Dynamic Stresses of Lactic Acid Bacteria Associated to Fermentation Processes

Despite their negligible mass the microbial agents, starters and non starters, play a profound role in the characterization of the fermented foods in terms of chemical and sensorial properties. In fact, fermented foods may be defined as foods processed through the activity of microorganisms. Fermentation processes take a special place in the evolution of human cuisine, by altering the taste experience of food products, as well as extending the storage period. In particular, foods fermented with lactic acid bacteria (LAB) have constituted an important part of human diet and of fermentation processes (involving various foods, including milk, meat, vegetables and fruits) since ancient times. They have played an essential role in the preservation of agricultural resources and in the improvement of nutritional and organoleptic properties of human foods and animal feed. Moreover, these organisms nowadays are increasingly used as health promoting probiotics, enzyme and metabolite factories and vaccine delivery vehicles

Potential of High Pressure Homogenization and Functional Strains for the Development of Novel Functional Dairy Foods

Functional foods are one of the fastest increasing fields in the global food industry since they are positively perceived by the consumers as dietary strategies to reduce the incidence of illness in the humankind. Actually, the use of biotechnological strategies, based on the use of functional and specific strains and sustainable technologies, such as high-pressure homogenization, can be a great chance to create innovation in the dairy field. Critical discussion on the actual scenario is the main topic of this chapter

Primi risultati del progetto LIFE+ sulle analisi microbiologiche delle acque nel Parco dei Gessi dell’Emilia Romagna

Dal 2010 è in corso il Progetto Life + 08NAT/IT/000369 “Gypsum” 2, cofinanziato dall’Unione Europea, finalizzato alla tutela e gestione dei principali ambienti gessosi dell’Emilia Romagna. Nell’ambito dell’Azione A3 è previsto un monitoraggio pluriennale dei principali acquiferi carsici sotto l’aspetto chimico e microbiologico. Nel corso del primo anno sono state analizzate le acque carsiche su circa 50 punti di controllo (inghiottitoi, fiumi, torrenti in grotta, e risorgenti). In generale l’obiettivo di questa sperimentazione è quello di valutare l’impatto di sostanze di origine agricola o di altre forme di inquinamento, legate ad insediamenti o attività antropiche o fattori naturali, in acque di grotta. La sperimentazione è stata sviluppata tramite tecniche microbiologiche classiche e di biologia molecolare (PCR 16S rRNA e PCR-DGGE), finalizzate alla caratterizzazione delle popolazioni microbiche presenti nei diversi siti di prelievo e alla determinazione di loro eventuali variazioni e/o evoluzioni. I valori di carica microbica totale determinati oscillavano da un massimo di 3.32 ad un minimo di 0.18 log UFC/ ml e da un massimo di 2.26 fino a valori al di sotto del limite di determinazione (1 log UFC/ml) per quanto riguarda i coliformi totali e fecali. Le analisi genetiche hanno mostrato la presenza di numerosi specie batteriche (Agrobacterium tumefaciens, Pseudomonas spp., Rahnella aquatilis, Stenotrophomonas maltophilia, Pedobacter swuonensis, Enterobacter spp., Aeromonas hydrophila, Citrobacter, Klebsiella and Raoultella). I microrganismi identificati possono avere diverse origini, alcuni provengono dal terreno, altri possono essere comuni contaminanti delle acque ed altri avere un’origine antropica (batteri fecali). Fino a questo step del progetto, l’analisi PCR-DGGE ha evidenziato le evoluzioni ecologiche, in termine di popolazioni microbiche, presenti tra i diversi campioni e i diversi siti di campionamento all’interno di una stessa grotta.The Project Life + 08NAT/IT/000369 “Gypsum” 2, co-financed by the European Union, has started in the spring of 2010. This project aims to protect and manage the main karst caves and sites of Emilia-Romagna region. The A3 action provides a periodic monitoring of the main karst aquifers in terms of chemistry and microbiology. During the first year and a half, karst waters of 50 control points were analysed (sinking streams, rivers and streams in caves, and resurgences). The objective of this study is to evaluate the impact, in the waters of the cave, of agricultural substances or other forms of pollution or settlements related to human activities or natural factors. The experiment was developed using traditional microbiology techniques and molecular biology techniques (PCR and 16S rRNA PCR-DGGE), focused on the characterization of microbial populations in the different sampling sites and determination of their variations and/or changes. The total microbial concentration ranged from a maxiimum of 3.32 or 2.26 to values below the limit of detection (1 log CFU/ml) for total and faecal colifroms, respectively. The genetic analysis showed the presence of numerous bacterial species (Agrobacterium tumefaciens, Pseudomonas spp., Rahnella aquatilis, Stenotrophomonas maltophilia, Pedobacter swuonensis, Enterobacter spp., Aeromonas hydrophila, Citrobacter, Klebsiella and Raoultella). The organisms identified have different origins, some come from the ground, others are common water contaminants and others derive from human activities (faecal bacteria). Up to now, PCR-DGGE revealed the ecological changes, in terms of microbial populations present in the samples, and different sampling sites within the same cave

Use of Lactobacillus crispatus to produce a probiotic cheese as potential gender food for preventing gynaecological infections

This research is aimed to evaluate the suitability of Squacquerone cheese to support the viability of Lactobacillus crispatus BC4, a vaginal strain endowed with a strong antimicrobial activity against urogenital pathogens and foodborne microorganisms, in order to recommend a gender food for woman wellbeing. The viability of L. crispatus BC4, used as adjunct culture, was evaluated during the refrigerated storage of Squacquerone cheese, as well as when the cheese was subjected to simulated stomach-duodenum passage tested by the patented Simulator of the Human Intestinal Microbial Ecosystem (SHIME). Moreover, the effects of L. crispatus BC4 addition were evaluated on product hydrolytic patterns, in terms of proteolysis, lipolysis and volatile molecule profiles. The data showed that L. crispatus BC4 maintained high viability, also in presence of physiological stress conditions, until the end of the refrigerated storage. Moreover, the inclusion of L. crispatus BC4 gave rise to cheese product with higher score of overall acceptability when compared to control cheese. In addition, the survival of L. crispatus BC4, carried in test cheese, in gastro intestinal conditions was confirmed by SHIME. The results showed that the vaginal Lactobacillus strain was more affected by the low pH of the stomach, simulated by the SHIME reactor, rather than to bile salts and pancreatic juices. Although only in vivo trials will be able to confirm the functionality of the cheese in the vaginal environment, these data represent a first step towards the employment of the Squacquerone cheese as probiotic food able to promote the woman's health by preventing gynaecological infections

New bread formulation with improved rheological properties and longer shelf-life by the combined use of transglutaminase and sourdough

The combined use of the protein reticulating enzyme transglutaminase (TGase) and a selected microbial consortium of Lactobacillus sanfranciscensis and Candida milleri for improving the rheological properties, aroma, and shelf-life of a bakery product was evaluated. A microbial TGase, showing the highest activity over a wide temperature range on different protein substrates, was selected among different types. Results showed that this TGase was able to produce isodipeptide bonds, especially in the gluten fraction, leading to the formation of protein aggregates, which improved the structure of a sourdough bakery product. The microbial TGase in combination with sourdough exhibited a positive synergistic effect allowing the production of flavor-enriched bread, with rheological properties similar to those of standard bread

Potential of Natural Antimicrobials for the Production of Minimally Processed Fresh-Cut Apples

Background: Minimally processed fruit are susceptible to microbial spoilage and loss of sensory quality. In this experimental work, in order to increase the shelf-life and to maintain quality parameter (texture and colour) of sliced apples (Malus communis, var. Golden delicious), the use of natural antimicrobials was proposed. Materials and methods: Natural antimicrobials were purposed to produce fresh-cut apples. Hexanal, citral, and combinations of hexanal+citral, citron essential oil+carvacrol, citral+2-(E)-hexenal, citral+citron essential oil and hexanal+2- (E)-hexenal were used in dipping step. After treatment, sample were stored at 6°C in ordinary atmosphere. During storage, yeast and lactic acid bacteria were monitored. Also volatile and electronic nose profiles, colour and texture analyses were considered. The samples were compared with a control (apples dipped in ascorbic and citric acid solution). Results: Yeast cell loads showed that natural antimicrobials changed naturally occurring yeast growth parameters. The combination of citron+carvacrol prolonged the yeast lag phase of 6 d comparing with control, while citral and hexanal+2-(E)- hexenal decreased the maximum reached yeast cell load and growth rate, respectively. After 8 d, samples with hexanal+2-(E)- hexenal and citral showed equivalent or even better quality attributes compared to the controls, suggesting that this approach is a useful tool for fresh-cut apple production. Highlight: Natural antimicrobial can be useful for the dipping of minimally processed apples Citral and hexanal+2-(E)-hexenal prolonged the apples shelf-life. Apples treated with Citral and hexanal+2-(E)-hexenal had good quality attributes

Cinetica della fermentazione alcolica e arresti di fermentazione

Cinetica della fermentazione alcolica e arresti di fermentazione (Maria Elisabetta Guerzoni, Diana Isabella Serrazanetti) ............................................................ “ 57 4.1 Introduzione .......................................................................................................................... “ 57 4.2 Dipendenza dal ceppo .......................................................................................................... “ 58 4.3 Risposta agli stress ................................................................................................................ “ 60 4.3.1 Stress osmotico .......................................................................................................... “ 60 4.3.2 Stress nutrizionale ...................................................................................................... “ 61 4.4 Importanza e frequenza degli arresti di fermentazione ......................................................... “ 62 4.5 Possibili fattori causali delle fermentazioni problematiche ................................................... “ 63 4.6 Ioni e squilibro ionico ............................................................................................................ “ 65 4.7 Temperatura e processi fermentativi ..................................................................................... “ 67 4.8 Etanolo e membrane cellulari ............................................................................................... “ 69 4.9 Conclusioni ............................................................................................................................ “ 71 Bibliografia ............................................................................................................................ “ 72Il Volume, a cui hanno collaborato ricercatori italiani noti per i loro studi nel campo, vuole fissare lo stato dell\u92arte sottolineando gli aspetti più rilevanti della ricerca. Tra gli argomenti principali trattati nel testo figurano l\u92ecologia microbica delle uve e dei mosti d\u92uva, le interazioni e gli aspetti metabolici positivi e negativi della crescita microbica sulla qualità e tipicità dei vini e sulla produzione di alcuni vini speciali. Particolare attenzione è stata data alla tassonomia, fisiologia, metabolismo, genomica di Saccharomyces cerevisiae. Principali argomenti trattati nel Volume: La fermentazione spontanea \u96 Saccharomyces cerevisiae \u96 Saccharomyces cerevisiae: metabolismo primario e produzione di aromi nel vino \u96 Cinetica della fermentazione alcolica e arresti di fermentazione \u96 La rifermentazione dei vini \u96 I vini ad invecchiamento biologico \u96 I lieviti non-Saccharomyces \u96 Batteri lattici nel vino \u96 I batteri acetici \u96 Ricerca, identificazione e caratterizzazione dei lieviti vinari \u96 Uso di colture starter e impiego di lieviti e batteri lattici in cantina \u96 Botrytis cinerea, marciume nobile e marciume grigio

2-methyibutyric and 3-methylbutyric acids: possible components of a feed back loop under stress conditions?

The exposure of lactic acid bacteria (LAB) to stressful conditions during fermentation involves a broad transcriptional response with many induced or repressed genes. The complex network of such responses will reflect upon the composition and organoleptic properties of the dough and final products. The over-production of 2-methylbutyric (2MetBut) and 3-methylbutyric (3MetBut) acids, by LAB, has been detected following exposure to different sublethal stress conditions. Serrazanetti et al. (2011) reported the over-production of these two compounds in Lactobacillus sanfranciscensis during acidic stress when the cells were grown in the presence of leucine (Leu) as the only branched chain amino acids (BCAAs) source. Metabolites coming from BCAAs catabolism increased up to seven times under acid stress (pH 3.6 and 5.8). Moreover, the gene expression analysis confirmed that some genes associated with BCAAs catabolism were overexpressed under acid conditions. The experiment with labelled Leu showed that 2MetBut originated also from Leu. While the overproduction of 3MetBut under acid stress can be attributed to the need to maintain a redox balance, the rationale for the production of 2MetBut from Leu can be found in a newly proposed biosynthesis pathway leading to 2MetBut and 3 mol of ATP per mol of Leu. But why do LAB need to catabolize in excess BCAAs in the presence of sublethal stress if they do not generate energy? A possible answer, suggested by Goffin et al. (2010), lies in the end products of BCAAs catabolism, a number of which could serve as signalling molecules for the interaction of Lactobacillus plantarum with its environment and maybe itself. In order to support this hypothesis the possible signalling-effect of 2MetBut and 3MetBut on the growth and the metabolism of some strains of LAB has been investigated. In particular, L. plantarum, L. sanfranciscensis and Lactobacillus brevis were exposed to BCAAs catabolism end products for 2 and 24 hours after which the volatile metabolites and the expression of some genes involved in Leu catabolism were analysed by GC-MS-SPME and RT-PCR, respectively