Luigi Grazia

Morphological and phenotypical characterization of Bacillus sporothermodurans

Aims:  Enumeration of resistant bacteria in ultra‐high temperature (UHT) treated milk; morphological characterization and phenotyping of resistant strains by traditional and nontraditional methods and their identification by molecular biology.

Effects of low electric treatment on yeast microflora

Aims: To contribute to the understanding of phenomena related to different intensity electric current treatments on the growth and metabolism of selected micro‐organisms using laboratory samples of pure and co‐cultures (Saccharomyces cerevisiae strain 404 and Hanseniaspora guilliermondii strain 465).

Effect of wine addition on microbiological characteristics, volatile molecule profiles and biogenic amine contents in fermented sausages

The aim was to evaluate the effect of wine addition during manufacturing of dry fermented sausages, in terms of safety aspects (biogenic amine accumulation), aroma profile and sensory characteristics. Three batches of salami were produced: without wine addition and with 7.5% or 15% (v/w) of white wine. The fermented sausages showed characteristics that can increase product diversification. Some of the sensory features (i.e. increased salty perception) can represent an important strategy because of the trend to reduce salt intake for health reasons. The presence of wine immediately reduced the pH and is a source of ethanol, which can have an inhibitory effect against undesirable microflora. The microbiological results observed regarding Enterobacteriaceae and enterococci were encouraging. The addition of wine did not negatively affect the ripening time or increase the presence of biogenic amines. The samples containing wine showed reduced concentrations of putrescine.

Controlling grape must fermentation in early winemaking phases: the role of electrochemical treatment

Aims: To contribute to an understanding of the phenomena related to the effect of low electric current (LEC) in grape must fermentation during laboratory and pilot plant scale winemaking, with selected co‐culture yeasts (Saccharomyces cerevisiae strain 404 and Hanseniaspora guilliermodii strain 465).

Effects of aw at packaging time and atmosphere composition on aroma profile, biogenic amine content and microbiological features of dry fermented sausages

The aim was to evaluate the effects of different water contents (corresponding to a(w) 0.940, 0.914, 0.895 and 0.875) of sausages at different times on the characteristics of typical Italian dry fermented sausages packaged under two different modified atmospheres (MAP) (100%N2 or 30%CO2/70%N2). During ripening and storage, samples were analyzed to evaluate pH and aw changes, microbial population, biogenic amine (BA) accumulation and aroma profile. The results showed that during storage under MAP several microbiological and enzymatic activities proceeded, leading to changes in aroma profile. In particular, higher hexanal concentrations in samples at lower aw and significant amounts of acetone, 2-butanone, ethanol and 2-butanol in samples at aw>0.900 were detected. Moreover, data showed modifications in BA content, such as higher accumulation in samples at aw>0.900 in MAP with 100%N2. This behavior depends, in first instance, on the aw of the sausages when packaged.

Chromosome arrangement, differentiation of growth kinetics and volatile molecule profiles in Kluyveromyces marxianus strains from Italian cheeses

Thirty-nine strains of Kluyveromyces marxianus from Pecorino di Farindola cheese in comparison with 3 strains from Parmigiano Reggiano cheese, 1 from fermented milk, 3 from cow whey and two type strains K. marxianus CBS 834(T) and Kluyveromyces lactis CBS 683(T) were tested for genetic and metabolic characteristics. Intraspecific diversity of chromosome arrangements was evaluated by pulsed field gel electrophoresis (PFGE) analysis. Among K. marxianus strains chromosome polymorphisms were evident with 11 patterns that differed in size and number of the chromosomal bands. The number of the bands varied from 4 to 7 with sizes ranging from about 1.0 to 2.7 Mb. Twelve strains were selected for determining their growth capacity and volatile compound production in two wheys (raw cheese whey and ricotta cheese whey) under limited oxygen availability. The growth kinetics highlighted four different biotypes and the influence of whey composition on K. marxianus development. The main volatile compounds detected after the growth were alcohols, acids, esters, ketones and aldehydes. Ethanol was the most abundant in both wheys. Aldehydes and other minor compounds were produced only when the strains were inoculated in ricotta cheese whey, while esters, butanoic, decanoic and octanoic acids were qualitatively and quantitatively more present in raw cheese whey. This study highlights a great genetic and metabolic biodiversity within Pecorino di Farindola K. marxianus strains and it could be exploited to improve the knowledge of this yeast for biotechnological uses.

Effect of a sublethal high‐pressure homogenization treatment on the fatty acid membrane composition of probiotic lactobacilli

High‐pressure homogenization (HPH) has been proposed to be applied directly to lactic acid bacterial cells at sublethal levels to enhance some functional properties. As the principal target of HPH are the cell surface envelope structures, the aim of this work was to study the effect of a HPH treatment, applied at 50 MPa, on cell membrane stress responses of already‐known functional strains, isolated from Argentinean products. Specifically, the membrane fatty acid composition of cells before and after the sublethal treatment was investigated, and the results showed that plasma membranes, their level of unsaturation and their composition are involved in response mechanisms adopted by microbial cells when subjected to a sublethal HPH stress. In fact, the data obtained demonstrated that the treatment was able to modify the fatty acid profile of the different strains, although a uniform response was not observed. Further studies are necessary both to elucidate the role of each fatty acid in the cell response mechanisms and to clarify the changes in membrane compositions induced by HPH treatment also in relation to the applicative potential of this technique.

Scaling-up in industrial winemaking using low electric current as an alternative to sulfur dioxide addition.

Aims:  To better understand the outcome of employing low electric current (LEC) technology as a new preservation and alternative in wine technology, and to contribute to its development. It is used in industrial‐scale winemaking with commercial yeast (Saccharomyces cerevisiae) during the grape must fermentation.

Autolysogeny and high isobutyl alcohol production inSaccharomyces cerevisiae

A relationship between very high isobutyl alcohol production and autolysogeny of cells was found in single sporeSaccharomyces cerevisiae cultures. Autolysis in autolysogenic cultures occurred at low temperatures (25°–5°C) as well as at high temperatures. Autolysogeny was always segregated at a 2:2 ratio from a natural strain. This indicates that it is a hereditary, monogenic, and recessive character.

A procedure for the sensory evaluation of Salama da sugo, a typical fermented sausage produced in the Emilia Romagna Region, Italy.

BACKGROUND Salama da sugo is a fermented sausage from the Ferrara tradition (Italy, Emilia-Romagna region), subjected to a long ripening period (4-6 months) and characterised by a high content of wine and spices in the mixture. It can be consumed after cooking and it is served with its sugo, i.e. the liquid extracted by cooking process. The aim of this work was to set up a method for the sensory profile of Salama da sugo as a request for Protected Geographical Indication (PGI) has been made to the European Commission. RESULTS A system of sample preparation that provides for the precooking in an autoclave and cooking in boiling water was set up. A specific sheet for sensory evaluation of Salama da sugo has been created and reports 23 descriptors identified during the lexicon development. The differences in sensory profile of four samples were evaluated and principal component analysis highlighted the more discriminant parameters, i.e. odour intensity, wine odour, spicy aroma, fat/lean connection, sweet, bitter, juiciness, chewiness and pricking. CONCLUSIONS The proposed method allows the standardisation of sensory profiling of Salama da sugo, and is also to verify compliance with the specification PGI.