Evaluating the influence of winemaking practices on biogenic amine production by wine microorganisms
Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2007.
Biogenic amines are nitrogenous compounds of low molecular weight found in most fermented foods, including wine. These biologically produced amines are essential at low concentrations for normal metabolic and physiological functions in animals, plants and micro-organisms. However, biogenic amines can have adverse effects at high concentrations and pose a health risk for sensitive individuals. Symptoms include nausea, hot flushes, headaches, red rashes, respiratory distress and fluctuations in blood pressure. A number of countries have implemented upper limits for histamine in food and wine. This development has already started to threaten commercial export transactions and may become more serious in the near future, especially in the competitive wine industry of today. The most important biogenic amines in wine include histamine, tyramine, putrescine, cadaverine and phenylethylamine which are produced from the amino acids histidine, tyrosine, ornithine, lysine and phenylalanine respectively. Biogenic amines are mainly produced in wine by microbial decarboxylation of the corresponding precursor amino acid. It may be produced by yeast during alcoholic fermentation, by lactic acid bacteria during malolactic fermentation, or potentially by spoilage microbes such as acetic acid bacteria and Brettanomyces. However, lactic acid bacteria are widely accepted as the main causative agents. Inoculation with commercial malolactic fermentation starter cultures that do not possess the relevant decarboxylase genes may inhibit the growth and activity of decarboxylase positive indigenous bacteria and as such control the production of biogenic amines in wine. In this study it was shown that co-inoculation of malolactic starter cultures together with alcoholic fermentation could reduce the incidence of biogenic amines in wine compared to conventional inoculation protocols; presumably because undesirable activities were restrained at an earlier stage during co-inoculation. It was also indicated in this work that in some cases the effect of co-inoculation on biogenic amine reduction may only be visible after a period of ageing. The frequency of biogenic amine occurrence in wines aged for a short period was generally higher in the presence of fermentation lees than in its absence. This work also included a preliminary investigation into the contribution of commercial wine yeast starter cultures to biogenic amine production. Diamines and polyamines (putrescine, spermidine and cadaverine) were produced to variable extents by all yeasts with very little or no production of physiologically important biogenic amines (histamine, tyramine and phenylethylamine). Another objective of this study was to evaluate the influence of common winemaking practices on biogenic amine production under winemaking conditions. We have shown that biogenic amine production by lactic acid bacteria could be influenced, amongst others, by the presence of precursor amino acids in the grape must or wine, the time of contact between juice or wine and grape skins, the time of contact between wine and yeast lees, the presence of microbial nutrients, wine pH, sulphite and ethanol levels, the phenolic composition of the wine and the number of decarboxylase positive lactic acid bacteria present in the wine. Lately, the wine industry is under increasing pressure to increase measures to ensure food safety and security and to eliminate any compound, present even in trace amounts that could reduce the wholesomeness of the wine. The need arises for a rapid and inexpensive method for quality control. In this study we investigated the potential to use Fourier transform infrared spectroscopy to rapidly screen for the presence of elevated levels of biogenic amines. This presents a novel method for the detection and quantification of total biogenic amines in wines.