Manuela Giordano

CIEL *a *b * parameters of white dehydrated grapes as quality markers according to chemical composition, volatile profile and mechanical properties

In the oenological sector, the withering process is of particular importance in the production of dry and sweet dessert wines due to the total or partial use of overripe and/or dehydrated grapes. This complex process leads to several changes in the chemical-physical characteristics of white grape berries affecting the wine quality and, at the end of the dehydration period, different visual attributes are usually present in the berry skins. The aim of this work, therefore, was to study the properties of Erbaluce dried grapes of varying external colors, classified into three groups based on reflectance colorimetry (green, gold and blue). The chemical composition, volatile profile and mechanical attributes were investigated, focusing on establishing relationships between CIEL*a*b* parameters of dehydrated grapes and their chemical-physical characteristics. The higher values of the glucose-fructose ratio, together with the higher content of sugars, gluconic acid and glycerol, but lower titratable acidity, suggests the presence of Botrytis cinerea Pers. infection in blue withered berries, which has been microbiologically confirmed. Regarding the instrumental mechanical properties, blue dehydrated grapes were characterized by a lower skin hardness and higher skin thickness in agreement with the higher weight loss experienced. Finally, the determination of free and bound volatile compounds showed that some of them were only found in blue withered berries, δ-lactones being considered the main chemical markers of the noble rot infection that are important for the odor character. C-10 alkyl massoia lactone was the most abundant volatile compound in blue botrytized grapes.

Phenolic Content, Antioxidant Potential, and Antimicrobial Activities of Fruit and Vegetable By-Product Extracts

The use of fruit and vegetable by-products as natural food additives has recently been suggested, due to their richness in polyphenols. The aim of this research study was to determine polyphenolic content and the antioxidative and antimicrobial activities of 13 fruit and vegetable by-product extracts obtained with three solvent mixtures. The Folin-Ciocalteu method was employed to calculate the total phenolic content, while antioxidant capacity was assessed with DPPH· and ABTS ·+. The highest total phenolic content and antioxidant capacity values were obtained for the acetonic extracts. Pomegranate peels and hazelnut skins showed the highest values of total phenolic content (212.3 and 166.3 mg GAE/g dw, respectively) and antioxidant capacity (95.7 and 92.9 of inhibition percentage, respectively, for DPPH· assay). The antimicrobial activity against twelve foodborne pathogens and spoilage microorganisms was evaluated. Pomegranate and apple peels showed the highest inhibition of Staphylococcus aureus and Pseudomonas fluorescens. The results obtained demonstrated that by-products could be used as natural food additives with beneficial health properties.

Prevalence and Biodiversity of Brettanomyces bruxellensis in Wine from Northwestern Italy

Brettanomyces bruxellensis is a catalyst in the transformation of hydroxycinnamic acids, compounds that naturally occur in grapes, producing volatile phenols that reduce the sensory quality of wine. Depending on their concentrations, volatile phenols can confer off-odors described as phenolic, animal, mousy, wet wool, medicinal, smoky, and spicy. We used a multidisciplinary approach for the detection and quantification of the presence of B. bruxellensis in 87 Italian wines, applying culture-independent and dependent methods (quantitative PCR and traditional microbiological analysis, respectively). Headspace solid-phase microextraction was used to quantify ethylphenols and vinylphenols. Results showed that there was no correlation between culture-dependent and culture-independent methods. Strain biodiversity was investigated by SAU-PCR and showed a differentiation of the isolates based on geographical origin.

Use of response surface methodology for the assessment of changes in the volatile composition of Moscato bianco (Vitis vinifera L.) grape berries during ripening.

The changes in the volatile composition of Moscato bianco grapes were evaluated during ripening. Grape berries were sampled for five weeks (16-20 °Brix) and sorted for each date in ten density classes (1.05-1.12g/cm(3)). The highest total concentration of free terpenes was found at 19.3 °Brix; however, total concentration of the bound fraction increased significantly throughout ripening. Response surface methodology was used to assess the simultaneous effect of sampling time and berry density on the volatile composition, which was satisfactorily fitted to regression models for some key terpene compounds. Total free and bound terpenes were more affected by grape density than by sampling date. The same behaviour was observed for free and bound linalool and bound nerol, whereas the stronger effect of sampling date was exhibited for bound t-rose oxide, c-rose oxide and geraniol. The results showed that the sampling strategy impacted strongly on the aroma quality of berries.

Chemical, mechanical and sensory monitoring of hot air- and infrared-roasted hazelnuts (Corylus avellana L.) during nine months of storage

Roasted hazelnuts can be consumed as whole nuts, or as an ingredient in the confectionary and bakery industries and are highly appreciated for their typical taste, aroma and crunchy texture. In this work, two hazelnut types (TGT, Ordu) from two harvests were roasted using two different systems (hot air, infrared) at different time/temperature combinations, and the evolution of oxidative stability, the total phenolic content (TPC), the antioxidant capacity, the mechanical and acoustic properties and the sensory perception were determined during storage. The results showed that the oxidative stability was increased by roasting hazelnuts at 120°C for 40min with hot air system. Similar overall trends were not found for the TPC, the antioxidant capacity and the mechanical-acoustic properties. However, for the maintenance of high antioxidant activity, a storage time of 6months at 4°C is recommended. The two roasting systems gave hazelnuts with significant sensory differences only at high roasting temperature.

Shotgun Metagenomics and Volatilome Profile of the Microbiota of Fermented Sausages

ABSTRACT Changes in the microbial gene content and abundance can be analyzed to detect shifts in the microbiota composition due to the use of a starter culture in the food fermentation process, with the consequent shift of key metabolic pathways directly connected with product acceptance. Meat fermentation is a complex process involving microbes that metabolize the main components in meat. The breakdown of carbohydrates, proteins, and lipids can lead to the formation of volatile organic compounds (VOCs) that can drastically affect the organoleptic characteristics of the final products. The present meta-analysis, performed with the shotgun DNA metagenomic approach, focuses on studying the microbiota and its gene content in an Italian fermented sausage produced by using a commercial starter culture (a mix of Lactobacillus sakei and Staphylococcus xylosus), with the aim to discover the connections between the microbiota, microbiome, and the release of volatile metabolites during ripening. The inoculated fermentation with the starter culture limited the development of Enterobacteriaceae and reduced the microbial diversity compared to that from spontaneous fermentation. KEGG database genes associated with the reduction of acetaldehyde to ethanol (EC 1.1.1.1), acetyl phosphate to acetate (EC 2.7.2.1), and 2,3-butanediol to acetoin (EC 1.1.1.4) were most abundant in inoculated samples (I) compared to those in spontaneous fermentation samples (S). The volatilome profiles were highly consistent with the abundance of the genes; elevated acetic acid (1,173.85 μg/kg), ethyl acetate (251.58 μg/kg), and acetoin (1,100.19 μg/kg) were observed in the presence of the starters at the end of fermentation. Significant differences were found in the liking of samples based on flavor and odor, suggesting a higher preference by consumers for the spontaneous fermentation samples. Inoculated samples exhibited the lowest scores for the liking data, which were clearly associated with the highest concentration of acetic acid. IMPORTANCE We present an advance in the understanding of meat fermentation by coupling DNA sequencing metagenomics and metabolomics approaches to describe the microbial function during this process. Very few studies using this global approach have been dedicated to food, and none have examined sausage fermentation, underlying the originality of the study. The starter culture drastically affected the organoleptic properties of the products. This finding underlines the importance of starter culture selection that takes into consideration the functional characteristics of the microorganism to optimize production efficiency and product quality.

Potentially active spoilage bacteria community during the storage of vacuum packaged beefsteaks treated with aqueous ozone and electrolyzed water

The microbial contamination that occurs during the slaughtering process and during handling of the meat results in a shortening of the shelf-life of meat. In this study, which has had the aim of extending the shelf life of beefsteaks, pilot-scale treatments were carried out with aqueous ozone (AO) and electrolyzed water (EW) before vacuum packaging (VP). The development of the potentially active microbiota and the associated volatilome were followed over 15days of storage under refrigerated conditions (4°C), in order to define the potential long-term effects of the treatments and storage condition on microbiota. The targeted RNA-based amplicon sequencing identified Pseudomonas fragi as the most frequent species before and after the treatments with AO and EW, as well as in the untreated control. The tested treatments did not reduce the overall presence of this species, but they affected the intra-species distribution of its oligotypes, albeit slightly. With the progression of the refrigerated storage and the reduction of the oxygen availability, Lactobacillus sakei, Leuconostoc gasicomitatum and Lactococcus piscium became the dominant, potentially active, beef microbiota, as confirmed by microbiological data. When the OTU abundances and volatilome were coupled, a significant association was observed between the organic acids, esters and aldehydes and these lactic acid bacteria species. In spite of the limited effectiveness of the treatments over the short and long term, this study has provided a detailed view of beef spoilage using RNA as the sequencing target, strengthening and confirming the current knowledge based on DNA-amplicon sequencing.

On-vine withering process of ‘Moscato bianco’ grapes: effect of cane-cut system on volatile composition: On-vine withering process of ‘Moscato bianco’ grapes

BACKGROUND Cane-cut on-vine withering is a grape dehydration technique used for dry and sweet wine production. The aim of this work was to study the influence of the cane-cut technique applied at harvest to Moscato bianco grapes during the on-vine withering process to produce dehydrated berries with a different chemical composition and a volatile profile. RESULTS After 24 days of dehydration, an on-vine withering system using the cane-cut technique induced an increase in the total volatile content compared with grapes produced with a normal on-vine withering process. This increase was greater in glycosidically bound volatile compounds than in the free fraction. Bound linalool showed a significant increase of 52% when the cane-cut withering system was applied but the grapes that were normally withered appeared to be less prone to the loss of free linalool. A significant increase in the glycosylated forms of nerol and geraniol was also observed in the two on-vine withering systems on the 24th day compared with the control (fresh grapes at harvest date). CONCLUSION A cane-cut, on-vine withering system applied at harvest induced changes in the volatile composition of Moscato bianco grapes increasing total volatile content, consisting mainly of bound compounds, by the 24th day of dehydration. The grapes dehydrated on-vine using this new system also showed significantly greater content of most of the free volatile compounds detected.

Dynamics and Biodiversity of Bacterial and Yeast Communities during Fermentation of Cocoa Beans

In spite of the limited effectiveness of the considered inoculated starter strains, this study provides new information on the microbial development of box and heap cocoa fermentations, under inoculated and noninoculated conditions, as we coupled yeast/bacterial amplicon-based sequencing data with microbial metabolite detection. The information so far available suggests that microbial communities have played an important role in the evolution of aroma compounds. Understanding the pathways that microorganisms follow during the formation of aromas could be used to improve the fermentation processes and to enhance chocolate quality. ABSTRACT Forastero hybrid cocoa bean fermentations have been carried out in a box (B) and in a heap (H), with or without the inoculation of Saccharomyces cerevisiae and Torulaspora delbrueckii as starter cultures. The bacteria, yeasts, and microbial metabolites (volatile and nonvolatile organic compounds) were monitored during fermentation to assess the connection between microbiota and the release of metabolites during this process. The presence of starter cultures was detected, by means of culture-dependent analysis, during the first 2 days of both fermentations. However, no statistical difference was observed in any of the physicochemical or microbiological analyses. Plate counts revealed the dominance of yeasts at the beginning of both fermentations, and these were followed by acetic acid bacteria (AAB) and lactic acid bacteria (LAB). Hanseniaspora opuntiae, S. cerevisiae, Pichia pijperi, Acetobacter pasteurianus, and Lactobacillus fermentum were the most abundant operational taxonomic units (OTUs) during both fermentation processes (B and H), although different relative abundances were observed. Only the diversity of the fungal species indicated a higher level of complexity in the B fermentations than in the H fermentations (P < 0.05), as well as a statistically significant difference between the initially inoculated starter cultures (P < 0.01). However, the microbial metabolite analysis indicated different distributions of the volatile and nonvolatile compounds between the two procedures, that is, B and H (P < 0.05), rather than between the inoculated and noninoculated fermentations. The box fermentations showed faster carbohydrate metabolism and greater production of organic acid compounds, which boosted the formation of alcohols and esters, than did the heap fermentations. Overall, the microbial dynamics and associations between the bacteria, yeasts, and metabolites were found to depend on the type of fermentation. IMPORTANCE In spite of the limited effectiveness of the considered inoculated starter strains, this study provides new information on the microbial development of box and heap cocoa fermentations, under inoculated and noninoculated conditions, as we coupled yeast/bacterial amplicon-based sequencing data with microbial metabolite detection. The information so far available suggests that microbial communities have played an important role in the evolution of aroma compounds. Understanding the pathways that microorganisms follow during the formation of aromas could be used to improve the fermentation processes and to enhance chocolate quality.