Inhibition by yeast strain of tyrosinase activity in must and wine

The course of tyrosinase activity in musts is related to the strain of yeast used; with strain 633 the activity becomes practically non-detectable during the first days of growth. With other strains a drastic drop always occurs during the first 48 hours, followed by a recovery during the exponential phase of growth, in correlation to a substantial fall of phenols and to the exponential rise in colour. The inhibitory power on the tyrosinase in vitro is a widespread character in the yeast, even if quantitatively different: this character is not always associated with colour stability. Such a character, possessed to a remarkable measure by strains 633 and 36, is bound to the biosynthesis, even in synthetical media, of a compound capable of becoming bound to the protein units of enzyme, thus preventing the enzyme activity.Inhibition par la souche de levure de l'activité de la tyrosinase du moût et du vinLe cours de l'activité de la tyrosinase dans les moûts est rélié à la souche de levure employée: la souche 633 rend l'activité pratiquement inexistante pendant les premiers jours de son dévéloppement. D'autres souches provoquent une baisse drastique pendant les premières 48 heures, suivie par un récouvrement de l'activité de la tyrosinase pendant la phase exponentielle de leur dévéloppement en corrélation à une chute substantielle des composés phénoliques totaux et à la hausse exponentielle de la couleur. Le pouvoir inhibiteur sur la tyrosinase in vitro est un caractère diffusé des levures bien que quantitativement différent; ce caractère n'est pas toujours associé à la stabilité de la couleur des vins blancs. Tel caractère, possedé d'une façon remarquable par les souches 633 et 36, est lié à la biosynthèse, même dans les substrats synthétiques, d'un composé capable de se lier aux unités protéiques de l'enzyme, de façon à prévenir l'activité enzymatique

Prodotti della tradizione e contenuto di amine biogene alternative alla Low tyramine diet per la sostenibilità dei prodotti di nicchia e la salubrità del consumatore

Biogenic amines (BA) are present in a wide range of foods and mainly can be produced in high amounts by microorganisms through the activity of amino acid decarboxylases. Excessive consumption of foods with large concentrations of these compounds can induce adverse reactions such as nausea, headaches, rashes and changes in blood pressure. These problems are more severe in consumers with less efficient detoxification systems because of their genetic constitution or their medical treatments. The most common and powerful BA found in foods are histamine, tyramine and putrescine. Actually, there is no specific legislation regarding BA content in many fermented products, except for histamine; it is the only BA for which maximum levels in fish products have been set. So, it is generally assumed that these compounds should not be allowed to accumulate. Many factors such as bacterial density, synergistic effects between microorganisms, level of proteolysis (availability of substrate), pH, salt, use of starter cultures, sanitization procedures adopted and conditions and time of ripening process are found to have limiting effects on the build-up of amines. Moreover, improved knowledge of the factors involved in the synthesis and accumulation of BA should lead to reduce in their incidence in foods

A Survey of Antibiotic Resistance in Micrococcaceae Isolated from Italian Dry Fermented Sausages

The transfer of bacteria that are resistant to antimicrobial agents or resistance genes from animals to humans via the food chain is increasingly a problem. Therefore, it is important to determine the species and the numbers of bacteria involved in this phenomenon. For this purpose, 148 strains of microstaphylococci were isolated from three types of Italian dry fermented sausages. Eight of 148 strains belonged to the genera Kocuria and Micrococcus. The remaining 140 strains belonged to 11 different species of the genus Staphylococcus. The species most frequently isolated was Staphylococcus xylosus, followed by Staphylococcus saprophyticus and Staphylococcus aureus. Antibiotic resistance levels differed among the species and depended on the strain origin. Microstaphylococci were generally susceptible to beta-lactams, but 12 strains were resistant to methicillin, 8 were resistant to oxacillin, and 9 were resistant to penicillin G. No resistance was observed for aminoglicosides and cephalosporines. Many strains were resistant to sulfonamide, colistin suphate, tetracyclin, and bacitracin. Two strains of S. aureus, four strains of S. xylosus, and one strain of Staphylococcus sciuri were able to grow in the presence of 8 microg of vancomycin per g, but all strains were susceptible to teicoplanin. Twenty-two microstaphylococci were resistant to at least five of the tested antibiotics. The multiresistant strain S. aureus 899 was unaffected by eight antibiotics, including vancomycin and methicillin, indicating that a more prudent use of antibiotics in animal husbandry and better hygienic conditions during production should be encouraged because they can play a major role in reducing the incidence of such multiresistant microorganisms and the possible spread of the genetic elements of their resistance

Editorial: Biogenic amines in foods

Various issues related to the qualitative and quantitative presence of biogenic amines in cheese, dry sausages, wine, and fish were addressed. The possible scavenging of these compounds by technological processes and amineoxidase activity of some microorganisms is also reported

Biogenic Amines in Raw and Processed Seafood

The presence of biogenic amines (BAs) in raw and processed seafood, associated with either time/temperature conditions or food technologies is discussed in the present paper from a safety and prevention point of view. In particular, storage temperature, handling practices, presence of microbial populations with decarboxylase activity and availability of free amino acids are considered the most important factors affecting the production of BAs in raw seafood. On the other hand, some food technological treatments such as salting, ripening, fermentation, or marination can increase the levels of BAs in processed seafood. The consumption of high amount of BAs, above all histamine, can result in food borne poisoning which is a worldwide problem. The European Regulation established as maximum limits for histamine, in fishery products from fish species associated with high histidine amounts, values ranging from 100 to 200 mg/kg, while for products which have undergone enzyme maturation treatment in brine, the aforementioned limits rise to 200 and 400 mg/kg. Preventive measures and emerging methods aiming at controlling the production of BAs are also reported for potential application in seafood industries

Biogenic Amines in Italian Pecorino Cheese

The quality of distinctive artisanal cheeses is closely associated with the territory of production and its traditions. Pedoclimatic characteristics, genetic autochthonous variations, and anthropic components create an environment so specific that it would be extremely difficult to reproduce elsewhere. Pecorino cheese is included in this sector of the market and is widely diffused in Italy (∼62.000t of production in 2010). Pecorino is a common name given to indicate Italian cheeses made exclusively from pure ewes’ milk characterized by a high content of fat matter and it is mainly produced in the middle and south of Italy by traditional procedures from raw or pasteurized milk. The microbiota plays a major role in the development of the organoleptic characteristics of the cheese but it can also be responsible for the accumulation of undesirable substances, such as biogenic amines (BA). Bacterial amino acid decarboxylase activity and BA content have to be investigated within the complex microbial community of raw milk cheese for different cheese technologies. The results emphasize the necessity of controlling the indigenous bacterial population responsible for high production of BA and the use of competitive adjunct cultures could be suggested. Several factors can contribute to the qualitative and quantitative profiles of BA’s in Pecorino cheese such as environmental hygienic conditions, pH, salt concentration, water activity, fat content, pasteurization of milk, decarboxylase microorganisms, starter cultures, temperature and time of ripening, storage, part of the cheese (core, edge), and the presence of cofactor (pyridoxal phosphate, availability of aminases and deaminases). In fact physico-chemical parameters seem to favor biogenic amine-positive microbiota; both of these environmental factors can easily be modulated, in order to control growth of undesirable microorganisms. Generally, the total content of BA’s in Pecorino cheeses can range from about 100–2400 mg/kg, with a prevalence of toxicologically important BA’s, tyramine and histamine. The presence of BA is becoming increasingly important to consumers and cheese-maker alike, due to the potential threats of toxicity to humans and consequent trade implications

Quest for wine yeasts—An old story revisited

Numerous studies have described the yeast biota of grapes, and grape must in order to understand better the succession of yeasts during fermentation of wine. The origin of the wine yeasts has been rather controversial. By using more elaborate isolation methods, classical genetic analysis and electrophoretic karyotyping of monosporic clones, with this study, credible proof now exists that the vineyard is the primary source for the wine yeasts and that strains found on the grapes can be followed through the fermentation process