Contamination Of Sprouts Research Articles

Seed Disinfection Treatments Minimized Microbial Load and Enhanced Nutritional Properties of Fenugreek Sprouts Which Alleviated Diabetes-Negative Disorders in Diabetic Rats.

Sprouts are an attractive food product that contains high amounts of nutritional substances and has pro-health features. Sprout consumption has strongly increased despite its potential risk to health due to its microbial load. Both the safety and shelf life of sprouts may be negatively affected by a high microbial load. To reduce the microbial contamination in sprouts before consumption, the initial microbial load on the seeds needs to be controlled. Many herbal sprouts have been recommended for diabetes, and fenugreek is one of these sprouts. Thus, the current experiment aimed at disinfecting fenugreek seeds using microwave (5, 10, and 20 s) and hot water (30, 45, and 60 s) treatments for different durations. The best-disinfected sprouts with the highest nutritional properties were used to evaluate their influence on streptozocin-induced diabetic rats in comparison with fenugreek seed feeding. Microwave treatments showed the highest sprout length, fresh weight, total free amino acids, antioxidants, reducing sugars, and total phenols. Additionally, microwave seed treatments showed the lowest bacteria and mold counts on sprouts produced relative to hot water treatments, and the best seed treatment was a microwave for 20 s, which gave the best values in this respect. Feeding diabetic rats with different fenugreek seeds or sprout rates (0, 5, 7.5, and 10% w/w) improved body weight, restricted the growth of glucose levels, lowered total cholesterol and triglycerides, and improved HDL compared with the positive control group, and fenugreek sprouts at higher rates showed the maximum improvements in blood glucose, total cholesterol, and triglycerides. Treating fenugreek seed with microwave radiation for 20 s to disinfect the seeds before sprouting is recommended for lowering the microbial load with optimum nutritional and antioxidant activity, and feeding diabetic rats with these sprouts at the rate of 7.5 and 10% had promising effects on hyperglycemia and associated disorders.

Bacillus strain BX77: a potential biocontrol agent for use against foodborne pathogens in alfalfa sprouts.

Despite regulatory and technological measures, edible sprouts are still often involved in foodborne illness and are considered a high-risk food. The present study explored the potential of spore-forming Bacillus isolates to mitigate Salmonella and Escherichia coli contamination of alfalfa sprouts. Food-derived Bacillus strains were screened for antagonistic activity against S. enterica serovar Typhimurium SL1344 (STm) and enteropathogenic E. coli O55:H7. Over 4 days of sprouting, levels of STm and E. coli on contaminated seeds increased from 2.0 log CFU/g to 8.0 and 3.9 log CFU/g, respectively. Treatment of the contaminated seeds with the most active Bacillus isolate, strain BX77, at 7 log CFU/g seeds resulted in substantial reductions in the levels of STm (5.8 CFU/g) and E. coli (3.9 log CFU/g) in the sprouted seeds, compared to the control. Similarly, co-culturing STm and BX77 in sterilized sprout extract at the same ratio resulted in growth inhibition and killed the Salmonella. Confocal-microscopy experiments using seeds supplemented with mCherry-tagged Salmonella revealed massive colonization of the seed coat and the root tip of 4-day-old sprouted seeds. In contrast, very few Salmonella cells were observed in sprouted seeds grown with BX77. Ca-hypochlorite disinfection of seeds contaminated with a relatively high concentration of Salmonella (5.0 log CFU/g) or treated with BX77 revealed a mild inhibitory effect. However, disinfection followed by the addition of BX77 had a synergistic effect, with a substantial reduction in Salmonella counts (7.8 log CFU/g) as compared to untreated seeds. These results suggest that a combination of chemical and biological treatments warrants further study, toward its potential application as a multi-hurdle strategy to mitigate Salmonella contamination of sprouted alfalfa seeds.

Effect of slightly acidic electrolyzed water on natural Enterobacteriaceae reduction and seed germination in the production of alfalfa sprouts

Microbial contamination of sprouts commonly occurs because of the pathogens present on and in the seeds and the optimal conditions for bacteria growth provided during the germination and sprouting processes. This study examined the decontamination effect of slightly acidic electrolyzed water (SAEW), a ‘generally recognized as safe’ (GRAS) disinfectant, in the production process of alfalfa sprouts. SAEW with various available chlorine concentrations (ACC, 25, 35, 45 mg/L) and different pH levels (5.0, 5.7 and 6.4) was used to soak seeds for different length of time (0.5 and 6 h), after which the variations in natural Enterobacteriaceae, water absorption and seed germination (germination rate, weight and length of sprouts) were determined. The results showed that when the seeds were soaked with SAEW, albeit with different ACC (25, 35 and 45 mg/L) and pH levels (5.0, 5.7 and 6.4), a significant reduction of Enterobacteriaceae and no negative effect on sprout quality was observed. The water absorption and germination rates were also not significantly adversely affected by SAEW soaking. These findings suggest that SAEW could be used to decontaminate natural Enterobacteriaceae in the production of alfalfa sprouts, with no negative side effects on the alfalfa seeds.

Effect of plasma-activated water on microbial quality and physicochemical characteristics of mung bean sprouts

Abstract The efficacy of nonthermal plasma-activated water (PAW) in the decontamination of mung bean sprouts was evaluated in this work. After being treated with PAW for 30 min, the populations of total aerobic bacteria and total yeasts and moulds on mung bean sprouts were decreased by 2.32- and 2.84- log10 CFU/g, respectively. The PAW treatment had no significant effect on the antioxidant potential of mung bean sprouts as shown by using 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH•) scavenging activity assay, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) method, and ferric reducing antioxidant power (FRAP) assay (p > 0.05). Additionally, the PAW treatment caused no significant changes in the total phenolic and flavonoid contents, nor the sensory characteristics of mung bean sprouts (p > 0.05). Reactive species such as nitrates, nitrites, and H2O2 were generated in PAW, which presumably contributed to the disinfection efficacy of PAW. These data show that PAW can be used as a promising nonthermal technology for the control of microbial contamination in sprouts. Industrial relevance Edible sprouts are common food ingredients across the world. However, sprouts can be contaminated by pathogenic microorganisms, which may result in health risks to humans. Recently, PAW has been shown to be a safe and effective method for food surface sanitation. However, the application of PAW in the microbial control for sprouts is less investigated. In this study, the influences of PAW on the microbial load, chemical and sensory quality of mung bean sprouts were investigated for the first time. The results showed that PAW could effectively inactivate bacteria and yeasts and moulds on mung bean sprouts without resulting in significant changes in the antioxidant capacities, total phenolic and flavonoid contents, and sensory characteristics of mung bean sprouts. These data indicated that PAW can be used as a promising nonthermal technology for reducing microbial populations on sprouts.

Abundant production of exopolysaccharide by EAEC strains enhances the formation of bacterial biofilms in contaminated sprouts

ABSTRACTEnteroaggregative E. coli (EAEC) is associated with food-borne outbreaks of diarrhea and growth faltering among children in developing countries. A Shiga toxin-producing EAEC strain of serotype O104:H4 strain caused one of the largest outbreaks of a food-borne infection in Europe in 2011. The outbreak was traced to contaminated fenugreek sprouts, yet the mechanisms whereby such persistent contamination of sprouts could have occurred are not clear. We found that under ambient conditions of temperature and in minimal media, pathogenic Shiga toxin-producing EAEC O104:H4 227-11 and non-Shiga toxin-producing 042 strains both produce high levels of exopolysaccharide structures (EPS) that are released to the external milieu. The exopolysaccharide was identified as colanic acid (CA). Unexpectedly, Shiga-toxin producing EAEC strain 227-11 produced 3-6-fold higher levels of CA than the 042 strain, suggesting differential regulation of the CA in the two strains. The presence of CA was accompanied by the formation of large biofilm structures on the surface of sprouts. The wcaF-wza chromosomal locus was required for the synthesis of CA in EAEC 042. Deletion in the glycosyltransferase wcaE gene abolished the production of CA in 042, and resulted in diminished adherence to sprouts when co-cultured at ambient temperature. In conclusion, this work suggests that copious production of CA may contribute to persistence of EAEC in the environment and suggests a potential explanation for the large Shiga toxin-producing EAEC outbreak in 2011.

Plant-Microbe and Abiotic Factors Influencing Salmonella Survival and Growth on Alfalfa Sprouts and Swiss Chard Microgreens.

Microgreens, like sprouts, are relatively fast-growing products and are generally consumed raw. Moreover, as observed for sprouts, microbial contamination from preharvest sources may also be present in the production of microgreens. In this study, two Salmonella enterica serovars (Hartford and Cubana), applied at multiple inoculation levels, were evaluated for survival and growth on alfalfa sprouts and Swiss chard microgreens by using the most-probable-number (MPN) method. Various abiotic factors were also examined for their effects on Salmonella survival and growth on sprouts and microgreens. Community-level physiological profiles (CLPPs) of sprout/microgreen rhizospheres with different levels of S. enterica inoculation at different growth stages were characterized by use of Biolog EcoPlates. In the seed contamination group, the ability of S. enterica to grow on sprouting alfalfa seeds was affected by both seed storage time and inoculation level but not by serovar. However, the growth of S. enterica on Swiss chard microgreens was affected by serovar and inoculation level. Seed storage time had little effect on the average level of Salmonella populations in microgreens. In the irrigation water contamination group, the growth of Salmonella on both alfalfa sprouts and microgreens was largely affected by inoculation level. Surprisingly, the growth medium was found to play an important role in Salmonella survival and growth on microgreens. CLPP analysis showed significant changes in the microbial community metabolic diversity during sprouting for alfalfa sprouts, but few temporal changes were seen with microgreens. The data suggest that the change in rhizosphere bacterial functional diversity was dependent on the host but independent of Salmonella contamination.IMPORTANCE Sprouts and microgreens are considered "functional foods," i.e., foods containing health-promoting or disease-preventing properties in addition to normal nutritional values. However, the microbial risk associated with microgreens has not been well studied. This study evaluated Salmonella survival and growth on microgreens compared to those on sprouts, as well as other abiotic factors that could affect Salmonella survival and growth on microgreens. This work provides baseline data for risk assessment of microbial contamination of sprouts and microgreens. Understanding the risks of Salmonella contamination and its effects on rhizosphere microbial communities enables a better understanding of host-pathogen dynamics in sprouts and microgreens. The data also contribute to innovative preventive control strategies for Salmonella contamination of sprouts and microgreens.

Assessing the Public Health Impact and Effectiveness of Interventions To Prevent Salmonella Contamination of Sprouts

Sprouts have been a recurring public health challenge due to microbiological contamination, and Salmonella has been the major cause of sprout-associated outbreaks. Although seed treatment and microbiological testing have been applied as risk reduction measures during sprout production, the extent to which their effectiveness in reducing the public health risks associated with sprouts has not been well investigated. We conducted a quantitative risk assessment to measure the risk posed by Salmonella contamination in sprouts and to determine whether and how mitigation strategies can achieve a satisfactory risk reduction based on the assumption that the risk reduction achieved by a microbiological sampling and testing program at a given sensitivity is equivalent to that achieved by direct inactivation of pathogens. Our results indicated that if the sprouts were produced without any risk interventions, the health impact caused by sprouts contaminated with Salmonella would be very high, with a median annual estimated loss of disability-adjusted life years (DALYs) of 691,412. Seed treatment (with 20,000 ppm of calcium hypochlorite) or microbiological sampling and testing of spent irrigation water (SIW) alone could reduce the median annual impact to 734 or 4,856 DALYs, respectively. Combining seed treatment with testing of the SIW would further decrease the risk to 58 DALYs. This number could be dramatically lowered to 3.99 DALYs if sprouts were produced under conditions that included treating seeds with 20,000 ppm of calcium hypochlorite plus microbiological testing of seeds, SIW, and finished products. Our analysis shows that the public health impact due to Salmonella contamination in sprouts could be controlled if seeds are treated to reduce pathogens and microbiological sampling and testing is implemented. Future advances in intervention strategies would be important to improve sprout safety further.

Effect of the food production chain from farm practices to vegetable processing on outbreak incidence.

The popularity in the consumption of fresh and fresh-cut vegetables continues to increase globally. Fresh vegetables are an integral part of a healthy diet, providing vitamins, minerals, antioxidants and other health-promoting compounds. The diversity of fresh vegetables and packaging formats (spring mix in clamshell container, bagged heads of lettuce) support increased consumption. Unfortunately, vegetable production and processing practices are not sufficient to ensure complete microbial safety. This review highlights a few specific areas that require greater attention and research. Selected outbreaks are presented to emphasize the need for science-based ‘best practices’. Laboratory and field studies have focused on inactivation of pathogens associated with manure in liquid, slurry or solid forms. As production practices change, other forms and types of soil amendments are being used more prevalently. Information regarding the microbial safety of fish emulsion and pellet form of manure is limited. The topic of global climate change is controversial, but the potential effect on agriculture cannot be ignored. Changes in temperature, precipitation, humidity and wind can impact crops and the microorganisms that are associated with production environments. Climate change could potentially enhance the ability of pathogens to survive and persist in soil, water and crops, increasing human health risks. Limited research has focused on the prevalence and behaviour of viruses in pre and post-harvest environments and on vegetable commodities. Globally, viruses are a major cause of foodborne illnesses, but are seldom tested for in soil, soil amendments, manure and crops. Greater attention must also be given to the improvement in the microbial quality of seeds used in sprout production. Human pathogens associated with seeds can result in contamination of sprouts intended for human consumption, even when all appropriate ‘best practices’ are used by sprout growers.

Overview of Recent Events in the Microbiological Safety of Sprouts and New Intervention Technologies

Abstract There has been an increasing trend in consumption of sprouts worldwide due to their widespread availability and high nutrient content. However, microbial contamination of sprouts readily occurs due to the presence of pathogenic bacteria in seeds; and the germination and sprouting process provide optimal conditions for bacterial growth. In recent years, there has been a rise in the number of outbreaks associated with sprouts. These outbreaks occurred mainly in the US, Canada, UK, as well as Europe. More recently in 2011, there were 4 sprout‐related outbreaks, with the Escherichia coli O104:H4 outbreak in Germany causing around 50 deaths and 4000 illnesses reported. On top of pathogenic E. coli, Salmonella spp. are often associated with sprout‐related foodborne disease outbreaks. The contamination of sprouts has become a worldwide food safety concern. Hence, this review paper covers the outbreaks associated with sprouts, prevalence and characteristics of pathogens contaminating sprouts, their survival and growth, and the source of these pathogens. Physical, biological, and chemical interventions utilized to minimize microbial risks in sprouts are also discussed.

Microbial Contamination in Sprouts: How Effective Is Seed Disinfection Treatment?

Microbial contamination of sprouts by Salmonella and Escherichia coli O157 : H7 has been a common cause of foodborne diseases and a continuing challenge to the sprout industry. Seed disinfection treatment has been recommended as a major intervention step in a multihurdle approach to reduce the risk of illness associated with contaminated sprouts. U.S. Food and Drug Administration cited 20000 ppm calcium hypochlorite as an example treatment in its recommendation for seed treatment and this treatment has been considered the reference standard for seed disinfection treatment for over a decade. However, promising new disinfection treatments have emerged in recent years. In this study, we summarized published data and compared the efficacies of different disinfection methods in the reduction of microbial contamination on seeds. Our findings suggest that while biological interventions such as competitive exclusion and certain chemical treatments appear to be similar to 20000 ppm calcium hypochlorite for seed disinfection, physical methods especially high pressure may be more effective than the reference standard regardless of the type of bacteria or seed. The combination of 2 or more treatments, sequentially or simultaneously, may further improve disinfection results. Since treatments with high levels of chemical disinfectants, especially 20000 ppm calcium hypochlorite, can pose environmental and worker safety risks, alternative intervention approaches should be considered. Additional studies to confirm the greater efficacy of certain physical and combined seed disinfection treatments and to identify other effective management strategies are needed to further improve sprout safety.

The Efficacy of Satureja khuzistanica Essential Oil Treatment in Reducing Escherichia coli O157:H7 Load on Alfalfa Seeds Prior to Sprouting

AbstractAlong with the popularity of raw sprouts in the food baskets, the outbreaks associated with the consumption of the contaminated sprouts increased. In the present study, the antibacterial effect of the essential oil of Satureja khuzistanica in reducing the Escherichia coli O157:H7 population on alfalfa seeds prior to sprouting was evaluated.The essential oil (EO) was analyzed by gas chromatography/mass spectrometry. Alfalfa seeds were inoculated with E. coli O157:H7. The inoculated seeds were then treated with different concentrations of the essential oil of S. khuzistanica. The surviving populations of E. coli O157:H7 were enumerated by direct plating of the seeds on tryptic soy agar.The oil was rich in carvacrol. Direct surface‐plating on selective media showed the treatment resulted in a significant (P ≤ 0.05) reduction of E. coli O157:H7 population in a dose‐dependent manner. Increasing the washing time revealed a significant effect on reduction of E. coli O157:H7 population.The considerable antibacterial activity of the oil might be due to the high concentration of carvacrol. As the S. khuzistanica EO did not adversely affect alfalfa seed germination and had a strong antibacterial activity, the oil might be used as a natural antimicrobial product to overcome bacterial contamination of sprouts without compromising the viability.Practical ApplicationDuring the past decades, existing of chemical antibacterial has become increasingly unpopular in food industries. Consumers presume that these chemicals are threats to human health, because of their carcinogenicity, allergenicity, toxicity and environmental contaminations. For these reasons, nowadays, using of organic products is becoming more popular. Moreover, many foodborne pathogens are genetically adapted to synthetic antimicrobial compounds, thereby reducing the efficacy of such preventatives.It has been known that EOs have antimicrobial activities, rendering these natural products as good alternatives to synthetic bactericides. S. khuzistanica, with high concentration of carvacrol which is classified as GRAS (generally regarded as safe), could be one of these potential alternatives. This antimicrobial property favors its application in food industries as a reasonably safe agent.The confirmed antibacterial activities of S. khuzistanica, recommends its possible application in the field of food preservation for prolonging the shelf life of sprouts during postharvest and marketing processes.

새싹채소 오염세균의 에탄올과 유기산에 의한 제어

즉석섭취 신선편이식품 중의 하나인 새싹채소에 대한 수요가 증가하고 있으나, 오염 미생물 제어방법에 대한 정보가 거의 없는 상황이다. 따라서 본 연구는 국내 대형할인마트에서 유통 중인 새싹채소 20제품을 수집하여 세균수와 B. cereus를 살균소독하는 방법으로 에탄올과 초산, 구연산, 젖산 등의 유기산을 사용하여 그 효과를 평가하고자 하였다. 에탄올과 유기산을 각각 처리하였을 때보다 혼합처리한 실험구에서 세균생육저해가 현저하였으며, 유기산 중에서는 1% 젖산-20% 에탄올 처리구에서 10분 노출시간에 7~8 log CFU/g의 세균을 저감화 시킬 수가 있었다. 주요한 식중독 세균인 E. coli, S. typhimurium, B. cereus, S. aureus, E. faecalis에 직접 20% 에탄올-1% 젖산로 처리했을 때 10분 후에 세균의 감소가 5~7 log CFU/g 이루어졌으며, Gram 음성세균에서 효과가 더 좋았다. 새싹채소에서 에탄올 20%와 젖산, 초산, 구연산 1%를 처리한 후 관능검사는 처리 직후가 하루 후보다는 조직감, 갈변화, 이취 등에서 약간 더 양호한 것으로 나타났다. 따라서 차아염소산과 더불어 에탄올-젖산 등의 유기산의 적절한 조합으로 새싹채소의 오염 미생물을 저감화할 수 있는 것으로 보인다. Although bacterial outbreaks from ready-to-eat foods such as sprouts have increased, the information on microbial biocontrol by means of sanitizers is limited. Twenty sprouts of red cabbage, baby radish, alfalfa, and broccoli each were collected from the wholesale markets in Seoul. Ethanol and organic acids including acetic acid, citric acid, and lactic acid were used to control the amount of mesophilic bacteria and Bacillus cereus. Sanitizer mixtures of ethanol and organic acids showed a remarkable reduction of viable counts and, in particular, the sanitizer mixture comprised of 20% ethanol and 1% lactic acid seemed to be best by a reduction of 7~8 log CFU/g on the sprouts after a 10 minute exposure. At the same time, the sanitizer comprised of 20% ethanol and 1% lactic acid showed the same reduction for Escherichia coli, Salmonella typhimurium, B. cereus, Staphylococcus aureus, and Enterococcus faecalis, with more effect toward the Gram-negative bacteria. Sensory evaluation by texture, browning, off-flavour, and overall acceptability seemed better just after treatment when compared to one day after treatment with the sanitizer. Therefore, the sanitizers of ethanol-organic acid might be an effective means to control the bacterial contamination of sprouts in palce of sodium hypochloric acid.

Survival of Escherichia coli O157 and Salmonella in Seeds during Storage and Contamination of Sprouts Germinated from the Seeds

Radish, cress and alfalfa seeds contaminated with Escherichia coli O157 and Salmonella Enteritidis were stored at 4°C for 8 months. As a result, at contamination levels of 104 colony forming units (cfu) /10g, populations of S. Enteritidis in all seeds and those of.E. coli O157 in cress seeds were maintained for up to 8 months. When the seeds were grown, the edible parts of sprouts were heavily contaminated with the microorganisms. Although the population of E.coli O157 in radish and alfalfa seeds had greatly decreased, the microorganism was detected in the edible parts of sprouts from the seeds. At contamination levels of 102 cfu/10g, S. Enteritidis survived in alfalfa seeds at low population levels for up to 8 months and were detected at high population levels in sprouts from the seeds. These results suggested that E. coli O157 and S. Enteritidis could survive in seeds refrigerated for a long time and contaminate the sprouts from the seeds. Furthermore, E. coli O157 and S. Enteritidis were able to grow in the soaking water of seeds. Under a scanning electron microscope, we observed that the surface substrates of seeds were removed after soaking for a short time. Infrared spectroscopy revealed that the substrates were mainly composed of saccharides. These findings suggested that the growth of bacterial pathogens during sprouting of seeds depends on the surface saccharides of the seeds.

Growth dynamics of Salmonella enterica strains on alfalfa sprouts and in waste seed irrigation water.

Alfalfa sprouts and other seed sprouts have been implicated in numerous outbreaks of salmonellosis. The source of these epidemics appears to have been low-level contamination of seeds by Salmonella bacteria that developed into clinically significant populations during the seed germination process. To test the possibility that Salmonella enterica strains carry host range determinants that allow them to grow on alfalfa, strains isolated from alfalfa or other sources were surveyed for their ability to grow on germinating alfalfa seeds. An S. enterica serovar Cubana strain originally isolated from contaminated alfalfa sprouts multiplied most rapidly during the initial 24 h of the seed germination process. Germinating alfalfa seeds supported the multiplication of S. enterica cells prior to the emergence of the root radicle at 72 h. Thereafter, much lower rates of multiplication were apparent. The ability of S. enterica to grow on germinating alfalfa seeds was independent of the serovar, isolation source, or virulence of the strain. Isolates obtained from alfalfa attained population levels similar to those observed for strains isolated from contaminated meat products or stools. Each of the strains could be detected in the waste irrigation water, with populations being strongly correlated with those detected on the germinating alfalfa seeds. The S. enterica strains were capable of utilizing the waste irrigation water as a sole carbon and nitrogen source. S. enterica strains thus appear to grow saprophytically on soluble organics released from seeds during early phases of germination. The ability to detect S. enterica in the waste irrigation water early in the germination process indicates that this method may be used as a simple way to monitor the contamination of sprouts during commercial operations.