Bacteriological safety of sprouts: A brief review

Refrigerated storage stimulates isoflavone and γ-aminobutyric acid accumulation in germinated soybeans

This study aims to investigate the quality changes of germinated soybeans during refrigerated storage (4 °C), with an emphasis on the stimulatory effect of refrigeration on their special functional compounds. After germinating for two days, germinated soybeans were stored at 4 °C for seven days, while the germinated soybeans stored at 25 °C served as control group. The results showed that refrigerated storage significantly affected the physiological changes in germinated soybeans. The weight loss rate, browning rate, malondialdehyde (MDA) content and H2O2 content all decreased dramatically during refrigerated storage compared to the control group. The total phenolic and total flavonoid contents of germinated soybeans under refrigeration exhibited a trend of increasing and then decreasing over time. Additionally, during refrigerated storage, the total isoflavone content reached a peak of 8.72 g/kg on the fifth day, in which the content of daidzein and glycitin increased by 45% and 49% respectively, when compared with the control group. Moreover, the content of γ-aminobutyric acid (GABA) peaked on the first day, and kept a high level during storage. In which, the refrigerated group was 2.35-, 2.88-, 1.67-fold respectively after storage for three to seven days. These results indicated that refrigeration stimulated the biosynthesis of isoflavones and GABA in germinated soybeans during storage. More importantly, there was a sequential difference in the timing of the stimulation of the two functional components under refrigeration.

The nutritional profile of chia seeds and sprouts: tailoring germination practices for enhancing health benefits-a comprehensive review

Chia seeds have gained significant attention due to their unique composition and potential health benefits, including high dietary fibers, omega-3 fatty acids, proteins, and phenolic compounds. These components contribute to their antioxidant, anti-inflammatory effects, as well as their ability to improve glucose metabolism and dyslipidemia. Germination is recognized as a promising strategy to enhance the nutritional value and bioavailability of chia seeds. Chia seed sprouts have been found to exhibit increased essential amino acid content, elevated levels of dietary fiber and total phenols, and enhanced antioxidant capability. However, there is limited information available concerning the dynamic changes of bioactive compounds during the germination process and the key factors influencing these alterations in biosynthetic pathways. Additionally, the influence of various processing conditions, such as temperature, light exposure, and duration, on the nutritional value of chia seed sprouts requires further investigation. This review aims to provide a comprehensive analysis of the nutritional profile of chia seeds and the dynamic changes that occur during germination. Furthermore, the potential for tailored germination practices to produce chia sprouts with personalized nutrition, targeting specific health needs, is also discussed.

Influence of malting procedure on the isoflavonoid content of soybeans

The goal of this study was to analyse, whether malting technique (consisting of seed hydration, germination and drying) can be used to modify concentration of various isoflavonoids in soybean seeds. Seeds of three soybean varieties were germinated by different lengths of time (from 24 to 120 h) and dried by two different methods, typically used to produce so-called 'light' and 'caramel' malts. It was determined, that malting decreases concentration of 7-O-β-D-glucosides such as daidzin, genisitin and glycitin, while at the same time increasing concentration of aglycones (daidzein, genistein and glycitein). Increasing time of the germination period increased concentration of aglycones. 'Caramel' type malts were characterised with higher concentration of most of the isoflavonoids (daidzin, daidzein, genistin, genistein and glycitein) than 'light' type malts. Results of this study suggest that soybean malts can be an interesting substrate in the production of various food products with increased aglycone content.

Infectivity responses of Salmonella enterica to bacteriophages on maize seeds and maize sprouts

Salmonella enterica (S. enterica) is a major foodborne pathogen leading to a large number of outbreaks and bringing food safety concerns to sprouts. The control of S. enterica on maize sprouts is important because raw maize sprouts have been gaining attention as a novel superfood. Compared to conventional chemical methods, the applications of bacteriophages are regarded as natural and organic. This study investigated the effects of a 2 h phage cocktail (SF1 and SI1, MOI 1000) soaking on reducing the populations of three Salmonella enterica strains: S. Enteritidis S5-483, S. Typhimurium S5-536, and S. Agona PARC5 on maize seeds and during the storage of maize sprouts. The results showed that the phage cocktail treatment effectively reduced populations of S. enterica strains by 1-3 log CFU/g on maize seeds and decreased population of S. Agona PACR5 by 1.16 log CFU/g on maize sprouts from 7.55 log CFU/g at day 0 of the storage period. On the other hand, the upregulations of flagella gene pefA by 1.5-folds and membrane gene lpxA by 23-folds in S. Typhimurium S5-536 indicated a differential response to the phage cocktail treatment. Conversely, stress response genes ompR, rpoS, and recA, as well as the DNA repair gene yafD, were downregulated in S. Agona PARC5. This work shows the use of bacteriophages could contribute as a part of hurdle effect to reduce S. enterica populations and is beneficial to develop strategies for controlling foodborne pathogens in the production and storage of maize sprouts.

Surface disinfection of wheat kernels using gas phase hydroxyl-radical processes: Effect on germination characteristics, microbial load, and functional properties

Wheat kernels harbor a diverse microflora that can negatively affect the suitability of the grains for further processing. To reduce surface microflora, a kernel disinfection method is required that does not affect grain functionality. Three different versions of gas phase hydroxyl-radical processes were compared with the common method for grain disinfection, that is, a bleach treatment. The gas phase hydroxyl-radicals are generated by the UV-C mediated degradation of hydrogen peroxide and/or ozone in a near water-free process. It was found that treating kernels with a bleach solution could reduce total aerobic count (TAC) and fungal count to below the level of enumeration. In comparison, the gas phase hydroxyl-radical treatment, that is, H2 O2 -UV-ozone treatment, could support a 1.3 log count reduction (LCR) in TAC and a 1.1 LCR in fungal count. The microbial load reduction for the wholemeal samples was less pronounced as endophytic microorganisms were less affected by all treatments, hinting at a limited penetration depth of the treatments. Despite reducing the microbial load on the kernel surface through the bleach and H2 O2 -UV-ozone treatments, none of these treatments resulted in a reduced microbial count on grains that underwent sprouting after the treatments. No negative effect on germination power or development of the seedling was observed for any of the treatments. The gluten aggregation behavior and xylanase activity of the wholemeal also remained unchanged after the gas phase hydroxyl-radical treatments. Our findings suggest that UV-H2 O2 -ozone treatment shows promise for dry-kernel disinfection, but further optimization of the processing parameters is required.

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.

Sprouts as probiotic carriers: A new trend to improve consumer nutrition

Over the past few decades, efforts to eradicate hunger in the world have led to the generation of sustainable development goals to reduce poverty and inequality. It is estimated that the current coronavirus pandemic could add between 83 and 132 million to the total number of undernourished people in the world by 2021. Food insecurity is a contributing factor to the increase in malnutrition, overweight and obesity due to the quality of diets to which people have access. It is therefore necessary to develop functional foods that meet the needs of the population, such as the incorporation of sprouts in their formulation to enhance nutritional quality. Germination of grains and seeds can be used as a low-cost bioprocessing technique that provides higher nutritional value and better bioavailability of nutrients. Consequently, the manuscript describes relevant information about the germination process in different seeds, the changes caused in their nutritional value and the use of techniques within the imbibition phase to modify the metabolic profiles within the sprouts such as inoculation with lactic acid bacteria and yeasts, to generate a functional symbiotic food.

Unlocking the Potential of Sprouted Cereals, Pseudocereals, and Pulses in Combating Malnutrition

Due to the global rise in food insecurity, micronutrient deficiency, and diet-related health issues, the United Nations (UN) has called for action to eradicate hunger and malnutrition. Grains are the staple food worldwide; hence, improving their nutritional quality can certainly be an appropriate approach to mitigate malnutrition. This review article aims to collect recent information on developing nutrient-dense grains using a sustainable and natural process known as "sprouting or germination" and to discuss novel applications of sprouted grains to tackle malnutrition (specifically undernutrition). This article discusses applicable interventions and strategies to encourage biochemical changes in sprouting grains further to boost their nutritional value and health benefits. It also explains opportunities to use spouted grains at home and in industrial food applications, especially focusing on domestic grains in regions with prevalent malnutrition. The common challenges for producing sprouted grains, their future trends, and research opportunities have been covered. This review article will benefit scientists and researchers in food, nutrition, and agriculture, as well as agrifood businesses and policymakers who aim to develop nutrient-enriched foods to enhance public health.

Recent developments in applications of physical fields for microbial decontamination and enhancing nutritional properties of germinated edible seeds and sprouts: a review

Germinated edible seeds and sprouts have attracted consumers because of their nutritional values and health benefits. To ensure the microbial safety of the seed and sprout, emerging processing methods involving physical fields (PFs), having the characteristics of high efficiency and environmental safety, are increasingly proposed as effective decontamination processing technologies. This review summarizes recent progress on the application of PFs to germinating edible seeds, including their impact on microbial decontamination and nutritional quality and the associated influencing mechanisms in germination. The effectiveness, application scope, and limitation of the various physical techniques, including ultrasound, microwave, radio frequency, infrared heating, irradiation, pulsed light, plasma, and high-pressure processing, are symmetrically reviewed. Good application potential for improving seed germination and sprout growth is also described for promoting the accumulation of bioactive compounds in sprouts, and subsequently enhancing the antioxidant capacity under favorable PFs processing conditions. Moreover, the challenges and future directions of PFs in the application to germinated edible seeds are finally proposed. This review also attempts to provide an in-depth understanding of the effects of PFs on microbial safety and changes in nutritional properties of germinating edible seeds and a theoretical reference for the future development of PFs in processing safe sprouted seeds.

The conjugative transfer of plasmid-mediated mobile colistin resistance gene, mcr-1, to Escherichia coli O157:H7 and Escherichia coli O104:H4 in nutrient broth and in mung bean sprouts

The emergence of mobile colistin resistant gene (mcr-1) in Enterobacteriaceae has become a global public health concern. Dissemination of the mcr-1 gene through conjugation of bacteria associated with food may occur. This research investigated the transfer frequency of the mcr-1 gene among Escherichia coli in liquid media and during growth of mung bean sprouts. The donor strain E. coli NCTC 13846 (mcr-1 positive) and recipient strains of E. coli O157:H7 and E. coli O104:H4 were used. Mating experiments in vitro were conducted at 4, 25, and 37 °C for up to 36 h. The in vivo mating experiments (growing sprouts) were conducted in a sprout growth chamber with irrigation of 1 min/h over 6 days following inoculation of mung bean seeds with the donor and a recipient. The highest transfer frequencies in TSB media, 2.86E-07 and 3.24E-07, occurred at 37 °C after mating for 24 h for E. coli O104:H4 and E. coli O157:H7, respectively. Transconjugants were not detected in liquid media at 4 °C. Moreover, transfer frequency (5.68E-05 per recipient) of mcr-1 was greater during mung bean sprout growth for E. coli O104:H4 compared to E. coli O157:H7 (1.02E-05 per recipient) Day 3 to Day 6. This study indicates that the transfer of antibiotic resistant gene(s) among bacteria during mung bean sprout production may facilitate the spread of antibiotic resistant bacteria in the environment and to humans.

Dough Rheological Behavior and Bread Quality as Affected by Addition of Soybean Flour in a Germinated Form

This study analyzes the possibility of using soybeans as an addition to the main ingredients used to make bread, with the aim of improving its quality characteristics. To maximize the nutritional profile of soybeans they were subjected to the germination and lyophilization process before being used in bread making. The addition levels of 5%, 10%, 15%, and 20% germinated soybean flour (GSF) on dough rheology and bread quality were used. From the rheology point of view, the GSF addition had the effect of decreasing the values of the creep and recovery parameters: J_Co, J_Cm, μ_Co, J_max, J_Ro, J_Rm, and J_r. At the same time, the rheological parameters λ_C and λ_R increased. The GSF addition did not affect dough homogeneity as may be seen from EFLM analysis. Regarding the quality of the bread, it may be concluded that a maximum of 15% GSF addition in wheat flour had a desirable effect on loaf volume, porosity, elasticity, and sensory properties of the bread. The bread samples with GSF additions showed a higher brightness and a less pronounced red and yellow tint. When the percentage of GSF in wheat flour increased, the value of the firmness parameter increased and the value of the gumminess, cohesiveness, and resilience parameters decreased. The addition of GSF had a desirable influence on the crumb structure of the bread samples. Thus, taking into account the results of the determinations outlined above, it can be stated that GSF addition in wheat flour leads to bread samples with good quality characteristics.

Efficacy of Ascaroside #18 Treatments in Control of Salmonella enterica on Alfalfa and Fenugreek Seeds and Sprouts

A novel, natural, and effective antimicrobial intervention is in demand for improving the microbial safety of vegetable seeds/sprouts. This study assessed the efficacy of ascaroside treatment in the control of Salmonella enterica on alfalfa and fenugreek sprouts. Sanitized commercial seeds were treated with 1 mM or 1 µM ascaroside (ascr)#18, a plant immunity modulator (PIM) and dried for an hour before being inoculated with lyophilized S. Cubana or S. Stanley cells in sandy soil (104 CFU/g). Treated and untreated seeds were spouted on 1% water agar at 25°C in the dark. Seed or sprout samples were collected on days 0, 1, 3, 5, and 7, and the population of Salmonella was determined. Data were fit into the general linear arrangement, and means were separated using Fisher's least significant difference test. Seed type, strain type, treatment type, and sprouting time were significant factors (P ≤ 0.05) influencing Salmonella growth on sprouts. The populations of Salmonella were significantly higher on fenugreek than on alfalfa sprouts. S. Stanley had a significantly higher population than S. Cubana. The population of Salmonella increased from day 0 to day 3 and reached the peak population on Day 5. Treatments with both concentrations of ascaroside significantly decreased the populations of Salmonella compared to the controls. The mean Salmonella population reduction was ca. 4 or 1 log CFU/g by treatment with 1 mM and 1 µM of the PIM, respectively. Treatment with the PIM could be potentially used to improve the microbial safety of vegetable seeds and sprouts.

Analysis of Dynamics and Diversity of Microbial Community during Production of Germinated Brown Rice

Sprouts may be contaminated with different pathogenic and spoilage microorganisms, which lead far too easily to foodborne outbreaks. The elucidations of microbial profiles in germinated brown rice (BR) are important, but the changes in the microbial composition during germination are unknown. This study aimed to investigate the microbiota composition and to monitor the dominant microbial dynamics in BR during germination using both culture-independent and -dependent methods. BR samples (HLJ2 and HN) were collected from each stage of the germination processing. The populations of microbes (total viable counts, yeast/mold counts, Bacillus cereus, and Enterobacteriaceae) of two BR cultivars increased markedly with the prolongation of the germination time. High-throughput sequencing (HTS) showed that the germination process significantly influenced the microbial composition and reduced the microbial diversity. Similar microbial communities were observed between the HLJ2 and the HN samples, but with different microbial richness. The bacterial and fungal alpha diversity achieved the maximum for ungerminated samples and declined significantly after soaking and germination. During germination, Pantoea, Bacillus, and Cronobacter were the dominant bacterial genera, but Aspergillus, Rhizopus, and Coniothyrium dominated for the fungi in the BR samples. The predominance of harmful and spoilage microorganisms in BR during germination is mainly from contaminated seeds, which highlights the potential risk of foodborne illness from sprouted BR products. The results provide new insight into the microbiome dynamics of BR and may help to establish effective decontamination measures against pathogenic microorganisms during sprout production.

Seed Disinfestation Practices to Control Seed-Borne Fungi and Bacteria in Home Production of Sprouts

Concern over microbial contamination limits the adoption of home production of sprouts as a nutritious and sustainable food. Simple, accessible approaches to seed disinfection could support safe home seed sprouting. Here, we quantify bacterial and fungal contamination of seeds of 14 plant cultivars sold for home sprout production and test a range of chemical and physical methods for seed disinfestation appropriate for home use. Most seeds are contaminated with a variety of bacteria and fungi, and those microbes are usually limited to the seed surface. Heat treatments are not effective for seed disinfection because the high temperatures needed to effectively reduce microbial contamination also reduce seed germination. Two chlorine-based chemical disinfectants-dilute household bleach (0.6% sodium hypochlorite) and freshly generated hypochlorous acid (800 ppm chlorine)-were the most effective disinfection agents tested (up to a 5-log reduction in bacteria) that also did not harm seed germination.

Chia (Salvia hispanica L.) Seed Germination: a Brief Review

Chia (Salvia hispanica L.) is a seed native to northern Mexico and southern Guatemala that has started to be consumed in recent years in other regions of the world owing to its nutritional and functional properties. Germination of chia seeds seems to be able to further improve these properties, and it has been the subject of some studies. In general, germination has proven to be a simple and inexpensive process capable of improving the content of phenolic compounds and the antioxidant capacity of foods, as well as reducing antinutritional factors that interfere with nutrient absorption. A particular characteristic of chia seeds is that they produce mucilage when they are hydrated. For this reason, the germination conditions of the seed need to be adapted. The nutritional guidelines of some countries, such as Brazil, Germany and Sweden, recommend that the diet of the population should be more plant-based, thus encouraging the consumption of foods with a high content of bioactive compounds and nutrients, e.g., germinated seeds. This review briefly explored the germination conditions of chia seeds as well as the changes in phytonutrient content and antinutritional factors after their germination process. The main information available in the literature is that germination of chia seeds can increase the contents of protein, fiber, and total phenolic compounds. As a conclusion, germination of chia seeds is favorable for increasing their health benefits and nutritional value. However, chia germination parameters should be adjusted and microbiological risks should be properly evaluated.

Characterization of polyvalent Escherichia phage Sa157lw for the biocontrol potential of Salmonella Typhimurium and Escherichia coli O157:H7 on contaminated mung bean seeds

Seeds are one of the primary sources of contamination with foodborne pathogens, such as pathogenic Escherichia coli, and various Salmonella serovars, for produce, particularly sprouts. Due to the susceptibility of sprout growth to chemical-based antimicrobials and the rising issue of antimicrobial resistance, developing innovative antimicrobial interventions is an urgent need. Therefore, the objective of this study was to characterize Escherichia phage Sa157lw (or Sa157lw) for the biocontrol potential of Salmonella Typhimurium and E. coli O157:H7 on contaminated mung bean seeds. Phage Sa157lw was subjected to whole-genome sequencing and biological characterization, including morphology, one-step growth curve, and stress stability tests. Later, antimicrobial activity was determined in vitro and upon application on the mung bean seeds artificially contaminated with E. coli O157:H7 or Salmonella Typhimurium. Sa157lw possessed a contractile tail and belonged to the Kuttervirus genus under the Ackermannviridae family, sharing a close evolutionary relationship with E. coli phage ECML-4 and Kuttervirus ViI; however, tail spike genes (ORF_102 and ORF_104) were the primary region of difference. Comparative genomics showed that Sa157lw encoded a cluster of tail spike genes—including ORF_101, ORF_102, and ORF_104—sharing high amino acid similarity with the counterfeits of various Salmonella phages. Additionally, Sa157lw harbored a unique tail fiber (ORF_103), possibly related to the receptors binding of O157 strains. The genomic evidence accounted for the polyvalent effects of Sa157lw against E. coli O157:H7 and various Salmonella serovars (Typhimurium, Enteritidis, Agona, Saintpaul, and Heidelberg). Furthermore, the phage did not contain any virulence, antibiotic-resistant, or lysogenic genes. Sa157lw had a 30-min latent period on both E. coli O157:H7 and Salmonella Typhimurium, with an estimated burst size of 130 and 220 PFU/CFU, respectively, and was stable at a wide range of temperatures (4–60°C) and pH (pH4 to pH10). The phage application demonstrated a strong anti-E. coli O157:H7 and anti-Salmonella Typhimurium effects in 1.1 and 1.8 log reduction on the contaminated mung bean seeds after overnight storage at 22°C. These findings provide valuable insights into the polyvalent Sa157lw as a potential biocontrol agent of Salmonella Typhimurium and E. coli O157:H7 on sprout seeds.

Characterization of a T4-like Bacteriophage vB_EcoM-Sa45lw as a Potential Biocontrol Agent for Shiga Toxin-Producing Escherichia coli O45 Contaminated on Mung Bean Seeds

Application of lytic bacteriophages is a promising and alternative intervention technology to relieve antibiotic resistance pressure and control bacterial pathogens in the food industry. Despite the increase of produce-associated outbreaks caused by non-O157 Shiga toxin-producing E. coli (STEC) serogroups, the information of phage application on sprouts to mitigate these pathogens is lacking. Therefore, the objective of this study was to characterize a T4-like Escherichia phage vB_EcoM-Sa45lw (or Sa45lw) for the biocontrol potential of STEC O45 on mung bean seeds. Phage Sa45lw belongs to the Tequatrovirus genus under the Myoviridae family and displays a close evolutionary relationship with a STEC O157-infecting phage AR1. Sa45lw contains a long-tail fiber gene (gp37), sharing high genetic similarity with the counterpart of Escherichia phage KIT03, and a unique tail lysozyme (gp5) to distinguish its host range (STEC O157, O45, ATCC 13706, and Salmonella Montevideo and Thompson) from phage KIT03 (O157 and Salmonella enterica). No stx, antibiotic resistance, and lysogenic genes were found in the Sa45lw genome. The phage has a latent period of 27 min with an estimated burst size of 80 PFU/CFU and is stable at a wide range of pH (pH 3 to pH 10.5) and temperatures (-80°C to 50°C). Phage Sa45lw is particularly effective in reducing E. coli O45:H16 both in vitro (MOI = 10) by 5 log and upon application (MOI = 1,000) on the contaminated mung bean seeds for 15 min by 2 log at 25°C. These findings highlight the potential of phage application against non-O157 STEC on sprout seeds. IMPORTANCE Seeds contaminated with foodborne pathogens, such as Shiga toxin-producing E. coli, are the primary sources of contamination in produce and have contributed to numerous foodborne outbreaks. Antibiotic resistance has been a long-lasting issue that poses a threat to human health and the food industry. Therefore, developing novel antimicrobial interventions, such as bacteriophage application, is pivotal to combat these pathogens. This study characterized a lytic bacteriophage Sa45lw as an alternative antimicrobial agent to control pathogenic E. coli on the contaminated mung bean seeds. The phage exhibited antimicrobial effects against both pathogenic E. coli and Salmonella without containing virulent or lysogenic genes that could compromise the safety of phage application. In addition, after 15 min of phage treatment, Sa45lw mitigated E. coli O45:H16 on the contaminated mung bean seeds by a 2-log reduction at room temperature, demonstrating the biocontrol potential of non-O157 Shiga toxin-producing E. coli on sprout seeds.