Kevin M. Keener

In-package atmospheric pressure cold plasma treatment of cherry tomatoes

Cold plasma is increasingly under research for decontamination of foods, especially fresh fruits and vegetables. The effect of cold plasma on food quality, however, remains under researched. This study investigates the effects of cold plasma generated within a sealed package from a dielectric barrier discharge on the physical quality parameters and respiration rates of cherry tomatoes. Respiration rates and weight loss were monitored continuously, while other parameters are reported at the end of storage period. Differences among weight loss, pH and firmness for control and treated cherry tomatoes were insignificant towards the end of storage life. Changes in respiration rates and colour of tomatoes were recorded as a function of treatment, which were not drastic. The results implicate that cold plasma could be employed as a means for decontamination of cherry tomatoes while retaining product quality.

IMAGE PROCESSING METHOD TO DETERMINE SURFACE AREA AND VOLUME OF AXI-SYMMETRIC AGRICULTURAL PRODUCTS

ABSTRACT An image processing based method was developed to measure volume and surface area of ellipsoidal agricultural products such as eggs, lemons, limes, and peaches. The method assumes that each product has an axi-symmetric geometry and is a sum of superimposed elementary frustums of right circular cones. The product volume and surface area are calculated as the sum of the volumes and surface areas of individual frustums using Matlab®. The dimensions of individual frustums are determined from a digitized picture of the product acquired by a Charged Coupled Device (CCD) camera and processed in Adobe Photoshop®. The volumes and surface areas computed showed good agreement with analytical and experimental results. The developed method proved to be accurate, precise, and easy to use.

Bacterial inactivation by high‐voltage atmospheric cold plasma: influence of process parameters and effects on cell leakage and DNA

This study investigated a range of atmospheric cold plasma (ACP) process parameters for bacterial inactivation with further investigation of selected parameters on cell membrane integrity and DNA damage. The effects of high voltage levels, mode of exposure, gas mixture and treatment time against Escherichia coli and Listeria monocytogenes were examined.

The effects of edible coatings on chicken egg quality under refrigerated storage

Seventy-three billion chicken eggs are produced annually in the United States. However, less than 0.1% of these eggs are exported. Increasing the shelf-life of eggs may increase export sales. The goal of this research was to determine whether food-grade coatings on eggs may extend shelf-life under refrigerated storage. Four food-grade coatings were selected: paraffin wax, mineral oil, soy protein isolate, and whey protein isolate (WPI). These coatings were applied to fresh chicken eggs. The eggs were stored for 12 wk in refrigerated storage at 7 degrees C. Two replicates of the 12-wk study were conducted. Egg properties measured included Haugh units, albumen pH, yolk pH, albumen CO(2) content, vitelline membrane strength, water loss, shell strength, and shell color. Egg functionality measurements included foam volume, angel food cake volume, and emulsion stability. Statistical analysis was performed using the SAS PROC GLIMMIX method (P < 0.05). Results found that coated eggs maintained higher Haugh units beyond 6 wk compared with the uncoated eggs. Also, coated eggs maintained a higher CO(2) content and lower albumen pH than the uncoated eggs over the storage period. Vitelline membrane strength slightly decreased over time in uncoated eggs, but did not change in coated eggs. Overall, oil-, wax-, and WPI-coated eggs maintained higher vitelline membrane strength (14%) than the uncoated eggs. Coating of chicken eggs with a food-grade film (oil, wax, WPI) will extend shelf-life beyond 6 wk.

Performance of Grease Abatement Devices for Removal of Fat, Oil, and Grease

This study assessed the performance of a conventional grease abatement device and the impact of internal geometry modifications on fat, oil, and grease (FOG) removal efficiency. Analysis was performed using experimental results and computational fluid dynamics (CFD) on alternative inlet, outlet, and baffle wall designs. Numerical and experimental results indicated that the conventional two-compartment design leads to substantial FOG short circuiting when operated at a 20-min hydraulic retention time (HRT). Alterations to the inlet configuration and baffle wall arrangement yielded FOG removal enhancements with the 20-min HRT that approached removal performance levels obtained with the standard configurations at the 1-h HRT. CFD simulations effectively reproduced performance trends observed on the lab-scale with the exception of simulations using a distributive inlet tee, where CFD over predicted the removal performance.

Effect of high voltage atmospheric cold plasma on white grape juice quality

BACKGROUND This study focuses on the effects of novel, non-thermal high voltage atmospheric cold plasma (HVACP) processing on the quality of grape juice. A quality-based comparison of cold plasma treatment with thermal pasteurization treatment of white grape juice was done. RESULTS HVACP treatment of grape juice at 80 kV for 4 min resulted in a 7.4 log10 CFU mL-1 reduction in Saccharomyces cerevisiae without any significant (P > 0.05) change in pH, acidity and electrical conductivity of the juice. An increase in non-enzymatic browning was observed, but total color difference was very low and within acceptable limits. Spectrophotometric measurements showed a decrease in total phenolics, total flavonoids, DPPH free radical scavenging and antioxidant capacity, but they were found to be comparable to those resulting from thermal pasteurization. An increase in total flavonols was observed after HVACP treatments. CONCLUSION HVACP treatment of white grape juice at 80 kV for 2 min was found to be comparable to thermal pasteurization in all analyzed quality attributes. HVACP has shown the potential to be used as an alternative to thermal treatment of white grape juice.

Influence of carbon dioxide on the activity of chicken egg white lysozyme

Rapid cooling of shell eggs by using liquid CO(2) has shown increased bactericidal effects along with saturation of the egg albumen with CO(2). Lysozyme is a bactericidal enzyme present in chicken eggs, and it lyses gram-positive bacteria. Newly laid chicken eggs have an initial pH of 7.6 to 8.5 and are saturated with CO(2). During storage, the pH gradually increases to 9.7, accompanied by a loss of CO(2). It is hypothesized that the lysozyme activity is influenced by either CO(2) concentration or pH changes resulting from CO(2) loss. The objective of this study was to determine the lytic activity of purified lysozyme and chicken egg white (unpurified lysozyme) under varying conditions of temperature, pH, and CO(2) gas concentration. Lytic activity was determined by a standard microbial assay using lyophilized Micrococcus lysodeikticus. A 2 × 4 × 2 × 2 × 3 factorial design consisting of 2 temperatures (5 and 22°C), 4 pH (4.5, 6.5, 8.0, and 9.5), 2 treatments (with and without CO(2)), 2 types of lysozyme (purified and unpurified egg white), and 3 replicates was used. The highest lytic activity was found at pH 6.5 and 22°C. At pH 4.5 and 8.0, the addition of CO(2) increased lytic activity by more than 50% at both temperatures. At pH 6.5, lytic activity was maintained with CO(2) addition at both temperatures. At pH 9.5, lytic activity without CO(2) addition was high; however, adding CO(2) reduced lytic activity to zero. In conclusion, both pH and CO(2) treatment influence lysozyme activity.

Quality and Safety Assessment of Packaged Spinach Treated with a Novel Atmospheric, Non-Equilibrium Plasma System

The quality and safety of packaged salad is a major concern to consumers. Atmospheric, non-equilibrium plasma (ANEP) is a non-thermal processing technology capable of treating food inside a sealed package. The particular ANEP system used consists of a pair of electrodes with an adjustable gap distance in which a packaged food can be placed. In this study, whole spinach leaves were treated with ANEP. Samples consisted of single spinach leaves taken from a prepackaged bag of cut spinach leaves. These leaves were either left as such (control) or inoculated with E. coli O157:H7 and placed, aseptically, inside a polyethylene bag containing air or oxygen gas. The samples were treated for 5 min and stored at room temperature (22°C) or refrigeration (5°C) for ½ and 2 h, for inoculated samples, and 24 h. Oxygen, ozone, and nitrous oxide concentrations were measured along with leaf and electrode temperatures before treatment, after treatment, and after storage. Samples were recovered using common microbiological techniques. All samples showed reductions in spoilage organisms except air samples stored at room temperature. In particular, inoculated samples treated and stored in oxygen gas showed no surviving organisms after 24 h. For air treatment, ozone and nitrous oxides showed maximum concentrations, after 5 min, of approximately 1730 ppm and 460 ppm, respectively. The concentrations of these reactive species decreased with time and were not detectable after 24 h. It is suspected that ozone and nitrous oxides play a major role in the decontamination process. The treated spinach showed discoloration and wilting effects compared to control samples. This change in appearance may be caused by high levels of ozone and nitrous oxides generated. This is more likely due to ozone than nitrous oxides because the air treatment showed less visual damage. These results indicate that ANEP is capable of reducing spoilage organisms in packaged spinach. Further research is needed to optimize process parameters to minimize quality changes while maintaining bacterial reductions.

The Potential of Cold Plasma for Safe and Sustainable Food Production

Cold plasma science and technology is increasingly investigated for translation to a plethora of issues in the agriculture and food sectors. The diversity of the mechanisms of action of cold plasma, and the flexibility as a standalone technology or one that can integrate with other technologies, provide a rich resource for driving innovative solutions. The emerging understanding of the longer-term role of cold plasma reactive species and follow-on effects across a range of systems will suggest how cold plasma may be optimally applied to biological systems in the agricultural and food sectors. Here we present the current status, emerging issues, regulatory context, and opportunities of cold plasma with respect to the broad stages of primary and secondary food production.

Effects of Cold Plasma on Food Quality: A Review

Cold plasma (CP) technology has proven very effective as an alternative tool for food decontamination and shelf-life extension. The impact of CP on food quality is very crucial for its acceptance as an alternative food processing technology. Due to the non-thermal nature, CP treatments have shown no or minimal impacts on the physical, chemical, nutritional and sensory attributes of various products. This review also discusses the negative impacts and limitations posed by CP technology for food products. The limited studies on interactions of CP species with food components at the molecular level offers future research opportunities. It also highlights the need for optimization studies to mitigate the negative impacts on visual, chemical, nutritional and functional properties of food products. The design versatility, non-thermal, economical and environmentally friendly nature of CP offers unique advantages over traditional processing technologies. However, CP processing is still in its nascent form and needs further research to reach its potential.