Integrated in-package treatment of hydrogen peroxide and cold plasma for microbial inactivation of cabbage slices.

The efficacy of an in-package microbial inactivation method, combining H2O2 and atmospheric dielectric barrier discharge cold plasma (ADCP) treatments (H2O2-ADCP), in reducing contamination of Brassica oleracea (cabbage) slices was investigated. Cabbage slices were placed in a polyethylene terephthalate container with a H2O2-soaked polypropylene pad attached to the inside of the lid, followed by subjecting the closed container to ADCP treatment. The H2O2-ADCP treatment inactivated Escherichia coli O157:H7 and Listeria monocytogenes, resulting in reductions of 1.8 and 2.0 log CFU/g, respectively, which were greater than the sum of the inactivation effects observed with each individual treatment. The combined treatment decreased the count of Bacillus cereus spores and indigenous bacteria by 1.0 log spores/g and 1.3 log CFU/g, respectively. Moreover, the in-package method did not alter the moisture content or texture of cabbage slices. These results demonstrate the potential of H2O2-ADCP as a microbial decontamination method for packaged cabbage slices.

Improvement of the Antioxidant Activity, Water Solubility, and Dispersion Stability of Prickly Pear Cactus Fruit Extracts Using Argon Cold Plasma Treatment.

Microwave-powered cold plasma (CP) treatment was evaluated as a means to increase the antioxidant activity, water solubility, and dispersion stability of prickly pear cactus fruit (Opuntia ficus-indica (L.) Mill.) extract. The extract (2 g) was treated at various CP generation powers and treatment times at 25 °C to 28 °C. The antioxidant activity of the prickly pear cactus fruit extract increased by 1.8% and 1.7% after CP treatment at 750 W for 40 min and 856 W for 36 min, respectively. Both the water solubility and dispersion stability (delta backscattering) of the extract increased by 2.4% and 0.1%, respectively, following CP treatment at 644 W for 36 min. These results suggest the potential of CP treatment to increase the applicability of the prickly pear cactus fruit extract and possibly other insoluble natural antioxidant compounds in foods by improving their antioxidant activities and solubility in water. PRACTICAL APPLICATION: Prickly pear cactus fruit is a functional food with a high antioxidant concentration. This study demonstrated that cold plasma treatment improved the water solubility and dispersion stability of prickly pear cactus fruit extract without altering or improving its antioxidant activity. The obtained results suggested the potential of applying cold plasma technology to improve the applicability of the extract, which is difficult to solubilize in food systems, to various processed foods.

Development of a Microbial Decontamination System Combining Washing with Highly Activated Calcium Oxide Solution and Antimicrobial Coating for Improvement of Mandarin Storability.

A new microbial decontamination system combining washing with a natural antimicrobial solution and coating with a carnauba wax (CW)-based antimicrobial coating was developed and its effects on mandarin storability were investigated. Mandarins were washed with an antimicrobial solution and/or coated with grapefruit seed extract-CW (GSE/CW). Values for the disease incidence of Penicillium digitatum in untreated mandarins; mandarins coated with GSE/CW without washing; and mandarins coated with GSE/CW after washing with a fumaric acid (FA) solution of slightly acidic electrolyzed water, a highly activated calcium oxide (CaO) aqueous solution, or CaO solution followed by FA solution were 96.0, 70.0, 78.8, 50.0, and 72.2%, respectively. GSE/CW coating after CaO washing was most effective in inhibiting P. digitatum growth during storage at 25 °C. Compared to untreated samples, GSE/CW coating alone or after CaO washing retained CO2 generation, firmness, and total polyphenol content of mandarins at 25 °C. Such treatments also effectively maintained mandarin pH, ascorbic acid concentration, and antioxidant capacity at both 4 and 25 °C. Moreover, GSE/CW coating after CaO washing more effectively inhibited P. digitatum growth at 25 °C and maintained ascorbic acid concentration and antioxidant capacity at 4 and 25 °C than GSE/CW coating alone. The microbial decontamination system integrating CaO washing and GSE/CW coating demonstrates potential for improving mandarin storability by inhibiting P. digitatum growth and improving the preservation of quality properties and sensory characteristics. PRACTICAL APPLICATION: This is the first study to develop a microbial decontamination system involving both washing with a natural antimicrobial solution and carnauba wax coating containing grapefruit seed extract to improve the storability of fruits. This system demonstrated a primary effect of inhibiting fungi that cause mandarin surface decay at 25 °C via the highly activated calcium oxide wash and secondary effects of delaying quality degradation and inhibiting fungal growth by the action of the antimicrobial coating. These effects led to improvements in mandarin storability, along with enhanced visual appeal while not affecting taste, flavor, or texture.

Development of Anti-Insect Microencapsulated Polypropylene Films Using a Large Scale Film Coating System.

Films containing microencapsulated cinnamon oil (CO) were developed using a large-scale production system to protect against the Indian meal moth (Plodia interpunctella). CO at concentrations of 0%, 0.8%, or 1.7% (w/w ink mixture) was microencapsulated with polyvinyl alcohol. The microencapsulated CO emulsion was mixed with ink (47% or 59%, w/w) and thinner (20% or 25%, w/w) and coated on polypropylene (PP) films. The PP film was then laminated with a low-density polyethylene (LDPE) film on the coated side. The film with microencapsulated CO at 1.7% repelled P. interpunctella most effectively. Microencapsulation did not negatively affect insect repelling activity. The release rate of cinnamaldehyde, an active repellent, was lower when CO was microencapsulated than that in the absence of microencapsulation. Thermogravimetric analysis exhibited that microencapsulation prevented the volatilization of CO. The tensile strength, percentage elongation at break, elastic modulus, and water vapor permeability of the films indicated that microencapsulation did not affect the tensile and moisture barrier properties (P > 0.05). The results of this study suggest that effective films for the prevention of Indian meal moth invasion can be produced by the microencapsulation of CO using a large-scale film production system. PRACTICAL APPLICATION: Low-density polyethylene-laminated polypropylene films printed with ink incorporating microencapsulated cinnamon oil using a large-scale film production system effectively repelled Indian meal moth larvae. Without altering the tensile and moisture barrier properties of the film, microencapsulation resulted in the release of an active repellent for extended periods with a high thermal stability of cinnamon oil, enabling commercial film production at high temperatures. This anti-insect film system may have applications to other food-packaging films that use the same ink-printing platform.

Retardation of Listeria monocytogenes growth in mozzarella cheese using antimicrobial sachets containing rosemary oil and thyme oil.

An antimicrobial sachet containing microcellular foam starch (MFS) with embedded rosemary oil and thyme oil was developed to reduce bacterial growth in shredded mozzarella cheese. The efficacy of the volatiles of oils at various concentrations in reducing Listeria monocytogenes as well as the release of the oils from the MFS have been also determined in this study. The cheese, inoculated with a cocktail of 5 strains of L. monocytogenes (approximately 3 log CFU/g), was packaged in a Nylon/EVOH/PE bag. A paper sachet containing MFS embedded with rosemary oil and thyme oil, separately or together, was inserted into the bag. Rosemary and thyme oil volatiles released from the sachet restricted the growth of L. monocytogenes, resulting in a 2.5 log CFU/g reduction on day 9 at 10 °C. The volatile oils also showed inhibitory effects on the growth of lactic acid bacteria (LAB) and total aerobic bacteria (TAB). After 15 d at 10 °C, the numbers of LAB and TAB in the samples containing the sachet with both oils experienced a 1.2 and 1.4 log CFU/g reduction, respectively, compared to untreated samples. Nonetheless, the sachet treatment produced a distinct odor, unfavorably received by the panelists. The results suggest the potential for application of the sachet system for the reduction of growth of L. monocytogenes, LAB, and TAB in food products.

Indian meal moth (Plodia interpunctella)-resistant food packaging film development using microencapsulated cinnamon oil.

UNLABELLED: Insect-resistant laminate films containing microencapsulated cinnamon oil (CO) were developed to protect food products from the Indian meal moth (Plodia interpunctella). CO microencapsulated with polyvinyl alcohol was incorporated with a printing ink and the ink mixture was applied to a low-density polyethylene (LDPE) film as an ink coating. The coated LDPE surface was laminated with a polypropylene film. The laminate film impeded the invasion of moth larvae and repelled the larvae. The periods of time during which cinnamaldehyde level in the film remained above a minimum repelling concentration, predicted from the concentration profile, were 21, 21, and 10 d for cookies, chocolate, and caramel, respectively. Coating with microencapsulated ink did not alter the tensile or barrier properties of the laminate film. Microencapsulation effectively prevented volatilization of CO. The laminate film can be produced by modern film manufacturing lines and applied to protect food from Indian meal moth damage. PRACTICAL APPLICATION: The LDPE-PP laminate film developed using microencapsulated cinnamon oil was effective to protect the model foods from the invasion of Indian meal moth larvae. The microencapsulated ink coating did not significantly change the tensile and barrier properties of the LDPE-PP laminate film, implying that replacement of the uncoated with coated laminate would not be an issue with current packaging equipment. The films showed the potential to be produced in commercial film production lines that usually involve high temperatures because of the improved thermal stability of cinnamon oil due to microencapsulation. The microencapsulated system may be extended to other food-packaging films for which the same ink-printing platform is used.

Development of an anti-insect sachet using a polyvinyl alcohol-cinnamon oil polymer strip against Plodia interpunctella.

Plodia interpunctella is a major storage pest that penetrates into food packaging and causes serious economic losses, as well as posing health risks. The goal of this study was to develop effective anti-insect polymer strips against P. interpunctella by using plant essential oil (EO) and polyvinyl alcohol (PVA). The EO of cinnamon (Cinnamomum zeylanicum, CO) bark was used as an insect repellent, and fumigant mortality and the repellent activity of CO were measured to evaluate subsistent anti-insect properties through newly designed traps. Repellent activity was also examined with several foods to simulate the storage environment. The mortality rate with CO after fumigation for 120 h was 63%. In the repellent assay, CO-treated strips, but not control strips, effectively repelled P. interpunctella in both "with foods" and "without foods" groups. A PVA-CO strip sachet (PCO sachet) was developed to control the volatility of CO, and the PCO sachet demonstrated robust repellent activity. The loading contents of CO at the center and edges of strips were 39.41% and 39.59%, respectively, and through the results of FT-IR, it inferred that CO was physically diffused in the PVA polymer matrix, not forming chemical bonds. In a release test using a gas chromatography, the PCO sachet showed remarkable controlled release of CO. These results demonstrate that the anti-insect effects of CO can be maintained throughout the distribution and storage periods of foods using PCO sachets.

Plum coatings of lemongrass oil-incorporating carnauba wax-based nanoemulsion.

Nanoemulsions containing lemongrass oil (LO) were developed for coating plums and the effects of the nanoemulsion coatings on the microbial safety and physicochemical storage qualities of plums during storage at 4 and 25 °C were investigated. The emulsions used for coating were produced by mixing a carnauba wax-based solution (18%, w/w) with LO at various concentrations (0.5% to 4.0%, w/w) using dynamic high pressure processing at 172 MPa. The coatings were evaluated for their ability to inhibit the growth of Salmonella Typhimurium and Escherichia coli O157:H7 and their ability to preserve various physicochemical qualities of plums. Uniform and continuous coatings on plums, formed with stable emulsions, initially inhibited S. Typhimurium and E. coli O157:H7 by 0.2 to 2.8 and 0.8 to 2.7 log CFU/g, respectively, depending on the concentration of LO and the sequence of coating. The coatings did not significantly alter the flavor, fracturability, or glossiness of the plums. The antimicrobial effects of the coatings against S. Typhimurium and E. coli O157:H7 were demonstrated during storage at 4 and 25 °C. The coatings reduced weight loss and ethylene production by approximately 2 to 3 and 1.4 to 4.0 fold, respectively, and also retarded the changes in lightness and the concentration of phenolic compounds in plums during storage. The firmness of coated plums was generally higher than uncoated plums when stored at 4 °C and plum respiration rates were reduced during storage. Coatings containing nanoemulsions of LO have the potential to inhibit Salmonella and E. coli O157:H7 contamination of plums and may extend plum shelf life.

Quality change of apple slices coated with Aloe vera gel during storage.

Fresh-cut apples are easily susceptible to browning and microbial spoilage. In this study, an edible coating prepared from Aloe vera gel containing antibrowning solution was applied to preserve the quality of fresh-cut apples during storage. Fresh-cut apples were treated with both an Aloe vera gel and an Aloe vera gel containing 0.5% cysteine and then stored at 4 °C for 16 d. The color, firmness, weight loss, soluble solid content, titratable acidity, microbial analysis, and sensory evaluation were analyzed during storage. Fresh-cut apples coated with the Aloe vera gel showed delayed browning and reduced weight loss and softening compared to the control. The Aloe vera gel coating was also effective in reducing the populations of the total aerobic bacteria and yeast and molds. In particular, Aloe vera gel containing 0.5% cysteine was most effective in delaying browning and the reduction of microbial populations among the treatments. These results suggest that an Aloe vera gel coating can be used for maintaining the quality of fresh-cut apples.

Evaluation of the antioxidant activities and nutritional properties of ten edible plant extracts and their application to fresh ground beef.

In this study, we assessed the antioxidant efficacy and nutritional value of 10 leafy edible plants and evaluated their potential as natural antioxidants for meat preservation. We measured total phenolic content, 2,2-diphenyl-1-picryl-hydrazil (DPPH) radical scavenging activity, and vitamin C, chlorophyll, and carotenoid contents of 70% ethanol and water extracts of the edible plants. Based on these results, we investigated the effects of butterbur and broccoli extracts on lipid oxidation in ground beef patties. Plant extracts and butylated hydroxytoluene (BHT) were individually added to patties at both 0.1% and 0.5% (w/w) concentrations. Thiobarbituric acid reactive substance (TBARS) values and color parameters were tested periodically during 12 days of refrigerated storage. TBARS levels were significantly lower (p≤0.05) in the samples containing plant extracts or BHT than the non-treated control. In addition, the beef patties formulated with the selected plant extracts showed significantly (p≤0.05) better color stability than those without antioxidants. These results indicate that edible plant extracts are promising sources of natural antioxidants and can potentially be used as functional preservatives in meat products.

Insect-resistant food packaging film development using cinnamon oil and microencapsulation technologies.

UNLABELLED: Insect-resistant films containing a microencapsulated insect-repelling agent were developed to protect food products from the Indian meal moth (Plodia interpunctella). Cinnamon oil (CO), an insect repelling agent, was encapsulated with gum arabic, whey protein isolate (WPI)/maltodextrin (MD), or poly(vinyl alcohol) (PVA). A low-density polyethylene (LDPE) film was coated with an ink or a polypropylene (PP) solution that incorporated the microcapsules. The encapsulation efficiency values obtained with gum arabic, WPI/MD, and PVA were 90.4%, 94.6%, and 80.7%, respectively. The films containing a microcapsule emulsion of PVA and CO or incorporating a microcapsule powder of WPI/MD and CO were the most effective (P < 0.05) at repelling moth larvae. The release rate of cinnamaldehyde, an active repellent of cinnamaldehyde, in the PP was 23 times lower when cinnamaldehyde was microencapsulated. Coating with the microcapsules did not alter the tensile properties of the films. The invasion of larvae into cookies was prevented by the insect-repellent films, demonstrating potential for the films in insect-resistant packaging for food products. PRACTICAL APPLICATION: The insect-repelling effect of cinnamon oil incorporated into LDPE films was more effective with microencapsulation. The system developed in this research with LDPE film may also be extended to other food-packaging films where the same coating platform can be used. This platform is interchangeable and easy to use for the delivery of insect-repelling agents. The films can protect a wide variety of food products from invasion by the Indian meal moth.