Use of essential oils and biocontrol cultures for the improvement of shelf-life of fresh cut products

The demand of minimally processed fruits and vegetables has increased in the last years. However, their intrinsic characteristics may favor the growth of pathogens and spoilage microbiota. The negative effects on human health reported for some traditional chemical sanitizers have justified the search for substitutes to guarantee food safety and quality. In this work we have evaluate the potential of some essential oils and their components to improve the safety and the shelf life of Lamb’s lettuce (Valerianella locusta) and apples (Golden delicious). Moreover, the effects of selected lactic acid bacteria alone or in combination with essential oils or their components, on the shelf-life and safety as well as organoleptic properties of minimally processed products, were evaluated. Since the lack of knowledge of microbial cell targets of essential oils represent one of the most important limit to the use of these molecules at industrial level, another aim of this thesis was the study of the action mechanisms of essential oils and their components. The results obtained showed the beneficial effects of the natural antimicrobials as well as the selected lactic acid bacteria on minimally processed fruit and vegetable safety and shelf-life, without detrimental effects on the quality parameters. The beneficial effects obtained by the use of the selected biocontrol agents were further increased combining them with selected natural antimicrobials. The natural antimicrobial employed induced noticeable modifications of membrane fatty acid profiles and volatile compounds produced by microbial cells during the growth. The modification of the expression in genes involved in fatty acid biosynthesis suggesting that the cytoplasmic membrane of microbial cells is one of the major cellular target of essential oils and their components. The comprehension of microbial stress response mechanisms can contribute to the scaling up of natural antimicrobials and bio-control agents at industrial level

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

Use of Yarrowia lipolytica to Obtain Fish Waste Functional Hydrolysates Rich in Flavoring Compounds

Fishery processing industries generate large amounts of by-products. These by-products come from fish heads, skin, bones, thorns, and viscera. The disposal of these wastes represents an increasing environmental and health problem. Nowadays, there is a growing interest in how to utilize fish materials that are not used for human consumption. Among the different solutions proposed, the use of proteolytic and lipolytic microorganisms represents a green solution for waste valorization. In this work, first we screened several conventional and non-conventioal microorganisms for their proteolytic and lipolytic functions. Then, the most promising strains (Yarrowia lipolytica YL2, Y. lipolytica YL4, Bacillus amyloliquefaciens B5M and B. subtilis B5C) were tested on a fish waste-based solution. After 72 h incubation at room temperature, the supernatants obtained using the strains of Y. lipolytica showed the highest degree of hydrolysis (10.03 and 11.80%, respectively, for YL2 and YL4), the strongest antioxidant activity (86.4% in DPPH assay for YL2) and the highest formation of aldehydes (above 50% of the total volatile compounds detected). Hydrolysates of fish waste obtained with Y. lipolytica may be reused in feed and food formulations for their functional and flavoring characteristics

Suitability of the Nisin Z-producer Lactococcus lactis subsp. lactis CBM 21 to be Used as an Adjunct Culture for Squacquerone Cheese Production

This research investigated the technological and safety effects of the nisin Z producer Lactococcus lactis subsp. lactis CBM 21, tested as an adjunct culture for the making of Squacquerone cheese in a pilot-scale plant. The biocontrol agent remained at a high level throughout the cheese refrigerated storage, without having a negative influence on the viability of the conventional Streptococcus thermophilus starter. The inclusion of CBM 21 in Squacquerone cheesemaking proved to be more effective compared to the traditional one, to reduce total coliforms and Pseudomonas spp. Moreover, the novel/innovative adjunct culture tested did not negatively modify the proteolytic patterns of Squacquerone cheese, but it gave rise to products with specific volatile and texture profiles. The cheese produced with CBM 21 was more appreciated by the panelists with respect to the traditional one

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

Effects of Sub-Lethal High Pressure Homogenization Treatment on the Adhesion Mechanisms and Stress Response Genes in Lactobacillus acidophilus 08

Cell surface hydrophobicity (CSH) and adhesion are very important phenotypical traits for probiotics that confer them a competitive advantage for the resilience in the human gastrointestinal tract. This study was aimed to understand the effects over time of a 50 MPa hyperbaric treatment on the surface properties of Lactobacillus acidophilus 08 including CSH, autoaggregation, and in vitro adhesion (mucin layer and Caco-2 cells). Moreover, a link between the hurdle applied and the expression of genes involved in the general stress response (groEL and clpP) and adhesion processes (efTu and slpA) was evaluated. High pressure homogenization (HPH) at 50 MPa significantly increased the CSH percentage (H%), autoaggregation and in vitro adhesion on mucin of L. acidophilus 08 cells compared with the untreated cells. Moreover, the hyperbaric hurdle induced an upregulation of the stress response genes groEL and ef-TU together with a down regulation of the clpP and S-layer slpA genes. Looking at the protein profile, HPHtreatment showed an increase in the number or intensity of protein bands at high and low molecular weights

Ultrasound assisted osmotic dehydration of organic cranberries (Vaccinium oxycoccus): Study on quality parameters evolution during storage.

Cranberries are appreciated for their high amount of antioxidants such as flavonoids, anthocyanins,phenolic acids, carotenoids and vitamins. However, due to their sour and tart taste they request to beprocessed into sweeter dried fruits in order to be acceptable for the consumers. The aim of this work wasto analyse the effect of ultrasound assisted osmotic dehydration on mass transfer parameters and onquality characteristics during storage of cranberries. Ultrasound treatment was performed at the fre-quency of 21 kHz for 30 min in three osmotic solutions - 61.5% sucrose, 30% sucrose with an addition of0.1% of steviol glycosides and 40% trehalose on cut in half cranberries. Afterwards, the cranberry sampleswere subjected to osmotic dehydration process at 40C for 72 h. The osmodehydrated samples both withor without ultrasound pre-treatment were collected and stored at 10C in climatic chamber in micro-perforated plastic bags (PLA) for 8 weeks. The weight reduction, dry matter, water activity, colour, andmicrobiological analysis were performed after 1, 2, 4 and 8 weeks of storage. The obtained resultsindicated that ultrasound application significantly affected the mass transfer parameters during osmotictreatment, as well as it did the type of osmotic solution used. Thermal analysis showed variations insugar melting temperature and enthalpy as a result of osmotic treatment and storage. During the storage,lower weight loss and higher lightness were observed in US pre-treated samples. The sample thatpreserved the best chemico-physical and microbiological characteristics during storage was the onetreated with 61.5% sucrose solution, due to its lowest water activity

Unravelling the Potential of Lactococcus lactis Strains to Be Used in Cheesemaking Production as Biocontrol Agents

This research, developed within an exchange program between Italy and Canada, represents the first step of a three-year project intended to evaluate the potential of nisin-producing Lactococcus lactis strains isolated from Italian and Canadian dairy products to select a consortium of strains to be used as biocontrol agents in Crescenza and Cheddar cheese production. In this framework, the acidification and the production of nisin in milk, and the volatile molecule profiles of the fermented milk, were recorded. The strains were further tested for their anti-Listeria monocytogenes activity in milk. The data obtained highlighted good potential for some of the tested strains, which showed production of nisin beginning within 12 h after the inoculation and reaching maximum levels between 24 and 48 h. The highest inactivation levels of L. monocytogenes in milk was reached in the presence of the strains 101877/1, LBG2, 9FS16, 11FS16, 3LC39, FBG1P, UL36, UL720, UL35. The strains generated in milk-specific volatile profiles and differences in the presence of fundamental aromatic molecules of dairy products, such as 2-butanone and diacetyl. The results highlight the interesting potential of some L. lactis strains, the producer of nisin, to be further used as biocontrol agents, although the strains need to be tested for interaction with traditional thermophilic starters and tested in real cheesemaking conditions

Antioxidant and Functional Features of Pre-Fermented Ingredients Obtained by the Fermentation of Milling By-Products

The use of milling by-products as ingredients in food formulations has increased gradually over the past years, due to their well-recognized health properties. Fermentation performed with selected microbial strains or microbial consortia is the most promising way to reduce antinutritional factors of cereals and bran, while increasing their nutritional and functional properties. This work, developed within the BBI project INGREEN, was aimed to study the functional, nutritional and technological features of a pre-fermented ingredient obtained from the fermentation of a mixture of rye bran and wheat germ by a selected microbial consortium composed of yeasts (Kazachstania unispora and Kazachstania servazii) and lactic acid bacteria (Latilactobacillus curvatus) using as reference the unfermented mixture and the same mixture fermented by a baker’s yeast. The selected microbial consortium improved the complexity of the volatile molecules such as acids, alcohols and esters. A better retention of color parameters was maintained compared to the product fermented by a baker’s yeast. In addition, the fermentation by the selected consortium showed a significant increase in short chain fatty acids (more than 5-fold), antioxidant activity (22– 24%), total phenol content (53–71%), bioactive peptides (39–52%), a reduction of 20–28% in phytic acid content and an increase in prebiotic activity not only compared to the unfermented product but also compared to the preferment obtained with a baker’s yeast. Overall, the fermentation by the selected microbial consortium can be considered a valuable way to valorize milling by-products and promote their exploitation as food ingredients

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