Fate of anthocyanins in the presence of inactivated yeasts and yeast cell walls during simulation of wine aging.

In the present research, two inactivated yeast strains (W13 and BM45) and a commercial yeast cell wall preparation (YCW) already tested for their ability to removal ochratoxin A were used to simulate the wine aging. During the simulated aging, the concentrations of the main 4 anthocyanins decreased in both the control wine and the wines added with yeasts, although at rates depending on the type of yeast and on the nature of anthocyanins. Peonidin-3-O-glucoside decreased by about 20% in the control wine and by ~ 50% in the wines added with yeast strains or the commercial yeast preparation. Malvidin-3-O-glucoside decreased by about 80% in the control wine and in the wine added with YCW and by about 96% in the wines added with W13 and BM45 strains. Cyanidin-3-O-glucoside decreased by 47% in the control wine, by 65-66% in the wines added with W13 and BM45 strains, and by 73% in the wine added with YCW. Delphinidin-3-O-glucoside decreased by 100% already after 21-28 days of aging in all the wines.

Biotechnological application of yeasts in food science: Starter cultures, probiotics and enzyme production.

This review is an account of experiences of two research teams (from Italy to Spain); the leading idea is the following: yeasts represent valuable sources in food science and microbiology and are a kind of food factories, because of the potentiality of whole cells or for their produced compounds. This review covers three major areas: the first section addresses the role of yeasts as starter cultures with a special focus on wine. The second section is an update on probiotic yeasts. Finally, the focus of the last section is on enzymes produced by yeasts, with a short description of the removal of mycotoxin.

Impact of gluten-friendly™ technology on wheat kernel endosperm and gluten protein structure in seeds by light and electron microscopy.

The main aim of this paper was to assess the impact of Gluten-Friendly™ (GF) technology (Italian priority patent n° 102015000084813 filed on 17th December 2015) on wheat kernel endosperm morphology and gluten protein structure, using SEM, light and immunofluorescent microscopy. Microscopy was combined with immunodetection with specific antibodies for gliadins, γ-gliadins, LMW subunits and antigenic epitopes to gain a better understanding of the technology at a molecular level. The results showed significant changes to gluten proteins after GF treatment; cross-reactivity towards the antibodies recognizing almost the entire range of gluten proteins as well as the antigenic epitopes through the sequences QQSF, QQSY, PEQPFPQGC and QQPFP was significantly reduced. The present study confirms the results from our previous work and shows, for the first time, the mechanism by which a chemical-physical treatment abolishes the antigenic capacity of gluten.

In vitro removal of ochratoxin A by two strains of Saccharomyces cerevisiae and their performances under fermentative and stressing conditions.

AIMS: The aim of this research was to study the effect of time, temperature, sugar content and addition of diammonium phosphate (DAP) on ochratoxin A (OTA) removal by two strains of Saccharomyces cerevisiae using a completely randomized design. METHODS AND RESULTS: The strains were grown in a medium containing OTA (2 µg l(-1)), two sugar levels (200 and 250 g l(-1)), with or without DAP (300 mg l(-1)), and incubated at 25-30°C. The yeasts were able to decrease the toxin amount by c. 70%, with the highest removing effect observed after 3 days at 30°C in the presence of 250 g l(-1) of sugars and with DAP; after 10 days, the toxin was partially released into the medium. The strains produced high ethanol and glycerol contents, showed high tolerance to single/combined stress conditions and possessed ß-d-glucosidase, pectinase and xylanase activities. CONCLUSIONS: Ochratoxin A removal was affected by time, temperature, sugar and addition of DAP. Moreover, the phenomenon was reversible. SIGNIFICANCE AND IMPACT OF THE STUDY: Ochratoxin A removal could be an interesting trait for the selection of promising strains; however, the strains removing efficiently the toxin could release it back; thus, the selection of the starter should take into account both the removal and the binding ability of OTA.

Encapsulation of probiotic bacteria in lamb rennet paste: effects on the quality of Pecorino cheese.

Lamb rennet pastes containing encapsulated Lactobacillus acidophilus and a mix of Bifidobacterium longum and Bifidobacterium lactis were produced for Pecorino cheese manufacture from Gentile di Puglia ewe milk. Cheeses were denoted as RP cheese when made with traditional rennet paste, RP-L cheese when made with rennet paste containing L. acidophilus culture, and RP-B cheese when made with rennet paste containing a mix of B. lactis and B. longum. Biochemical features of Pecorino cheese were studied at 1, 15, 30, 60, and 120 d of cheese ripening. The effect of encapsulation and bead addition to rennet acted on a different way on the viability of probiotic. Lactobacillus acidophilus retained its viability for 4 to 5 d and then showed a fast reduction; on the other hand, B. longum and B. lactis experienced kinetics characterized by an initial death slope, followed by a tail effect due to acquired resistance. At 1 d of ripening, the levels of L. acidophilus and bifidobacteria in cheese were the lowest, and then increased, reaching the highest levels after 30 d; such cell loads were maintained throughout the ripening for L. acidophilus, whereas bifidobacteria experienced a decrease of about 1 log cfu/g at the end of ripening. Enzymatic activities and biochemical features of cheeses were influenced by the type of rennet used for cheesemaking. Greater enzymatic activity was recorded in RP-L and RP-B cheese due to the presence of probiotic bacteria released from alginate beads. A positive correlation was found between enzymatic activities and water-soluble nitrogen and proteose-peptone in RP-B and RP-L cheeses; water-soluble nitrogen and proteose-peptone were the highest in RP-B. Principal component analysis distinguished RP-L from the other cheeses on the basis of the conjugated linoleic acid content, which was higher in the RP-L due to the ability of L. acidophilus to produce conjugated linoleic acid in the cheese matrix.

Modelling the interactions between Pseudomonas putida and Escherichia coli O157:H7 in fish-burgers: use of the lag-exponential model and of a combined interaction index.

AIMS: The objective of the current study was to examine the interactions between Pseudomonas putida and Escherichia coli O157:H7 in coculture studies on fish-burgers packed in air and under different modified atmospheres (30 : 40 : 30 O(2) : CO(2) : N(2), 5 : 95 O(2) : CO(2) and 50 : 50 O(2) : CO(2)), throughout the storage at 8 degrees C. METHODS AND RESULTS: The lag-exponential model was applied to describe the microbial growth. To give a quantitative measure of the occurring microbial interactions, two simple parameters were developed: the combined interaction index (CII) and the partial interaction index (PII). Under air, the interaction was significant (P < 0.05) only within the exponential growth phase (CII, 1.72), whereas under the modified atmospheres, the interactions were highly significant (P < 0.001) and occurred both in the exponential and in the stationary phase (CII ranged from 0.33 to 1.18). PII values for E. coli O157:H7 were lower than those calculated for Ps. putida. CONCLUSIONS: The interactions occurring into the system affected both E. coli O157:H7 and pseudomonads subpopulations. The packaging atmosphere resulted in a key element. SIGNIFICANCE AND IMPACT OF THE STUDY: The article provides some useful information on the interactions occurring between E. coli O157:H7 and Ps. putida on fish-burgers. The proposed index describes successfully the competitive growth of both micro-organisms, giving also a quantitative measure of a qualitative phenomenon.

Combined effect of MAP and active compounds on fresh blue fish burger.

The combined effects of three essential oils [thymol, lemon extract and grapefruit seed extract (GFSE)] and modified atmosphere packaging conditions (MAP) on quality retention of blue fish burgers was studied and discussed. In particular, samples were packaged in air and in three different gas mix compositions: 30:40:30 O(2):CO(2):N(2), 50:50 O(2):CO(2) and 5:95 O(2):CO(2). During a 28-day storage period at 4 degrees C, the nutritional, microbiological and sensorial quality of the packed products was assessed. The potential development of biogenic amines was also evaluated. The obtained results highlight the possibility to improve the microbial quality of blue fish burgers by using very small amount of thymol (110ppm), GFSE (100ppm) and lemon extract (120ppm) in combination with MAP. Based primarily on microbiological results, the combined use of the tested natural preservatives and a packaging system characterized by a high CO(2)-concentration, was able to guarantee the microbial acceptability of fish burgers until the 28th day of storage at 4 degrees C. On the other hand, results from sensory analyses showed that sensorial quality was the sub-index that limited the burgers shelf life (to about 22-23days), even if the proposed strategy was also effective in minimizing the sensory quality loss of the product having no effect on its nutritional quality.

Combined effects of chitosan and MAP to improve the microbial quality of amaranth homemade fresh pasta.

In this work a study on the combined effects of chitosan and modified atmosphere packaging (MAP) to improve the microbiological quality of amaranth-based homemade fresh pasta is presented. In particular, two different chitosan concentrations were combined to three different MAP conditions and tested against the following spoilage microorganisms: mesophilic bacteria, Staphylococcus spp., yeasts, moulds and total coliforms. Their viable cell concentrations were monitored for about 2 months at 4 degrees C. Results suggest that there is a combined effect between MAP and chitosan in delaying the microbial quality loss of pasta during storage. Moreover, it was also found that among the tested MAP conditions, the combination of 30:70 N2:CO2 is the most efficient, promoting an extension of the microbial acceptability limit beyond two months.

Effects of the high pressure of homogenization on some spoiling micro-organisms, representative of fruit juice microflora, inoculated in saline solution.

AIMS: This study was aimed to investigate the effects of a high-pressure homogenization (HPH) treatment on some micro-organisms, involved in the spoilage of fruit juices. METHODS AND RESULTS: Lactobacillus plantarum, Lactobacillus brevis, Bacillus coagulans cells, Saccharomyces bayanus, Pichia membranaefaciens and Rhodotorula bacarum were separately inoculated in a saline solution (0.9% NaCl); the initial inoculum was ca. 5 log CFU ml(-1). Then, the samples were processed through a homogenizer at 10-150 MPa for 1, 2 or 3 times. Yeasts were completely inactivated at 50-110 MPa with a single pass treatment, while lactic acid bacteria counts were reduced to approximately 1 log CFU ml(-1) after a three-steps HPH processing. CONCLUSIONS: Yeasts were the most sensitive micro-organisms, followed by B. coagulans. On the other hand, lactic acid bacteria appeared resistant to HPH. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study provided some useful information on the susceptibility of microflora of juices to homogenization; moreover, they suggested that HPH could be used successfully to inactivate yeasts.

Use of natural compounds to improve the microbial stability of Amaranth-based homemade fresh pasta.

A study on the use of natural antimicrobial compounds to improve the microbiological stability of refrigerated amaranth-based homemade fresh pasta is presented in this work. In particular, the antimicrobial activity of thymol, lemon extract, chitosan and grapefruit seed extract (GFSE) has been tested against mesophilic and psychrotrophic bacteria, total coliforms, Staphylococcus spp., yeasts and moulds. A sensory analysis on both fresh and cooked pasta was also run. Results suggest that chitosan and GFSE strongly increase the microbial acceptability limit of the investigated spoilage microorganisms, being the former the most effective. Thymol efficiently reduces the growth of mesophilic bacteria, psychrotrophic bacteria and Staphylococcus spp., whereas it does not affect, substantially, the growth cycle of total coliforms. Lemon extract is the less effective in preventing microbial growth. In fact, it is able to delay only total mesophilic and psychrotrophic bacterial evolution. From a sensorial point of view no significant differences were recorded between the control samples and all the types of loaded amaranth-based pasta.

Microbiological and sensorial quality assessment of ready-to-cook seafood products packaged under modified atmosphere.

The effects of modified atmosphere packaging (MAP) (30:40:30 O(2):CO(2):N(2) and 5:95 O(2):CO(2)) on the quality of 4 ready-to-cook seafood products were studied. In particular, the investigation was carried out on hake fillets, yellow gurnard fillets, chub mackerel fillets, and entire eviscerated cuttlefish. Quality assessment was based on microbiological and sensorial indices determination. Both packaging gas mixtures contributed to a considerable slowing down of the microbial and sensorial quality loss of the investigated seafood products. Results showed that sensorial quality was the subindex that limited their shelf life. In fact, based primarily on microbiological results, samples under MAP remained acceptable up to the end of storage (that is, 14 d), regardless of fish specie. On the other hand, results from sensory analyses showed that chub mackerel fillets in MAP were acceptable up to the 6th storage d, whilst hake fillets, yellow gurnard fillets, and entire cuttlefish became unacceptable after 10 to 11 d. However, compared to control samples, an increase in the sensorial shelf life of MAP samples (ranging from about 95% to 250%) was always recorded. Practical Application: Modified atmosphere packaging (MAP) is an inexpensive and uncomplicated method of extending shelf life of packed seafood. It could gain great attention from the fish industrial sector due to the fact that MAP is a practical and economic technique, realizable by small technical expedients. Moreover, there is great attention from the food industry and retailers to react to the growing demand for convenience food, thus promoting an increase in the assortments of ready-to-cook seafood products.

Chitosan: antimicrobial activity and potential applications for preserving minimally processed strawberries.

In this research the possible use of chitosan coating on fresh-cut strawberries was investigated. Manually sliced strawberries were treated with a solution of 1% chitosan, packaged in modified atmosphere with high (80%) and low (5%) percentage of oxygen and then stored at 4, 8, 12 and 15 degrees C. Changes in microbiological quality were measured and the shelf life of the samples, as stability time, was kinetically modelled in order to check the effects of storage temperature on the most relevant microbial indices for product quality. A chitosan coating inhibited the growth of microorganisms and affected significantly and positively the stability time of the products, above all when the samples were packaged in modified atmosphere (with low and high percentage of oxygen). Besides, the presence of high percentage of oxygen, combined with chitosan coating, seemed to affect positively the colour. The data revealed that applying a chitosan coating prolonged effectively the quality and extended the shelf life of fresh-cut strawberries.

Study on the synergic effect of natural compounds on the microbial quality decay of packed fish hamburger.

The effectiveness of natural compounds in slowing down the microbial quality decay of refrigerated fish hamburger is addressed in this study. In particular, the control of the microbiological spoilage by combined use of three antimicrobials, and the determination of their optimal composition to extend the fish hamburger Microbiological Stability Limit (MAL) are the main objectives of this work. Thymol, grapefruit seed extract (GFSE) and lemon extract were tested for monitoring the cell growth of the main fish spoilage microorganisms (Pseudomonas fluorescens, Photobacterium phosphoreum and Shewanella putrefaciens), inoculated in fish hamburgers, and the growth of mesophilic and psychrotrophic bacteria. A Central Composite Design (CCD) was developed to highlight a possible synergic effect of the above natural compounds. Results showed an increase in the MAL value for hamburgers mixed with the antimicrobial compounds, compared to the control sample. The optimal antimicrobial compound composition, which corresponds to the maximal MAL value determined in this study, is: 110 mgL(-1) of thymol, 100 mgL(-1) of GFSE and 120 mgL(-1) of lemon extract. The presence of the natural compounds delay the sensorial quality decay without compromising the flavor of the fish hamburgers.

Alicyclobacillus acidoterrestris: new methods for inhibiting spore germination.

For a long period the thermal processing has been considered as the only way to reduce the initial spore number of Alicyclobacillus acidoterrestris and prevent the spoilage of acidic beverage. New methods, however, were proposed by the literature to control spore germination both in laboratory media and in real systems. After a brief introduction on the impact of A. acidoterrestris in food microbiology and a description of enumeration methods and heat processing applied by the juices manufactures, a review of innovative approaches to inhibit and/or control spore germination is proposed. In particular, this paper focuses on two different topics; the 1st is the use of some natural compounds (monolaurin, lysozyme, nisin and essential oils) or some chemicals, conventional (like sodium-benzoate, organic acids, surfactants and chlorine dioxide) or not conventional (chlorine dioxide as gas). The 2nd topic is a description of some innovative methods to reduce the initial spore number (high hydrostatic and homogenisation pressures, radiation and microwaves).

Effects of high-pressure homogenization on the survival of Alicyclobacillus acidoterrestris in a laboratory medium.

AIMS: This study was aimed to investigate the effectiveness of high-pressure homogenization (HPH) against Alicyclobacillus acidoterrestris. METHODS AND RESULTS: The susceptibility of three different strains of A. acidoterrestris (DSMZ 2498, Gamma4 and c8) to HPH (500-1700 bar) was studied. The experiments were performed in a laboratory medium (malt extract broth) on cells and spores. HPH caused a significant reduction of the initial cell number (1-2 log CFU ml(-1) at the highest pressures) in Gamma4 and DSMZ 2498 strains, whereas the effect on the spores was less significant. CONCLUSIONS: This study showed that the susceptibility of A. acidoterrestris to HPH was strain-dependent: DSMZ 2498 seemed the most susceptible strain, whereas c8 was the most resistant one. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of our study will provide useful information on the sensitivity of an emerging spoilage micro-organism, such as A. acidoterrrestris, to HPH.

A study on the antimicrobial activity of thymol intended as a natural preservative.

A quantitative investigation on the inhibitory activity of thymol against some microorganisms that could represent a potential spoilage risk both in acid and mild thermally treated foods is presented in this work. In order to assess potential biostatic or biocidal activity of thymol, both the growth kinetics and dose-response profiles were obtained and analyzed. A suitable macrodilution methodology based on a turbidimetric technique was adopted to produce inhibitory data used for characterizing microbial susceptibility against thymol at sub-MIC levels. Microbial growth was monitored through absorbance measurements at 420 nm as a function of contact time with the active compound. Moreover, for each tested microorganism, the noninhibitory concentration (NIC) and the MIC were quantified. Results prove that thymol can exert a significant antimicrobial effect on each phase of the growth cycle. The microbial susceptibility and resistance were found to be nonlinearly dose related. It is worth noting that significant biostatic effects were observed at sub-MIC levels.

Controlled release of antimicrobial compounds from highly swellable polymers.

The suitability of antimicrobial release films made from highly swellable polymers for use in food packaging was evaluated. The possibility of modulating the release kinetics of active compounds either by regulating the degree of cross-link of the polymer matrix or by using multilayer structures was addressed. The release kinetics of lysozyme, nisin, and sodium benzoate (active compounds with different molecular weights) were determined at ambient temperature (25 degrees C). The effectiveness of the proposed active films in inhibiting microbial growth was addressed by determining the antimicrobial efficiency of the released active compounds. Micrococcus lysodeikticus, Alicyclobacillus acidoterrestris, and Saccharomyces cerevisiae were used to test the antimicrobial efficiency of released lysozyme, nisin, and sodium benzoate, respectively. Results indicate that the release kinetics of both lysozyme and nisin can be modulated through the degree of cross-link of the polymer matrix, whereas multilayer structures need to be used to control the release kinetics of sodium benzoate. All the active compounds released from the investigated active films were effective in inhibiting microbial growth.

Development of a structured model for batch cultures of lactic acid bacteria.

A combined stochastic-deterministic model able to predict the growth curve of microorganisms, from inoculation to death, is presented. The proposed model is based on the assumption that microorganisms can experience two different physiological states: non-proliferating and proliferating. The former being the physiological state of the cells right after their inoculation into the new extracellular environment; the latter the state of microorganisms after adaptation to the new medium. To validate the model, a Lactobacillus bulgaricus strain was tested in a medium at pH 4.6 at two different temperatures (42 degrees C and 35 degrees C). Curves representing the bacterial growth cycle were satisfactorily fitted by means of the proposed model. Moreover, due to the mechanistic structure of the proposed model, valuable quantitative information on the following was obtained: rate of conversion of non-proliferating cells into proliferating cells, growth and death rate of proliferating cells, and rate of nutrient consumption.

A general approach to describe the antimicrobial agent release from highly swellable films intended for food packaging applications.

A mathematical model able to describe the release kinetics of antimicrobial agents from crosslinked polyvinylalcohol (PVOH) into water is presented. The model was developed by taking into account the diffusion of water molecules into the polymeric film, the counter-diffusion of the incorporated antimicrobial agent from the film into water, and the polymeric matrix swelling kinetic. To validate the model the water sorption kinetics as well as the release kinetics of three antimicrobial agents (i.e., lysozyme, nisin and sodium benzoate, all approved to be used in contact with food) were determined at ambient temperature (25 degrees C). The three investigated active agents were entrapped in four films of PVOH with a different degree of crosslink. The model was successfully used to fit all the above sets of data, corroborating the validity of the hypothesis made to derive it.

Occurrence and characterization of yeasts isolated from milks and dairy products of Apulia region.

One hundred and five strains of yeasts isolated from milk of different animal origin and from typical Apulian cheeses were studied to identify and characterize yeast strains for further selection as starter cultures for cheese production. The most prevalent isolates belonged to the species Trichosporon cutaneum (15.24%), Candida catenulata (10.48%) and Yarrowia lipolytica (8.57%). In order to evaluate the potential use as starter cultures, the occurrence of some selected properties, such as fermentation of glucose and lactose, assimilation of lactic acid, citric acid and lactose, growth at 4 degrees C and production of lipolytic and proteolytic enzymes in the strains belonging to the most frequent species was tested. C. catenulata and C. zeylanoides were positive for assimilation of lactic and citric acids and showed psychrotrophic aptitude. T. cutaneum was positive for all properties tested except for glucose and lactose fermentations. Y. lipolytica was endowed with remarkable lipolytic activity also at 4 degrees C and was positive for assimilation of lactic and citric acids, growth at 4 degrees C and proteolytic activity.