Carl L. Griffis

Control of Listeria Monocytogenes by Lauric Arginate on Frankfurters Formulated with or without Lactate/Diacetate

Listeria monocytogenes (Lm) is a food safety concern that can be associated with ready-to-eat (RTE) meat and poultry products because of its persistence in the processing environment. Listeriosis has a fatality rate of 28% in immuno-compromised individuals. RTE meats receive a lethal heat treatment but may become contaminated by Lm after this treatment. Federal regulators and manufacturers of RTE meats are working to find additional ways to control postprocess contamination by Lm in RTE meats. This research was initiated to validate combinations of antimicrobials that would produce an immediate lethality of at least 1 log of Lm on artificially contaminated frankfurters, and also suppress Lm growth to less than 2 logs throughout the extended shelf life at refrigerated temperatures (4 degrees C). Based on our studies, 22-ppm lauric arginate (LAE, ethyl-N-dodecanoyl-L-arginate hydrochloride) gave more than a 1-log reduction of Lm surface inoculated onto frankfurters within 12 h. The combination of either 1.8%/0.13% or 2.1%/0.15% potassium lactate/sodium diacetate (L/D) in combination with 22 ppm LAE caused more than a 2-log reduction at 12 h. Storage studies revealed that complementary interactions of L/D and LAE also met the 2nd requirement. This combination initially reduced Lm by 2 logs and suppressed growth to less than 2 logs even at the end of the 156-d storage life for frankfurters. These results confirmed that the combination of L/D with LAE as a postprocessing-prepackaging application could be useful in complying with the USDAs Alternative 1 that requires validation for the control of Lm on RTE frankfurters.

Electrostatic Sprays of Food-Grade Acids and Plant Extracts are More Effective than Conventional Sprays in Decontaminating Salmonella Typhimurium on Spinach

About 40000 people fall victim to Salmonella infections every year in the United States. Recent occurrences of Salmonella contaminated spinach and its recalls have accelerated the need for efficient antimicrobials targeting these pathogens. Our study was aimed at evaluating the inhibitory properties of malic, tartaric, and lactic acids, and grape seed extract (GSE) alone and in combinations and their application methods against Salmonella Typhimurium-inoculated spinach using a response surface method. Fresh spinach leaves were washed, disinfected with sodium hypochlorite solution (0.04% v/v), rewashed with sterile deionized (DI) water, and inoculated with a 2nd-day culture of S. Typhimurium (7.0 log CFU/mL). Adhered S. Typhimurium population on day 0 were 7.5 log CFU/g. These were treated with individual and combinations of organic acids with GSE or DI water (control) adjusted to the same pH as that of the test solutions with both the modes of application and leaves were refrigerated at 4 °C. Malic acid (2%) in combination with GSE (3%) or lactic acid (3%) sprayed electrostatically showed reductions of 2.6 to 3.3 log CFU/g compared to lower log reductions (0.0 to 0.3 log CFU/g) by day 14 if sprayed conventionally. These findings indicate that malic acid in combination with GSE/lactic acid solutions applied by electrostatic spraying exhibited higher inhibition of pathogens than conventional spraying and can be used for commercial applications to enhance food safety.

Electrostatic Spraying of Food-Grade Organic and Inorganic Acids and Plant Extracts to Decontaminate Escherichia coli O157:H7 on Spinach and Iceberg Lettuce

UNLABELLED The prevalence of foodborne illnesses is continually on rise. In the U.S.A., Escherichia coli O157:H7 (E. coli) has been associated with several outbreaks in minimally processed foods. Spinach and lettuce pose higher food safety risks and recurring food recalls suggest the insufficiency of current disinfection strategies. We aimed at offering a natural antimicrobial alternative using organic acids (malic, tartaric, and lactic acids [MA, TA, and LA, respectively]) and grape seed extract (GSE) and a novel application method using electrostatic spraying to evenly distribute the antimicrobials onto produce. Spinach and lettuce samples were washed, sanitized with sodium hypochlorite solution (6.25 mL/L), dip inoculated in water containing E. coli (7.0 log CFU/mL) for 24 h, and rewashed with sterile water to remove nonadhered pathogens. The samples were sprayed electrostatically with MA, LA, and GSE alone and in combinations and for comparison, with phosphoric acid (PA) and pH controls with deionized water adjusted to 1.5/2.3/3.6 and stored at 4 °C. When combined with LA (3%), MA (3%) showed 2.1 to 4.0 log CFU/g reduction of E. coli between the days 1 and 14 on spinach and 1.1 to 2.5 log CFU/g reduction on lettuce. Treatment with PA (1.5%) and PA (1.5%)-GSE (2%) exhibited 1.1 to 2.1 log CFU/g inhibition of E. coli on spinach during the 14-d storage. Our findings demonstrated the efficacy of electrostatic spraying of MA, LA, and GSE on fresh produce to improve the safety and lower the public health burden linked to produce contamination. PRACTICAL APPLICATION Electrostatic spraying is an emerging technique that can be adopted to improve the distribution and application of antimicrobials during fresh produce sanitation. Relatively simple and quick, the process can access most/all parts of produce surface and offer protection from food pathogens. The use of malic and lactic acids with or without grape seed extract can serve as effective antimicrobials when sprayed electrostatically, lowering the risk from postcontamination issues with spinach and iceberg lettuce. This application technology can be extended to improve the commercial food safety of other produce, fruits, poultry, and meat.

Spray application of liquid smoke to reduce or eliminate Listeria monocytogenes surface inoculated on frankfurters.

In a simulated post process contamination scenario liquid smoke was sprayed on the frankfurters after peeling, and then inoculated with Listeria monocytogenes (Lm). Samples that did not receive a liquid smoke spray remained at approximately 2 log cfu/cm(2) during the 48h of storage while the levels on the liquid smoke treated frankfurters continued to decline until they were below detection level (1 cfu/100 cm(2)). A shelf-life study lasting 140 days indicated that liquid smoke suppressed the growth of Lm for up to 130 days. An application of 2 or 3 ml liquid smoke at packaging resulted in at least a 1 log reduction of Lm within 12h post packaging.

Attachment of Salmonella typhimurium to skins of chicken scalded at various temperatures

Microtopography of chicken skin was studied by varying scalding temperature to determine the least favorable skin surface for salmonellae attachment. Birds were scalded at 52, 56, and 60°C, and the changes of skin morphology were examined by light and transmission electron microscopy throughout the whole processing. Breast skins obtained immediately after picking were inoculated with Salmonella typhimurium, and the attachment was quantified by using scanning electron microscopy and microbiological plating techniques. Skins scalded at 52 and 56°C retained most of the epidermis, although the latter temperature caused the loss of twice as much stratum corneum layers and produced a smoother surface than the former. Skins at 60°C began to lose most of epidermal layers during scalding and exposed dermal surface after picking, which was sometimes covered with thin fragmental epidermis or basal tissue. The number of salmonellae attached to 60°C-processed skins was 1.1~1.3 logs higher than those attached to the skins processed at 52 and 56°C, as measured by scanning electron microscopy. Microbiological plating, however, showed no significant difference in attachment among three skins processed at different temperatures. This was probably due to the insensitivity of the plating method to differentiate attachment strengths of salmonellae to the skin. The above results suggest that removal of whole epidermis should be avoided in processing to reduce salmonellae attachment to the skin.

INTERNAL TEMPERATURE OF COOKED CHICKEN MEAT THROUGH INFRARED IMAGING AND TIME SERIES ANALYSIS

A non-invasive method for the estimation of internal temperature of chicken meat immediately after cooking was developed. In this study, a statistical model to express the internal temperature of chicken breast muscle samples in terms of the external temperature and time is presented. For non-invasive and accurate external temperature measurement, an infrared camera based on focal plane array technology and with spectral band of 3.4 to 5 µm was employed. From temperature versus time data, the external temperature (measured from infrared imaging) with internal temperature (measured with embedded thermocouples) and time was correlated through time series analysis. Temperature time series observations were obtained from chicken breast muscle samples with similar thickness and shape, cooked in an industrial multipurpose oven at different cooking conditions. A time series autoregressive model to estimate internal temperature from external temperature data and time is proposed here. An estimation of internal temperature within an accuracy of ±1.22°C for cooling times between 0 and 450 s, and within an accuracy of ±0.55°C for zero seconds (immediately after cooking) resulted from this analysis. This method has great potential for the real-time determination of internal temperature of cooked chicken meat in industrial lines, which can aid quality control personnel and regulators to verify that the minimum endpoint temperature is achieved to ensure food safety.

A system for studying the composting process

Abstract A bench-scale composting system has been developed that permits the natural composting process to occur in the laboratory. The composting material is enclosed in an airtight chamber from which heat loss is restricted by a temperature-controlled water jacket. Carbon dioxide and ammonia are removed from the air in the enclosed chamber and quantified. Test runs demonstrate that temperature increases in the composting material result entirely from internally generated heat.

Effect of electrical stimulation on bacterial contamination of chicken legs

Electrical stimulation was investigated as a method to eliminate or reduce the number of Salmonella typhimurium attached to chicken legs. Salmonellae-inoculated legs were attached to either cathode or anode or placed in an electrical field. In addition, the effect of electrical stimulation on various bacteria in an electrolyte solution was studied in order to determine the feasibility of using this method to prevent cross-contamination of poultry carcasses during processing. Stimulation was accomplished using a square wave with an amplitude of 8.5 to 14.5 volts, a frequency of 0.33 Hz or 100 KHz, and a duty cycle of 67%. Results indicate that electrical stimulation is effective in killing bacteria in solution and in reducing the number of salmonellae attached to chicken legs when legs are attached to anodes. Slight meat damage did occur, however, when chicken legs were connected to either anode or cathode1.z.

Destruction of Salmonella in poultry chiller water using electrical stimulation

Electrical current in combination with a salt was evaluated as a method to destroy Salmonella typhimurium in poultry chiller water. Chiller water from a poultry processing plant was mixed with a salt, sodium chloride (NaCl), sodium nitrate (NaNO3), sodium carbonate (Na2CO3) or trisodium phosphate (Na3PO4), inoculated with S. typhimurium at 1 ¥ 104 CFU/mL, and then treated at 4° C for 60 min using pulsed electrical signals at 10 mA/cm2 current, 1 kHz frequency, and 50% duty cycle. Samples taken at different time intervals were serially diluted, plated on xylose Iysine desoxycholate (XLD) agar, and incubated at 37° C for 18 to 24 h before the colony forming units (CFU) were counted. To detect injured cells, samples were pre-enriched in buffered peptone water at 37° C for 4 to 5 h and then were plated. The results showed that the bacterial death rate, the decimal reduction time or the time required to destroy 90% of S. typhimurium in chiller water, was 2.7 to 3.1 min with 0.15 M NaCl or 0.015 M Na3PO4, 4.7 min with 0.015 M NaCl, and 9.3 to 10.4 min with 0.15 and 0.015 M NaNO3 or 0.015 M Na2CO3. The bacterial death time of S. typhimurium in the treatments with NaCl decreased as salt concentration or electrical current increased.

Pressurized water versus ethanol as a Silybum marianum extraction solvent for inhibition of low-density lipoprotein oxidation mediated by copper and J774 macrophage cells

Silybum marianum contains flavonolignans, termed silymarin (SM), that are therapeutic agents for many inflammation-based diseases including atherosclerosis. Oxidation of human low-density lipoprotein was induced by CuSO4 or J774 macrophage cells and measured by the formation of thiobarbituric acid reactive substances (TBARS). SM was extracted by pressurized hot water (PHWE) or ethanol, and the effects of these extracts on TBARS formation were evaluated in comparison with those of SM preparations made from blending masses of individual flavonolignan standards in ratios identical to those of the water and ethanol extracts. Ethanol-extracted SM and its blended counterpart inhibited the generation of TBARS by 82% and 43%, respectively, at 150 mumol/L doses. TBARS levels in the presence of 150 micromol/L of the PHWE and its blended SM counterpart were reduced by 84% and 38%, respectively. Extracts from milk thistle fruit displayed higher protective effects than blended SM solutions of the same concentration with an identical compositional makeup. The appearance of degradation peaks in the water extract did not create any cytotoxic effects. Results of this study confirm that PHWE can be used to extract flavonolignans from milk thistle and that these extracts may possess therapeutic potential different from or beyond that of traditional organic solvent preparations.