Inhibitory effects of low concentration electrolyzed water and other sanitizers against foodborne pathogens on oyster mushroom

In this study we investigated the effects of low concentration electrolyzed water (LcEW) and several other sanitizers (strong acid electrolyzed water (SAEW), aqueous ozone (AO), 1% citric acid (CA) and sodium hypochlorite solution (NaOCl)) on the inactivation of natural microflora (total aerobic bacteria counts (TBC) and yeasts and moulds (YM)) and foodborne pathogens (Escherichia coli O157:H7, Listeria monocytogenes, Salmonella Typhimurium and Bacillus cereus) on oyster mushroom. The effects of temperature and treatment time on the antimicrobial activity of LcEW to reduce the populations of foodborne pathogens were also determined. LcEW showed the strongest bactericidal efficacy among all the sanitizers on TBC, YM and pathogens by reductions of 1.35, 1.08 and 1.90–2.16 log CFU/g after 3 min treatment at room temperature (23 ± 2 °C), respectively. There was no significant difference between the antimicrobial effects of LcEW and SAEW (P > 0.05). Among those sanitizers, their relative influence of inactivation was LcEW > NaOCl > CA > AO.     

Selection of a decontamination treatment for fresh Tuber aestivum and Tuber melanosporum truffles packaged in modified atmospheres

The objective of this study was to develop a surface disinfection method which, combined with modified atmosphere packaging (MAP), prolonged the shelf-life of Tuber aestivum and Tuber melanosporum truffles. T. aestivum was washed with sodium hypochlorite (500 ppm chlorine), hydrogen peroxide (5%) and ethanol (70%) alone or in combination with ultrasound (35 Hz) for 10 min at 4 °C. Dipping in ethanol 70% with ultrasound was found to be the most effective treatment, achieving 4 logarithmic reductions for pseudomonads, reductions greater than 2 logarithmic units for Enterobacteriaceae, lactic acid bacteria and molds and 1.5 logarithmic reductions for yeasts. Finally, both truffle species were decontaminated with the selected treatment, packaged with a microperforated film and stored at 4 °C for 28 days. In this situation the microbial counts and the sensory quality were maintained throughout storage and the shelf-life of both truffle species were prolonged to 28 days.     

Microbial composition of turbid rice wine (Makgeolli) at different stages of production in a real processing line

The aim of this study was to examine for changes in microbial populations during the production of turbid rice wine (also known as Makgeolli) at different production plants and to identify critical points for the control of microbial quality. Samples from raw ingredients (water, rice and wheat flour), materials from different production stages (steamed ingredients, the base of fermentation, primary and secondary fermentation stages at different time points), and the final rice wine products (non–sterilized and sterilized) were analyzed. The microbiological content of samples was assessed by quantitative (aerobic plate counts, lactic acid bacteria, fungi, acetic acid bacteria, coliforms and Bacillus cereus) and qualitative (Escherichia coli and eight foodborne pathogens) analyses. Aerobic plate counts for rice and wheat flour were relatively low (3.1 and 1.9 log CFU/g, respectively), as were those for lactic acid bacteria (1.6 and 2.1 log CFU/g), and fungi counts (2.2 and 0.7 log CFU/g). All counts increased to 7.8–7.9 log CFU/ml in the base of fermentation after the addition of Nuruk and Koji, and these counts were maintained at 8–9 log CFU/ml during fermentation. Acetic acid bacteria were not detected in the ingredients, but were isolated from the base of fermentation (1.2–2.8 log CFU/ml). Heat sterilization reduced aerobic pate counts significantly from 8.4 to 2.1 log CFF/ml, and lactic acid bacteria, fungi and acetic acid bacteria were reduced to non-detectable or negligible levels. Isolated microorganisms were considered as autochthonous to the environment or were artificially introduced with the starter culture. B. cereus was widely distributed throughout the manufacturing process, and may have been introduced from the raw material (present in 100% rice and 41.7% wheat flour samples). B. cereus counts were not significantly affected by sterilization, suggesting that it may exist at low levels as spores in the final products. No coliforms and other pathogens were detected in any samples. The raw materials, the base of fermentation, and sterilization stage were identified as important points for the control of microbial quality during the fermentation process.     

Effects of spray volume, type of surface tissue and inoculum level on the survival of Escherichia coli on beef sprayed with 5% lactic acid

Membrane, fat and cut muscle surfaces of beef were inoculated with Escherichia coli at numbers about 4, 1 or −1 log cfu/cm². The inoculated meat was sprayed with water or 5% lactic acid at volumes of 0.5, 0.1 or 0.02 ml/cm². Spraying with water reduced the numbers of E. coli on membrane surfaces by up to 1 log unit, but had little effect on the numbers of E. coli on fat or cut muscle surfaces. Spraying with 5% lactic acid reduced the highest numbers of E. coli on membrane surfaces by up to 4 log units; but those numbers on fat or cut muscle surfaces were reduced by ≤1.5 log unit, and the reductions declined with decreasing volumes of 5% lactic acid. With inocula of 1 log cfu/cm², spraying lactic acid in any volume reduced the numbers of E. coli on membrane or fat surfaces by about 1 log unit, and the numbers on cut muscle surfaces by between 0.8 and 0.2 log unit. E. coli were detected in enrichment cultures of samples from all surfaces inoculated with E. coli at −1 log cfu/cm² and sprayed with 5% lactic acid at 0.5 ml/cm². The findings indicate that spraying relatively heavily contaminated cuts or trimmings with 5% lactic acid at ≥0.1 ml/cm² can be expected to reduce numbers of E. coli and, presumably, associated pathogens by between 0.5 and 1 log unit. However, such a treatment is likely to be at best marginally effective for reduce the numbers of these organisms on lightly contaminated product.     

Application of disinfectant sprays after chilling to reduce the initial microbial load and extend the shelf-life of chilled chicken carcasses

The objective of this study was to evaluate the effects of various disinfectant sprays on initial microbial load and conduct a shelf-life study of chilled chicken carcasses. Chilled chicken carcass samples obtained after chilling were sprayed for 15 s in a purpose-built spray rig with sodium hypochlorite (SH, 50 & 100 mg/L), chlorine dioxide (CD, 50 & 100 mg/L), lactic acid (LA, 1 & 2%), acid electrolyzed oxidizing water (AEOW) and slightly acid electrolyzed oxidizing water (SAEOW). Untreated carcasses were used as the control. Back, leg and breast skin were removed from each carcass after treatment to determine the total viable counts (TVC) and total coliforms. Sprays of 2% LA, AEOW and SAEOW were the most effective treatments with reductions of 0.47–0.83 log CFU/cm² and 0.49–0.96 log MPN/cm² in TVC and total coliforms, respectively. Samples treated with AEOW and SAEOW had 2 days of microbial shelf-life extension compared to the controls, which exceeded the TVC limit of 7 log CFU/cm² at day 6. Even longer extension was obtained for the 2% LA treated samples. The total coliforms, pH and total volatile basic nitrogen (TVBN).TVBN values of the 2% LA, AEOW and SAEOW treated samples were significantly (P < 0.05) lower than those of the controls during storage. Predominantly, the TBARS values of the AEOW and SAEOW treated samples were not statistically different from those of the controls (P > 0.05); however, the 2% LA treatment accelerated lipid oxidization, manifested as the highest TBARS value (2.09 mg MDA/kg) at day 8. Conclusively, this study indicated that the application of AEOW and SAEOW sprays to chilled chicken carcasses after chilling can reduce initial microbial load and maintain quality attributes during refrigerated storage.     

Quantitative investigation on the effects of chemical treatments in reducing Listeria monocytogenes populations on chicken breast meat

The effectiveness of treatments for the reduction of Listeria monocytogenes surface-inoculated in chicken breast meat was investigated. The treatments consisted of dipping breasts in chemical solutions for 15 min: buffered phosphate (control), calcium hypochlorite, trichloroisocyanuric acid, sodium acetate, sodium lactate, l-lactic acid or trisodium phosphate. The rates of inactivation observed with the chlorine compounds were similar, and in the presence of 100 mg/l of active chlorine viability decreased by 4.41 log units, compared with less than 1.0 log unit decrease observed when cells were submitted to 45 mg/l of active chlorine. Sodium lactate at 2.5% was a more effective antilisterial agent, producing a reduction of 3.88 log units. The present study extends existing findings on the importance of the use of lactic acid, sodium acetate, sodium lactate, trisodium phosphate (chemically classified as GRAS) and chlorine compounds on the inactivation of L. monocytogenes.     

Pathogen reductions associated with traditional processing of landjäger

To determine if traditional processing would reduce Escherichia coli O157:H7 (EC), Listeria monocytogenes (LM), and Salmonella spp. (S) in landjäger, beef and pork trim (95% lean) and pork fat was experimentally-inoculated to obtain a pathogen population of ca. 8 log₁₀ CFU/g. The trim was spray-treated with 4.5% lactic acid (30 min, 25 °C), ground, mixed with seasonings, and a starter culture added. Sausages were stuffed, pressed, fermented (to pH 4.8), cold smoked, and dried to a water activity of 0.88. Sausages were vacuum packaged, stored (20 days, ca. 23 °C), and evaluated for microbial populations, pH, and water activity. Lactic acid treatment of beef trim reduced EC, S, and LM 0.23, 0.42, and 0.22 log₁₀ CFU/g, respectively. Subsequent fermentation and drying reduced EC, LM, and S 3.94, 4.11, and 4.29 log₁₀ CFU/g respectively. Average log reductions of 7.83, 6.19, and 7.21 log₁₀ CFU/g were observed for EC, LM and S, respectively, for the duration of the study. This study demonstrates that traditional processing of landjäger may result in a ca. 5 log reduction of foodborne pathogens.     

Decontamination of incoming beef trimmings with hot lactic acid solution to improve microbial safety of resulting dry fermented sausages – A pilot study

In the study, beef trimmings intended for sausage production were subjected to different decontamination treatments based on lactic acid-hot water combination, with aim to eliminate or reduce foodborne pathogens Escherichia coli O157, Salmonella Typhimurium and Listeria monocytogenes in resultant dry, fermented sausages. In finished sausages, produced from untreated trimmings, “natural” reductions of inoculated E. coli O157 and Salmonella Typhimurium were on average 1.9 logs, L. monocytogenes count remained unchanged, and no detectable concentrations of biogenic amines were found. The same type of sausages were also produced by using beef trimmings which was pathogen-inoculated and then decontaminated by: hot, 4% lactic acid in water solution (90 °C for 10 s; treatment HLA1); or hot, 4% lactic acid in water solution (85 °C for 20 s; treatment HLA2), or hot, 4% lactic acid in water solution (80 °C for 30 s; treatment HLA3). The use of HLA-decontaminated beef trimmings resulted in total E. coli O157 reductions of at least 3.9 logs and in total Salmonella Typhimurium reductions of at least 3.6 logs, whilst biogenic amines were not detected in finished sausages. The overall sensorial acceptability of finished sausages produced with HLA-decontaminated beef trimmings was somewhat diminished. Further work is required to optimise the HLA-based incoming beef treatments.     

Growth of Escherichia coli,Salmonella enterica and Listeria spp., and their inactivation using ultraviolet energy and electrolyzed water,on ‘Rocha’ fresh-cut pears

The present study aimed at evaluating the growth of Escherichia coli, Salmonella enterica, and Listeria spp. and studying the efficacy of Ultraviolet-C (UV-C) irradiation, acidic electrolyzed (AEW) and neutral electrolyzed (NEW) waters in the reduction of these bacteria on ‘Rocha’ pear. Fresh-cut pieces were inoculated and incubated at 4–20 °C for 8 days. Inoculated pears were treated with UV-C (2.5–10 kJ/m²), AEW, NEW and sodium hypochlorite (SH) and microbiological and quality parameters were evaluated. The three bacteria, inoculated at 6.1–6.2 log cfu/g, grew on the pear at high growth rates at 12 and 20 °C reaching populations of 8.1–8.6 log cfu/g, in 24 h. At 8 °C the microorganisms increased their populations by at least 1 log cfu/g in three days. At 4 °C adaptation phases of less than 24 h for Listeria spp. were measured before exponential growth occurred and the enterobacteria did not grow despite having survived for 8 days. AEW and NEW caused microbial reductions similar to SH, of approximately 1 log cfu/g, while the best UV-C dose (7.5 kJ/m²) of at least 2.4 log cfu/g. Fresh-cut pears were a good substrate for foodborne bacteria emphasizing the importance of preventing contaminations and cross contaminations. The UV-C was more effective than the chemical decontaminations, as it provided superior microbial reductions without greatly affecting the quality of pears.     

Antibacterial mechanism of lactic acid on physiological and morphological properties of Salmonella Enteritidis,Escherichia coli and Listeria monocytogenes

Lactic acid is widely used to inhibit the growth of important microbial pathogens, but its antibacterial mechanism is not yet fully understood. The objective of this study was to investigate the antibacterial mechanism of lactic acid on Salmonella Enteritidis, Escherichia coli and Listeria monocytogenes by size measurement, TEM, and SDS-PAGE analysis. The results indicated that 0.5% lactic acid could completely inhibit the growth of Salmonella Enteritidis, E. coli and L. monocytogenes cells. Meanwhile, lactic acid resulted in leakage of proteins of Salmonella, E. coli and Listeria cells, and the amount of leakage after 6 h exposure were up to 11.36, 11.76 and 16.29 μg/mL, respectively. Measurements of the release of proteins and SDS-PAGE confirmed the disruptive action of lactic acid on cytoplasmic membrane, as well as the content and activity of bacterial proteins. The Z-Average sizes of three pathogens were changed to smaller after lactic acid treatment. The damaged membrane structure and intracellular structure induced by lactic acid could be observed from TEM images. The results suggested that the antimicrobial effect was probably caused by physiological and morphological changes in bacterial cells.     

Effects of combined treatments of high pressure, temperature and antimicrobial products on germination of mung bean seeds and microbial quality of sprouts

The effects of several combinations of pressure, temperature and two antimicrobial agents, hypochlorite and carvacrol, applied separately on mung bean seeds, on their germination capability and on native microbial loads of sprouts developed from treated seeds, was studied by using response surface methodology (RSM). Seed viability decreased as pressure increased, at all concentrations of both hypochlorite and carvacrol. Enhanced reductions of total aerobic mesophilic bacteria, total and faecal coliforms and yeast and moulds populations were observed as pressure and hypochlorite/carvacrol concentrations increased. The optimal treatment at 250 MPa of seeds soaked in 18000 ppm and 1500 ppm of calcium hypochlorite and carvacrol, respectively, maintained an acceptable germination rate (80% and 60%, respectively) and improved the microbial quality of the respective sprouts with reductions of more than 5 log cfu/g. These reduction levels can be considered a preservative goal for industrial mung bean sprout production.     

Microbial load reduction of sweet basil using acidic electrolyzed water and lactic acid in combination with mild heat

Sweet basil has been used worldwide as an ingredient for several cuisines. However, it can be contaminated with pathogens; especially Escherichia coli and Salmonella spp. are mainly introduced by poor hygiene during harvesting, cleaning, packaging and distribution. This study aimed to study the efficacy of lactic acid (LA) and acidic electrolyzed water (AEW) against mesophilic bacteria on sweet basil. In addition, a combination treatment was also investigated, using mild heat with the selected sanitizer to disinfect sweet basil inoculated with S. Typhimurium and E. coli. The 2% LA treatment showed high efficiency in microbial decontamination, and mesophilic bacteria were reduced by about 3 log CFU/g. Additionally, the decontamination efficacy of LA increased when combined with mild heat. The use of 2% LA at 50 °C showed the highest microbial reduction in sweet basil, in which mesophilic bacteria, S. Typhimurium, and E. coli were reduced by 4.62, 3.80 and 3.61 log CFU/g, respectively. These findings indicate that LA can be more effective than AEW in disinfection and provides greater efficiency when combined with mild 50 °C heat.     

Reduction of Escherichia coli O157:H7 and Salmonella enteritidis on mung bean seeds and sprouts by slightly acidic electrolyzed water

High microbial populations on mung beans and its sprouts are the primary reason of a short shelf life of these products, and potentially present pathogens may cause human illness outbreak. The efficiency for inactivating Escherichia coli O157:H7 (E. coli O157:H7) and Salmonella enteritidis (S. enteritidis), which were artificially inoculated on mung bean seeds and sprouts, by means of slightly acidic electrolyzed water (SAEW, pH 5.0 to 6.5) generated through electrolysis of a mixture of NaCl and hydrochloric acid solution in a non-membrane electrolytic chamber, was evaluated at the different available chlorine concentrations (ACCs, 20–120 mg/l) and treatment time (3–15 min), respectively. The effect of SAEW treatment on the viability of seeds was also determined. Results indicate that the ACC had more significant effect on the bactericidal activity of SAEW for reducing both pathogens on the seeds and sprouts compared to treatment time (P < 0.05). The seeds and sprouts treated with SAEW at ACCs of 20 and 80 mg/l resulted in a reduction of 1.32–1.78 log₁₀ CFU/g and 3.32–4.24 log₁₀ CFU/g for E. coli, while 1.27–1.76 log₁₀ CFU/g and 3.12–4.19 log₁₀ CFU/g for S. enteritidis, respectively. The germination percentage of mung bean seeds was not significantly affected by the treatment of SAEW at an ACC of 20 mg/l for less than 10 min (P > 0.05). The finding of this study implies that SAEW with a near-neutral pH value and low available chlorine is an effective method to reduce foodborne pathogens on seeds and sprouts with less effects on the viability of seeds.     

Radiofrequency pasteurization of inoculated ground beef homogenate

Inactivation of nonpathogenic Escherichia coli in ground beef homogenate using radio-frequency (RF) heating both individually and in combination with antimicrobial treatments was investigated. Beef homogenate was prepared in phosphate buffer (pH 5.8). Inoculated beef homogenate was heated in an RF oven without antimicrobials to end-point temperatures of 50 °C resulting in 0.84 log reductions and 55 °C resulting in 0.94 log reductions. Adding antimicrobials-potassium, sodium, and ammonium bicarbonates (0.5 and 1.5%); citric acid (0.5%); potassium lactate (2.5%); and a blend of potassium bicarbonate (1.5%) and citric acid (0.5%) to the beef homogenates before RF heating did not inactivate E. coli. E. coli inactivation was also not affected in beef homogenates containing antimicrobials when heated to 50 °C in the RF oven. Heating to 55 °C did reduce E. coli more than 5 log (CFU/mL) reduction of E. coli in homogenates containing 2.5% potassium bicarbonate, 0.5% citric acid, and blends of citric acid and potassium bicarbonate at varying concentrations (0.5% citric acid + 0.5% Citric acid and 1.5% bicarbonate). This study offers scope and potential for the application of RF assisted pasteurization with antimicrobial systems as interventions to enhance the overall ground beef safety. The findings of this study should provide potential to explore industrial scale RF pasteurization of beef and other meat products while ensuring that the quality characteristics are maintained.     

Surface physiological changes induced by lactic acid on pathogens in consideration of pKa and pH

Antimicrobials affected the surface characteristics and membrane integrity of bacterial cells. The objective of this study was to investigate the physiological changes on the surface of Salmonella Enteritidis (ATCC 14028), Escherichia coli (CGMCC 1.2385), and Listeria monocytogenes (ATCC 19115) induced by lactic acid. Lactic acid was more effective than hydrochloric acid (HCl) at the same pH in inhibiting the growth of these pathogens. The results of zeta potential indicated that surface charges of three pathogens were significantly disturbed by lactic acid treatment. After exposure to 0.5% lactic acid, a rough cell surface with discrete ridges and concave collapses were observed by scanning electron microscopy (SEM). Meanwhile, the release of intracellular potassium (K⁺) also suggested the damage of cytoplasmic membrane. As an effective antimicrobial, lactic acid led to leakage of intracellular K⁺, damage of membrane permeability and integrity, and changes of surface charge in the pathogens.     

Does antibiotic resistance influence shiga-toxigenic Escherichia coli O26 and O103 survival to stress environments?

The presence of antibiotic-resistant bacteria in the food supply chain is a major concern. There is a great need to revalidate the effectiveness of the intervention strategies commonly used in food processing environments for multidrug-resistant strains. The purpose of this study was to determine the survival of antibiotic-resistant O26 and O103 Shiga-toxin producing Escherichia coli (STEC) strains to lactic acid (2.5, 3.5, 5%), sodium hypochlorite (0.2, 0.5, 1 ppm free chlorine), and heat (60, 61, 62.5 °C) treatments. Six strains from STEC serotypes O26 and O103 with three distinctive antibiotic-resistant profiles (susceptible, low and high resistance) were selected for the study. As expected, the rates of inactivation were faster at increasing biocide concentrations or temperature level. The Weibull model provided a better fit than the traditional log-linear model due to the appearance of nonlinear patterns. A 5% lactic acid treatment for 10 min reduced the population of all STEC strains by 5 log CFU/ml. Sodium hypochlorite treatment (1 ppm for 5 min) achieved a similar reduction. Thermal D values for O26 and O103 serotypes ranged from 0.37 to 2.09 and 0.37–1.71 min, respectively. No statistical differences (P > 0.05) in tolerance were found between the two STEC serotypes to the different treatments. The antibiotic profile was not related to the ability to tolerate any of the treatments. Only the susceptible strain showed a relative higher resistance to the lactic acid and lower resistance to sodium hypochlorite treatment. These results would contribute to assess the risk for the presence of STEC strains in food processing environments.     

Application of slightly acidic electrolyzed water as a potential non-thermal food sanitizer for decontamination of fresh ready-to-eat vegetables and sprouts

The sanitization efficacy of slightly acidic electrolyzed water (SAEW) against food pathogens on selected fresh ready-to-eat (RTE) vegetables and sprouts was evaluated and compared to sodium hypochlorite (NaOCl) solution. RTE vegetables and sprouts were dip-inoculated with Escherichia coli (E. coli) and Salmonella spp. and dip-treated with SAEW, NaOCl solution for 5 min. SAEW treatment significantly (p < 0.05) reduced the total aerobic mesophilic bacteria from Chinese celery, lettuce and daikon sprouts by 2.7, 2.5 and 2.45 log₁₀CFU/g, respectively relative to un-treated. Pathogens were significantly (p < 0.05) reduced from Chinese celery, lettuce and daikon sprouts by 2.7, 2.8 and 2.8 log₁₀CFU/g (E. coli) and 2.87, 2.91 and 2.91 log₁₀CFU/g (Salmonella spp.), respectively following a SAEW treatment. SAEW and NaOCl solution showed no significant sanitization difference (p > 0.05). Results demonstrate that SAEW at low chlorine concentration and a near neutral pH is a potential non-thermal food sanitizer that could represent an alternative to NaOCl solution and would reduce the amount of free chlorine used in fresh-cut vegetables industry, since the same microbial reduction as NaOCl solution is obtained.     

Industry-level changes in microbial contamination on market hog and broiler chicken carcasses between two locations in the slaughter process

Pork and poultry products have been implicated in a substantial proportion of microbial foodborne illnesses such as salmonellosis and campylobacteriosis. Understanding the similarities and differences between the effectiveness of interventions applied during slaughter to the two commodities can help identify opportunities to reduce the risk of foodborne illness. This study uses data from two national surveys and censored data techniques to assess the concentrations of microbial contamination on broiler chickens and market hogs at two points in the slaughter process. Statistical distributions are fitted to estimate the average concentrations of microbial contamination, the variability in these concentrations, and the average reduction in contamination between the two locations for pork and chicken produced in the United States. The concentrations of Salmonella and generic Escherichia coli (GEC) are estimated for hog carcasses; the concentrations of Salmonella, GEC, and Campylobacter are estimated for chicken carcasses. These datasets are also used to study the magnitude of seasonal changes in concentrations of microbial contamination and to demonstrate the potential utility of using the reduction in the average aerobic plate count between the pre-evisceration and post-chill stages of the slaughter process as an indicator of the corresponding reduction in other species of bacteria. The study finds interventions for hog carcasses achieve much larger reductions in contamination than those applied to chicken. However, the variability in the concentration of Salmonella contamination on pork is significantly higher, suggesting an opportunity to decrease risk by ensuring more consistent reductions across the industry. The study also finds, for both commodities, that the log₁₀ reductions in the concentrations of GEC are similar to the log₁₀ reductions in Salmonella, while the log reduction in Campylobacter on chicken was substantially greater than for both GEC and Salmonella. Additional analyses demonstrate modest seasonal increases in contamination only on hog carcasses as well as demonstrating that reductions in APC are indicative of reductions in all other organisms, suggesting its potential as an effective indicator organism.     

Efficacy of combinations of high pressure treatment, temperature and antimicrobial compounds to improve the microbiological quality of alfalfa seeds for sprout production

The effect of combined treatments of pressure, temperature and two disinfectant agents (hypochlorite and carvacrol) applied on alfalfa seeds, on their germination capability as well as on the reduction of the native microbial load of sprouts developed from treated seeds was evaluated by using response surface methodology (RSM). The germination percentage decreased as pressure and carvacrol concentration increased, while calcium hypochlorite concentration had no significant impact on seed viability. The counts of total aerobic mesophilic bacteria, total and faecal coliforms and moulds and yeast were reduced with increasing pressure and hypochlorite and carvacrol concentrations. The optimal conditions for improving the microbiological quality of alfalfa seeds (reductions between 4.5 and 5 log CFU/g) for sprouts production were 200 MPa and hypochlorite concentration of 18,000 ppm. On the contrary, the process parameters of the combined treatment HP/carvacrol that ensure the microbial safety of sprouts (250 MPa and 1500 ppm of carvacrol) reduced the germination percentage to unacceptable levels.     

Effect of corona discharge plasma jet treatment on decontamination and sprouting of rapeseed (Brassica napus L.) seeds

Sprout-related outbreaks of foodborne illnesses are increasingly becoming a food safety concern. Different pathogenic microorganisms that originate from sprout seeds are known to play a crucial role in the pathogenesis of such outbreaks. Therefore, in order to decontaminate and also to enhance the germination of seeds, the applications of non-thermal plasma based techniques are increasingly being investigated in the field of agricultural science as an alternative to conventional pre-germination treatments. This work was aimed to evaluate the effectiveness of corona discharge plasma jet (CDPJ) for microbial decontamination of rapeseed seeds, and also studied the plasma treatment effect on the seed germination and physicochemical properties of sprouts (grown from the plasma-treated seeds). Aerobic bacteria, molds and yeast, Bacillus cereus, Escherichia coli, Salmonella spp. were detected as contaminants in the seeds. All the detected microorganisms were reduced in the range of 1.2–2.2 log CFU/g upon the CDPJ treatment for 3 min. The inactivation patterns are better explained using pseudo-first-order kinetics. The plasma treatment of seeds up to 2 min showed positive effects on their germination rate and seedling growth. Physicochemical and sensory characteristics of rape sprouts were unaffected due to the CDPJ treatment of their respective seeds. Therefore, the CDPJ treatment of rapeseed seeds has not only reduced the seed microbial load, but also contributed to the enhancement of their germination rate and seedling growth, without adversely affecting the physicochemical and sensory characteristics of their corresponding sprouts.