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

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

Physiology and Biochemistry of Sourdough Yeasts

The cereal dough is a dynamic system which is characterised by continuous changes in nutrients availability and physic-chemical condition changes. Depending on the type of flour and bread making technology, starvation conditions can be also envisaged. The imbalance between yeast consumption and starch hydrolysis might lead to the rapid depletion of soluble carbohydrates. Overall, microbial starvation induces a quiescent state whose length is conditioned by the presence of the limiting factors. Yeast responds to a changing environment not with a small adjustment in a key control points but with the coherent transcriptional relation as a large set of genes. During fermentation of sourdough yeasts cells may encounter different environmental states. Co-fermentation with lactic acid bacteria and yeasts determines environmental fluctuations not only of availability of nutrients, but also of organic acids concentration, decrease of pH and changes on the texture profile. Maintaining optimal functionality in the presence of such external variability is a central evolutionary constraint. The exposure of microbial cells to stressful and fluctuating conditions during fermentation involves a broad transcriptional response with many induced or repressed genes. The selective pressure exerted by the environmental conditions encountered by yeast cells during sourdough fermentation, accounts for the consolidated dominance of selected yeast species, such as in particular C. milleri and S. cerevisiae. The nutrient availability or limitations are likely the factors that modulate the microbial ecology of sourdough. However, within the sourdough ecosystem there are numerous mechanisms whereby one species may influence the growth of another species. The chapter describe the stress response, of those species, to nutrient availability (starvation), DY, pH (acid stress), presence of sugars, salts and polysaccharides (osmotic stress), oxygen (oxidative stress), temperature fluctuations (heat shock and cold stress) and interactions between lactic acid bacteria and yeasts (e.g., S. cerevisiae, C. milleri and L. sanfranciscensis), and between yeasts (e.g., S. cerevisiae and C. milleri). Moreover, both environmental process parameters and the interaction with lactic acid bacteria affect the metabolism of yeast in terms of fusel alcohols and namely branched chain amino acids metabolites, carbonyl compounds and unsaturated fatty acids oxidation products and induce also the inter-species signalling molecules production. An overview of baker\u2019s yeast in bread making industry is also included. Traditional cultivation methods in combination with phenotypic and genotypic identification adopted to characterize the yeasts of ripe dough revealed the presence of more then 2, 3 species belonging especially to the genera Saccharomyces and Candid

Innovative strategies based on the use of essential oils and their components to improve safety, shelf-life and quality of minimally processed fruits and vegetables

Minimally processed fruits and vegetables are one of the major growing sector in food industry. Although important for their nutritional values and convenience, their composition and physicochemical properties affect their microbiological shelf life and overall quality. On the other hand, processing steps as washing, if well performed, can partially reduce the occurring microflora and the use of sanitizers are perceived negatively by the consumers. For this reasons, researchers have proposed some alternatives to the use of traditional sanitizers, such as essential oils which are complex mixtures of volatile compounds, characterized by a strong sensorial impact and produced by many plants as secondary metabolites. In this perspective, this review discusses the growing importance of minimally processed fruits and vegetables and the potential application of essential oils and their components as natural antimicrobial. Finally, the mechanisms of action of these molecules have being reviewed taking into account their use in food systems

Effects of PBS-based packaging on the shelf-life and spoilage profiles of soft cheeses

The intense use and accumulation of non-degradable plastics, which leads to the growing problem of waste disposal, and the lowering in the availability of fossil resources have strongly increased the interest and efforts in using renewable resources to develop biodegradable-based packaging materials. A number of bio-based materials and their innovative applications in food-related packaging have therefore gained much attention over the past several years. The main bio-sourced polymer currently used in food packaging is polylactic acid, but polybutylene succinate (PBS) can be considered a promising polymer from renewable resources for packaging industry for the coming years due to the prediction of a large development of succinic acid production by fermentation of gluco-based resources. The potentialities of PBS in this area are explored within the EU project SUCCIPACK (Grant agreement 289196) which aims to develop sustainable, active, and intelligent food packaging materials based on green PBS that can be flexibly used by packaging and food industries. Aspect that are taken into consideration include the optimization of the synthesis and compounding of polymer and copolymer grades for industrial plastic transformation processes to obtain films, trays and pouches. Also tailored packaging functionalities are obtained through surface treatments to control gas barrier properties and introduce antimicrobials. The performance of the novel packaging materials are assessed for selected food products, including soft cheeses, raw meat, fish products, ready-to-eat vegetables and ready meals for vegetarian. The objective of this preliminary work was to test the effects of PBS packaging material on the shelf-life of two soft cheeses such as ricotta and squacquerone. In particular microbial populations, volatile organic compounds, color and sensory properties were monitored over a 20-days storage at 4\ub0C and compared to control products packaged with the traditional materials. Microbial data of the evolution of main spoilage microorganisms were modelled with the Gompertz equation to calculate the products shelf-life and evaluate possible shifts in microbial population due to the innovative packaging. Volatile microbial metabolites were determined by electronic nose and solid-phase micro-extraction gaschromatography/mass-spectrometry (SPME/GC-MS) analysis. Also the real oxygen permeability of the whole packaged products was measured. The comparison of all the data collected showed that the packaging material and conditions used affected the microbiota and its evolution during storage resulting in significant differences in the volatile metabolites released with a potential impact on cheese sensory attributes