Daniela Campaniello

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.

Antifungal activity of eugenol against Penicillium, Aspergillus, and Fusarium species.

The antifungal activity of eugenol in a model system against aspergilli (Aspergillus niger, Aspergillus terreus, and Emericella nidulans), penicilli (Penicillium expansum, Penicillium glabrum, and Penicillium italicum), and fusaria (Fusarium oxysporum and Fusarium avenaceum) was investigated. Minimum detection time (time to attain a colony diameter of 1 cm) and the kinetic parameters were evaluated. The effectiveness of the active compound seemed to be strain or genus dependent; 100 mg/liter represented a critical value for P. expansum, P. glabrum, P. italicum, A. niger, and E. nidulans because a further increase of eugenol resulted in fungistatic activity. The radial growth of A. terreus and F. avenaceum was inhibited at 140 mg/liter, and growth of F. oxysporum was completely inhibited at 150 mg/liter.

Growth of Listeria monocytogenes in fresh-cut coconut as affected by storage conditions and inoculum size

In this study, the effects of packaging atmosphere (air and modified atmosphere, 65% N2, 30% CO2, and 5% O2), temperature (2, 4, 8, and 12 degrees C) and inoculum size (low inoculum, 102 CFU/g; high inoculum, 5 x 10(5) CFU/g) on the growth of Listeria monocytogenes in minimally processed coconut were investigated. Growth data were fitted to the Gompertz equation, and the sanitary risk time (the time, in days, necessary to observe an increase of 2 log CFU/g in the level of the pathogen) was also calculated. At a higher inoculum level, the health risk was more marked; moreover, as shown by parameter A of the Gompertz equation (maximum increase of cell load data), the sanitary risk time seemed not to be influenced by temperature or by atmosphere type. At a low inoculum level in the air-stored product, the sanitary risk time was strongly influenced by temperature, and a modified atmosphere caused a significant increase in the maximum cell load reached in the stationary phase. The results show that L. monocytogenes not only survives but is able to proliferate on fresh-cut coconut stored in air as well as in a modified atmosphere, even at a very low temperature (2 degrees C); moreover, the presence of a high cell load can lead to a health risk because this pathogen can grow to risk level during the shelf life of the product.

Decontamination of ochratoxin A by yeasts: possible approaches and factors leading to toxin removal in wine.

Biological decontamination of mycotoxins using microorganisms is one of the well-known strategies for the management of mycotoxins in foods and feeds. Yeasts are an efficient biosorbant, used in winemaking to reduce the concentration of harmful substances from the must which affect alcoholic fermentation (medium-chain fatty acids) or which affect wine quality in a negative way (ethyl phenols and sulphur products). In recent years, several studies have demonstrated the ability of yeasts to remove ochratoxin A (OTA) by live cells, cell walls and cell wall extracts, yeast lees. In spite of the physical and chemical methods applied to remove the toxin, the biological removal is considered a promising solution, since it is possible to attain the decontamination without using harmful chemicals and without losses in nutrient value or palatability of decontaminated food. In addition, adsorption is recognized as economically viable, technically feasible and socially acceptable. This paper intends to review the current achievements of OTA removal mediated by yeasts, the recent updates in the selection of strains acting at the same time as starters and as biological tools to remove OTA and the factors affecting the removal process.

Selection of promising lactic acid bacteria as starter cultures for sourdough: using a step-by-step approach through quantitative analyses and statistics

BACKGROUND The main goal of this research was to show how to use a qualitative assessment of some technological properties of lactic acid bacteria (LAB), combined with the evaluation of the growth index (GI), to select promising starter cultures for sourdough. RESULTS Fifty-four strains of LAB were isolated from a single factory, identified by molecular tools and studied for their growth as a function of NaCl (20, 40 and 65 g L(-1)), temperature (45, 15 and 10 °C), pH 9.2 and acidification in MRS broth. The growth was evaluated through absorbance and data were modelled as GI. GIs were used to build frequency histograms and to run a principal component analysis (PCA). In this way, six strains, identified as Lactobacillus plantarum and able to grow in a wide range of conditions (temperature, pH and salt) and/or able to decrease the pH by 1.77-2.0 units, were selected and tested in a model system (flour and water) to study the acidification after 24 h and their viability after 14 days. CONCLUSION The main result of this paper was to show how a simple step-by-step approach could be a useful tool to select promising starter cultures for sourdough. The method was based on (1) strain identification, (2) assessment of some traits through the GI, combined with simple statistical approaches (frequency histograms and PCA), and (3) preliminary validation in model systems.

Thermal Treatments for Fruit and Vegetable Juices and Beverages: A Literature Overview

Fruit and vegetable juices and beverages are generally preserved by thermal processing, currently being the most cost-effective means ensuring microbial safety and enzyme deactivation. However, thermal treatments may induce several chemical and physical changes that impair the organoleptic properties and may reduce the content or bioavailability of some nutrients; in most cases, these effects are strongly dependent on the food matrix. Moreover, the efficacy of treatments can also be affected by the complexity of the product and microorganisms. This review covers researches on this topic, with a particular emphasis on products derived from different botanical sources. Technologies presented include conventional and alternative thermal treatments. Advances toward hurdle-based technology approaches have been also reviewed.

The role of Plant Growth Promoting Bacteria in improving nitrogen use efficiency for sustainable crop production: a focus on wheat

Due to the increase in both human population growth and environmental pressure, it is necessary to raise agricultural productivity without enhancing environmental footprint. Within this context, soil inoculation with PGPB (Plant Growth Promoting Bacteria) may be considered a promising tool of integrated management systems. In particular, PGPB may improve plant growth either directly, by facilitating resource use or modulating plant hormone levels, or indirectly by decreasing the inhibitory effects of various pathogenic agents. PGPB comprise different functional and taxonomic groups of bacteria like Pseudomonas, Bacillus, Rhizobium and others. Their ability to either mobilize mineral or organic bound nutrients from the pedosphere or to fix atmospheric N2 and make it available to the plants, is a crucial feature in their application. In literature some data are available on the use of commercial PGPB, while less efforts have been made on the study of the effect of autochthonous PGPB isolated from soils on sustainability of cropping systems; thus a literature survey on these aspects was carried out with special focus on wheat, a staple food for a large part of world population. In particular, the main topic of this review is the potential of PGPB to enhance use efficiency of agro-environmental resources focusing on the interaction PGPB-wheat for improving nitrogen use efficiency.

Encapsulation of Active Compounds in Fruit and Vegetable Juice Processing: Current State and Perspectives

The production of value-added and/or functional juices has increased significantly in recent years, following an increased consumer demand to promote health and/or prevent disease through diet and nutrition. Micro and nano-encapsulation are promising technologies to protect and deliver sensitive compounds, allowing a controlled release in the target sites. This paper offers an overview of current applications, limits and challenges of encapsulation technologies in the production of fruit and vegetable juices, with a particular emphasis on products derived from different botanical sources.

How to routinely assess transition, adhesion and survival of probiotics into the gut: a case study on propionibacteria

Summary Two commercial promising probiotic strains (Propionibacterium jensenii and Propionibacterium freudenreichii) were studied to evaluate two basic probiotic requisites (adhesion and survival during the transit into the gut); two commercial starter cultures (Lactobacillus plantarum and Lactobacillus delbrueckii subsp. bulgaricus) were used as references. As an additional goal, the technological robustness was evaluated as growth as a function of pH, temperature and salt. Adhesion was studied as biofilm formation and hydrophobicity, whereas a simplified protocol was used to simulate the transit into the gut, along with the assessment of survival at pH 2.5 and in the presence of 0.3% bile salts. Propionibacteria were hydrophobic and form biofilm on glass slides, thus confirming the correlation of these properties and with the ability to adhere. None of the strains survived after the simulation of the transit into the gut, but this property could be induced in propionibacteria using a simple protocol of adaptive evolution. This paper suggests the possibility of using hydrophobicity as a screening tool to assess adhesion in propionibacteria and highlights the necessity of using a complete protocol of simulation of the gut to study the resistance to the conditions of stomach and intestine to avoid false-positive results.

Survival of Listeria monocytogenes and Staphylococcus aureus in Synthetic Brines. Studying the Effects of Salt, Temperature and Sugar through the Approach of the Design of Experiments

The fermentation of table olives relies on a complex microbiota of lactic acid bacteria (LAB), yeasts, and enterobacteria. Producers often add sugar to increase the growth rate of LAB, “but this practice could also increase the survival rate of some pathogens. Therefore, the main topic of this paper was to study the effect of sugar, salt and temperature on the survival of Staphylococcus aureus and Listeria monocytogenes in a synthetic brine through the theory of the Design of Experiments (simplex centroid). The addition of sugar could prolong the survival time of L. monocytogenes by 40 days, whereas an increase of the temperature caused a decrease of survival from 18 to 3 days. The survival time of S. aureus was prolonged by 50 days by combining sugar (2–4 g/l) and low temperatures (5–15°C). The use of desirability approach and prediction profiles suggests that the prolongation of the survival time of L. monocytogenes could be related to a shift in the geometrical shape of the death kinetic. This paper offers a structured statistical approach on the variables acting on the survival of two pathogens in brines and represents the first step to set up and design a predictive approach for olive producers.