Effects of combined fumaric Acid-UV-C treatment and rapeseed protein-gelatin film packaging on the postharvest quality of ‘Seolhyang’ strawberries

‘Seolhyang’ strawberries were treated with fumaric acid (FA) and UV-C irradiation and packed with rapeseed protein-gelatin (RG) film containing 1% grapefruit seed extract (GSE). The initial population of total aerobic bacteria in the strawberries was 2.9 log CFU/g, while that of samples treated with FA plus UV-C and packed with RG film was 1.3 log CFU/g. For yeast and mold populations, the control had 2.6 log CFU/g, while samples treated with the combined treatment had 1.0 log CFU/g. These results suggest that combined postharvest treatment and RG film packaging can be useful for maintaining the quality of ‘Seolhyang’ strawberries.     

A comparative study on the effectiveness of chlorine dioxide gas, ozone gas and e-beam irradiation treatments for inactivation of pathogens inoculated onto tomato, cantaloupe and lettuce seeds

The increase in reported food-borne outbreaks linked with consumption of raw fruits and vegetables has motivated new research focusing on prevention of pre-harvest produce contamination. This study evaluates and compares the effectiveness of three non-thermal technologies, chlorine dioxide gas, ozone gas and e-beam irradiation, for inactivation of Salmonella enterica and Escherichia coli O157:H7 on pre-inoculated tomato, lettuce and cantaloupe seeds, and also their corresponding effect on seeds germination percentage after treatments. Samples were treated with 10 mg/l ClO₂ gas for 3 min at 75% relative humidity, with 4.3 mg/l ozone gas for 5 min and with a dose of 7 kGy electron beam for 1 min. Initial load of pathogenic bacteria on seeds was ~ 6 log CFU/g. Results demonstrate that all treatments significantly reduce the initial load of pathogenic bacteria on seeds (p < 0.05). In particular, after ozone gas treatments 4 log CFU/g reduction was always observed, despite the seeds and/or microorganisms treated. ClO₂ and e-beam treatments were noticeably more effective against Salmonella on contaminated tomato seeds, where 5.3 and 4.4 log CFU/g reduction were respectively observed. Germination percentage was not affected, except for cantaloupe seeds, where the ratio was significantly lowered after ClO₂ treatments. Overall, the results obtained show the great applicability of these non-thermal inactivation techniques to control and reduce pathogenic bacteria contamination of seeds.     

Combined treatment of fumaric acid with aqueous chlorine dioxide or UV-C irradiation to inactivate Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes inoculated on alfalfa and clover sprouts

Effect of fumaric acid, chlorine dioxide (ClO₂), and UV-C treatment was examined on the inactivation of microorganisms in alfalfa and clover sprouts. Clover sprouts were irradiated with UV-C light (1–10 kJ/m²), and the treatment decreased the population of total aerobic bacteria by 1.03–1.45 log CFU/g. Clover sprouts inoculated with pathogenic bacteria were treated with various concentration of fumaric acid, and 0.5 g/100 ml fumaric acid treatment was the most effective. In addition, the combined treatment of fumaric acid (0.5 g/100 ml)/UV-C (1 kJ/m²) reduced the populations of Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes inoculated on clover sprouts by 3.02, 2.88, and 2.35 log CFU/g. Alfalfa sprouts were treated with ClO₂, fumaric acid, and the combination of fumaric acid/ClO₂. The combined treatment was the most effective, and it reduced the total aerobic bacteria by 3.18 log CFU/g as well as the initial populations of E. coli O157:H7, S. typhimurium, and L. monocytogenes inoculated on alfalfa sprouts by 4.06, 3.57, and 3.69 log CFU/g. These results suggest that the combined treatment of fumaric acid with UV-C or ClO₂ can be useful for improving the microbial safety of alfalfa and clover sprouts.     

Effect of rapeseed protein–gelatin film containing grapefruit seed extract on ‘Maehyang’ strawberry quality

To develop a packaging film for ‘Maehyang’ strawberries, an edible film containing antimicrobial grapefruit seed extract (GSE) was manufactured. Addition of GSE to the rapeseed protein–gelatin (RG) film inhibited the growth of pathogenic bacteria such as Escherichia coli O157:H7 and Listeria monocytogenes. Packaging of ‘Maehyang’ strawberries with the RG film containing 1.0% GSE decreased the populations of total aerobic bacteria and of yeast and moulds in the strawberries by 1.03 and 1.34 log CFU g^?1, respectively, after 14 days of storage, compared to that of the control. Sensory evaluation of the GSE‐RG film‐packaged strawberries produced better sensory scores than did the control. These results suggest that RG film containing GSE can be used to package strawberries and to extend shelf life.     

Preparation of a barley bran protein–gelatin composite film containing grapefruit seed extract and its application in salmon packaging

The physical properties of a composite film prepared from barley bran protein and gelatin (BBG) were investigated. Tensile strength (TS) and elongation at break (E) values of the BBG film decreased as barley bran protein content increased. TS increased with increasing gelatin content, but E values decreased. The optimal conditions for the preparation of the BBG film were 3 g barley bran protein, 3 g gelatin, and 1 g sorbitol in 100 mL film-forming solution. In order to inhibit the growth of pathogenic bacteria, a BBG film containing grapefruit seed extract (GSE) was prepared. After 15 days of storage, populations of Escherichia coli O157:H7 and Listeria monocytogenes inoculated on salmon packaged with the BBG film containing GSE decreased by 0.53 and 0.50 log CFU/g, respectively, compared to the control. Also, packing salmon with the BBG film containing GSE decreased the peroxide value and thiobarbituric acid value by 23.0% and 23.4%, respectively.     

Use of high-concentration-short-time chlorine dioxide gas treatments for the inactivation of Salmonella enterica spp. inoculated onto Roma tomatoes

Salmonella outbreaks have been recently linked to the consumption of fresh tomatoes. Thus, there is a need to develop systems that reduce the risk of microbial contamination to increase product shelf-life and keep fresh fruit attributes. The objectives of this study were to evaluate high-concentration-short-time chlorine dioxide gas treatments effects on Salmonella-inoculated Roma tomatoes and determine the optimal treatment conditions for microbial inactivation and shelf-life extension. Effects of ClO₂ concentration (2, 5, 8 and 10 mg/l) and exposure time (10, 30, 60, 120 and 180 s) on inoculated Roma tomatoes were studied. Salmonella enterica strains, serotype Montevideo, Javiana and Baildon, were used to experimentally inoculate the food product. After ClO₂ treatments, tomatoes were stored at room temperature for 28 days. Inherent microbial population, change in tomato color, and chlorine dioxide gas residuals were evaluated. ANOVA analysis showed that both ClO₂ concentration and treatment time were significant (p < 0.01) for Salmonella inactivation. Surviving Salmonella populations of 3.09, 2.17 and 1.16 log CFU/cm² were obtained treating tomatoes with 8 mg/l ClO₂ for 60 s, 10 mg/l ClO₂ for 120 s, and 10 mg/l for 180 s, respectively (initial Salmonella population: 6.03 ± 0.11 log CFU/cm²). The selected treatments significantly reduced background microflora (p < 0.05), while fruit color and residual contents were not significantly different (p > 0.05), as compared to the control. Results suggest the potential for high-concentration-short-time treatments ClO₂ gas as an effective pathogen inactivation technology for large-scale produce packing operations.     

Physical properties of a composite film containing sunflower seed meal protein and its application in packaging smoked duck meat

Sunflower seed meal protein (SP) films were prepared using various plasticizers, cross-linking agents, Cloisite Na⁺ or red algae, and their physical properties, such as tensile strength (TS), elongation at break (E), and water vapor permeability (WVP) were determined. The TS, E, and WVP of the SP film containing sucrose and fructose (2:1) as a plasticizer and cinnamaldehyde as a cross-linking agent were 3.05 MPa, 34.42%, and 2.25 × 10⁻⁹ g m/m² s Pa, respectively. The incorporation of Cloisite Na⁺ improved the physical properties of the SP film. The TS of the SP/Cloisite Na⁺ composite film containing 3% Cloisite Na⁺ increased by 2.19 MPa, and the WVP of the composite film decreased by 0.52 × 10⁻⁹ g m/m² s Pa compared to the SP film. The incorporation of red algae also improved the TS of the SP film. The TS of the SP composite film containing 1.2% red algae increased by 3.82 MPa compared to the SP film. In addition, an SP/red algae composite film containing grapefruit seed extract (GSE) was prepared and used in food packaging. After 12 days of storage, the population of Listeria monocytogenes inoculated on smoked duck meats packed with the SP/red algae composite film containing 1.2% GSE decreased by 1.31 log CFU/g compared to the control packaging. Therefore, these results suggest that SP composite films can be prepared by the addition of red algae to the SP film–forming solution and that the SP/red algae composite film containing GSE can be used as an antimicrobial food packaging material.     

An innovative water-assisted UV-C disinfection system to improve the safety of strawberries frozen under cryogenic conditions

Strawberries inoculated with Salmonella enterica, Listeria monocytogenes (10⁸ CFU/mL, 50 μL) and murine norovirus (MNV-1; 10⁶ TCID₅₀/mL, 50 μL), were washed for 2 min in a water-assisted UV-C light tank (WUVC) combined or not with 40 mg/L of peracetic acid (WUVC+PA), and 200 mg/L of free chlorine solution (NaClO) with the UV-C lamps switched off. Moreover, a ‘conventional’ dry UV-C treatment (DUVC) was also tested. After 2-min exposure, washing sanitization with chemical agents gave the highest reduction for both bacteria (ca. ≥ 3.3 log CFU/g) and MNV-1 (≥1.8 log TCID₅₀/mL). DUVC treatment proved to be the least effective technology (≤0.6 log CFU/g for bacteria and 1.5 log TCID₅₀/mL for MNV-1). Regarding wash water, no presence of L. monocytogenes and S. enterica were reported with WUVC+PA and NaClO sanitization. After disinfection, samples were frozen at −70 ± 2 °C in a cryogenic freezing cabinet with liquid nitrogen (N₂). For both pathogens, frozen storage after washing substantially enhanced their inactivation in the first 3 days (1.1–4.9 log UFC/g) compared to the reductions obtained the following sampling points (0.0–0.8 log UFC/g). After 90 days, L. monocytogenes and S. enterica were not detected on the samples treated with water-assisted methodologies (WUVC, WUVC+PA and NaClO treatments), whilst MNV-1 was little affected. Further studies are needed to improve norovirus inactivation on frozen strawberries.Industrial relevanceThe present work provides relevant information to the frozen food industry regarding a suitable decontamination alternative to chlorine sanitation. Low-dose immersion-assisted UV-C allows inactivation and inhibition of pathogenic microbiota while generates non-toxic byproducts and allows reusing the process water, contributing to the so-called “smart green growth” attended to provide a more innovative and sustainable future for the food industry.     

Microbial decontamination of black peppercorns by simultaneous treatment with cold plasma and ultraviolet C

An intervention technology employing simultaneous ultraviolet (UV)-C and cold plasma (CP) treatments was developed to inactivate indigenous mesophilic aerobic bacteria in black peppercorns. At higher UV intensity of UV-CP treatment and water activity of black peppercorns, microbial inactivation levels increased up to 0.6 and 1.7 log CFU/g, respectively. Using a response surface analysis, optimum CP voltage and treatment time for inactivating indigenous bacteria in black peppercorns by UV-CP treatment were predicted to be 10.3 kV and 22.1 min, respectively; these inactivated indigenous bacteria and Bacillus tequilensis spores by 3.4 log CFU/g and 1.7 log spores/g, respectively, with minimal increase in temperature (4.5 ± 1.2 °C). The bacterial inactivation rate (3.4 log CFU/g) achieved by UV-CP treatment was higher than the sum (2.7 log CFU/g) of the inactivation rates of individual UV and CP treatments. UV-CP treatment did not alter the color of black peppercorns and shows potential for application in non-thermal microbial decontamination of black peppercorns.Industrial relevanceThis study has developed a novel system for non-thermal microbial inactivation in black peppercorns using simultaneous UV-C and CP treatment (UV-CP treatment). UV-CP treatment was effective in inactivating indigenous bacteria in black peppercorns, including Bacillus tequilensis spores, and had an additive effect on microbial inactivation. The efficacy of treatment in microbial inactivation increased with higher water activity of black peppercorns. The bacterial inactivation efficacy was also influenced by the UV intensity and treatment time. The results of this study demonstrated that UV-CP treatment has the potential to be employed as a non-thermal technology to disinfect black peppercorns and possibly other spices, without affecting their color.     

Ultraviolet light and Ultrasound as non-thermal treatments for the inactivation of microorganisms in fresh ready-to-eat foods

The effects of two non thermal disinfection processes, Ultraviolet light (UV 254 nm) and Ultrasound (US) on the inactivation of bacteria and color in two freshly cut produces (lettuce and strawberry) were investigated. The main scope of this work was to study the efficacy of UV and US on the decontamination of inoculated lettuce and strawberries with a cocktail of four bacteria, Escherichia coli, Listeria innocua, Salmonella Enteritidis and Staphylococcus aureus. Treatment of lettuce with UV reduced significantly the population of E. coli, L. innocua, S. Enteritidis and S. aureus by 1.75, 1.27, 1.39 and 1.21 log CFU/g, respectively. Furthermore, more than a 2-log CFU/g reduction of E. coli and S. Enteritidis was achieved with US. In strawberries, UV treatment reduced bacteria only by 1–1.4 log CFU/g. The maximum reductions of microorganisms, observed in strawberries after treatment with US, were 3.04, 2.41, 5.52 and 6.12 log CFU/g for E. coli, S. aureus, S. Enteritidis and L. innocua, respectively. Treatment with UV and US, for time periods (up to 45 min) did not significantly (p > 0.05) change the color of lettuce or strawberry. Treatment with UV and US reduced the numbers of selected inoculated bacteria on lettuce and strawberries, which could be good alternatives to other traditional and commonly used technologies such as chlorine and hydrogen peroxide solutions for fresh produce industry. These results suggest that UV and US might be promising, non-thermal and environmental friendly disinfection technologies for freshly cut produce.     

The application of high-concentration short-time chlorine dioxide treatment for selected specialty crops including Roma tomatoes (Lycopersicon esculentum), cantaloupes (Cucumis melo ssp. melo var. cantaloupensis) and strawberries (Fragaria × ananassa)

The effects of high-concentration short-time chlorine dioxide (ClO₂) gas treatment on food-borne pathogens inoculated onto the surface of tomatoes, cantaloupes, and strawberries were studied. Produce were spot-inoculated with a mixture of Salmonella enterica (serotypes Montevideo, Javiana and Baildon), Escherichia coli O157:H7 (serotypes 204 P, EDL 933 and C792) or Listeria monocytogenes (serotypes Scott A, F 5069 and LCDC 81-861), and treated with ClO₂ gas at 10 mg/l for 180 s. After ClO₂ gas treatment, surviving populations were determined and shelf-life studies were conducted (microbial spoilage population, change in color and overall appearance). Significant microbial reduction (p < 0.05) was observed for all treated samples. Nearly a 5 Log CFU/cm²Salmonella reduction was found on tomatoes, cantaloupe and strawberries, while a ∼3 Log CFU/cm² reduction was observed for E. coli and Listeria on all produce surfaces. E. coli and Listeria appeared to be more resistant to ClO₂ gas as compared to Salmonella spp. Treatments significantly (p < 0.05) reduced initial microflora population, while produce color surface was not significantly influenced, as compared to the control (p > 0.05). Results obtained suggest the potential use of high-concentration short-time ClO₂ gas treatment as an effective online pathogen inactivation technology for specialty crops in large-scale produce packing operations.     

Application of an active alginate coating to control the growth of Listeria monocytogenes on poached and deli turkey products

The relatively high prevalence of Listeria monocytogenes in ready-to-eat (RTE) turkey products is of great concern. The overall objective of this study was to develop antimicrobial edible coating formulations to effectively control the growth of this pathogen. The antimicrobials studied were nisin (500 IU/g), Novagard CB 1 (0.25%), Guardian NR100 (500 ppm), sodium lactate (SL, 2.4%), sodium diacetate (SD, 0.25%), and potassium sorbate (PS, 0.3%). These were incorporated alone or in binary combinations into five edible coatings: alginate, κ-carrageenan, pectin, xanthan gum, and starch. The coatings were applied onto the surface of home-style poached and processed deli turkey discs inoculated with ~ 3 log CFU/g of L. monocytogenes. The turkey samples were then stored at 22 °C for 7 days. For poached and processed deli turkey, the coatings were found to be equally effective, with pectin being slightly less effective than the others. The most effective poached turkey treatments seemed to be SL (2.4%)/SD (0.25%) and Nisin (500 IU/g)/SL (2.4%), which yielded final populations of 3.0 and 4.9 log CFU/g respectively compared to the control which was 7.9 log CFU/g. For processed deli turkey, the most effective antimicrobial treatments seemed to be Nisin (500 IU/g)/SD (0.25%) and Nisin (500 IU/g)/SL (2.4%) with final populations of 1.5 and 1.7 log CFU/g respectively compared to the control which was 6.5 log CFU/g. In the second phase of the study, home-style poached and store-purchased roasted (deli) turkey inoculated with the pathogen at a level of ~ 3 log CFU/g were coated with alginate incorporating selected antimicrobial combinations and stored for 8 weeks at 4 °C. Alginate coatings supplemented with SL (2.4%)/PS (0.3%) delayed the growth of L. monocytogenes with final counts reaching 4.3 log CFU/g (home-style poached turkey) and 6.5 log CFU/g (roasted deli turkey) respectively while the counts in their untreated counterparts were significantly higher (P < 0.05) reaching 9.9 and 7.9 log CFU/g, respectively. This study therefore demonstrates the effectiveness of using alginate-based antimicrobial coatings to enhance the microbiological safety and quality of RTE poultry products during chilled storage.     

Application of high pressure processing to reduce verotoxigenic E. coli in two types of dry-fermented sausage

The effect of high pressure processing (HPP) on the survival of verotoxigenic Escherichia coli (VTEC) in two types of Norwegian type dry-fermented sausages was studied. Two different types of recipes for each sausage type were produced. The sausage batter was inoculated with 6.8 log₁₀ CFU/g of VTEC O103:H25. After fermentation, drying and maturation, slices of finished sausages were vacuum packed and subjected to two treatment regimes of HPP. One group was treated at 600 MPa for 10 min and another at three cycles of 600 MPa for 200 s per cycle. A generalized linear model split by recipe type showed that these two HPP treatments on standard recipe sausages reduced E. coli by 2.9 log₁₀ CFU/g and 3.3 log₁₀ CFU/g, respectively. In the recipe with higher levels of dextrose, sodium chloride and sodium nitrite E. coli reduction was 2.7 log₁₀ CFU/g in both treatments. The data show that HPP has a potential to make the sausages safer and also that the effect depends somewhat on recipe.     

High hydrostatic pressure processing reduces Salmonella enterica serovars in diced and whole tomatoes

Fresh and fresh-cut tomatoes have been associated with numerous outbreaks of salmonellosis in recent years. One effective post harvest treatment to reduce Salmonella enterica in tomatoes may be high pressure processing (HPP). The objectives of the study were to determine the potential for HPP to reduce S. enterica serovars Newport, Javiana, Braenderup and Anatum in tryptic soy broth (TSB) and to determine the effect of HPP to reduce the most pressure resistant of the four serovars from fresh diced and whole tomatoes. To evaluate pressure resistance, TSB containing 8 log CFU/ml of one of the four serovars was packaged in sterile stomacher bags and subjected to one of three different pressures (350, 450 or 550 MPa) for 120 s. The most pressure resistant S. enterica serovar evaluated was Braenderup. Subjecting the broth culture to 350, 450 and 550 MPa resulted in a 4.53, 5.74 and 7.09 log reduction in S. Braenderup, respectively. Diced tomatoes (150 g) and whole red round tomatoes (approximately 150 g) were inoculated with 0.1 ml of 9.1 log CFU/ml S. Braenderup, and subjected to the same pressure treatments (350, 450 or 550 MPa). Significant reductions of S. Braenderup concentrations in diced tomatoes (P < 0.05) were seen after processing at 350 (0.46 CFU/g), 450 (1.44 log CFU/g), and 550 MPa (3.67 log CFU/g). In whole tomatoes, significant reductions (P < 0.05) were also seen at 350 (1.41 log CFU/g), 450 (2.25 log CFU/g) and 550 MPa (3.35 log CFU/g). HPP may be an effective post harvest strategy to reduce low levels of S. enterica contamination in whole and diced tomatoes.     

Combined antimicrobial effect of oregano essential oil and caprylic acid in minced beef

Oregano essential oil (OEO) and caprylic acid (CA) are highly aromatic natural antimicrobials with limited individual application in food. We proved their combined additive effect when used in meat. Application of 0.5% CA and 0.2% OEO (v/w) with 0.1% of citric acid in vacuum packed minced beef inoculated with Listeria monocytogenes at a concentration of 5 log cells/g reduced counts of lactic acid bacteria by 1.5 log CFU/g and counts of psychrotrophic bacteria and L. monocytogenes by more than 2.5 log CFU/g at the end of storage at 3 °C for 10 days. In sensory evaluation the samples with OEO showed during the whole experiment statistically better scores than control, whereas the samples treated with CA showed worse colour attributes.     

A pilot-scale evaluation of using gaseous chlorine dioxide for decontamination of foodborne pathogens on produce and low-moisture foods

Small-scale studies have shown that chlorine dioxide gas, ClO_2(g), was effective for decontamination of produce, nuts, and spices. This study conducted a pilot-scale evaluation to identify effective ClO_2(g) treatment parameters for commercial-scale applications. The gas was produced by a generator utilizing sodium chlorite and chlorine gas for decontamination of Shiga toxin-producing Escherichia coli (STEC), Listeria monocytogenes, and Salmonella inoculated on tomatoes, blueberries, baby-cut carrots, almonds, and peppercorns. Inoculated samples and 45 kg tomatoes in a 1,246-L treatment chamber were exposed to various ClO_2(g) concentrations (mg/L) and times 9 (hr) at 70–95% RH to determine the treatment effects on the pathogen reductions. Results showed that the treatment caused higher reductions on produce. A ClO_2(g) treatment of 1 mg/L-3 hr at 70% RH reduced 4.9–6.8, 5.1–5.6, and 4.2–6.3 log CFU/g of STEC, L. monocytogenes, and Salmonella, respectively, on produce, with the highest reductions on baby-cut carrots. For almonds and peppercorns, ClO_2(g) treatments under higher RH caused higher reductions. The treatment of 2 mg/L-9 hr or 3 mg/L-4 hr at 95% RH reduced >4.0 log of STEC and Salmonella on almonds, and 1 mg/L-5 hr at 85% RH achieved >5.0 log reductions on peppercorns. Applying moisture to the surfaces of almonds caused >4.0 log reductions using 1 mg/L-5 hr at 95% RH. This study identified effective ClO_2(g) treatment parameters for achieving >4.0 log reductions of common pathogens on tomatoes, blueberries, baby-cut carrots, almonds, and peppercorns and showed that ClO_2(g) generator is suitable for large-scale decontamination. These findings can be used for pilot-scale ClO_2(g) decontamination of these products and for testing using ClO_2(g) for commercial-scale decontamination trials.     

Physical properties of a barley protein/nano‐clay composite film containing grapefruit seed extract and antimicrobial benefits for packaging of Agaricus bisporus

Barley protein (BP) was extracted from barley flour, and a BP film was prepared. To improve the physical properties of the BP film, nano‐clay was incorporated. Among the films prepared, the composite film containing 4% BP/1% Cloisite Na⁺ had the best physical property. The composite film containing grapefruit seed extract (GSE) was prepared and used as a packaging film for the button mushroom. Packing of the mushroom with this film inhibited microbial growth during storage. After 7 days of storage, packaging of mushrooms with the film containing 0.7% GSE reduced the populations of total aerobic bacteria and yeast and moulds by 0.95 and 0.58 log CFU/g, respectively, compared with the control. These results suggest that the BP/Cloisite Na⁺ film containing GSE can be used as an environment‐friendly packaging for maintaining mushroom quality during storage.     

Preparation of red algae film containing grapefruit seed extract and application for the packaging of cheese and bacon

Red algae (RA) film containing grapefruit seed extract (GSE) was used as a wrapping film for cheese and bacon. RA film containing 1% GSE was prepared to inhibit the growth of pathogenic bacteria such as Escherichia coli O157:H7 and Listeria monocytogenes. Wrapping of cheese and bacon with the film decreased the populations of E. coli O157:H7 and L. monocytogenes. After 15 days of storage, wrapping of cheese with the RA film reduced the populations of E. coli O157:H7 and L. monocytogenes by 1.21 and 0.85 log CFU/g, respectively, compared to control. Bacon wrapped with the RA film also decreased the populations of E. coli O157:H7 and L. monocytogenes by 0.45 and 0.76 log CFU/g, respectively. Wrapping of bacon with the RA film decreased peroxide and thiobarbituric acid values. These results suggest that RA film containing GSE is a useful wrapping material for extending the shelf lives of cheese and bacon.     

Efficacy of adding detergents to sanitizer solutions for inactivation of Escherichia coli O157:H7 on Romaine lettuce

Numerous Escherichia coli O157:H7 outbreaks have been linked to consumption of fresh lettuce. The development of effective and easily implemented wash treatment could reduce such incidents. The purpose of this study was to evaluate the addition of food-grade detergents to sanitizer solutions for inactivation of E. coli O157:H7 on Romaine lettuce. Freshly-cut leaves of Romaine lettuce were dip-inoculated to achieve a final cell concentration of 7.8 ± 0.2 log CFU/g, air-dried for 2 h, and stored overnight at 4 °C. Leaves were then washed for 2 min in an experimental short chain fatty acid formulation (SCFA) or in one of the following solutions with or without 0.2% dodecylbenzenesulfonic acid or 0.2% sodium 2-ethyl hexyl sulfate: 1) deionized water; 2) 100 ppm chlorine dioxide; 3) 100 ppm chlorine; and 4) 200 ppm chlorine. Following wash treatment, samples were blended in neutralizing buffer (1:3) and surface plated on the selective media CT-SMAC. The efficacy of wash treatments, with or without the detergents, in inactivating E. coli O157:H7 cells on lettuce leaves were not significantly different. The most effective wash solution was SCFA, which was capable of reducing E. coli O157:H7 populations by more than 5 log CFU/g. The rest of the wash treatments resulted in a population reduction of less than 1 log CFU/g. The effectiveness of SCFA surpasses that of other sanitizer treatments tested in this study and requires further research to optimize treatments to preserve lettuce quality. Conventional detergents did not enhance the efficacy of any of the wash treatments tested during this study.     

Inhibitory effects of lactic acid and lauricidin on spoilage organisms of chicken breast during storage at chilled temperature

Different concentrations of lauricidin (LU, containing 1% lactic acid) and lactic acid alone (LA) were evaluated for their effectiveness in reducing naturally occurring microflora of raw chicken breasts. Chicken breasts were dipped in 0 (control), 0.5, 1.0, 1.5, and 2.0% solutions of LU (w/v) or LA (v/v) for 10, 20, and 30 min and stored at 4 °C for 14 d. Total Plate Counts (TPC) and populations of Pseudomonas spp. and Enterobacteriaceae were determined before and after dipping and after storing for 1, 3, 7, 10, and 14 d. Additionally, Hunter L, a, and b values and pH of the chicken breast were also determined. From the obtained results, TPC on chicken breast treated with LU was found to be decreased by 0.92 to 1.2 log CFU/g from a mean initial log 5.69 CFU/g, while those dipped in LA decreased by 0.53 to 2.36 log CFU/g. Pseudomonas population on chicken breast dipped in LU decreased by 0.79 to 1.77 log CFU/g from an initial 3.90 log CFU/g, while in LA treated it decreased by 0.39 to 1.82 log CFU/g. Enterobacteriaceae counts were also found to be reduced by 0.14 to 1.14 log CFU/g on chicken breast dipped in LU, while the reduction was from 0.59 to 2.18 log CFU/g in chicken breast dipped in LA. The major bacterial types isolated from LU treated chicken breast belonged to the Enterobacteriaceae group, which included: Enterobacter, E. coli and Citrobacter. Whereas, in the LA treated breast it belonged to: Pseudomonas, E. coli, and Kocuria rhizophila (formerly Micrococcus luteus). Dipping chicken breast in LU and LA caused a significant decrease (p ≤ 0.05) in their pH values. Also, treatment with LU and LA caused a slight darkening in color (decreased Hunter L value), increase in redness (increased Hunter a value), and increase in yellowness (increased Hunter b value). Based on the results obtained in the present study, Lactic acid and Lauricidin showed high potential to be used as a sanitizer in reducing the population of spoilage microorganisms naturally occurring on raw chicken, and can be explored commercially for extension of their shelf life.