The market sales of ready-to-use fresh vegetables have grown rapidly in recent decades as a result of changes in consumer attitudes, especially consumption of fresh-cut lettuce and carrot due to their use in prepared salads. Chlorine solutions have been widely used to sanitise fruit and vegetables in the fresh-cut industry. However, the association of chlorine with the possible formation of carcinogenic chlorinated compounds in water has called into question the use of chlorine in food processing. There is a real need to find alternatives for preservation of fresh-cut fruit and vegetables in order to improve the efficacy of washing treatments. Alternatives or modified methods have been proposed, as antioxidants, irradiation, ozone, organics acids, modified atmosphere packaging, whey permeate, etc.; however, none have yet gained widespread acceptance by the industry. For this reason the development of alternatives and markers in order to measure the efficacy of these alternatives are needed.

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Extending and Measuring the Quality of Fresh-cut Fruit and Vegetables: a Review

Factors influencing the microbial safety of fresh produce: A review

Essential oil nanoemulsions as antimicrobial agents in food.

Essential oils are complex blends of a variety of volatile molecules such as terpenoids, phenol-derived aromatic components, and aliphatic components having a strong interest in pharmaceutical, sanitary, cosmetic, agricultural, and food industries. Since the middle ages, essential oils have been widely used for bactericidal, virucidal, fungicidal, antiparasitical, insecticidal, and other medicinal properties such as analgesic, sedative, anti-inflammatory, spasmolytic, and locally anaesthetic remedies. In this review their nanoencapsulation in drug delivery systems has been proposed for their capability of decreasing volatility, improving the stability, water solubility, and efficacy of essential oil-based formulations, by maintenance of therapeutic efficacy. Two categories of nanocarriers can be proposed: polymeric nanoparticulate formulations, extensively studied with significant improvement of the essential oil antimicrobial activity, and lipid carriers, including liposomes, solid lipid nanoparticles, nanostructured lipid particles, and nano- and microemulsions. Furthermore, molecular complexes such as cyclodextrin inclusion complexes also represent a valid strategy to increase water solubility and stability and bioavailability and decrease volatility of essential oils.

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Essential Oils Loaded in Nanosystems: A Developing Strategy for a Successful Therapeutic Approach

Nano-encapsulation of fish oil in nano-liposomes and its application in fortification of yogurt.

Eugenol and trans-cinnamaldehyde are natural compounds known to be highly effective antimicrobials; however, both are hydrophobic molecules, a limitation to their use within the food industry. The goal of this study was to synthesize spherical poly (DL-lactide-co-glycolide) (PLGA) nanoparticles with entrapped eugenol and trans-cinnamaldehyde for future antimicrobial delivery applications. The emulsion evaporation method was used to form the nanoparticles in the presence of poly (vinyl alcohol) (PVA) as a surfactant. The inclusion of antimicrobial compounds into the PLGA nanoparticles was accomplished in the organic phase. Synthesis was followed by ultrafiltration (performed to eliminate the excess of PVA and antimicrobial compound) and freeze-drying. The nanoparticles were characterized by their shape, size, entrapment efficiency, and antimicrobial efficiency. The entrapment efficiency for eugenol and trans-cinnamaldehyde was approximately 98% and 92%, respectively. Controlled release experiments conducted in vitro at 37 °C and 100 rpm for 72 h showed an initial burst followed by a slower rate of release of the antimicrobial entrapped inside the PLGA matrix. All loaded nanoparticles formulations proved to be efficient in inhibiting growth of Salmonella spp. (Gram-negative bacterium) and Listeria spp. (Gram-positive bacterium) with concentrations ranging from 20 to 10 mg/mL. Results suggest that the application of these antimicrobial nanoparticles in food systems may be effective at inhibiting specific pathogens.

Practical Application:  Nanoencapsulation of lipophilic antimicrobial compounds has great potential for improving the effectiveness and efficiency of delivery in food systems. This study consisted of synthesizing PLGA nanoparticles with entrapped eugenol and trans-cinnamaldehyde. By characterizing these new delivery systems, one can understand the controlled-release mechanism and antimicrobial efficiency that provides a foundation that will enable food manufacturers to design smart food systems for future delivery applications, including packaging and processing, capable of ensuring food safety to consumers.

Poly (DL-lactide-co-glycolide) (PLGA) nanoparticles with entrapped trans-cinnamaldehyde and eugenol for antimicrobial delivery applications.

We investigated the effects of low-dose electron beam irradiation (1.0, 1.5 and 3.2 kGy) on the quality of commercially prepackaged fresh romaine lettuce hearts. The impact of the irradiation treatment on the functionality of the package was also evaluated. Irradiated samples showed slight changes in color, but these changes were not significantly different ( P >0.05) from the nonirradiated (control) samples. Sample firmness decreased by 49.58% (leaves) and 29.13% (ribs), as the dose level increased. Sensory attributes such as overall quality, color, sogginess, and off-flavor were found less acceptable at the higher dose level. Irradiation affected the respiration rates inside the packages, with lower (10.38%) O 2 and higher CO 2 levels than the control. Irradiation at 1.5 and 3.2 kGy dose levels improved the oxygen barrier capability of the low-density polyethylene (LDPE) bags (7.67% and 4.48%, respectively). Water vapor permeability was unaffected at all the irradiation dose levels. The stiffness of LPDE films did not change due to irradiation treatment. Results from sensory evaluation of produce overall quality suggest a potential fungicidal effect of low-dose irradiation (1.0 kGy) of packaged romaine lettuce hearts without altering the overall quality of the produce as well as the LDPE-packaging characteristics.

Quality of packaged romaine lettuce hearts exposed to low-dose electron beam irradiation

Understanding E. coli internalization in lettuce leaves for optimization of irradiation treatment.

Recent outbreaks associated to the consumption of raw or minimally processed vegetable products that have resulted in several illnesses and a few deaths call for urgent actions aimed at improving the safety of those products. Electron beam irradiation can extend shelf-life and assure safety of fresh produce. However, undesirable effects on the organoleptic quality at doses required to achieve pathogen inactivation limit irradiation. Ways to increase pathogen radiation sensitivity could reduce the dose required for a certain level of microbial kill. The objective of this study was to evaluate the effectiveness of using natural antimicrobials when irradiating fresh produce. The minimum inhibitory concentration of 5 natural compounds and extracts (trans-cinnamaldehyde, eugenol, garlic extract, propolis extract, and lysozyme with ethylenediaminetetraacetate acid (disodium salt dihydrate) was determined against Salmonella spp. and Listeria spp. In order to mask odor and off-flavor inherent of several compounds, and to increase their solubility, complexes of these compounds and extracts with β-cyclodextrin were prepared by the freeze-drying method. All compounds showed bacteriostatic effect at different levels for both bacteria. The effectiveness of the microencapsulated compounds was tested by spraying them on the surface of baby spinach inoculated with Salmonella spp. The dose (D10 value) required to reduce the bacterial population by 1 log was 0.190 kGy without antimicrobial addition. The increase in radiation sensitivity (up to 40%) varied with the antimicrobial compound. These results confirm that the combination of spraying microencapsulated antimicrobials with electron beam irradiation was effective in increasing the killing effect of irradiation.



Practical Application:  Foodborne illness outbreaks attributed to fresh produce consumption have increased and present new challenges to food safety. Current technologies (water washing or treating with 200 ppm chlorine) cannot eliminate internalized pathogens. Ionizing radiation is a viable alternative for eliminating pathogens; however, the dose required to inactivate these pathogens is often too high to be tolerated by the fresh produce without undesirable quality changes. This study uses natural antimicrobial ingredients as radiosensitizers. These ingredients were encapsulated and applied to fresh produce that was subsequently irradiated. The process results in high level of microorganism inactivation using lower doses than the conventional irradiation treatments.

Microencapsulated antimicrobial compounds as a means to enhance electron beam irradiation treatment for inactivation of pathogens on fresh spinach leaves.

Despite the impressive advances in electron beam irradiation, the technology is not ready for application to alt types of fresh and/or minimally processed fruits and vegetables. The relationships between food product quality (nutrients, colour and texture) and irradiation dose are still needed. Cantaloupes (Cucumis melo, L.) have become a product of interest due to the recent food-borne illness outbreaks related to their consumption in the United States and other countries. The main goal of this study was to verify whether treatment of cantaloupes using electron beam technology has any detrimental effects on the product quality. Whole and fresh-cut packaged cantaloupes were irradiated using a linear electron beam accelerator with the single beam (10 MeV) fixture. Samples were stored at 10 0C for zero, 4, 8 and 12 days along with control (non-irradiated) samples and tested for colour, texture (firmness), size (density), sugars and carotene content to determine the effect of irradiation dose level (1.0, 1.5 and 3.1 kGy). Results indicated that irradiation of cantaloupes, as whole fruits with dose up to 1.OkGy, caused no significant changes on the fruit's physical and nutritional quality attributes. Irradiating at higher doses had an undesirable effect on product quality. The fresh-cut packaged cantaloupe may be irradiated up to 1.5 kGy without worsening the product quality attributes. In both cases, carotene content slightly increased as irradiation dose increased. In general, samples irradiated with dose levels between 1.0-1.5 kGy had better quality attributes than the non-irradiated samples.

Elena Castell-Perez

Papers

Poly (DL-lactide-co-glycolide) (PLGA) nanoparticles with entrapped trans-cinnamaldehyde and eugenol for antimicrobial delivery applications.

Quality of packaged romaine lettuce hearts exposed to low-dose electron beam irradiation

Understanding E. coli internalization in lettuce leaves for optimization of irradiation treatment.

Microencapsulated antimicrobial compounds as a means to enhance electron beam irradiation treatment for inactivation of pathogens on fresh spinach leaves.

Electron Beam Irradiation Treatment of Cantaloupes: Effect on Product Quality