Simultaneous Optimization of Acetaldehyde and DMS Concentrations for Better Sensory Quality of Beer Fermented on an Industrial Scale.

The levels of selected volatile components that affected the sensory properties of a lager beer were optimized under high-gravity brewing conditions (15.5 °P) in an industrial plant. The influence of different pitching rates (6-10 million cells/mL), aeration levels (8-12 mg/L), times (4.5-13.5 h) of filling CCTs (cylindroconical tanks, 3850 hl), and fermentation temperatures (8.5-11.5 °C) on the contents of acetaldehyde, diacetyl, acetone, 2,3-pentanedion, dimethyl sulfide (DMS), and on the sensory properties of beer were investigated. Response surface methodology (RSM, Box-Behnken design) was used to research the possibilities for optimizing the concentration of selected volatile components and sensory properties of bottom-fermented lager beers. Statistical analyses of the results showed that the experimental factors had a significant influence (R-squared for the original model with no significant lack-of-fit) on some of the volatile components. Based on the Multiple Response Optimization analysis, the values of independent factors that ensured the highest beer sensory quality were the following: a pitching rate of 10 million cells per mL; a fermentation temperature of 11.5 °C; an aeration level of 12 mg/L; and a CCT filling time of 4.5 h. These results proved that RSM modelling can be successfully applied to optimize fermentation and lagering processes in an industrial plant to manufacture lagers of enhanced sensory quality.

Isolation and identification of microorganisms including lactic acid bacteria and their use in microbial deacidification of wines from domestic vineyards.

The aim of this study was to identify various bacteria isolated from grapes and their wines. Additionally we investigated the capacity of lactic acid bacteria for microbiological deacidification of wines produced in Poland. We have identified Oenococcus oeni, Lactobacillus acidophilus and Lactobacillus delbrueckii. During the microbial deacidification process, we observed decreases of total acidity and increases of volatile acidity, with statistically significant changes noted for O. oeni in Marechal Foch and Seyval Blanc, and for Lb. acidophilus in Frontenac. On the other hand, a statistically significant increase in pH was observed in Marechal Foch and Seyval Blanc following deacidification by O. oeni.

Antioxidant activity of apples--an impact of maturity stage and fruit part.

BACKGROUND: Recently, many studies have been oriented towards improving methods and efficiency of antioxidants recovery from different fruit and their wastes.The aim of the study was to evaluate antioxidant potential of apple seeds and peel, which constitute the fruit industry wastes, and compare it to apple flesh. Antioxidant activity of apples at different maturity and storage stage were analysed too. MATERIAL AND METHODS: The Idared and the Sampion cultivars of apples were used in the study. Antioxidant activity was estimated using ABTS and DPPH assays, and polyphenols profile was determined by HPLC method. RESULTS: Seeds of analysed apple cultivars were characterised by a significantly higher antioxidant capacity and by higher concentrations of polyphenols analysed when compared to their peel and flesh. There were present two predominant compounds: phloridzin in seeds (84% and 72%) and quercetin glycosides in peels (54% and 38%, Idared and Sampion cultivars, respectively). No quercetin glycosides in seeds were found. The capacity to scavenge an ABTS radical, but not DPPH, decreased during ripening of apples, while cold storage resulted in enhanced antioxidant potential. CONCLUSION: It can be concluded that unripe apples together with apple seeds and peel (fruit industry wastes) constitute a valuable source of polyphenols.

Influence of indigenous yeasts on the fermentation and volatile profile of plum brandies.

The aim of this study was to determine the influence of different yeasts isolated from fresh blue plum fruits (Aureobasidium sp.) and spontaneously fermenting plum musts (Kloeckera apiculata and Saccharomyces cerevisiae), as well as commercial wine and distillery strains, on the fermentation and chemical composition of plum brandies. Gas chromatography methods were used to detect major volatile components. The most rapid fermentation occurred in musts inoculated with S. cerevisiae. However, the highest concentration of ethanol was detected in samples after spontaneous fermentation (8.40% v/v). Plum brandies obtained after distillation contained from 66.3 (K. apiculata) up to 74.3% v/v ethanol (spontaneous fermentation). The samples after spontaneous fermentation were distinguished by a high content of acetoin, ethyl acetate and total esters, accompanied by a low level of methanol and fusel alcohols. Non-Saccharomyces yeasts were responsible for higher concentrations of esters and methanol, while S. cerevisiae strains resulted in increased levels of higher alcohols. It was also found that isolated indigenous strains of S. cerevisiae synthesized relatively low amounts of higher alcohols compared to commercial cultures. Samples obtained using the distillery strain of S. cerevisiae received the highest score (18.2) during sensory analysis and were characterized by a well-harmonised taste and aroma.

Influence of prefermentative treatments and fermentation on the antioxidant and volatile profiles of apple wines.

The aim of this study was to determine the influence of different factors such as fruit processing, pectinolytic enzyme application, strain of yeast (Johannisberg-Riesling, Steinberg), cell immobilization on the alginate, and type of fermentation on the antioxidant profile and volatile composition of apple wines. Champion and Idared apples were used during experiments. The factors used influenced significantly (p < 0.05) antioxidant capacity, polyphenol profile, and volatile composition of apple wines. Pulp fermentation caused formation of higher amounts of ethanol and favorably influenced the antioxidant activity of wines. Procyanidins B2 and C1 as well as epicatechin and catechin prevailed among polyphenols in these samples. Cell immobilization positively affected the ethanol content, but decreased the antioxidant activity, of wines. Volatile composition of wines was mainly influenced by strain of yeast and type of fermentation. Apple wines fermented spontaneously were characterized by more esters and methanol and fewer higher alcohols compared to inoculated samples.

The profile of volatile compounds and polyphenols in wines produced from dessert varieties of apples.

The aim of this study was to determine the influence of apple variety (Sampion, Idared and Gloster) on the polyphenol profile, volatile composition and sensory characteristics of apple wines. Apples were harvested from the orchard in Garlica Murowana (Poland) and the experiments were conducted on a laboratory scale. Statistically significant differences were detected in the chemical composition of the analyzed wines. The highest antioxidant activity was found in Sampion wines, which was associated with a relatively high concentration of chlorogenic acid and procyanidins. These samples also contained high amounts of acetaldehyde, ethyl acetate and methanol. Idared wines showed a similar polyphenol profile, but they had lower antioxidant capacity and were characterized by a high level of butanol and acetic acid. Gloster wines were distinguished from other samples by a lower concentration of polyphenols and higher concentration of fusel alcohols. During sensory evaluation, wines produced from Idared apples scored the highest value for overall quality.