Utjecaj DL-jabučne kiseline na metabolizam L-jabučne kiseline tijekom alkoholnog vrenja

Insufficient wine acidity can affect wine quality and stability. To overcome this problem, DL-malic acid can be added to the grape juice prior to fermentation. We have investigated the effect of DL-malic acid on wine fermentations and its influence on the final concentration of L-malic acid, naturally present in grape juice. To this end yeast strains that metabolise L-malic acid in different ways were tested and compared; namely, Schizosaccharomyces pombe (efficient L-malic acid degrader), Saccharomyces cerevisiae (non-degrader), hybrid strain S. cerevisiae x S. uvarum (intermediate degrader) and Saccharomyces uvarum (promoting L-malic acid synthesis). In all cases, D-malic acid passively entered the yeast cells and did not undergo malo-alcoholic fermentation. However, its presence in the juice, as a component of the mixture of D- and L- malic acid (DL-malic acid), reduced the amount of L-malic acid that can be degraded or synthesised by yeasts during malo-alcoholic fermentation.Nedovoljna kiselost vina može utjecati na njegovu kakvoću i stabilnost. Da bi se riješio taj problem, može se moštu prije vrenja dodati DL-jabučna kiselina. Ispitan je utjecaj DL-jabučne kiseline na fermentaciju vina i njezin utjecaj na konačnu koncentraciju L jabučne kiseline koja se nalazi u moštu. Stoga su ispitani i uspoređeni sojevi kvasca koji metaboliziraju L-jabučnu kiselinu, i to Schizosaccharomyces pombe (djelotvoran razgrađivač L-jabučne kiseline), S. cerevisiae (ne razgrađuje), hibridni soj S. cerevisiae x S. uvarum (djelomično razgrađuje) i S. uvarum (promotor sinteze jabučne kiseline). U svim slučajevima D-jabučna kiselina pasivno ulazi u stanice kvasca i ne provodi jabučno-alkoholno vrenje. Međutim, njezina prisutnost u grožđanom soku, kao dio smjese D- i L jabučne kiseline (DL-jabučna kiselina) snizuje količinu jabučne kiseline koja se može razgraditi ili sintetizirati s kvascima tijekom jabučno-alkoholnog vrenja

Whey starter addition during maturation of evening milk: effects on some characteristics of cheese milk and Parmigiano–Reggiano cheese

International audienceAbstractCheese milk “maturation” during natural creaming in large flat vat is a critical step in the production of Parmigiano–Reggiano cheese. Thanks to an improved management, during the last years, a generalized reduction of mesophilic microbial counts has occurred, which did not favour an adequate increase in milk acidity during natural creaming. For this reason, some cheesemakers have introduced the practice to add a rate of natural whey starter in active fermentation in the evening milk to favourize its “maturation”. The aim of this work was to verify the effects of this practice on the characteristics of Parmigiano–Reggiano milk and on some chemical, microbiological and sensory properties of the ripened cheese. Thirty-six cheesemaking trials were carried out in a dairy: 12 with 0.2% of young whey starter addition, 12 with 0.4% and 12 as control. The addition of young whey starter improved the coagulation properties of the cheese milk and did not affect the normal succession of thermophilic and mesophilic lactic acid bacteria during the cheese ripening. The chemical composition of the ripened cheeses was not affected by the practice of whey starter addition. From the sensory point of view, the addition of natural whey starter improved the compliance scores and decreased the defects, as eyes and cracks. This work confirmed the empirical observations of some cheesemakers. The adoption of this technique has considerable technological importance, improving the coagulation properties of the milk and the sensory characteristics of the cheese

Utjecaj autolize bakterija mliječno-kiselog vrenja na senzorske značajke fermentiranih namirnica

Lactic acid bacteria autolysis is due to intracellular hydrolytic enzymes that act on specific parts of the cell wall causing the release of biologically active compounds, in particular enzymes, to the medium. Consequently, the role of lactic acid bacteria in the transformation of foodstuffs does not involve merely the fermentation stage but also the later maturation and aging stage thanks to the compounds released to the medium that combine in order to change the sensorial profile of the product. This phenomenon is particularly important for cheese types subjected to very long aging, for salami ripening and for red aged wines.Autoliza bakterija mliječno-kiselog vrenja nastaje djelovanjem intracelularnih hidrolitičkih enzima koji u reakciji sa specifičnim dijelovima staničnog zida uzrokuju izlazak biološki aktivnih spojeva, osobito enzima, u podlogu. Stoga utjecaj tih bakterija na promjene u namirnicama nije ograničen samo na fermentaciju već i na vrijeme zrenja i starenja zbog spojeva koji su iz stanica ušli u medij, što dovodi do promjena senzorskih značajki proizvoda. Taj je proces posebno važan za vrste sira koje dugo sazrijevaju, za zrenje salame i za proizvodnju odležanih crvenih vina

Reduction of concentrated feed in dairy cows in the Parmigiano Reggiano area: effects on milk production and quality.

A project of technological research, funded by Emilia Romagna Region and aimed to a higher sustainability of dairy chain, involved an experimental trial testing the effect of a reduction of concentrate feed in Frisona cows producing milk for Parmigiano Reggiano Cheese making. Two groups of 15 cows each, with milk production at 9 days in milk (DIM) of 31.7 and 32.1 kg/d, were fed mixed meadow hay ad libitum and a growing amount of concentrate feed up to 15 kg (C group) or 12 kg (T group) at the peak of lactation (about 60 days). Milk production, milk fat and protein were recorded from each cow at 9, 47, 96, 131, 166, and 207 DIM; fatty acid composition of milk was analysed on 5 pooled samples/group at 47, 131, and 207 DIM. Milk collected from the two groups of cows at day 161 and 168 was used for micro cheese making. Milk production and milk fat were unaffected by diet, whereas milk protein was lower in T cows at 166 (3.18 vs 3.39%; p<.01) and 207 (3.17 vs 3.31%; p<.05) DIM. Fatty acid composition of T milk showed at 47 DIM significantly lower % of MUFA and PUFA, and higher % of SFA, resulting in higher SFA/UFA ratio (1.70 vs 1.38; p<.01). Both n-3 and n-6 fatty acids were significantly lower in T milk at 47 DIM (n-3: 1.21 vs 1.44%; n-6: 4.05 vs 4.57%) and at 131 DIM (n-3: 1.18 vs 1.37%: n-6: 3.89 vs 4.83%). CLA levels were similar in the milk of the two groups. The milk collected for cheese making (60 l/group) had similar chemical and bacteriological composition, with the exception of a higher content of thermophilic Lactobacilli in T milk. Rennet coagulation characteristics showed lower curd firmness at 30’ in T milk (a30: 24.80 vs 29.48 mm; p<.05), whereas the other cheese making traits were not significantly different between the two groups. Bacteriological traits of the ripened cheese (60 days) from the two groups were also similar. The results of this field trial indicate that a reduction of 20% of concentrate feed in the diet of high producing cows did not affect milk amount, milk fat and cheese making traits, but caused a partial deterioration in milk protein, fatty acid composition and rennet coagulation. Further research might evaluate the whole lactation, reproductive performances, nutritional and health status. A part of the results of the research was presented at 6th AITeL Congress (Trento, September 20th 2018)

Presenza di alcool etilico negli alimenti.

L’alcol etilico può essere presente, oltre che nelle bevande alcoliche, in numerosi altri alimenti sia pure in misura limitata. In questi casi, l’etanolo può essere di origine fermentativa per sviluppo di lieviti o di batteri eterolattici oppure può derivare da trattamenti eseguiti sui prodotti finiti o sulle materie prime. Gli alimenti in questione sono rappresentati da diversi salumi e formaggi lavorati con tecnologie tradizionali, vegetali fermentati (crauti e olive), pane e prodotti da forno e latti fermentati. Le conseguenze della presenza di etanolo nei singoli alimenti vengono discussi sia dal punto di vista del rischio derivante da ingestione involontaria del composto sia dal punto di vista del conferimento delle caratteristiche sensoriali

Utjecaj autolize bakterija mliječno-kiselog vrenja na senzorske značajke fermentiranih namirnica

Lactic acid bacteria autolysis is due to intracellular hydrolytic enzymes that act on specific parts of the cell wall causing the release of biologically active compounds, in particular enzymes, to the medium. Consequently, the role of lactic acid bacteria in the transformation of foodstuffs does not involve merely the fermentation stage but also the later maturation and aging stage thanks to the compounds released to the medium that combine in order to change the sensorial profile of the product. This phenomenon is particularly important for cheese types subjected to very long aging, for salami ripening and for red aged wines.Autoliza bakterija mliječno-kiselog vrenja nastaje djelovanjem intracelularnih hidrolitičkih enzima koji u reakciji sa specifičnim dijelovima staničnog zida uzrokuju izlazak biološki aktivnih spojeva, osobito enzima, u podlogu. Stoga utjecaj tih bakterija na promjene u namirnicama nije ograničen samo na fermentaciju već i na vrijeme zrenja i starenja zbog spojeva koji su iz stanica ušli u medij, što dovodi do promjena senzorskih značajki proizvoda. Taj je proces posebno važan za vrste sira koje dugo sazrijevaju, za zrenje salame i za proizvodnju odležanih crvenih vina

La microbiologia enologica del passato e del futuro. 5) 5 - I lieviti autoctoni in fermentazioni scalari e in associazione,

Sono chiamati “autoctoni” i lieviti presenti in un territorio vitivinicolo ben delimitato e responsabili del conferimento delle caratteristiche di qualità e di tipicità dei vini pregiati. Questi lieviti, riferibili sia al genere Saccharomyces che al gruppo dei non-Saccharomyces, una volta caratterizzati sotto l’aspetto enologico, possono essere usati per la produzione di quei vini con il metodo della fermentazione scalare o con il metodo della fermentazione in associazione

Vini spumanti e frizzanti

I vini spumanti, per nascita e per tradizione, sono considerati prodotti d'\ue9lite ed \ue8 quindi ragionevole che chi intenda produrre vini spumanti voglia proporre un prodotto di qualit\ue0. L'attuale livello di tecnologia, frutto di costante ricerca nel settore enologico, permette di ottenere vini spumanti e frizzanti di elevata qualit\ue0, spesso riconosciuta dai marchi DOP e IGP: i disciplinari di produzione sono infatti spesso pi\uf9 restrittivi rispetto alle normative comunitarie e nazionali. In questo libro, viene fatto il punto sulle tecnologie per la produzione dei vini spumanti e dei vini frizzanti, che con l'attuale livello tecnologico, non hanno nulla da invidiare ai primi

Effects of Lactic Acid Bacteria Autolysis on Sensorial Characteristics of Fermented Foods

Lactic acid bacteria autolysis is due to intracellular hydrolytic enzymes that act on specific parts of the cell wall causing the release of biologically active compounds, in particular enzymes, to the medium. Consequently, the role of lactic acid bacteria in the transformation of foodstuffs does not involve merely the fermentation stage but also the later maturation and aging stage thanks to the compounds released to the medium that combine in order to change the sensorial profile of the product. This phenomenon is particularly important for cheese types subjected to very long aging, for salami ripening and for red aged wines