The purpose of this study was to investigate the efficacy of pulsed light (PL), a new formula of sanitizer (HEN) consisting of hydrogen peroxide, EDTA and Nisin, as well as synergy of PL and HEN ...sanitizer (PL-HEN) wash in inactivating E. coli O157:H7 on spinach. The treatment effect on microbial loads and apparent quality during 13 days storage at 4 °C was also determined. A bacterial cocktail containing three strains of E. coli O157:H7 was used as inoculum based on their association with produce-related outbreaks. Spinach leaves were spot inoculated on surface before treating with PL (1–63J/cm2), HEN sanitizer wash (2 min) or their combinations. PL inactivation was influenced significantly at low doses. Treatment dose of 15.75 J/cm2, equivalent to 15 s intense PL treatment, was found optimal above which adverse quality effect was evident. The optimal PL dose resulted 2.7 log CFU/g reduction of E. coli O157:H7 while a rapid 2 min wash in sanitizer formulation HEN, provided comparatively low, 1.8 log CFU/g, reduction of the pathogen. Two different sequences of PL and HEN treatment combinations were tested. In PL-HEN treatment, inoculated leaves were first treated at optimal PL dose (15.75 J/cm2) followed by 2 min immersion in HEN whereas in HEN-PL treatment, leaves were first washed in HEN before PL exposure. HEN-PL treatment indicated a compound inactivation activity (4.6 logs reduction) while PL-HEN treatment indicated a strong synergistic inactivation as E. coli cells were not detectable after treatment indicating >5 log reduction. The PL-HEN treatment not only significantly reduced spoilage microbial populations on spinach but also slowed their growth during storage. Furthermore, the visual and firmness quality of spinach were not significantly affected by the PL-HEN treatment. Overall, our results demonstrate that integrated PL-HEN technology can be used to enhance microbial safety of spinach.
•Pulsed light (PL) is effective for surface decontamination of E. coli O157:H7 on spinach.•Combinations of PL and sanitizer formula showed additive or synergistic effects.•PL-sanitizer combination inactivated >5 log10 CFU/g of spot inoculated E. coli.•Spinach quality is not significantly impacted by the combined treatment.•PL-sanitizer technology could potentially be used as an alternative to chlorine washing.
For health reasons, people are consuming fresh-cut fruits with or without minimal processing and, thereby, exposing themselves to the risk of foodborne illness if such fruits are contaminated with ...bacterial pathogens. This study investigated survival and growth parameters of Escherichia coli O157:H7, Salmonella, Listeria monocytogenes, and aerobic mesophilic bacteria transferred from cantaloupe rind surfaces to fresh-cut pieces during fresh-cut preparation. All human bacterial pathogens inoculated on cantaloupe rind surfaces averaged ∼4.8 log CFU/cm(2), and the populations transferred to fresh-cut pieces before washing treatments ranged from 3 to 3.5 log CFU/g for all pathogens. A nisin-based sanitizer developed in our laboratory and chlorinated water at 1,000 mg/liter were evaluated for effectiveness in minimizing transfer of bacterial populations from cantaloupe rind surface to fresh-cut pieces. Inoculated and uninoculated cantaloupes were washed for 5 min before fresh-cut preparation and storage of fresh-cut pieces at 5 and 10°C for 15 days and at 22°C for 24 h. In fresh-cut pieces from cantaloupe washed with chlorinated water, only Salmonella was found (0.9 log CFU/g), whereas E. coli O157:H7 and L. monocytogenes were positive only by enrichment. The nisin-based sanitizer prevented transfer of human bacteria from melon rind surfaces to fresh-cut pieces, and the populations in fresh-cut pieces were below detection even by enrichment. Storage temperature affected survival and the growth rate for each type of bacteria on fresh-cut cantaloupe. Specific growth rates of E. coli O157:H7, Salmonella, and L. monocytogenes in fresh-cut pieces were similar, whereas the aerobic mesophilic bacteria grew 60 to 80 % faster and had shorter lag phases.
The purpose of this investigation was to identify and quantify the volatile chemical spoilage indexes (CSIs) for raw Atlantic salmon (Salmo salar) fillets stored under aerobic storage conditions at ...4, 10 and 21 °C in relation to microbial and sensory shelf lives. The volatile organic compounds (VOCs) were analyzed with SPME-GC-MS technique. Through multivariate chemometric method, hierarchical cluster analysis (HCA) and Pearson's correlations, the CSIs: trimethylamine (TMA), ethanol (EtOH), 3-methyl-1-butanol (3Met-1But), acetoin and acetic acid (C2) were selected from the group of 28 detected VOCs. At the moment of microbiological shelf life established at total viable count (TVC) of 7.0 log CFU/g, the CSIs achieved levels of 11.5, 38.3, 0.3, 24.0 and 90.7 μg/g of salmon for TMA, EtOH, 3M-1But, acetoin and C2, respectively. Pseudomonas spp. was found as major specific spoilage organism (SSOs), suitable for shelf life prediction using modified Gompertz model at the cut-off level of 6.5 log CFU/g. H2S producing bacteria and Brochothrix thermosphacta were considered as important spoilage microorganisms; however, they were not suitable for shelf life estimation. Partial least square (PLS) regression revealed possible associations between microorganisms and synthetized VOCs, showing correlations between Pseudomonas spp. and 3Met-1But and aldehydes synthesis, lactic acid bacteria were linked with EtOH, C2 and esters, and B. thermosphacta with acetoin formation.
•Microbial and sensory shelf lives were compared for raw salmon stored aerobically.•Pseudomonas ssp. were found major SSOs, suitable for shelf life predictions.•Chemical spoilage indexes (CSIs) were identified and quantified using SPME-GC-MS.•The CSIs are: trimethylamine, ethanol, 3-methyl-1-butanol, acetoin and acetic acid.•PLS revealed probable bacteria-volatile associations during salmon deterioration.
Fresh-cut cantaloupes have been associated with outbreaks of Salmonellosis. Minimally processed fresh-cut fruits have a limited shelf life because of deterioration caused by spoilage microflora and ...physiological processes. The objectives of this study were to use a wet steam process to 1) reduce indigenous spoilage microflora and inoculated populations of Salmonella, Escherichia coli O157:H7 and Listeria monocytogenes on the surface of cantaloupes, and 2) reduce the populations counts in cantaloupe fresh-cut pieces after rind removal and cutting. The average inocula of Salmonella, E. coli O157:H7 and Listeria monocytogenes was 107CFU/ml and the populations recovered on the cantaloupe rind surfaces after inoculation averaged 4.5, 4.8 and 4.1logCFU/cm2, respectively. Whole cantaloupes were treated with a wet steam processing unit for 180s, and the treated melons were stored at 5°C for 29days. Bacterial populations in fresh-cut pieces prepared from treated and control samples stored at 5 and 10°C for up to 12days were determined and changes in color (CIE L*, a*, and b*) due to treatments were measured during storage. Presence and growth of aerobic mesophilic bacteria and Salmonella, E. coli O157:H7 and L. monocytogenes were determined in fresh-cut cantaloupe samples. There were no visual signs of physical damage on all treated cantaloupe surfaces immediately after treatments and during storage. All fresh-cut pieces from treated cantaloupes rind surfaces were negative for bacterial pathogens even after an enrichment process. Steam treatment significantly (p<0.05) changed the color of the fresh-cut pieces. Minimal wet steam treatment of cantaloupes rind surfaces designated for fresh-cut preparation will enhance the microbial safety of fresh-cut pieces, by reducing total bacterial populations. This process holds the potential to significantly reduce the incidence of foodborne illness associated with fresh-cut fruits.
•Wet steam processing killed Salmonella, E. coli O157:H7 and Listeria monocytogenes bacteria inoculated on cantaloupes rind surfaces•This process reduced transfer of all bacterial pathogens to fresh-cut pieces•Recovery of bacterial pathogens in fresh-cut pieces from treated melons averaged <2 CFU/g•There were no visual signs of damage on all treated cantaloupes and during storage.•This process holds the potential to significantly reduce the incidence of foodborne illness associated with contaminated fresh-cut fruits
Surface structure and biochemical characteristics of bacteria and produce play a major role in how and where bacteria attach, complicating decontamination treatments. Whole cantaloupe rind surfaces ...were inoculated with Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes at 10(7) CFU/ml. Average population size of Salmonella, Escherichia coli O157:H7, and L. monocytogenes recovered after surface inoculation was 4.8 ± 0.12, 5.1 ± 0.14, and 3.6 ± 0.13 log CFU/cm(2), respectively. Inoculated melons were stored at 5 and 22°C for 7 days before washing treatment interventions. Intervention treatments used were (i) water (H2O) at 22°C, (ii) H2O at 80°C, (iii) 3% hydrogen peroxide (H2O2) at 22°C, and (iv) a combination of 3% H2O2 and H2O at 80°C for 300 s. The strength of pathogen attachment (SR value) at days 0, 3, and 7 of storage was determined, and then the efficacy of the intervention treatments to detach, kill, and reduce transfer of bacteria to fresh-cut pieces during fresh-cut preparation was investigated. Populations of E. coli O157:H7 attached to the rind surface at significantly higher levels (P < 0.05) than Salmonella and L. monocytogenes, but Salmonella exhibited the strongest attachment (SR value) at all days tested. Washing with 3% H2O2 alone led to significant reduction (P < 0.05) of bacteria and caused some changes in bacterial cell morphology. A combination treatment with H2O and 3% H2O2 at 8°C led to an average 4-log reduction of bacterial pathogens, and no bacterial pathogens were detected in fresh-cut pieces prepared from this combination treatment, including enriched fresh-cut samples. The results of this study indicate that the microbial safety of fresh-cut pieces from treated cantaloupes was improved at day 6 of storage at 5°C and day 3 of storage at 10°C.
The objective of this study was to evaluate inactivation of inoculated Salmonella enterica on grape tomato stem scars exploiting integrated treatment of organic acid wash (AW) followed by ...chitosan-allyl isothiocyanate (CT-AIT) coating. The treatment effect on microbial loads and fruit quality during 21days storage at 10°C was also determined. A bacterial cocktail containing three serotypes of Salmonella enterica was used for this study based on their association with produce-related outbreaks. Tomatoes were spot inoculated on stem scars and then immersed in an organic acid solution (700ml) containing 0.5% (v/v) each of acetic (AA) and formic acid (FA) to wash under mild agitation for 1min at ambient temperature (22°C) followed by 1min dipping in a coating solution containing 6mlAIT/g CT. AW in 0.5% organic acid (AA+FA) for 1min reduced Salmonella population by 2.7logCFU/g from an initial load of 7.8logCFU/g, while additional coating treatment of AW tomatoes reduced the pathogens on stem scars to undetectable levels (<0.7logCFU/g), achieving, in combination, a >7logCFU/g reduction for the pathogen. Although the populations of Salmonella in the controls (approx. 7.8logCFU/g stem scar) did not change significantly during 21days of storage at 10°C, the populations were reduced to undetectable level in the integrated (AW plus CT-AIT) treated stem scars on day 1 and no regrowth was observed during storage. The treatment significantly (p<0.05) reduced background bacterial loads to approx. 1.3logCFU/g and the population remained unchanged through day 21 at 10°C. The treatment also completely inactivated mold and yeast on day 1 with no growth reoccurrence. These results indicate that the integrated treatment can provide a safe and effective intervention strategy for grape tomatoes.
•Integrated inactivation of Salmonella with antimicrobial wash and coating is highly effective.•Combination of acid wash and antimicrobial coating reduced Salmonella by 7 log on tomato.•Strong decontamination and favorable quality effects suggest potential application in produce industry.
The microbial safety of produce continues to be a real concern. The objective of this study was to investigate the efficacy of high intensity short time pulsed light (PL) application on survival of ...Salmonella in packaged cherry tomato. Treatment effects on reduction of native microbiota and quality were also evaluated. Stem scars of cherry tomatoes, inoculated with a three serotypes cocktail of Salmonella enterica, was treated with PL for up to 60 s. Polyethylene (PE) films of 25.4, 50.8 and 76.2 μm thickness were used for packaging treatment. A10 s treatment equivalent to a fluence dose of 10.5 J/cm2 was considered optimum. Both packaged and direct PL treatments provided >1 log reduction of the pathogen in 10 s (10.5 J/cm2). Direct treatment for 10 s resulted in 1.9 ± 0.17 log CFU/g reduction of Salmonella. For packaged tomatoes, log reductions decreased with increasing film thickness but not significantly (p < .05). Also, no significant difference in PL decontamination efficacy between packaged and unpackaged tomatoes was observed. Treatment significantly reduced the initial populations of aerobic mesophilic bacteria (3.6 ± 0.31 log), molds and yeast (2.43 ± 0.22 log) by >1 log, respectively. Packaged tomatoes were softer after treatment but not significantly. Storage time did not affect fruit firmness. No significant change in the visual appearance of fruits were observed after treatment and during 14 days of storage. Overall, the results of this study demonstrate that high intensity short time PL treatment may be used to enhance microbial safety and reduce postprocessing contamination of packaged cherry tomato.
A high intensity short time pulsed light application of tomatoes contaminated with Salmonella showing rapid, reliable decontamination of the pathogen. Inoculated tomatoes when subjected to pulsed light treatment reduced pathogen population rapidly by more than 1 log in 10s without affecting the fruit quality. Pulsed light can penetrate through food packaging enclosure to kill microorganisms on the food surface to minimize postprocessing contamination in the supply chain.
Radio frequency electric fields (RFEF) and UV-light treatments have been reported to inactivate bacteria in liquid foods. However, information on the efficacy of bacterial inactivation by combined ...treatments of RFEF and UV-light technologies is limited. In this study, we investigated the relationship between cell injury and inactivation of
Escherichia coli K-12 in apple juice treated with a combination of RFEF and UV-light. Apple juice purchased from a wholesale distributor was inoculated with
E. coli K-12 at 7.8 log CFU/ml, processed with a laboratory scale RFEF unit at 20
kHz, 15
kV/cm for 170
µs at a flow rate of 540
ml/min followed by UV-light treatment (254
nm) for 12
s at 25, 30 and 40
°C. Treated samples were analyzed for leakage of UV-substances as a function of membrane damage and were plated (0.1
ml) on Sorbitol MacConkey Agar (SMAC) and Trypticase Soy Agar (TSA) plates to determine the viability loss and percent injury. At 40
°C, UV-light treatment alone caused 5.8 log reduction of
E. coli in apple juice while RFEF caused only 2.8 log reduction. A combination of the two processing treatments did not increase cell injury or leakage of intracellular bacterial UV-substances more than that from the UV-light treatment. Similarly, the viability loss determined was not significantly (
P
<
0.05) different than UV-light treatment alone. However, the UV-substances determined in apple juice treated with RFEF was significantly (
P
>
0.05) different than UV-light treated samples. The results of this study suggest that RFEF treatment causes more injury to the bacterial cells leading to more leakage of intracellular UV-substances than cells treated with UV-light alone. Also, the effect of the two processing treatment combination on bacterial inactivation was not additive.
Microbial safety of fresh produce continues to be a major concern. Novel antimicrobial methods are needed to minimize the risk of contamination. This study investigated the antimicrobial efficacy of ...pulsed light (PL), a novel nisin-organic acid based antimicrobial wash (AW) and the synergy thereof in inactivating E. coli O157:H7 on Romaine lettuce. Treatment effects on background microbiota and produce quality during storage at 4 °C for 7 days was also investigated. A bacterial cocktail containing three outbreak strains of E. coli O157:H7 was used as inoculum. Lettuce leaves were spot inoculated on the surface before treating with PL (1–60 s), AW (2 min) or combinations of PL with AW. PL treatment for 10 s, equivalent to fluence dose of 10.5 J/cm2, was optimal and resulted in 2.3 log CFU/g reduction of E. coli O157:H7, while a 2 min AW treatment, provided a comparable pathogen reduction of 2.2 log CFU/g. Two possible treatment sequences of PL and AW combinations were investigated. For PL-AW combination, inoculated lettuce leaves were initially exposed to optimum PL dose followed by 2 min AW treatment, whereas for AW-PL combination, inoculated lettuce were subjected to 2 min AW treatment prior to 10 s PL treatment. Both combination treatments (PL-AW and AW-PL) resulted in synergistic inactivation as E. coli cells were not detectable after treatment, indicating >5 log pathogen reductions. Combination treatments significantly (P < 0.05) reduced spoilage microbial populations on Romaine lettuce and also hindered their growth in storage for 7 days. The firmness and visual quality appearance of lettuce were not significantly (P > 0.05) influenced due to combination treatments. Overall, the results reveal that PL and AW combination treatments can be implemented as a novel approach to enhance microbial safety, quality and shelf life of Romaine lettuce.
Display omitted
•Pulsed light and antimicrobial wash individually provided about 2 log reduction of E. coli O157:H7 on Romaine lettuce.•Combinations acted synergistically providing >5 log reductions of E. coli O157:H7.•Quality of lettuce was not impacted by the combined treatments.•Combined treatment method could potentially be used as an alternative to chlorine washing.
•Emerging nonthermal technologies capable of meeting consumer demand.•Integrated nonthermal treatment can assure microbial safety and quality of produce.•Membrane processing can eliminate microbial ...cells and spores from milk and liquid eggs.•Membrane processed milk and egg are superior quality compared to pasteurized product.
This article reviews emerging techniques that are applied in the produce and dairy industry to ensure product safety. Microbial safety of produce, dairy and egg continues to be a major concern. According to Economic Research Service, USDA the cost of foodborne illnesses in the U.S. tops $15.6 billion. Food can be contaminated by human pathogens anywhere in the farm to table continuum. Foods are often processed to ensure safety. Food processing technologies are action or method that is used to maintain foods at certain desirable properties.
The traditional processing method is thermal technology which refers to the application of heat energy. Thermal processing is an effective way of preserving food because the great majority of harmful pathogens are killed at temperatures close to the boiling point of water. However, consumer demand for more natural fresh-like food and raised economic standards have triggered the development of emerging technologies to replace traditional well-established thermal processing. In recent years, many new sophisticated nonthermal preservation techniques have developed for fruits, vegetables, milk and eggs to extend the quality and shelf-life, minimize risk, protect the environment, and improve functional, sensory, and nutritional properties. Many of emerging preservation technologies have already reached commercial adoption in specific applications while many others remain promising. Development of suitable equipment, especially for continuous processing and standardization of the process parameters for easy regulatory approval will pave the way for improved emerging technologies.
PDF
