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ARS Home » Northeast Area » Wyndmoor, Pennsylvania » Eastern Regional Research Center » Residue Chemistry and Predictive Microbiology Research » Research » Research Project #420972


Location: Residue Chemistry and Predictive Microbiology Research

2015 Annual Report

1a. Objectives (from AD-416):
To determine sensory, nutritional and/or product quality impacts of efficacious food processing interventions and combinations of interventions. To develop antimicrobial packaging-based treatments for controlling pathogens. To identify compounds of potential concern formed by novel non-thermal food processing interventions. To develop/optimize treatment processes and combinations to control pathogens and to minimize loss of product quality and value.

1b. Approach (from AD-416):
An integrated approach to enhance microbial safety while maintaining product quality will be adopted by combining efficacious treatments and processes with antimicrobial packaging. Current antimicrobial treatments, processes, and intervention technologies that have been demonstrated to be effective in inactivating human pathogens will be modified and evaluated to confirm their effectiveness in obtaining a minimum 3 log CFU/g reduction of E. coli O157:H7 and Salmonella spp. on fresh and fresh-cut produce (mainly leafy green vegetables and tomatoes). Novel intervention technologies with higher efficacy of pathogen reduction will be developed and optimized. The impact of efficacious chemical and physical intervention technologies on sensory properties, nutrients, and shelf-life will be determined using the intensity (time, concentration, dose, etc.) that achieves a 3-log CFU/g reduction of the pathogens. In addition, new antibrowning/antimicrobial formulas will be developed to minimize risk of L. monocytogenes contamination during processing of cut fruit while inhibiting tissue browning. Furthermore, accumulation of chemical by-products as a result of chemical sanitizers and physical interventions will be investigated. Antimicrobial packaging as the final defense against human pathogens will be developed for a variety of food products (fresh-cut produce, meats, etc.) to reduce or control the re-growth of surviving pathogens during storage. Finally, combinations of efficacious intervention technologies with antimicrobial packaging will be evaluated for additive or synergistic inhibition of pathogens and preservation of product quality. Strategies and treatments will be developed to minimize adverse effects of intervention technologies and antimicrobial packaging on product quality. By combining efficacious intervention technologies and treatments with antimicrobial packaging, a 5-log reduction of common pathogens may be achieved. Intervention technologies either alone or in combination with antimicrobial packaging will be transferred to industry to enhance microbial safety of commercial food products.

3. Progress Report:
Within this fiscal year, research has been conducted to evaluate product quality changes as a result of antimicrobial treatments and to combine novel intervention technologies and treatments with antimicrobial coating and film to accomplish milestones in objectives 1, 2 and 4 of the project. Detailed progress to achieve the overall objectives is listed below. Optimizing extraction conditions for lignin extraction is in progress. Identifying and evaluating new antimicrobial materials are one of the important approaches to the development of antimicrobial food packaging. Our previous study demonstrated that lignin possesses antimicrobial and antioxidant properties. However these properties could be affected by the lignin extraction conditions using corn stover as a starting material. Different treatment temperatures, times, and solid-to-liquid ratios were investigated for yield, antimicrobial and antioxidant activities of lignin extracts. The optimum extraction conditions at 50 degrees C, 120 min, and 1/8 for the ratio of corn stover solids to extracting liquid (4% sodium hydroxide) resulted in 4.07 g lignin yield per 12g of corn stover residue. Thus, lignin byproducts showed the potential for their antioxidant and antimicrobial application. Aerosolized antimicrobials have a potential to be more effective in inactivating human pathogens than traditional sanitizer washing due to their higher penetration ability. A study was conducted to evaluate the effects of applying aqueous sanitizers as fine droplets on quality of tomatoes fruit. Cherry tomatoes were treated with atomized FDA (Food and Drug Administration)-approved sanitizers and with combinations of organic acids followed by 21 days of storage at 10 degree C. Changes in color, texture, and nutrients of treated fruit were evaluated in comparison with non-treated control fruits. Results showed that the treatments had no consistent effects on appearance, texture or contents of ascorbic acid, lycopene, and total antioxidants. Furthermore, the shelf-life of tomatoes was not impacted. The results demonstrated that aqueous sanitizers can be applied as an aerosol to maintain quality of tomatoes. Contamination of fresh or minimally processed produce with pathogenic bacteria remains a major public health concern. An integration of processing and packaging is advantageous from the point of safety and quality because treatment intensities required for each individual operation in the integrated treatment strategy are often less compared to single treatment method, which result in less negative impact on product quality. Research has been conducted to integrate organic acid wash with an advanced chlorine-based packaging system for treating tomato fruit. A 2-min wash of stem scar inoculated tomato under mild agitation in water containing 0.5 % of formic and acetic acid mixtures followed by chlorine-based antimicrobial packaging was able to cause a 6-log reduction of a three-serotype mixture of Salmonella enterica, leaving tomato completely free of target pathogen. The integrated treatment also achieved complete reduction of aerobic mesophilic background microorganisms. No visual alteration of color was observed. This integrated treatment approach using rapid acid washes followed by active antimicrobial packaging can ensure safe and effective removal of foodborne pathogens and would greatly benefit the produce industry. In collaboration with other scientists, a series of a newly synthesized phenolic fatty acids were tested for their antimicrobial and antioxidant properties. Results showed that the novel compounds were effective against Gram-positive bacteria such as Listeria, being able to inhibit the growth of bacteria at concentrations below 10 part per million. The compounds also had moderate antioxidant ability. Strawberry is a popular fruit with rich in vitamins and antioxidants, but the possible pathogen contamination is a concern. In this study, antimicrobial coating alone, or in combination with antimicrobial washing, was evaluated for the ability to inhibit the growth of a six-strain composite of E. coli O157: H7, Salmonella, and native microflora on strawberries. The combined treatments significantly inhibited the growth of E. coli O157:H7, Salmonella, and native bacteria as well as mold and yeast on strawberries over 3 weeks at 4 degree C. In addition, the coating treatment reduced the loss of weight and firmness, and color of strawberry during storage. Root, tuber and bulb crops come from soil, hence easily contaminated with pathogenic and spoilage microorganisms, resulting in short shelf life and safety concern. In this study, parsnip was used as a model food, and treated with the combination of sanitizer washing, antimicrobial coating and modified aerosphere package. Preliminary results show that total bacterial population did not grow during 74 days of storage at 4 degree C. Yeasts and molds were reduced to non-detectable level after the treatments and storage, and notable loss in quality was not observed. The treatments may be applied on tuber and root crops for reducing microbial contamination.

4. Accomplishments
1. Antimicrobial packaging combined with pulsed electric field (PEF) pasteurization to improve quality and safety of juice. FDA requires all commercial juice and beverage products be pasteurized. ARS researchers at Wyndmoor, Pennsylvania, investigated an integrated approach for enhancing microbial safety and extending shelf life of juice and beverage products. In this study, pure pomegranate juice was processed in bench scale and commercial scale PEF systems, and packaged in antimicrobial-coated bottles. Juices treated with the combination of PEF and antimicrobial bottles had a shelf-life over 84 days, which significantly extended the microbiological shelf-life of pomegranate juice. The results demonstrated that the combination of antimicrobial packaging and PEF processing is an innovative approach for extending shelf-life and enhancing safety of juice.

2. Development of new edible coating solutions and films using natural biopolymers and nanotechnology. The contamination of foodborne pathogens in ready-to-eat meat products has been a concern for the meat industry. ARS researchers at Wyndmoor, Pennsylvania, developed edible antimicrobial composite films from micro-emulsions containing all-natural compounds using high pressure homogenization (HPH) technology. HPH treatment significantly reduced polymer particle sizes in the emulsion to about one micrometer. The films from the coating solution were softer, less rigid, and more stretchable than those without HPH treatments. The composite films inactivated Listeria innocua in a culture medium by 99.9999% after 2 days at 22 degree C and Listeria innocua on the surface of ready-to-eat meat samples by 99.99% after 35 days at 10 degree C. The new edible antimicrobial film and coating could be used to enhance safety of ready-to-eat foods.

3. Bio-based antimicrobials for safer fresh produce. Postharvest washing is an important step for controlling foodborne pathogens for the fresh produce industry. ARS researchers at Wyndmoor, Pennsylvania, investigated the feasibility of several types of bio-based antimicrobials on inactivation of Escherichia coli O157:H7 in wash water and on baby spinach leaves. Results demonstrated that a vitamin B1-derived compound and a bio-surfactant isolated from yeast reduced E. coli O157:H7 by more than 99%. Therefore, the natural and bio-based antimicrobials offer attractive and environmentally friendly alternatives to currently used sanitizer(s).

4. Development of novel antimicrobial formulation and safe and effective integrated treatment for produce safety. Chlorine is commonly used by the fresh produce industry. However, the efficacy of chlorine in inactivating human pathogens on fresh produce is very limited, and there is a concern on the formation of potential harmful chemical by-products. ARS researchers at Wyndmoor, Pennsylvania, developed a unique antimicrobial formulation, HEN, combining sanitizer activity of hydrogen peroxide with a surfactant (EDTA) and nisin. In a laboratory study, the integrated approach using a low dose (0.6 kilojoule per square meter) ultraviolet (UV) treatment in combination with 2 min wash in HEN yielded significantly higher inactivation (99.998%) of Salmonella spp. compared to current chlorine based wash (99.5%) alone on tomato fruit. Hence the newly developed integrated method employing a 10 sec UV treatment with 2 min washes in HEN solution is more effective than current chlorine-based washes. The new integrated approach can be used by fruit industry to reduce the contamination with foodborne pathogens.

5. Improving microbial safety of low moisture foods. Human pathogens such as B. cereus can survive well in low moisture foods such as flours over a long periods of time, and results in outbreaks of foodborne illness and recalls of contaminated products. ARS scientists in Wyndmoor, Pennsylvania, investigated the effectiveness of ionizing radiation on naturally contaminated B. cereus (both spores and vegetative forms) in mesquite pod flour. The flour, a gluten-free food, is one of the most important food staples for indigenous people. Results showed that irradiation at a moderate dose of 6 kilogray reduced population of the pathogen in the flour with initial population of more than 100,000 cells per gram to a non-detectable level. The information from the study would be helpful to FDA in making a science-based decision for the approval of irradiation of low-moisture foods and to food industry in enhancing the microbial safety of low moisture food.

Review Publications
Jin, Z.T., Guo, M., Yang, R. 2014. Combination of pulsed electric field processing with antimicrobial bottle for extending microbiological shelf-life of pomegranate juice. International Journal of Food Science and Technology. 26:153-158.
Fan, X. 2014. Furan formation from fatty acids as a result of storage, gamma irradiation, UV-C and heat treatments. Journal of Agricultural and Food Chemistry. DOI:10.1016/j.foodchem.2014.12.002.
Jin, Z.T., Guo, M., Zhang, H.Q. 2015. Upscaling from benchtop processing to industrial scale production: More factors to be considered for pulsed electric field food processing. Journal of Food Engineering. 146:72-80.
Yun, J., Fan, X., Li, X., Jin, Z.T., Jia, X., Mattheis, J.P. 2015. Natural surface coating to inactivate Salmonella enterica Serovar Typhimurium and maintain quality of cherry tomatoes. International Journal of Food Microbiology. 193:59-67.
Gurtler, J., Bailey, R., Jin, Z.T., Fan, X. 2014. Inactivation of an E.coli 0157:H7 and Salmonella composite on fresh strawberries by varying antimicrobial washes and vacuum perfusion. International Journal of Food Microbiology. 139:113-118.
Lacombe, A.C., Niemira, B.A., Gurtler, J., Fan, X., Sites, J.E., Boyd, G., Chen, H. 2015. Atmospheric cold plasma inactivation of Aerobic Microorganisms on blueberries and effects on quality attributes. Food Microbiology. 46:479-484.
Gurtler, J., Bailey, R., Cray, W.C., Hinton Jr, A., Meinersmann, R.J., Ball, T.A., Jin, Z.T. 2015. Salmonella spp. isolated from ready-to-eat pasteurized liquid egg produce: thermal resistance, biochemical profile, and fatty acid analysis. International Journal of Food Microbiology. 206:109-117.
Kara, H.H., Xiao, F., Sarker, M.I., Jin, Z.T., Sousa, A.M., Liu, C., Tomasula, P.M., Liu, L.S. 2015. Antibacterial poly(lactic acid) (PLA) films grafting electrospun PLA/Ally isothioscyanate (AITC) fibers for food packaging. Journal of Applied Polymer Science. DOI: 10.1002/APP.42475.
Mukhopadhyay, S., Ukuku, D.O., Juneja, V.K. 2015. Effects of different combined non-thermal treatments against Salmonella enterica on plum tomatoes. Food Control. 56:147-154. DOI: 10.1016/j.foodcont.2015.03.020.
Juneja, V.K., Cadavez, V., Gonzales-Barron, U., Mukhopadhyay, S. 2014. Modelling the effect of pH, sodium chloride and sodium pyrophosphate on the thermal resistance of Escherichia coli O157:H7 in ground beef. Food Research International. 69:289-304.
Ukuku, D.O., Onwulata, C.I., Thomas-Gahring, A.E., Mukhopadhyay, S., Tunick, M.H. 2014. Behavior of native microbial populations of WPC-34 and WPC-80 whey protein stored at different temperatures. Journal of Food Processing and Technology. DOI: 10.4172/2157-7110l.1000304.
Fan, X., Sokorai, K.J. 2015. Formation of trichloromethane in chlorinated water and fresh-cut produce and as a result of reacting with citric acid. Postharvest Biology and Technology. 109:65-72.
Fan, X., Felker, P., Sokorai, K.J. 2015. Decontamination of mesquite pod flour, naturally contaminated with Bacillus cereus and formation of furan by ionizing irradiation. Journal of Food Protection. 78(5):954-962.
Zhang, Q., Mukhopadhyay, S., Hwang, C., Xu, X., Juneja, V.K. 2015. Modeling the survival of Salmonella on slice cooked ham as a function of apple skin polyphenols, acetic acid, oregano essential oil and carvacrol. Journal of Food Processing and Technology. DOI: 10.1111/jfpp.12486.
Ukuku, D.O., Geveke, D.J., Mukhopadhyay, S., Olanya, O.M., Juneja, V.K. 2014. Survival, injury and inactivation of Escherichia coli 0157:H7, salmonella and aerobic mesophilic bacteria in apple juice and cider amended with nisin-edta. Journal of Food Processing and Technology. 5:385.