S.I. Roura

Antimicrobial Effectiveness of Bioactive Packaging Materials from Edible Chitosan and Casein Polymers: Assessment on Carrot, Cheese, and Salami

Antimicrobial packaging is one of the most promising active packaging systems for controlling spoilage and pathogenic microorganisms. In this work, the intrinsic antimicrobial properties of chitosan (CH) were combined with the excellent thermoplastic and film-forming properties of sodium caseinate (SC) to prepare SC/CH film-forming solutions and films. The antimicrobial effectiveness of SC, CH, and SC/CH coatings on the native microfloras of cheese, salami, and carrots was evaluated. In vitro assays through the test tube assay indicated that the most significant antimicrobial effect was achieved by CH and SC/CH solutions on carrot and cheese native microfloras. SC film-forming solutions did not exert antimicrobial activity on any of the native microflora studied. SC, CH, and SC/CH films stored in controlled environments showed that the retention of the antimicrobial action was observed until 5-d storage, at 65% relative humidity in both temperatures (10 °C and 20 °C). In vivo assays were also performed with SC, CH, and SC/CH applied as coatings or wrappers on the 3 food substrates. CH and SC/CH applied at both immersion and wrapper exerted a significant bactericidal action on mesophilic, psychrotrophic, and yeasts and molds counts, showing the 3 microbial populations analyzed a significant reduction (2.0 to 4.5 log CFU/g). An improvement of the bactericidal properties of the CH/SC blend respect to those of the neat CH film is reported. The ionic interaction between both macromolecules enhances its antimicrobial properties. Practical Application: The continuous consumer interest in high quality and food safety, combined with environmental concerns has stimulated the development and study of biodegradable coatings that avoid the use of synthetic materials. Among them, edible coatings, obtained from generally recognized as safe (GRAS) materials, have the potential to reduce weight loss, respiration rate, and improve food appearance and integrity. They can be used in combination with other food preservation techniques in order to extend the effectiveness of the food preservation chain. Moreover, antimicrobial films and coatings have innovated the concept of active packaging and have been developed to reduce, inhibit, or delay the growth of microorganisms on the surface of food in contact with the package. The use of antimicrobials packaging films to control the growth of microorganisms in food can have a significant impact on shelf-life extension and food safety. In addition, antimicrobial films can be prepared by the combination of inherent antimicrobial materials (that is, CH), with good film-forming protein-based ones (that is, SC). Therefore, the objective of this work is to study the performance of 2 biodegradable and edible biopolymers and their combination as natural packages for selected food products.

Essential oils as biopreservatives: different methods for the technological application in lettuce leaves.

Investigations were carried out to assess the efficiency of 3 essential oils, clove, tea tree, and rosemary, as natural preservatives during the postharvest of lettuce leaves. The effect of different concentration (1 and 0.5 MIC) of plant essential oils applied in 3 forms (spray, immersion, and capsules) was studied on lettuce leaves. The evolution of different microbial populations was evaluated during refrigerated storage. The application forms of the biopreservatives were shown to be an important factor in determining the effectiveness of the essential oils. Clove and tea tree essential oils at 1 MIC and applied embedded in lactose capsules presented a significant inhibition on mesophilic, psicrotrophic, and coliforms populations, while rosemary in none of the 3 technological applications forms exerted inhibitory effect on all microbial populations evaluated. Essential oils (at 0.5 MIC) applied by spray, immersion, and embedded in lactose capsules exerted lower inhibitory effects, with respect to 1 MIC, on the different microbial populations present on lettuce leaves. At the end of the storage (7 d), lettuce samples treated with tea tree, clove, and rosemary (at 1 and 0.5 MIC) by spray were the only organoleptically acceptable. It is concluded that clove and tea tree essential oils can control different microbial population present in lettuce. Practical Application: The exploration of naturally occurring antimicrobials in food preservation receives increasing attention due to consumer awareness of natural food products. Biopreservatives are useful in extending the shelf life of foods, reducing or eliminating pathogenic bacteria and increasing overall quality of food products. The effectiveness of essential oil application in foods is the result of factor associations such as applications forms, concentration applied, the way of action, storage temperatures. The application methods (spray, immersion, and embedded in lactose capsules) and the concentration of essential oils have been shown to be important factors in determining the effectiveness of these biopreservatives. The oil concentrations required to produce a certain level of inhibition in actual foods could be questionable due to the organoleptic impact. However, these novel natural preservatives in combination with other factors in obstacle technologies are an alternative to control the pathogen growth minimizing undesirable changes in organoleptic characteristics.

Isolation and Identification of Bacillus spp. and Related Genera from Different Starchy Foods

UNLABELLED Samples of butternut squash, potatoes, rice, and wheat flour were analyzed. Bacillus spp. and related species belonging to Paenibacillus and Brevibacillus genera were found in 96% of the samples. In butternut squash, predominant species were Bacillus pumilus and Paenibacillus polymyxa together with other Bacillus spp. species (B. cereus, B. licheniformis, B. sphaericus, and B. subtilis). In all the potato samples, Bacillus species were detected (B. cereus, B. mycoides, and B. licheniformis). Also, Bacillus spp. were detected in 100% of the unhusked rice samples, while incidence in white rice samples was 83%. In total rice samples, B. pumilus, Brevibacillus brevis, and Paenibacillus macerans were the main species and B. cereus, P. polymyxa, B. subtilis, and Brevibacillus laterosporus had the lower percentage. The most important species found in wheat flour was P. polymyxa with colony forming units per gram of about 10(2). As the identified species were potentially causatives of foodborne diseases, attention should be given to sanitary and temperature conditions as critical factors that influence the safety and shelf life of these products. PRACTICAL APPLICATION Foodborne illness produce by B. cereus have been associated with a wide variety of food. In addition, some other Bacillus species have been related to foodborne disease in humans. Information about the virulence mechanisms of other Bacillus spp. is scanty and their risk is underestimated. Identifying the group of food and the food processes in which Bacillus cereus or other Bacillus spp. would be hazardous for human health is vital for the prevention of foodborne outbreak. In this study, we determined the incidence of Bacillus spp. and related genera in some food items of agriculture origin from Argentina. This research is relevant to identify the presence of potentially pathogen Bacillus species and related genera in this type of food.

Effectiveness of edible coatings combined with mild heat shocks on microbial spoilage and sensory quality of fresh cut broccoli (Brassica oleracea L.).

UNLABELLED The use of edible coatings and mild heat shocks is proposed as postharvest treatments to prevent microbial deterioration of refrigerated broccoli. Minimally processed broccoli was coated with either chitosan or carboxymethyl-cellulose (CMC) combined or not with a previous application of a mild heat shock. The evolution of microbial populations (mesophilic, psycrotrophic, Enterobacteriaceae, molds and yeast, and lactic acid bacteria) was studied during 20 d of storage and fitted to Gompertz and logistic models. Results revealed that, at the end of the storage, chitosan coating significantly reduced all microbiological population counts, except lactic acid bacteria; while higher reduction was observed with chitosan coating combined with a heat shock treatment. A significant delay at the beginning of the exponential phase was observed for all the bacterial populations analyzed. On the other hand, CMC coating, with and without a previous thermal treatment, did not exert any antibacterial effect. Excellent agreement was found between experimental microbial counts and predicted values obtained from Gompertz and logistic models. Kinetic modeling was found to be valuable for prediction of microbiological shelf life of broccoli during storage. Results showed that the application of chitosan coating effectively maintained microbiological quality and extended shelf life of minimally processed broccoli. According to these results, the use of the edible chitosan coating alone or in combination with a heat mild shock appear to be a viable alternative for controlling microbiological growth and sensory attributes in minimally processed broccoli. PRACTICAL APPLICATION The continuous consumer interest in high quality and food safety, combined with environmental concern has induced to the development and study of edible coatings that avoid the use of synthetic materials. The edible coatings, formed from generally recognized as safe materials, have the potential to reduce weight loss, respiration rate, and improve food appearance and integrity. It is one of the most effective methods to maintain food quality. On the other hand, heat treatments have been demonstrated to be effective as a nonchemical means of improving postharvest quality for a variety of horticultural products. The applications of mild heat shocks combined with edible coatings constitute an alternative for the natural preservation of crops for which the use of synthetic chemicals is objectionable.

Ultrastructure of Actomyosin in Pre- and Post-Spawning Hake (Merluccius hubbsi Marini) During Frozen Storage

Abstract The degradation of actomyosin in fillets from pre- and post-spawning hake under frozen storage is studied by electron microscopy and by analysis of changes in protein solubility. The ratio of salt soluble protein did not present significant changes during 240 days of frozen storage for post-spawning hake. Meanwhile the same ratio for pre-spawning hake presented a steady decrease. In post-spawning hake the proteins retain some of the characteristics of the native structure with some aggregate formation up to 60 days of storage. In pre-spawning hake the formation of aggregates is already extensive after only 15 days of storage. The solubility of proteins from pre-spawning hake decreased continuously reflecting the changes in the ultrastructure of actomyosin complex. For post-spawning hake, only the formation of soluble aggregates was observed after 240 days of frozen storage.

Using natural antimicrobials to enhance the safety and quality of fresh and processed fruits and vegetables: Application techniques and quality issues

This chapter describes the use of natural antimicrobials as an alternative to synthetic disinfectants in order to assure safety, preserve quality, and extend the shelf life of fruits and vegetables. It also discusses secondary responses induced by the application of natural agents (antioxidant and flavoring effects).

Fruit Processing Byproducts as a Source of Natural Antifungal Compounds

Nowadays, there has been an increasing concern of consumers on foods free or with lower levels of synthetic chemical preservatives, because they could be toxic for humans and the environment. Concomitantly, consumers have also demanded foods with long shelf life and fruit producers and processors must deal with the perishable character of its products and the large percentage of byproducts, such as peels, seeds, and unused flesh that are generated by different steps of the industrial process. It has been reported that the wasted byproducts present high contents of antifungal compounds, providing a potential alternative to protect foods or feeds from fungal contamination. The aim of this chapter is to highlight the importance of the integral exploitation of the fruit byproducts, analyzing the current state of the situation. Additionally, the chapter reviews the most recent investigations on bioactive compounds with antifungal properties extracted from fruit residuals and their possible utilization as antimicrobials not only for the food but also for the cosmetic and pharmaceutical industries.

Clove (Syzygium aromaticum) Oils

Abstract Clove essential oil (Syzygium aromaticum) has been used as a topical anesthetic and flavoring for years. It is known to have antimicrobial, antiinflammatory, and antioxidant activity, mostly related to its content of eugenol and other polyphenolic compounds. Other uses of clove have also arisen, like insect repellent or growth promoter agent. Clove essential oil has a controlling effect over native microflora and over pathogenic microorganisms such as Escherichia coli O157:H7. Clove has been successfully employed as a surface sanitizer agent in lettuce seeds and as a biopreservative in leafy green vegetables (applied either preharvest or postharvest). The application of clove on leafy vegetables also reduced peroxidase activity. Clove essential oil should be considered as viable alternative to chlorine as a sanitizer agent due to its low toxicity and low environmental impact.

Casein and Chitosan Polymers: Use in Antimicrobial Packaging

Abstract Minimal processing operations can alter the integrity of fruits and vegetables and bring about negative effects on quality. Also, the presence of microorganisms on the surface of produce may compromise food safety. Traditionally, edible coatings have been used as a strategy to reduce the deleterious effects that minimal processing imposes on intact vegetable tissues. Biologically active molecules, such as those in chitosan and edible coating from milk protein, have significant potential to curb contaminations associated with food, as well as increasing concerns regarding the negative environmental impact of conventional packaging materials. The protein-polysaccharide complexes could exhibit better functional properties than proteins and polysaccharides alone. An improvement of the bactericidal properties of the CH/SC blend respect to those of the neat CH film is reported. The ionic interaction between both macromolecules enhances its antimicrobial properties. This chapter aims to summarize the most important information on chitosan and casein films from a bioactivity point of view, and to highlight their potential for food preservation technology.

Plant Essential Oils as Antifungal Treatments on the Postharvest of Fruit and Vegetables

Food safety is one of the major issues related to fresh fruit and vegetables. Microbial growth is one of the most important causes of postharvest fruit losses, being fungi the main causal agent associated with the postharvest diseases. The preservation of the ‘freshness’ quality of these products is relevant due to their economical impact. As an alternative to synthetic preservatives, natural antimicrobial agents have attracted the attention of modern consumers and the fresh produce industry. Particularly, natural antimicrobials based on plant essential oils are gaining support. This chapter is a comprehensive review of the use of essential oils from different sources and their constituents on the control of postharvest fungal decay and overall quality preservation of fresh fruit and vegetables. Emphasis has been on the sources of essential oils and their constituents studied up to now, and their effects on controlling postharvest fungal decay, either in vitro or in vivo, and their effect on overall quality and storage life of fresh commodities.