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/pit ratio were at maximum levels.
This work aimed to assess the growth and survival of four foodborne pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, and Staphylococcus aureus) in beer. The ...effects of ethanol, pH, and storage temperature were investigated for the gram-negative pathogens (E. coli O157:H7 and Salmonella Typhimurium), whereas the presence of hops ensured that the gram-positive pathogens (L. monocytogenes and S. aureus) were rapidly inactivated in alcohol-free beer. The pathogens E. coli O157:H7 and Salmonella Typhimurium could not grow in the mid-strength or full-strength beers, although they could survive for more than 30 days in the mid-strength beer when held at 4°C. These pathogens grew rapidly in the alcohol-free beer; however, growth was prevented when the pH of the alcohol-free beer was lowered from the "as received" value of 4.3 to 4.0. Pathogen survival in all beers was prolonged at lowered storage temperatures.
The aim of this study was to investigate the factors affecting the survival and growth of four food-borne pathogens (
Escherichia coli O157:H7,
Salmonella Typhimurium,
Listeria monocytogenes, and
...Staphylococcus aureus) in sweet and fermenting brewery wort. The Gram-negative pathogens (
E. coli and
Salm. Typhimurium) were capable of growth during the initial stages of fermentation in hopped wort, although they were quickly inactivated when added during the later stages of fermentation. When the wort was left unpitched, the two Gram-negative pathogens grew unabated. Pathogen growth and survival was enhanced as the pH was increased, and as both the ethanol and original gravity were decreased. Although having no effect on the Gram-negative pathogens, low levels of hop iso-α-acids were sufficient to inhibit
L. monocytogenes, and a synergistic antimicrobial effect between iso-α-acids and pH was observed.
S. aureus failed to initiate growth in all of the test worts. There appears to be no reason for concern of the safety of a “typical” wort during fermentation, however due attention should be paid when wort is stored or antimicrobial hurdles are lowered, for example in the production of reduced and alcohol-free beer, and in unpasteurised products.
ABSTRACT
Lactic acid bacteria are the most frequently encountered beer‐spoilage bacteria, and they may render beer undrinkable due to the production of lactic acid, diacetyl, and turbidity. ...Microbrewed beer is typically sold unpasteurised, leaving it more susceptible to spoilage by lactic acid bacteria. In this study, the incidence of lactic acid bacteria in bottled microbrewed beer from Victoria, Australia was investigated. A total of 80 beers from 19 breweries were screened for lactic acid bacteria. Almost 30% contained culturable lactic acid bacteria, and many had lactic acid levels well above the flavour threshold. Ethanol, hops, and the pH levels of the beers were not predictors for spoilage in the beers examined, and contamination appeared to be more closely linked to the source brewery. The 45 lactic acid strains isolated from these beers were identified by RAPD‐PCR, with Lactobacillus brevis being the most frequently isolated species. All isolates were capable of spoiling beer and contained putative hop resistance genes. At typical beer levels, pH and ethanol had no effect on the growth of the particular spoilage bacteria isolated in this study.
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.
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).
Tradicionalne metode obrade crnih maslina obuhvaćaju niz postupaka namakanja prije fermentacije. U ovom je radu istražen utjecaj takve prethodne obrade na spontanu fermentaciju maslina Kalamata. ...Utvrđeno je da je njihovim namakanjem uklonjena značajna količina i organskih spojeva ugljika i fenolnih spojeva. Najviše ih je pronađeno u vodi nakon četiri namakanja, a daljnjim namakanjem nije se povećala količina ispranih tvari. Mikrobiološkom analizom vode nakon namakanja utvrđen je veliki broj bakterija (uključujući i mliječno-kisele bakterije) i kvasaca. Ponovljenim namakanjem uklonjeni su inhibitorni fenolni spojevi, što dovodi do smanjenja lag faze i porasta specifične brzine rasta kvasaca i
mliječno-kiselih bakterija tijekom naknadne spontane fermentacije maslina. Međutim, nakon 13 uzastopnih namakanja pojačao se rast plijesni što uzrokuju kvarenje tijekom fermentacije.
39 - Pathogens in Beer Menz, Garry; Aldred, Peter; Vriesekoop, Frank
Beer in Health and Disease Prevention,
2008
Book Chapter
Pathogenic (disease-causing) microorganisms cannot survive in beer due to the presence of various inhibitory factors/hurdles. The major intrinsic hurdles that a pathogen must overcome to survive in a ...beer are the presence of ethanol produced by yeasts during fermentation (up to 10% (v/v), typically 3.5–5.0% (v/v)), hop (Humulus lupulus) bittering compounds (approx. 17–55 parts per million iso-α-acids), low pH (approx. 3.9–4.4), carbon dioxide (approx. 0.5% (w/w)), low oxygen (<0.1 ppm), and the lack of nutritive substances. Ethanol and hops interfere with essential cell membrane functions, the low pH hinders enzyme activity, the lack of nutrients and oxygen starves many potential pathogens, whilst elevated dissolved carbon dioxide lowers the pH, inhibits enzymes, affects cell membranes, and creates an anaerobic environment. In addition to these intrinsic factors, many stages of the brewing process reduce the potential for contamination, such as mashing, wort boiling, pasteurization, filtration, aseptic packaging and cold storage. Various studies have shown that the survivability of pathogens such as Escherichia coli, Salmonella Typhimurium, and Vibrio cholerae in most beers is very poor. However, beers without, or with, reduced levels of one or more of these antimicrobial “hurdles” are more prone to the survival and/or growth of pathogenic organisms. Examples are low-alcohol and unpasteurized beer, for which special attention must be paid to ensure their safety.
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