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.

Preservation of red pepper flakes using microwave-combined cold plasma treatment.

BACKGROUND: Red pepper flakes are often contaminated with various microorganisms; however, any technologies aiming to decontaminate the flakes should also maintain their quality properties. This study investigated the effect of microwave-combined cold plasma treatment (MCPT) at different microwave power densities on microbial inactivation and preservation of red pepper flakes. Red pepper flake samples inoculated with spores of Bacillus cereus or Aspergillus flavus and without inoculation were subjected to MCPT at 900 W for 20 min at either low microwave power density (LMCPT, 0.17 W m-2 ) or high microwave power density (HMCPT, 0.25 W m-2 ). RESULTS: The numbers of B. cereus and A. flavus spores on red pepper flakes after LMCPT and HMCPT were initially reduced by 0.7 ± 0.1 and 1.4 ± 0.3 log spores cm-2 and by 1.5 ± 0.3 and 1.5 ± 0.2 log spores cm-2 respectively and remained constant for 150 days at 25 °C. Immediately after HMCPT, the concentrations of capsaicin and ascorbic acid in the flakes were significantly lower than in untreated samples; however, no difference in concentration was detected during storage. Neither LMCPT nor HMCPT affected the antioxidant activity or color of the flakes during storage. LMCPT also did not affect the sensory properties and the concentrations of capsaicin and dihydrocapsaicin of the flakes, indicating its suitability in preserving their quality properties. CONCLUSION: MCPT may provide an effective non-thermal treatment for food preservation which can improve the microbial safety and stability of red pepper flakes while maintaining intact their qualitative properties. © 2018 Society of Chemical Industry.

In-package atmospheric cold plasma treatment of bulk grape tomatoes for microbiological safety and preservation.

Effects of dielectric barrier discharge atmospheric cold plasma (DACP) treatment on the inactivation of Salmonella and the storability of grape tomato were investigated. Grape tomatoes, with or without inoculation with Salmonella, were packaged in a polyethylene terephthalate (PET) commercial clamshell container and cold plasma-treated at 35 kV at 1.1 A for 3 min using a DACP system equipped with a pin-type high-voltage electrode. DACP treatment inactivated Salmonella (p < 0.05) without altering the color or firmness of the grape tomatoes (p > 0.05). DACP treatment inactivated Salmonella uniformly in both layers of the double-layer configuration of the grape tomatoes regardless of the position of the tomatoes in each layer. Salmonella was most efficiently inactivated when the headspace to tomato volume ratio of the container was highest. Integration of rolling of tomatoes during treatment significantly increased the Salmonella reduction rates from 0.9 ±â€¯0.2 log CFU/tomato to 3.3 ±â€¯0.5 log CFU/tomato in the double-layer configuration of the tomato samples. Rolling-integrated DACP also initially reduced the number of total mesophilic aerobic bacteria and yeast and molds in the double-layer configuration of tomato samples by 1.3 ±â€¯0.3 and 1.5 ±â€¯0.2 log CFU/tomato, respectively. DACP treatment effectively reduced the growth of Salmonella and indigenous microorganisms at 10 and 25 °C, and did not influence the surface color, firmness, weight loss, lycopene concentration and residual ascorbic acid of grape tomatoes during storage at 10 and 25 °C. DACP treatment holds promise as a post-packaging process for improving microbial safety against Salmonella and storability of fresh grape tomatoes.

Edible Coating Using a Chitosan-Based Colloid Incorporating Grapefruit Seed Extract for Cherry Tomato Safety and Preservation.

Grapefruit seed extract (GSE)-containing chitosan-based coating was developed and applied to cherry tomatoes to protect them from Salmonella invasion and improve their storability. The coating colloids were produced by mixing a chitosan colloid (1% [w/w] chitosan) with GSE at various concentrations (0.5%, 0.7%, 1.0%, and 1.2% [w/w]) using high-shear mixing (10000 rpm, 2 min). Coatings with chitosan colloids containing GSE at 0.0%, 0.5%, 0.7%, and 1.0% (w/w) inactivated Salmonella on cherry tomatoes by 1.0 ± 0.3, 1.2 ± 0.3, 1.6 ± 0.1, and 2.0 ± 0.3 log CFU/cherry tomato, respectively. Coatings both with and without GSE (1.0%) effectively inhibited the growth of Salmonella and total mesophilic aerobes, reduced CO2 generation, and retarded titratable acidity decrease during storage at 10 and 25 °C. The advantage of incorporating GSE in the formulation was demonstrated by delayed microorganism growth and reduced weight loss at 25 °C. The chitosan-GSE coating did not affect lycopene concentration, color, and sensory properties (P > 0.05). Chitosan-GSE coating shows potential for improving the microbiological safety and storability of cherry tomatoes, with stronger efficacy at 25 °C than that of chitosan coating without GSE. PRACTICAL APPLICATION: A novel chitosan coating containing grape fruit seed extract (GSE) improved the microbiological safety against Salmonella and storability of cherry tomatoes without altering their flavor, demonstrating its strong potential as an effective postharvest technology. Chitosan coating containing GSE might be preferable over chitosan coating without GSE for application to tomatoes that are stored at room temperature in that it more effectively inhibits microbial growth and weight loss than the coating without GSE at 25 °C.

Effects of processing parameters on the inactivation of Bacillus cereus spores on red pepper (Capsicum annum L.) flakes by microwave-combined cold plasma treatment.

The efficacy of microwave-combined cold plasma treatment (MCPT) for inactivating Bacillus cereus spores contaminating red pepper (Capsicum annum L.) flakes was investigated. The effects of red pepper drying method, particle size, and water activity (aw) were also evaluated at two levels of microwave power (1700 and 2500W/cm2). The inactivation effect of MCPT was higher at higher microwave power. Spore reduction was more effective with vacuum-dried red pepper than far-infrared-dried flakes. A significantly higher level of spore reduction was observed with the red pepper sample with a smaller surface to volume ratio when one surface (exterior surface) was inoculated (p<0.05). Spore reduction by MCPT at high microwave power increased from 1.7 to 2.6logspores/cm2 when the aw of flake increased from 0.4 to 0.9 (p<0.05). MCPT did not change the color of red pepper flakes. MCPT demonstrated potential as a microbial decontaminating technology for red pepper flakes.

Microbial decontamination of onion powder using microwave-powered cold plasma treatments.

The effects of microwave-integrated cold plasma (CP) treatments against spores of Bacillus cereus and Aspergillus brasiliensis and Escherichia coli O157:H7 on onion powder were investigated. The growth of B. cereus, A. brasiliensis, and E. coli O157:H7 in the treated onion powder was assessed during storage at 4 and 25 °C, along with the physicochemical and sensory properties of the powder. Onion powder inoculated with B. cereus was treated with CP using helium as a plasma-forming gas, with simultaneous exposure to low microwave density at 170 mW m-2 or high microwave density at 250 mW m-2. High microwave density-CP treatment (HMCPT) was more effective than low microwave density-CP treatment (LMCPT) in inhibiting B. cereus spores, but induced the changes in the volatile profile of powder. Increase in treatment time in HMCPT yielded greater inhibition of B. cereus spores. Vacuum drying led to greater inhibition of spores of B. cereus and A. brasiliensis than hot-air drying. HMCPT at 400 W for 40 min, determined as the optimum conditions for B. cereus spore inhibition, initially reduced the numbers of B. cereus, A. brasiliensis, and E. coli O157:H7 by 2.1 log spores/cm2, 1.6 log spores/cm2, and 1.9 CFU/cm2, respectively. The reduced number of B. cereus spores remained constant, while the number of A. brasiliensis spores in the treated powder increased gradually during storage at 4 and 25 °C and was not different from the number of spores in untreated samples by the end of storage at 4 °C. The E. coli counts in the treated powder fell below the level of detection after day 21 at both temperatures. HMCPT did not affect the color, antioxidant activity, or quercetin concentration of the powder during storage at both temperatures. The microwave-integrated CPTs showed potential for nonthermal decontamination of onion powder.

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.

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.

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.