Demo-scale up-flow anaerobic sludge blanket reactor coupled with hybrid constructed wetlands for energy-carbon efficient agricultural wastewater reuse in decentralized scenarios.

The impact of climate change on water availability and quality has affected agricultural irrigation. The use of treated wastewater can alleviate water in agriculture. Nevertheless, it is imperative to ensure proper treatment of wastewater before reuse, in compliance with current regulations of this practice. In decentralized agricultural scenarios, the lack of adequate treatment facilities poses a challenge in providing treated wastewater for irrigation. Hence, there is a critical need to develop and implement innovative, feasible, and sustainable treatment solutions to secure the use of this alternative water source. This study proposes the integration of intensive treatment solutions and natural treatment systems, specifically, the combination of up-flow anaerobic sludge blanket reactor (UASB), anaerobic membrane bioreactor (AnMBR), constructed wetlands (CWs), and ultraviolet (UV) disinfection. For this purpose, a novel demo-scale plant was designed, constructed and implemented to test wastewater treatment and evaluate the capability of the proposed system to provide an effluent with a quality in compliance with the current European wastewater reuse regulatory framework. In addition, carbon-sequestration and energy analyses were conducted to assess the sustainability of the proposed treatment approach. This research confirmed that UASB rector can be employed for biogas production (2.5 L h-1) and energy recovery from organic matter degradation, but its effluent requires further treatment steps to be reused in agricultural irrigation. The AnMBR effluent complied with class A standards for E. coli, boasting a concentration of 0 CFU 100 mL-1, and nearly negligible TSS levels. However, further reduction of BOD5 (35 mg L-1) is required to reach water quality class A. CWs efficiently produced effluent with BOD5 below 10 mg L-1 and TSS close to 0 mg L-1, making it suitable for water reuse and meeting class A standards. Furthermore, CWs demonstrated significantly higher energy efficiency compared to intensive treatment systems. Nonetheless, the inclusion of a UV disinfection unit after CWs was required to attain water class B standards.

Effect of Combined High-Pressure Homogenization and Biotechnological Processes on Chitin, Protein, and Antioxidant Activity of Cricket Powder-Based Ingredients.

The main objective of this work was to evaluate the combined effect of a biotechnology process, based on selected yeast strains, and a high-pressure homogenization (HPH) treatment on the microbiological quality, structural organization of proteins, chitin content, and antioxidant activity of a mixture of cricket powder (Acheta domesticus) and water. Compared to untreated samples, the cricket matrix treated with HPH four times at 180 MPa promoted the growth of the inoculated Yarrowia lipolytica and Debaryomyces hansenii strains. HPH did not affect the concentration of chitin; however, the combination with microorganisms tended to reduce the content. Although the antioxidant activity increased from 0.52 to 0.68 TAC mM/TE after a 48 h incubation in the control, it was further improved by the combination of HPH and D. hansenii metabolism, reaching a value of 0.77 TAC mM/TE. The combination of the two approaches also promoted a reduction in the intensity of bands with molecular weights between 31 and 21.5 kDa in favor of bands with a lower molecular weight. In addition, HPH treatment reduced the number of accessible thiols, suggesting protein structure changes that may further impact the technological properties of cricket powder.

Essential Oils and Their Combination with Lactic Acid Bacteria and Bacteriocins to Improve the Safety and Shelf Life of Foods: A Review.

The use of plant extracts (e.g., essential oils and their active compounds) represents an interesting alternative to chemical additives and preservatives applied to delay the alteration and oxidation of foods during their storage. Essential oils (EO) are nowadays considered valuable sources of food preservatives as they provide a healthier alternative to synthetic chemicals while serving the same purpose without affecting food quality parameters. The natural antimicrobial molecules found in medicinal plants represent a possible solution against drug-resistant bacteria, which represent a global health problem, especially for foodborne infections. Several solutions related to their application on food have been described, such as incorporation in active packaging or edible film and direct encapsulation. However, the use of bioactive concentrations of plant derivatives may negatively impact the sensorial characteristics of the final product, and to solve this problem, their application has been proposed in combination with other hurdles, including biocontrol agents. Biocontrol agents are microbial cultures capable of producing natural antimicrobials, including bacteriocins, organic acids, volatile organic compounds, and hydrolytic enzymes. The major effect of bacteriocins or bacteriocin-producing LAB (lactic acid bacteria) on food is obtained when their use is combined with other preservation methods. The combined use of EOs and biocontrol agents in fruit and vegetables, meat, and dairy products is becoming more and more important due to growing concerns about potentially dangerous and toxic synthetic additives. The combination of these two hurdles can improve the safety and shelf life (inactivation of spoilage or pathogenic microorganisms) of the final products while maintaining or stabilizing their sensory and nutritional quality. This review critically describes and collects the most updated works regarding the application of EOs in different food sectors and their combination with biocontrol agents and bacteriocins.

Sublethal HPH treatment is a sustainable tool that induces autolytic-like processes in the early gene expression of Saccharomyces cerevisiae.

Sublethal HPH treatments have been demonstrated to impact the technological properties and functions of treated microorganisms by inducing specific enzymes/genes or modulating membrane structures and inducing autolysis. In this work, the early effects of a 100 MPa HPH treatment on the winery starter Saccharomyces cerevisiae ALEAFERM AROM grown in synthetic must were assessed. While there were no differences in cell cultivability during the first 48 h between treated and untreated cells, a reduction in volatile metabolites released by HPH-treated cells during the first 2 h was observed. This reduction was only temporary since after 48 h, volatile molecules reached similar or even higher concentrations compared with the control. Moreover, the gene expression response of HPH-treated cells was evaluated after 1 h of incubation and compared with that of untreated cells. A massive rearrangement of gene expression was observed with the identification of 1220 differentially expressed genes (DEGs). Most of the genes related to energetic metabolic pathways and ribosome structure were downregulated, while genes involved in ribosome maturation, transcription, DNA repair, response to stimuli and stress were upregulated. These findings suggest that HPH induces or promotes an autolytic-like behaviour that can be exploited in winemaking.

Characterization and evaluation of the influence of an alginate, cocoa and a bilayer alginate-cocoa coating on the quality of fresh-cut oranges during storage.

BACKGROUND: Fresh-cut products are ready-to-use goods which retain the fresh characteristics of raw produce. However, numerous factors restrict the quality and shelf-life of fresh-cut products. One of the most promising, convenient and safe technologies to preserve the quality and to prolong the shelf-life of fresh fruits and vegetables is the application of edible coatings. RESULTS: The aim of this study was to investigate the effects of different coatings (alginate-based, cocoa-based and a combination of them) on physicochemical, microbiological and sensory characteristics of fresh-cut oranges during storage. Preliminary rheological analyses were performed on coatings in order to characterize them. The three different coated orange samples were packaged in polyethylene terephthalate trays under atmospheric conditions and stored for 9 days at 6 °C. During storage, all samples were analysed for water activity, moisture, colour, texture, microbiological analyses and sensory quality. Orange samples coated with sodium alginate maintained the highest quality characteristics in terms of texture and microbiological properties, but not from a sensory point of view. Samples coated only with cocoa presented very high sensory attributes, but the lowest microbiological and textural quality. Samples covered in both alginate and cocoa demonstrated the best quality parameters throughout the whole storage period, including high sensory characteristics and the lowest microbiological cell loads (yeast and mesophilic aerobic bacteria under the threshold limit of 6.0 log cfu g-1 ). CONCLUSION: The bilayer coating represented the best solution in order to develop new ready to-eat-fresh oranges with both high textural and sensory attributes and prolonged shelf-life. © 2022 Society of Chemical Industry.

High-Pressure Homogenization and Biocontrol Agent as Innovative Approaches Increase Shelf Life and Functionality of Carrot Juice.

Recently, application of high-pressure homogenization (HPH) treatments has been widely studied to improve shelf life and rheological and functional properties of vegetable and fruit juices. Another approach that has drawn the attention of researchers is the use of biocontrol cultures. Nevertheless, no data on their possible combined effect on fruit juices shelf life and functionality have been published yet. In this work, the microbial, organoleptic, and technological stability of extremely perishable carrot juice and its functionality were monitored for 12 and 7 days (stored at 4 and 10 °C, respectively) upon HPH treatment alone or in combination with a fermentation step using the biocontrol agent L. lactis LBG2. HPH treatment at 150 MPa for three passes followed by fermentation with L. lactis LBG2 extended the microbiological shelf life of the products of at least three and seven days when stored at 10 °C and 4 °C, respectively, compared to untreated or only HPH-treated samples. Moreover, the combined treatments determined a higher stability of pH and color values, and a better retention of ß-carotene and lutein throughout the shelf-life period when compared to unfermented samples. Eventually, use of combined HPH and LBG2 resulted in the production of compounds having positive sensory impact on carrot juice.

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, HPH-treatment showed an increase in the number or intensity of protein bands at high and low molecular weights.

Probiotic and Metabolic Characterization of Vaginal Lactobacilli for a Potential Use in Functional Foods.

The main aim of this work was to verify the metabolic and functional aptitude of 15 vaginal strains belonging to Lactobacillus crispatus, Lactobacillus gasseri, and Limosilactobacillus vaginalis (previously Lactobacillus vaginalis), already characterized for their technological and antimicrobial properties. In order to evaluate the metabolic profile of these vaginal strains, a phenotype microarray analysis was performed on them. Functional parameters such as hydrophobicity, auto-aggregation, deconjugation of bile salts, adhesion to an intestinal cell line (Caco-2), and a simulated digestion process were evaluated for these strains. A good number of these strains showed hydrophobicity values higher than 70%. Regarding the auto-aggregation assay, the most promising strains were L. crispatus BC9 and BC1, L. gasseri BC10 and BC14, and L. vaginalis BC17. Moreover, L. crispatus BC4, BC6, BC7, and BC8 were characterized by strong bile salts hydrolase activity (BHS). In addition, L. crispatus BC8 and L. vaginalis BC17 were characterized by a medium ability to adhere to Caco-2 cells. Data related to digestion process showed a strong ability of vaginal lactobacilli to withstand this stress. In conclusion, the data collected show the metabolic versatility and several exploitable functional properties of the investigated vaginal lactobacilli.

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.

Evaluation of the fate of Lactobacillus crispatus BC4, carried in Squacquerone cheese, throughout the simulator of the human intestinal microbial ecosystem (SHIME).

Lactobacillus crispatus strain BC4, isolated from the human healthy vaginal environment and characterised by a strong antimicrobial activity against urogenital pathogens and foodborne microorganisms, was employed as a probiotic culture in the cheesemaking of the soft cheese Squacquerone. Such cheese is intended as a "gender food", that could be used as a hedonistic dietary strategy to reduce the incidence of woman vaginal dysbiosis and infections, given the evidence that a probiotic strain able to survive to the entire digestive process once ingested, can pass from intestine to vagina. This work was aimed to evaluate the resistance of L. crispatus BC4, carried in Squacquerone cheese, to different challenges of the human gastrointestinal tract, including the colon stage. The digestion process was tested using a Simulator of the Human Intestinal Microbial Ecosystem (SHIME®). The viability and metabolic activity of L. crispatus BC4 during the colon simulation were monitored by qPCR and gas chromatography, respectively, also in the presence of a complex microbiota. The results showed that L. crispatus BC4 survival was not affected by the gastric condition, while it was significantly affected by bile salts and pancreatic juice in small intestine conditions, where it decreased of approx. 0.6 log (colony-forming units) CFU/g. Differently, during colon simulation L. crispatus BC4 was able to grow in sterile colon conditions and to maintain viability in the presence of a complex microbiota. Moreover, during colon simulation, L. crispatus BC4 was metabolically active as demonstrated by the higher production of short chain fatty acids (SCFA) and lactate. In the presence of a complex gut microbiota, a decrease of lactate was observed, due to its conversion into propionate (anti-cholesterol activity) and butyrate (anti-inflammatory activity) by cross-feeding. However, no differences in propionate and butyrate production could be observed between control cheese and cheese containing L. crispatus BC4. Despite this may appear as a negative outcome, it must be taken into account that, in this setup, only a single dose of the cheese was tested and the outcome of the colonization and impact of the gut microbiota might be different when daily repeated doses are tested.

Use of Essential Oils to Increase the Safety and the Quality of Marinated Pork Loin.

This study aimed at evaluating the effects of the addition of an oil/beer/lemon marinade solution with or without the inclusion of oregano, rosemary and juniper essential oils on the quality, the technological properties as well as the shelf-life and safety of vacuum-packed pork loin meat. The results obtained suggested that, aside from the addition of essential oils, the marination process allowed to reduce meat pH, thus improving its water holding capacity. Instrumental and sensorial tests showed that the marination also enhanced the tenderness of meat samples, with those marinated with essential oils being the most positively perceived by the panelists. In addition, microbiological data indicated that the marinated samples showed a lower microbial load of the main spoiling microorganisms compared to the control samples, from the 6th to the 13th day of storage, regardless of the addition of essential oils. Marination also allowed to inhibit the pathogens Salmonella enteritidis, Listeria monocytogenes and Staphylococcus aureus, thus increasing the microbiological safety of the product. Overall outcomes suggest that the oil/beer/lemon marinade solution added with essential oils might represent a promising strategy to improve both qualitative and sensory characteristics as well as the safety of meat products.

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.

Lactobacillus paracasei A13 and High-Pressure Homogenization Stress Response.

Sub-lethal high-pressure homogenization treatments applied to Lactobacillus paracasei A13 demonstrated to be a useful strategy to enhance technological and functional properties without detrimental effects on the viability of this strain. Modification of membrane fatty acid composition is reported to be the main regulatory mechanisms adopted by probiotic lactobacilli to counteract high-pressure stress. This work is aimed to clarify and understand the relationship between the modification of membrane fatty acid composition and the expression of genes involved in fatty acid biosynthesis in Lactobacillus paracasei A13, before and after the application of different sub-lethal hyperbaric treatments. Our results showed that Lactobacillus paracasei A13 activated a series of reactions aimed to control and stabilize membrane fluidity in response to high-pressure homogenization treatments. In fact, the production of cyclic fatty acids was counterbalanced by the unsaturation and elongation of fatty acids. The gene expression data indicate an up-regulation of the genes accA, accC, fabD, fabH and fabZ after high-pressure homogenization treatment at 150 and 200 MPa, and of fabK and fabZ after a treatment at 200 MPa suggesting this regulation of the genes involved in fatty acids biosynthesis as an immediate response mechanism adopted by Lactobacillus paracasei A13 to high-pressure homogenization treatments to balance the membrane fluidity. Although further studies should be performed to clarify the modulation of phospholipids and glycoproteins biosynthesis since they play a crucial role in the functional properties of the probiotic strains, this study represents an important step towards understanding the response mechanisms of Lactobacillus paracasei A13 to sub-lethal high-pressure homogenization treatments.

Volatile Molecule Profiles and Anti-Listeria monocytogenes Activity of Nisin Producers Lactococcus lactis Strains in Vegetable Drinks.

This work aimed to evaluate the potential of 15 nisin producing Lactococcus lactis strains, isolated from dairy products, for the fermentation of soymilk and carrot juice. In particular, the acidification and the production of nisin in the food matrices were recorded. Moreover, three strains (LBG2, FBG1P, and 3LC39), that showed the most promising results were further scrutinized for their anti-Listeria monocytogenes activity and volatile molecules profile during fermentation of soymilk and carrot juice. Lactococcus lactis strains LBG2, FBG1P, and 3LC39 resulted the most interesting ones, showing rapid growth and acidification on both food matrices. The higher amounts of nisin were detected in soymilk samples fermented by the strain LBG2 after 24 and 48 h (26.4 mg/L). Furthermore, the rapid acidification combined with the production of nisin resulted in a strong anti-Listeria activity, reducing the pathogen loads below the detection limit, in carrot juice samples fermented by the strains LBG2 and FBG1P and in soymilk by the strain LBG2. The fermentation increased the presence of volatile molecules such as aldehydes and ketones with a positive impact on the organoleptic profile of both the fermented products. These results highlighted the interesting potential of three nisin producing L. lactis strains for the production of fermented carrot juice and soymilk. In fact, the fermentation by lactic acid bacteria, combined or not with other mild technologies, represents a good strategy for the microbiological stabilization of these products. Furthermore, the increase of molecules with a positive sensory impact, such as aldehydes and ketones, in the fermented products suggests a possible improvement of their organoleptic characteristics.

Formation of Ethyl Carbamate during the Production Process of Cantonese Soy Sauce.

The aim of this work was to clarify the formation of ethyl carbamate (EC) and its influence factors throughout the production process of Cantonese soy sauce. The results showed that EC was not detected in the koji-making and early moromi fermentation stages, but started to be generated when pH of the moromi decreased to about 4.9-at the same time, the levels of ethanol, urea and citrulline increased significantly. Most EC was formed during raw soy sauce hot extraction (40.6%) and sterilization (42.9%) stages. The EC content exhibited the highest correlation with ethanol throughout the whole production process (R = 0.97). The simulation soy sauce produced in laboratory led the same conclusion-moreover, the contents of EC, ethanol and citrulline were higher in soy sauce fermented at 30 °C than in soy sauce fermented at 15 °C. Extraction of raw soy sauce by squeezing contributed little to EC formation. Further research showed that citrulline and ethanol led to significant increases in EC levels in raw soy sauce upon heating. These results indicate that ethanol and citrulline are two critical precursors of EC and that EC is mainly formed during the heat treatment stage of soy sauce.

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.

Flow Cytometric Assessment of the Morphological and Physiological Changes of Listeria monocytogenes and Escherichia coli in Response to Natural Antimicrobial Exposure.

Essential oils (EOs) or their components represent one of the most promising natural, safe, and feasible alternatives to prevent the growth of food-borne pathogens like Listeria monocytogenes and Escherichia coli in food matrices. Although antimicrobial properties of EOs and their components are well-documented, limited and fragmented information is available on the changes induced by these compounds, even at sub-lethal concentrations, in the physiological properties of microbial cells. The aim of this study was to explore the morpho-physiological changes of L. monocytogenes Scott A and E. coli MG 1655 induced after 1 h exposure to different sub-lethal and lethal concentrations of citral, carvacrol, (E)-2-hexenal, and thyme EO. For this purpose, different cell viability parameters such as membrane integrity, esterase activity, and cytoplasmic cell membrane potential were measured by flow cytometry. Flow cytometric data revealed specific response patterns in relation to the strain, the natural antimicrobial and its concentrations. Both the target microbial strains showed an increased cell membrane permeabilization without a loss of esterase activity and cell membrane potential with increasing citral, carvacrol and thyme EO concentrations. By contrast, (E)-2-hexenal did not significantly affect the measured physiological properties of L. monocytogenes Scott A and E. coli MG 1655. The used approach allowed identifying the most effective natural antimicrobials in relation to the microbial target.

Gene expression responses of Listeria monocytogenes Scott A exposed to sub-lethal concentrations of natural antimicrobials.

One of the emerging strategies proposed to prevent the presence and the growth of Listeria monocytogenes in food products is the use of natural antimicrobial compounds like essential oils (EOs) or their components alone or in combination with other mild hurdles. The aim of this study was to explore the gene expression mechanisms of L. monocytogenes Scott A exposed for 1 h to different sub-lethal antimicrobial concentrations of (E)-2-hexenal, citral, carvarcol and thyme EO in order to understand the impact of these molecules on the main metabolic pathways of this pathogenic strain. RT-qPCR has been performed on L. monocytogenes cells exposed to the target antimicrobials. The presence of the antimicrobials induced a clear unbalance in the catabolic processes, suggesting a shift from oxidation to fermentation metabolism (pdhD, pgm). Moreover, the results highlighted how antimicrobials belonged to the same chemical class induced different stress response mechanisms on L. monocytogenes Scott A. The information about the cell responses to the exposure to the natural antimicrobials selected is crucial to understand which cell target(s) can be affected, and consequently how the inhibition of pathogens survival can be further enhanced.

Effect of thyme essential oil and Lactococcus lactis CBM21 on the microbiota composition and quality of minimally processed lamb's lettuce.

The main aim of this work was to evaluate, at pilot scale in an industrial environment, the effects of the biocontrol agent Lactococcus lactis CBM21 and thyme essential oil compared to chlorine, used in the washing step of fresh-cut lamb's lettuce, on the microbiota and its changes in relation to the time of storage. The modification of the microbial population was studied through pyrosequencing in addition to the traditional plate counts. In addition, the volatile molecule and sensory profiles were evaluated during the storage. The results showed no significant differences in terms of total aerobic mesophilic cell loads in relation to the washing solution adopted. However, the pyrosequencing data permitted to identify the genera and species able to dominate the spoilage associations over storage in relation to the treatment applied. Also, the analyses of the volatile molecule profiles of the samples during storage allowed the identification of specific molecules as markers of the spoilage for each different treatment. The sensory analyses after 3 and 5 days of storage showed the preference of the panelists for samples washed with the combination thyme EO and the biocontrol agent. These samples were preferred for attributes such as flavor, acceptability and overall quality. These results highlighted the effect of the innovative washing solutions on the quality of lettuce through the shift of microbiota towards genera and species with lower potential in decreasing the sensory properties of the product.

Microencapsulation of functional strains by high pressure homogenization for a potential use in fermented milk.

This study was aimed to evaluate the potential of high pressure homogenization for the microencapsulation of two probiotic lactic acid bacteria, Lactobacillus paracasei A13 and Lactobacillus salivarius subsp. salivarius CET 4063 to produce functional fermented milks. Microcapsules of the considered functional microorganisms were obtained by HPH treatments at 50MPa in the presence of sodium alginate and vegetable oil. The microencapsulated microorganisms were then inoculated as adjuncts to produce fermented milks. As controls were used fermented milks in which the two probiotic lactobacilli were inoculated without encapsulation. The viability of the strains was monitored during almost 2months of refrigerated storage. The survival of lactic acid bacteria after the gastric-duodenal simulated test was determined. Fermented milk texture parameters, the presence of exo-polysaccharides and the production of volatile molecules were also evaluated over storage. The microcapsules, for both the considered probiotic strains, were homogeneous and with a size<100µM and therefore did not adversely affect the sensory properties of the fermented milks. The encapsulation decreased the hyperacidity phenomena generally related to the inclusion of probiotic microorganisms in fermented milks. The lower acidity of the products due to the microencapsulation was fundamental for the improvement of the viability of the starter culture and the sensory characteristics of the products. The microencapsulation conditions increased the resistance to the simulated digestion processes, although the strain Lb. paracasei A13 generally showed a higher resistance to the gastric barrier respect to Lb. salivarius CECT 4063. By contrast, the data obtained showed a reduction of EPS production by the microencapsulation. The volatile profiles showed specific profiles in relation to the probiotic strain used and microencapsulation process. In conclusion, the results of this study underlined the applicative potential of HPH microencapsulation of probiotic microorganisms to produce fermented milk with improved functionality and with enhanced sensory properties.