Abstract
Malolactic fermentation (MLF) is a biological process that, in addition to deacidifying, also improves biological stability and changes the chemical and sensorial characteristics of wines. However, multiple biotic and abiotic factors, present in must and wine, make the onset and completion of MLF by indigenous malolactic bacteria or added commercial starters difficult. This work illustrates the metabolic and fermentative dynamics in winemaking Fiano wine, using a commercial starter of Saccharomyces cerevisiae and the selected strain Lactobacillus plantarum M10. In particular, an inoculum of malolactic starter was assessed at the beginning of alcoholic fermentation (early co-inoculum), at half alcoholic fermentation (late co-inoculum), and post alcoholic fermentation (sequential inoculum). The malolactic starter, before its use, was pre-adapted in sub-optimal growth conditions (pH 5.0). In sequential inoculum of the Lb. plantarum M10, even in a wine with high acidity, has confirmed its good technological and enzymatic characteristics, completing the MLF and enriching the wine with desirable volatile compounds.
Highlights
Malolactic fermentation (MLF) does represent the enzymatic conversion of L-malic acid to L-lactic acid and CO2, but it includes other metabolic activities by lactic acid bacteria (LAB), which influence the aromatic compounds and provide biological stability to wine [1,2,3]
MLF takes place at the end of alcoholic fermentation and is mainly carried out by lactic acid bacteria belonging to two species: Oenococcus oeni and Lb. plantarum
Scientific literature has highlighted that malolactic starters are selected according to very strict criteria and are able to survive in extremely difficult conditions [4,5,6,7,8]
Summary
Malolactic fermentation (MLF) does represent the enzymatic conversion of L-malic acid to L-lactic acid and CO2, but it includes other metabolic activities by lactic acid bacteria (LAB), which influence the aromatic compounds and provide biological stability to wine [1,2,3]. Despite current scientific and technical knowledge, the malolactic fermentation often remains unpredictable and difficult to manage This is because the bacterial performances are strongly affected by different biological and chemical-physical variables: nutritional competition with yeasts, pH, medium-chain fatty acids, sulfur dioxide, alcohol levels. Despite that the influence of malolactic Lb. plantarum strains on the quality of wine has been widely investigated [29], our knowledge is still limited Certain wine, such as Fiano, obtained from white grapes variety grown in Southern Italy, contain low levels of free volatile but are characterized by remarkably high concentrations of aromatic glycosylated precursors that can be transformed into odor-active volatiles during winemaking. We have investigated the effects of malolactic starter, pre-adapted in sub-optimal growth conditions, and used at the beginning, at half-time, or after alcoholic fermentation
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