Estudio de la degradación de los aceites de oliva sometidos a fritura. I. Determinación estadística del parámetro que mejor cuantifica esta degradación

On designing this experiment, besides estimating the initial homogeneity of the six oils, which have been studied, all the factors are controlled in a way that only one variable namely, thermoxidation affects the degradation. After the corresponding statistical treatment of the results had been carried out, the conclusion reached was that polar fraction parameter results to been the most specific, besides being the one that best measures the alteration of the heated olive oils.Al diseñar este experimento además de presuponer una homogeneidad inicial en los seis aceites estudiados, se controlaron todos los factores, de forma, que sólo hubiera una variable, la termooxidación, que afectase a la degradación. La conclusión a la que se llegó, después del correspondiente tratamiento estadístico de los resultados, es que el parámetro fracción polar es el más específico y el que mejor mide la alteración de los aceites de oliva calentados

Effect of oxygen and lipid supplementation on the volatile composition of chemically defined medium and Chardonnay wine fermented with Saccharomyces cerevisiae

Oxygen or lipids are required to complete stressful alcoholic fermentation. Lack of these nutrients can inhibit sugar uptake and growth, which leads to incomplete or 'stuck' fermentation. Oxygen or lipids supplementation not only restores yeast fermentative activity and also affects formation of yeast volatile metabolites. To clarify the effect of oxygen and lipid supplementation on the formation of flavour active metabolites during wine fermentation, we evaluated the addition of these two nutrients to chemically defined grape juice and filter clarified Chardonnay must. Lipid addition increased the concentration of esters, higher alcohols and volatile acids, whereas oxygen increased the concentration of higher alcohols and altered the proportion of acetate to ethyl esters and the proportion of branch-chain acids to medium-chain fatty acids. Combined addition of lipids and oxygen showed an additive effect on concentration of higher alcohols whereas oxygen suppressed the enhancing effect of lipids on formation of esters and volatile acids. Our results demonstrate the potential of lipid and oxygen supplementation for the manipulation of wine aroma in white wine fermentation.C.Varela, D.Torrea, S.A.Schmidt, C.Ancin-Azpilicueta, P.A.Henschk

Histamine in Australian wines - a survey between 1982 and 2009

Biogenic amines are found in a range of fermented foods and beverages, including wine. Absorption of these compounds in elevated concentrations may induce headaches, gastro-intestinal and respiratory distress. The main biogenic amines found in wine are histamine, tyramine, cadaverine and putrescine. Even though concentrations of histamine in wine are generally ten-fold lower than found in some fresh and other fermented foods, their presence may contribute to an adverse reaction when consumed in combination with other histamine-containing foods. It is well established that the main contribution of biogenic amines in wines is from lactic acid bacteria metabolism, especially during or after malolactic fermentation (MLF). A survey for histamine content of Australian red and white wines produced during 1982–1990 demonstrated a wide range of concentrations (mean 1.58 and 0.21 mg/L, respectively). A second survey of histamine content in red and white wines produced during 2003–2009 (mean 1.75 and 0.59 mg/L, respectively) showed that there were minimal changes in the mean histamine concentration over the period of the two sets of wines. All 238 Australian wines from 1982–1990 and 99 of 100 wines from 2003–2009 were below the former regulatory recommended limit of 10 mg/L for histamine in wine and were low compared to other wine-producing countries. Seven other biogenic amines measured in the Australian wines from 2003–2009 also had low means compared to other wine-producing countries.Eveline J. Bartowsky and Creina S. Stockle