexico, the United Kingdom, and the United States), and their bacterial content was enumerated. The presence of bacteria on banknotes was found to be influenced by the material of the notes, and there was a strong correlation between the number of bacteria per square centimeter and a series of indicators of economic prosperity of the various countries. The strongest correlation was found with the "index of economic freedom," indicating that the lower the index value, the higher the typical bacterial content on the banknotes in circulation. Other factors that appear to influence the number of bacteria on banknotes were the age of the banknotes and the material used to produce the notes (polymer-based vs. cotton-based). The banknotes were also screened for the presence of a range of pathogens. It was found that pathogens could only be isolated after enrichment and their mere presence does not appear to be alarming. In light of our international findings, it is recommended that current guidelines as they apply in most countries with regard to the concurrent hygienic handling of foods and money should be universally adopted. This includes that, in some instances, the handling of food and money have to be physically separated by employing separate individuals to carry out one task each; whereas in other instances, it could be advantageous to handle food only with a gloved hand and money with the other hand. If neither of these precautions can be effectively implemented, it is highly recommended that food service personnel practice proper hand washing procedures after handling money and before handling food.
Description:
A simple and effective method for the analysis of thiamine (B1) and riboflavin (B2) vitamers, in unmalted and malted grains, by high performance liquid chromatography (HPLC) has been developed. This method makes use of trichloroacetic acid (TCA) as an extraction medium to effectively clean up the sample and analyze the vitamer content with high accuracy (R2 > 0.9992; %RSD < 5%). This method was employed in the routine analysis of a wide range of malted and unmalted grains, and it was found that lighter colored malts contain higher concentrations (2–5 times higher) of thiamine and riboflavin vitamers compared to darker colored malts. The malting process has no effect on the overall riboflavin content; however, both steeping and kilning processes cause increases in thiamine vitamer content. Roasting profiles show that thiamine and riboflavin vitamer concentrations are significantly effected when the temperature reaches 120 °C, which explains why roasted products have lower vitamer content than paler malts.
Description:
A simple and effective method for the analysis of thiamine (B
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.