Andrea Caridi

Enological functions of parietal yeast mannoproteins

Parietal yeast mannoproteins play a very important role in the overall vinification process. Their production and release, both during winemaking and aging on lees, depends on the specific yeast strain and the nutritional conditions. The following enological functions of parietal yeast mannoproteins have been described: (a) adsorption of ochratoxin A; (b) combination with phenolic compounds; (c) increased growth of malolactic bacteria; (d) inhibition of tartrate salt crystallization; (e) interaction with flor wines; (f) prevention of haze; (g) reinforcement of aromatic components; (h) wine enrichment during aging on fine lees; (i) yeast flocculation and autolysis in sparkling wines. Further discoveries related to their enological functions are foreseeable. Yeast-derived mannoproteins may well induce chemical, sensorial and health benefits, thus greatly improving wine quality.

Ripening and seasonal changes in microbial groups and in physico-chemical properties of the ewes’ cheese Pecorino del Poro

Three batches ofPecorino del Poro, ewes’ cheese made f raw milk, were examined throughout a 28-day ripening time at three different seasons. High logarithmic counts per gram of cheese for mesophilic coccal-shaped lactic acid bacteria (6.70–12.45), mesophilic lactobacilli (4.82–11.73), thermophilic coccal-shaped lactic acid bacteria (2.30–9.90), and thermophilic lactobacilli (2.95– 8.15) were found. Coccal-shaped lactic acid bacteria were the dominant microorganisms throughout ripening. The microorganisms used as an indicator of hygiene during manufacture of the cheeses, coliforms and Escherichia coli, were considerably lower, as were enterococci and yeasts. Coliforms and E. coli decreased sharply throughout ripening. Physico-chemical parameters such as pH (5.07–7.03), dry matter (46.34–72.79%), ether extract (31.35–51.84% ofdry matter), crude protein (29.93–44.73% ofdry matter), and chloride content (2.36–4.11% ofdry matter) were also determined. Probably, the use ofselected autochthonous mesophilic lactococci as a starter would control or suppress the growth ofundesirable microorganisms. The results obtained suggest the need for improvements in milking and dairy conditions. r 2003 Elsevier Science Ltd. All rights reserved.

Ripening and seasonal changes in microbiological and chemical parameters of the artisanal cheese Caprino d’Aspromonte produced from raw or thermized goat's milk

Abstract The aim of the present research was to monitor the microbiological and the chemical characteristics of Caprino d’Aspromonte, a cheese produced from raw or thermized goats milk, to regulate, if necessary, the production process. In spring 2000, and again in summer 2000 and winter 2001, three independent batches of cheese were analysed after 0, 14 and 28 days of ripening. High logarithmic counts per gram of cheese for mesophilic coccal-shaped lactic acid bacteria (6.94–11.90), thermophilic coccal-shaped lactic acid bacteria (4.08–9.43), mesophilic lactobacilli (3.63–9.60), and thermophilic lactobacilli (2.78–8.36) were found. Coliforms, Escherichia coli , enterococci, and yeasts were considerably lower. Physico-chemical parameters such as pH (5.09–6.89), dry matter (42.69–66.97%), ether extract (19.36–34.33%), crude protein (14.25–27.21%), and chloride content (0.92–2.60%) were also determined. Micro-organisms indicating low level of hygiene were high and several cheeses failed the standards laid down by the Italian legislation. Lactic acid bacteria, cocci and rods, are the dominant microflora throughout ripening. Enterococci are two log units lower than in other goats cheeses made from raw milk. The majority of the yeasts do not ferment the lactose with production of gas. To increase cheese quality, it is necessary to improve the hygiene conditions of milking, milk-storage, and cheesemaking.

Inhibition of malolactic fermentation by cryotolerant yeasts

White wines produced by some cryotolerant strains of Saccharomyces cerevisiae are more resistant to malolactic fermentation than those produced by normal strains: e.g. for two months of storage, the wines, inoculated with Leuconostoc oenos or Lactobacillus plantarum, were fully stabilized with levels of 51-65 mg total SO 2 /l and 5.70-5.75 g titratable acidity/l. The use of these yeasts in wine-making can decrease the quantities of sulfites added to stabilize wines.

Wine colour adsorption phenotype: an inheritable quantitative trait loci of yeasts

Aims:  In this work, a population of 88 descendants derived from three wine strains of Saccharomyces cerevisiae was tested for the enological trait ‘wine colour adsorption’ (WCA) to evaluate its inheritability.

Protective agents used to reverse the metabolic changes induced in wine yeasts by concomitant osmotic and thermal stress

Aims: The reversion of the metabolic changes induced in wine yeasts by stressors.

Influence of dairy Penicillium spp. on nutrient content of citrus fruit peel

Abstract The aim of this study is to improve the nutritional value of bergamot fruit peel by solid-state fermentation with three strains of Penicillium camemberti and seven strains of Penicillium roqueforti . To assess the effect of their growth on the chemical composition of the substrate, the following analytical determinations were carried out before and after microbial colonization: crude protein, pure protein, non-proteic nitrogen, dry matter, ether extract, ash, neutral detergent fiber, acid detergent fiber, hemicellulose, cellulose, organic matter, and gross energy. The colonization with the moulds produces substantial changes in the chemical composition of the bergamot fruit peel, notably significant increases in crude protein, ether extract, gross energy, and structural carbohydrates. The solid-state fermentation activity of these moulds could prove a cost-effective way of recycling citrus fruit peel in animal feed, thus increasing its nutritional value by single cell protein. Nevertheless further research on the matter must be carried out, especially on the estimation of the biomass digestibility – in vitro, in sacco or in vivo – and on the check for eventual mycotoxins (roquefortin, cyclopiazoic acid) produced by the moulds in the cellulose waste.

Evolution during wine aging of colour and tannin differences induced by wine starters

The ability of threeSaccharomyces cerevisiae strains, with different colour adsorption aptitude, to induce and maintain colour differences in wines obtained from the Calabrian Gaglioppo and Magliocco black grape varieties was studied during one year of aging. The evolution of wine tannin content was also considered. Total polyphenols, colour parameters and total tannin values exhibited, both for Gaglioppo and Magliocco wines, significant (P < 0.05) or highly significant (P < 0.01) differences among strains. It is interesting to note that yeasts appear to exhibit a different adsorption aptitude for anthocyanins and tannins. The strain that gave wine with high values for the colour parameters was not the same as the one that produced wine with high values of tannins. The obtained results suggest that the choice of yeast strain in winemaking affects, in a significant way, the phenolic composition of wines with direct consequences on their colour and tannin content. Moreover, the interaction between grape cultivar and yeast is close and important, because grape variety, due to its phenolic composition, modulates yeast strain adsorption activity.

In-vitro screening ofSaccharomyces strains for ochratoxin A removal from liquid medium

The aptitude of twentySaccharomyces sensu stricto strains to remove ochratoxin A from a synthetic medium containing 1.1 ng/mL, about half of the European Community limit, was evaluated using four to six mg of biomass (wet weight)/mL. Seven satins show high levels of ochratoxin A removal, 0.72-1.10 ng/mL, equivalent to 66–100% of the available toxin, and unitary removing ativity of 14.31–27.24 pg/mg of biomass. Further research will be carried out to study the mechanism of OTA removal and to confirm the ability of the most efficacious strains ofSaccharomyces sensu stricto to remove OTA from contaminated wort and grape must during alcoholic fermentation.

Winemaking from Gaglioppo grapes with hybrid strains of Saccharomyces

The fermentative behavior of two hybrid wine yeast strains (first-generation hybrid-strain 12 233×6167—obtained by hybridization of the cryotolerant strainS. bayanus 12 233 with the mesophilic strainsS. cerevisiae 6167, and TT254×6392 arising by hybridization of the thermotolerant strainS. cerevisiae TT254 with the mesophilic strainS. cerevisiae 6392) was compared with that of a commercial wine yeast strainS. cerevisiae K1 in must from black grapes of the Calabrian variety Gaglioppo. The goal was to obtain wines with a high content of ‘polyphenols’ from a grape must with a limited phenolic content such as the Gaglioppo must. The progress of the winemaking was estimated according to residual sugars; at the end of fermentation, the wines were decanted, bottled and principal physico-chemical characteristics determined. Our results point to the possibility to select wine yeasts (significantly differing in the above parameters) by their ability to interact with phenolic compounds.