jueves, 12 de julio de 2012

Evaluación de la eficacia de la lisozima frente a las bacterias lácticas según las condiciones de vinificación


EVALUACIÓN DE LA EFICACIA DE LA LISOZIMA FRENTE A LAS BACTERIAS LÁCTICAS SEGÚN LAS CONDICIONES DE VINIFICACIÓN

Azzolini, M.; Tosi, E.; Veneri, G.; Zapparoli, G.; South African Journal of Enology and Viticulture 31 (2) 99–105

En este estudio se evaluó la eficacia de la lisozima en el control de las bacterias lácticas (BL). En una vinificación en bodega, las BL indígenas se inhibieron parcial y completamente cuando se adicionó lisozima a uvas tintas y blancas respectivamente.

Estos resultados se confirmaron utilizando dos cepas seleccionadas de Lactobacillus brevis y Oenococcus oeni para contaminar el mosto. En la vinificación en tinto, la población de células disminuyó sólo temporalmente y la fermentación maloláctica acabó en momentos diferentes, en función del pH del mosto y de la dosis de de lisozima.

En la vinificación en blanco, la velocidad de mortalidad de las células fue diferente en función de la dosis de lisozima, más que de los valores de pH.

Durante la fermentación, la actividad de la lisozima fue estable o disminuyó en función de la ausencia o presencia de mosto de uva respectivamente.

El estudio pone de manifiesto que la eficacia de la lisozima se ve fuertemente afectada por el tipo de vinificación.

EVALUATING THE EFFICACY OF LYSOZYME AGAINST LACTIC ACID BACTERIA UNDER DIFFERENT WINEMAKING SCENARIOS

This study evaluated the efficacy of lysozyme in winemaking to control lactic acid bacteria (LAB).

In a winery vinification, indigenous LAB were partially and completely inhibited when lysozyme was added to red and white grape must respectively. This result was confirmed by using two selected strains of Lactobacillus brevis and Oenococcus oeni to contaminate the grape must. In the red wine microvinification, the cell population decreased only temporarily and malolactic fermentation terminated at different times, depending on the grape must pH and lysozyme dosage. In the white wine microvinification, cell mortality rates differed according to lysozyme dosage
rather than pH values. During the fermentation, lysozyme activity was stable or decreased, depending on the absence or presence of grape must respectively.

The study highlighted that lysozyme efficacy is strongly affected by the type of vinification.

THE USE OF LYSOZYME IN VINIFICATION

Lysozyme is a natural protein with bactericidal activity against Gram-positive bacteria, including lactic acid bacteria (LAB). The use of this enzyme has been shown to be an effective antimicrobial in many foods (Hughey & Johnson, 1987). In the winemaking process, hen egg lysozyme is utilised to control spontaneous LAB
growth that often causes spoilage or stuck fermentation (Gerbaux et al., 1999; Delfini et al., 2004; Bartowsky, 2009). The benefits derived from the control of wine spoilage LAB are mainly the reduction in the risk of increased volatile acidity, as well as an increase in biogenic amines. The main technological interest
of lysozyme is to reduce the traditional use of sulphur dioxide, which can cause health concerns in consumers (Bartowsky, 2009; Sonni et al., 2009).

It has been ascertained that the efficacy of lysozyme in inhibiting undesirable LAB varies according to species and winemaking conditions (Gerbaux et al., 1999; Gao et al., 2002). Several strains, which are potentially detrimental to wine quality, are resistant to this enzyme (Delfini et al., 2004). A lytic cocktail of Streptomyces
spp., assayed to control LAB and acetic acid bacteria, was described as a valid alternative to lysozyme because of its higher activity against resistant strains (Blättel et al., 2009). Moreover, lysozyme is less active in red vinification than in white, although it has been demonstrated that its activity is not compromised in the former (Bartowsky & Hensche, 2004; Delfini et al., 2004). Isabel
et al. (2009) reported the use of lysozyme as being very beneficial to maintain low histamine levels and ensure Oenococcus oeni implantation in red vinification. Nevertheless, Tirelli and De Novi (2007) proved that lysozyme is unstable in young red wine, thus doubting its effectiveness in controlling malolactic fermentation (MLF). Although lysozyme does not seem to cause important changes in wine aroma, high amounts of this antimicrobial agent could increase the risk of colour instability and the formation of precipitate (Bartowsky & Hensche, 2004). Weber et al. (2007) did not exclude adverse allergic reactions to wines treated with lysozyme, but, for Kirschner et al. (2009), this risk is avoided if the wines are filtered. Moreover, the use of lysozyme involves significant additional costs for winemakers (enzyme purchase, clarification and fining procedures).

Although the use of lysozyme was approved by the Office International de la Vigne et du Vin (OIV) more than a decade ago, some questions remain open. The recommended lysozyme dosage is too generic because it does not consider that lytic activity is
strongly affected by contingent winemaking conditions. Hence, from the applied point of view, a more thorough evaluation of its efficacy in defined oenological environments would be informative.

This study evaluated the effects of lysozyme added to grape must for controlling LAB growth. Before alcoholic fermentation, microbial spoilage can be favoured by the vinification of defective grapes together with high pH and temperatures (Ribéreau-Gayon et al., 2006). Two indigenous strains of Lactobacillus brevis and O. oeni were used in grape musts as contaminant bacteria in laboratory-scale winemaking trials. L. brevis is one of the most important wine spoilage LAB, while the uncontrolled growth of indigenous O. oeni strains is often undesirable. The activity of the muramidase was evaluated in terms of must pH and its dosage. The different results from the red and white vinifications are lastly discussed.

More information: http://www.sasev.org/journal-sajev/sajev-articles/volume-31-2/Azzolini%20et%20al%20pp%2099%20to%20105.pdf/view

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