Luis J. Bastarrachea

Biodegradable Poly(butylene adipate‐co‐terephthalate) Films Incorporated with Nisin: Characterization and Effectiveness against Listeria innocua

Biodegradable poly(butylene adipate-co-terephthalate) (PBAT) films incorporated with nisin were prepared with concentrations of 0, 1000, 3000, and 5000 international units per cm(2) (IU/cm(2)). All the films with nisin inhibited Listeria innocua, and generated inhibition zones with diameters ranging from 14 to 17 mm. The water vapor permeability and oxygen permeability after the addition of nisin ranged from 3.05 to 3.61 x 10(11) g m m(-2) s(-1) Pa(-1) and from 4.80 x 10(7) to 11.26 x 10(7) mL.m.m(-2).d(-1).Pa(-1), respectively. The elongation at break (epsilon(b)) was not altered by the incorporation of nisin (P > 0.05). Significant effect was found for the elastic modulus (E) and the tensile strength (sigma(s)) (P < 0.05). The glass transition and melting temperatures with the presence of nisin ranged from -36.3 to -36.6 degrees C and from 122.5 to 124.2 degrees C, respectively. The thermal transition parameters such as the crystallization and melting enthalpies and crystallization temperature were influenced significantly (P < 0.05) by incorporation of nisin into films. The X-ray diffraction patterns exhibited decreasing levels of intensity (counts) as the concentration of nisin increased in a range of 2theta from 8 degrees to 35 degrees . Formation of holes and pores was observed from the environmental scanning electron microscopy images in the films containing nisin, suggesting interaction between PBAT and nisin.

Effects of Air and Freeze Drying on Phytochemical Content of Conventional and Organic Berries

U.S. sales of organic products continue to climb due to consumer perception of both environmental and health benefits of organic produce. The objectives of this study were to evaluate the effects of air and freeze drying and blanching treatment prior to air drying on phytochemical content of conventional and organic red raspberries and blueberries. Total anthocyanins and phenolics contents and total antioxidant activity were determined in two cultivars of blueberry (‘Duke’ and ‘Reka’) and in ‘Meeker’ red raspberry harvested under two different techniques (hand and machine). The phytochemical content was determined after subjecting the berries to air and freeze drying with or without blanching pretreatment. In general, no consistent differences were noted between the phytochemical concentrations in fresh conventional and organic berries. The effect of drying on the retention of phytochemicals depended on drying technique, cultivar, and production system (conventional or organic). Blanching prior to air drying significantly increased the effective moisture diffusivity in both berries, thus reducing the drying time. In general, air drying caused significant reductions in anthocyanins, phenolics, and antioxidant activity in both blueberries and raspberries. Compared to air drying, freeze drying improved retention of phytochemicals during processing and in some cases it even increased the concentration of phytochemicals. The application of blanching resulted in enhanced moisture transport, thus reducing the drying time. The blanching treatment prior to air drying increased the retention of phytochemicals in dried berries.

Antimicrobial Coatings with Dual Cationic and N-Halamine Character: Characterization and Biocidal Efficacy

A method to prepare an antimicrobial coating for food-handling materials is reported. Alternating layers of branched polyethylenimine and styrene maleic anhydride copolymer were applied onto the surface of polypropylene. The resulting coatings had low surface energy and presented enhanced antimicrobial character due to the presence of both cationic and N-halamine forming structures. In its unchlorinated form, the coating inactivated Listeria monocytogenes by ∼3 logarithmic cycles. In the form of N-halamines >5 logarithmic cycles were reached. Microbial inactivation kinetics showed a Weibullian behavior when the coating was unchlorinated and a sigmoidal behavior when chlorinated. Microscopy confirmed that the reduction in the microbial load was due to biocidal effects of the coating and not bacterial adhesion onto the modified surface. The modified surface was able to be repeatedly rechlorinated. Such rechargeable antimicrobial coatings may support improving food safety by reducing cross-contamination of microorganisms from food-processing equipment.

Antimicrobial Food Equipment Coatings: Applications and Challenges

Emerging technologies in antimicrobial coatings can help improve the quality and safety of our food supply. The goal of this review is to survey the major classes of antimicrobial agents explored for use in coatings and to describe the principles behind coating processes. Technologies from a range of fields, including biomedical and textiles research, as well as current applications in food contact materials, are addressed, and the technical hurdles that must be overcome to enable commercial adaptation to food processing equipment are critically evaluated.

Antimicrobial N‐halamine Modified Polyethylene: Characterization, Biocidal Efficacy, Regeneration, and Stability

UNLABELLED Development of antimicrobial materials that regenerate antimicrobial activity represents a novel technology in preventing microbial cross-contamination. We report a method for the application of regenerably antimicrobial N-halamines onto the surface of polyethylene (PE) materials through layer-by-layer (LbL) assembly of polyethyleneimine and poly(acrylic acid). A total of 5, 10, 15, and 20 bilayers were applied. Modified PE had from 49.3 to 293.5 nmol cm(-2) antimicrobial N-halamines from 5 to 20 bilayers after 10 min of chlorination. Each variant of N-halamine modified PE was able to reduce by >5 logarithmic cycles Listeria monocytogenes. The stability of N-halamine modified PE was characterized after extended exposure to chlorine, acidic solutions, and an alkaline cleaner. After an initial conditioning period, materials generated more than double the quantity of N-halamines present on as prepared materials, retaining regenerability for up to 100 chlorination cycles. After the equivalent of 300 washing cycles by buffers (pH values 3, 5, and 7) or a commercial alkaline detergent, there was no change in the number of antimicrobial N-halamines on the modified materials. These results indicate that the reported LbL deposition technique results in antimicrobial N-halamine materials capable of long-term reuse and exposure to harsh chemicals as expected in a food-processing environment. Such robust, regenerably antimicrobial materials could be an effective technology in the food industry to prevent cross-contamination of pathogenic and spoilage microorganisms. PRACTICAL APPLICATION The food contact surface of polyethylene was modified by layer-by-layer deposition of 2 polymers, resulting in a rechargeably antimicrobial surface. Repeated exposure to chlorine regenerated its antimicrobial activity, resulting in greater than 99.999% reduction in Listeria monocytogenes. Materials were stable against repeated washing and exposure to acidic environments. These food contact materials could support current cleaning and sanitization protocols in improving food safety in the processing environment.

On mechanism behind UV-A light enhanced antibacterial activity of gallic acid and propyl gallate against Escherichia coli O157:H7

Possible mechanisms behind the enhanced antimicrobial activity of gallic acid (GA) and its ester propyl gallate (PG) in the presence of UV-A light against Escherichia coli O157:H7 were investigated. GA by itself is a mild antimicrobial and has a pro-oxidant ability. We found that the presence of UV-A light increases the uptake of GA by the bacteria. Once GA is internalized, the interaction between GA and UV-A induces intracellular ROS formation, leading to oxidative damage. Concurrently, GA + UV-A also inhibits the activity of superoxide dismutase (SOD), magnifying the imbalance of redox status of E. coli O157:H7. In addition to ROS induced damage, UV-A light and GA also cause injury to the cell membrane of E. coli O157:H7. UV-A exposed PG caused oxidative damage to the cell and significantly higher damage to the cell membrane than GA + UV-A treatment, explaining its higher effectiveness than GA + UV-A treatment. The findings presented here may be useful in developing new antimicrobial sanitation technologies for food and pharmaceutical industries.

Enhanced antimicrobial effect of ultrasound by the food colorant Erythrosin B

The synergistic combination of the food colorant Erythrosin B (E-B, FD&C 3) (0, 25, and 50μM) and low-frequency ultrasound (20kHz, 0.86-0.90WmL-1) was evaluated against Listeria innocua. Although E-B was antibacterial by itself, the inactivation rate significantly increased in a concentration-dependent manner upon exposure to ultrasound and followed a sigmoidal behavior. The enhanced antimicrobial effect of E-B in the presence of ultrasound can be explained in part from a microbubble disappearance study in which it was confirmed that the presence of E-B enhances inertial cavitation, thereby enhancing the antimicrobial effect of ultrasound. The inactivation rate in a sequential treatment, where L. innocua was sonicated for 4min followed by exposure to 25μM Erythrosin B, was comparable to that obtained by the simultaneous treatment, indicating complementary mechanisms of inactivation. Fluorescence microscopy showed attachment of E-B to the cells, which may explain its intrinsic antimicrobial property. Other mechanism may include the confirmed decrease in the cavitation threshold of water by addition of E-B, resulting in more effective cavitation. The study offers a proof-of-concept of a novel approach to complement ultrasound treatment for enhanced microbial inactivation.

Photoirradiated caffeic acid as an antimicrobial treatment for fresh produce

The antimicrobial efficacy of 400 nm photoirradiated caffeic acid (CA, 5 mM) was evaluated against Escherichia coli O157:H7 and Listeria innocua. A stronger antimicrobial effect was observed on E. coli than on L. innocua where the combined treatment resulted in 4 and 1 log(CFU/mL) reductions, respectively. The treatments effects on cellular metabolism (resazurin assay), uptake of CA (fluorescence technique) and membrane damage (propidium iodide assay) were studied in both species. CA uptake increased in both species, but membrane damage was only observed in E. coli O157:H7. The treatment had minimal impact on metabolic activity in both species. The treatment applied to the surface of spinach leaves was found to be effective against E. coli O157:H7. The novel treatment proposed in this study has the potential to improve the microbial food safety of fresh produce.