Antimicrobial potential of cauliflower, broccoli, and okara byproducts against foodborne bacteria

Colonization of Raphanus sativus by human pathogenic microorganisms

Contamination of vegetables with human pathogenic microorganisms (HPMOs) is considered one of the most important problems in the food industry, as current nutritional guidelines include increased consumption of raw or minimally processed organic vegetables due to healthy lifestyle promotion. Vegetables are known to be potential vehicles for HPMOs and sources of disease outbreaks. In this study, we tested the susceptibility of radish (Raphanus sativus) to colonization by different HPMOs, including Escherichia coli PCM 2561, Salmonella enterica subsp. enterica PCM 2565, Listeria monocytogenes PCM 2191 and Bacillus cereus PCM 1948. We hypothesized that host plant roots containing bactericidal compounds are less prone to HPMO colonization than shoots and leaves. We also determined the effect of selected pathogens on radish growth to check host plant-microbe interactions. We found that one-week-old radish is susceptible to colonization by selected HPMOs, as the presence of the tested HPMOs was demonstrated in all organs of R. sativus. The differences were noticed 2 weeks after inoculation because B. cereus was most abundant in roots (log10 CFU - 2.54), S. enterica was observed exclusively in stems (log10 CFU - 3.15), and L. monocytogenes and E. coli were most abundant in leaves (log10 CFU - 4.80 and 3.23, respectively). The results suggest that E. coli and L. monocytogenes show a higher ability to colonize and move across the plant than B. cereus and S. enterica. Based on fluorescence in situ hybridization (FISH) and confocal laser scanning microscopy (CLSM) approach HPMOs were detected in extracellular matrix and in some individual cells of all analyzed organs. The presence of pathogens adversely affected the growth parameters of one-week-old R. sativus, especially leaf and stem fresh weight (decreased by 47-66 and 17-57%, respectively). In two-week-old plants, no reduction in plant biomass development was noted. This observation may result from plant adaptation to biotic stress caused by the presence of HPMOs, but confirmation of this assumption is needed. Among the investigated HPMOs, L. monocytogenes turned out to be the pathogen that most intensively colonized the aboveground part of R. sativus and at the same time negatively affected the largest number of radish growth parameters.

Population dynamics of Listeria spp., Salmonella spp., and Escherichia coli on fresh produce: A scoping review

Collation of the current scope of literature related to population dynamics (i.e., growth, die-off, survival) of foodborne pathogens on fresh produce can aid in informing future research directions and help stakeholders identify relevant research literature. A scoping review was conducted to gather and synthesize literature that investigates population dynamics of pathogenic and non-pathogenic Listeria spp., Salmonella spp., and Escherichia coli on whole unprocessed fresh produce (defined as produce not having undergone chopping, cutting, homogenization, irradiation, or pasteurization). Literature sources were identified using an exhaustive search of research and industry reports published prior to September 23, 2021, followed by screening for relevance based on strict, a priori eligibility criteria. A total of 277 studies that met all eligibility criteria were subjected to an in-depth qualitative review of various factors (e.g., produce commodities, study settings, inoculation methodologies) that affect population dynamics. Included studies represent investigations of population dynamics on produce before (i.e., pre-harvest; n = 143) and after (i.e., post-harvest; n = 144) harvest. Several knowledge gaps were identified, including the limited representation of (i) pre-harvest studies that investigated population dynamics of Listeria spp. on produce (n = 13, 9% of pre-harvest studies), (ii) pre-harvest studies that were carried out on non-sprouts produce types grown using hydroponic cultivation practices (n = 7, 5% of pre-harvest studies), and (iii) post-harvest studies that reported the relative humidity conditions under which experiments were carried out (n = 56, 39% of post-harvest studies). These and other knowledge gaps summarized in this scoping review represent areas of research that can be investigated in future studies.

Effect of storage temperature and produce type on the survival or growth of Listeria monocytogenes on peeled rinds and fresh-cut produce

Whole and fresh-cut produce are minimally processed and susceptible to microbial contamination. This study evaluated the survival or growth of L. monocytogenes on peeled rinds, and fresh-cut produce at different storage temperatures. Fresh-cut fruits and vegetables, including cantaloupe, watermelon, pear, papaya, pineapple, broccoli, cauliflower, lettuce, bell pepper, and kale (25 g pieces) were spot inoculated with 4 log CFU/g of L. monocytogenes and stored at 4 or 13°C for 6  days. Cantaloupe and bell pepper rind disks (20 cm²), mimicking whole produce were inoculated with low inoculum level (4 log CFU/mL) and high inoculum level (6 log CFU/mL) and stored at 24°C up to 8  days and 4°C up to 14  days, respectively. L. monocytogenes counts on fresh-cut pear samples stored at 4°C increased significantly by 0.27 log CFU/g. However, Listeria levels on kale (day 4), cauliflower (day 6), and broccoli (day 2) were significantly reduced by 0.73, 1.18, and 0.80 log CFU/g, respectively, at 4°C. At 13°C, the bacterial counts increased significantly after a day of storage on fresh-cut watermelons (increasing by 1.10 log CFU/g) and cantaloupes (increasing by 1.52 log CFU/g). Similar increases were observed on pears (1.00 log CFU/g), papayas (1.65 log CFU/g), and green bell peppers (1.72 log CFU/g). Pineapple samples did not support the growth of L. monocytogenes at 13°C with a significant reduction of 1.80 log CFU/g by day 6. L. monocytogenes levels significantly increased in fresh-cut lettuce at 13°C but remained stable on kale, cauliflower, and broccoli after 6  days of storage. Stable population was observed also on cantaloupe rinds up to 8  days at 24°C. While on the outer surface of bell peppers, the population level decreased below the detectable limit of the test (10 CFU/20 cm²) after 14  days of storage at 4°C. The results demonstrated variable survival behavior of L. monocytogenes on fresh-cut produce with produce type and storage temperature.

Side Streams of Vegetable Processing and Its Bioactive Compounds Support Microbiota, Intestine Milieu, and Immune System

The industry of vegetable processing generates large amounts of by-products, which often emerge seasonally and are susceptible to microbial degradation. Inadequate management of this biomass results in the loss of valuable compounds that are found in vegetable by-products that can be recovered. Considering the possibility of using waste, scientists are trying to reuse discarded biomass and residues to create a product of higher value than those processed. The by-products from the vegetable industry can provide an added source of fibre, essential oils, proteins, lipids, carbohydrates, and bioactive compounds, such as phenolics. Many of these compounds have bioactive properties, such as antioxidative, antimicrobial, and anti-inflammatory activity, which could be used, especially in the prevention or treatment of lifestyle diseases connected with the intestinal milieu, including dysbiosis and immune-mediated diseases resulting in inflammation. This review summarises the key aspects of the health-promoting value of by-products and their bioactive compounds derived from fresh or processed biomass and extracts. In this paper, the relevance of side streams as a source of beneficial compounds with the potential for promoting health is considered, particularly their impact on the microbiota, immune system, and gut milieu because all of these fields interact closely to affect host nutrition, prevent chronic inflammation, and provide resistance to some pathogens.

Comparative nutritional and antimicrobial analysis of Himalayan black and yellow soybean and their okara

BACKGROUND

Soybean is believed to have good nutraceutical potential which is important for human health. Yellow soybean (YS) is generally used for the production of soymilk and other products, while black soybean (BS) is less explored. During the production of soymilk, residue, called okara is generated which is reported to have a good amount of nutrient content. Studies are generally performed with YS while BS is less explored. The present work is a comparison of the nutraceutical potential of BS and YS and their okara, mainly in terms of proximate, minerals, antinutrients, and isoflavone content and bioactivity of all types of samples in terms of antioxidant and antimicrobial activity.

RESULTS

Compared to raw soybean, protein content decreased significantly in both types of okara. Phytochemicals like ascorbic acid, catechin, quercetin, and gallic acid were significantly (P < 0.05) high in BS residue in comparison to respective raw soybean. Among isoflavones, daidzin and genistin were found significantly varying among all the samples, and glycitin and glycitein were not present in YS.

CONCLUSION

The nutraceutical potential and antimicrobial activity were comparative for both the raw beans and their okara, while the phytochemical contents and antioxidant activity were higher in the case of BS and its okara. © 2022 Society of Chemical Industry.

Agri-Food Surplus, Waste and Loss as Sustainable Biobased Ingredients: A Review

Ensuring a sustainable supply of food for the world’s fast growing population is a major challenge in today’s economy, as modern lifestyle and increasing consumer concern with maintaining a balanced and nutritious diet is an important challenge for the agricultural sector worldwide. This market niche for healthier products, especially fruits and vegetables, has increased their production, consequently resulting in increased amounts of agri-food surplus, waste, and loss (SWL) generated during crop production, transportation, storage, and processing. Although many of these materials are not utilized, negatively affecting the environmental, economic, and social segments, they are a rich source of valuable compounds that could be used for different purposes, thus preventing the losses of natural resources and boosting a circular economy. This review aimed to give insights on the efficient management of agri-food SWL, considering conventional and emerging recovery and reuse techniques. Particularly, we explored and summarized the chemical composition of three worldwide cultivated and consumed vegetables (carrots, broccoli and lettuce) and evaluate the potential of their residues as a sustainable alternative for extracting value-added ingredients for the development of new biodynamic products.

Phytochemical characterization, and antioxidant and antimicrobial activities of white cabbage extract on the quality and shelf life of raw beef during refrigerated storage

Brassica vegetables are well-characterized, containing a wide-spectrum of phenolic compounds that are responsible for their diverse biological activities like antioxidant and antimicrobial activities. This study explored the preservative effect of Brassica oleracea var. capitate f. alba (white cabbage; WC) on beef under refrigerated conditions for 16 days. The antimicrobial activities of WC were evaluated against foodborne pathogenic bacteria and fungi. The antioxidant activity was determined on the basis of total phenolic and flavonoid contents, through employing DPPH and ABTS assays. The chemical composition was analyzed by GC-MS analysis. The results indicated that among the different solvent extracts, white cabbage chloroform extract [WCCE] exhibited outstanding bioactive properties due to the presence of 4-nitro-3-(trifluoromethyl)phenol, and the effects of WCCE at different levels (A and B) on the quality and shelf life of beef in storage were evaluated. The color parameters (lightness, yellowness, and redness), texture analysis, and pH values were monitored constantly with 4 days interval, and microbial analysis was conducted. The results showed that WCCE-A treatment significantly reduced the total viable counts, psychrotrophic bacteria, and yeast-molds when compared with WCCE-B and control during refrigeration storage, with the activity varying in a dose-dependent manner (p < 0.05). Significantly, the WCCE-A treatments had better appearance compared with the control after 16 days of storage. All results confirmed that WCCE which is rich in bioactive compounds, effectively maintains the quality of beef compared to the control by retarding lipid oxidation and microbial growth at refrigeration temperature and also emphasize the potential applications of this plant in different industrial sectors.

The Bacillus cereus Food Infection as Multifactorial Process

The ubiquitous soil bacterium Bacillus cereus presents major challenges to food safety. It is responsible for two types of food poisoning, the emetic form due to food intoxication and the diarrheal form emerging from food infections with enteropathogenic strains, also known as toxico-infections, which are the subject of this review. The diarrheal type of food poisoning emerges after production of enterotoxins by viable bacteria in the human intestine. Basically, the manifestation of the disease is, however, the result of a multifactorial process, including B. cereus prevalence and survival in different foods, survival of the stomach passage, spore germination, motility, adhesion, and finally enterotoxin production in the intestine. Moreover, all of these processes are influenced by the consumed foodstuffs as well as the intestinal microbiota which have, therefore, to be considered for a reliable prediction of the hazardous potential of contaminated foods. Current knowledge regarding these single aspects is summarized in this review aiming for risk-oriented diagnostics for enteropathogenic B. cereus.

Broccoli (Brassica oleracea L. var. italica) Sprouts as the Potential Food Source for Bioactive Properties: A Comprehensive Study on In Vitro Disease Models

Broccoli sprouts are an excellent source of health-promoting phytochemicals such as vitamins, glucosinolates, and phenolics. The study aimed to investigate in vitro antioxidant, antiproliferative, apoptotic, and antibacterial activities of broccoli sprouts. Five-day-old sprouts extracted by 70% ethanol showed significant antioxidant activities, analyzed to be 68.8 μmol Trolox equivalent (TE)/g dry weight by 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulphonic (ABTS) assay, 91% scavenging by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, 1.81 absorbance by reducing power assay, and high phenolic contents by high-performance liquid chromatography (HPLC). Thereafter, sprout extract indicated considerable antiproliferative activities towards A549 (lung carcinoma cells), HepG2 (hepatocellular carcinoma cells), and Caco-2 (colorectal adenocarcinoma cells) using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, with IC₅₀ values of 0.117, 0.168 and 0.189 mg/mL for 48 h, respectively. Furthermore, flow cytometry confirmed that Caco-2 cells underwent apoptosis by an increase of cell percentage in subG1 phase to 31.3%, and a loss of mitochondrial membrane potential to 19.3% after 48 h of treatment. Afterward, the extract exhibited notable antibacterial capacities against Bacillus subtilis and Salmonella Typhimurium with minimum inhibition concentration (MIC) values of 0.39 and 0.78 mg/mL, appropriately, along with abilities against Staphylococcus aureus and Escherichia coli with an MIC value of 1.56 mg/mL. Thus, broccoli sprouts were confirmed as a potential food source for consumers’ selection and functional food industry.

Occurrence of Salmonella typhimurium resistance under sublethal/repeated exposure to cauliflower infusion and infection effects on Caernohabditis elegans host test organism

Resistant bacteria to antimicrobials are increasingly emerging in medical, food industry and livestock environments. The present research work assesses the capability of Salmonella enterica var Typhimurium to become adapted under the exposure to a natural cauliflower antimicrobial by-product infusion in consecutive repeated exposure cycles. Caenorhabditis elegans was proposed as in vivo host-test organism to compare possible changes in the virulent pattern of the different rounds treated S. enterica var Typhimurium and untreated bacterial cells. According to the obtained results, S. enterica var Typhimurium was able to generate resistance against a repeated exposure to cauliflower by-product infusion 5% (w/v), increasing the resistance with the number of exposed repetitions. Meanwhile, at the first exposure, cauliflower by-product infusion was effective in reducing S. enterica var Typhimurium (≈1 log₁₀ cycle), and S. enterica var Typhimurium became resistant to this natural antimicrobial after the second and third treatment-round and was able to grow (≈1 log₁₀ cycle). In spite of the increased resistance observed for repeatedly treated bacteria, the present study reveals no changes on C. elegans infection effects between resistant and untreated S. enterica var Typhimurium, according to phenotypic parameters evaluation (lifespan duration and egg-laying).

Agro-Food Byproducts as a New Source of Natural Food Additives

Nowadays, the agro-food industry generates high amounts of byproducts that may possess added value compounds with high functionality and/or bioactivity. Additionally, consumers' demand for healthier foodstuffs has increased over the last years, and thus the food industry has strived to answer this challenge. Byproducts are generally secondary products derived from primary agro-food production processes and represent an interesting and cheaper source of potentially functional ingredients, such as peptides, carotenoids, and phenolic compounds, thus promoting a circular economy concept. The existing body of work has shown that byproducts and their extracts may be successfully incorporated into foodstuffs, for instance, phenolic compounds from eggplant can be potentially used as a mulfitunctional food additive with antimicrobial, antioxidant, and food colorant properties. As such, the aim of this review is to provide insights into byproducts and their potential as new sources of foodstuffs additives.

Consumed Foodstuffs Have a Crucial Impact on the Toxic Activity of Enteropathogenic Bacillus cereus

Enteropathogenic Bacillus cereus cause diarrhea due to the production of enterotoxins in the intestine. To start this process, spores have to be ingested together with contaminated food and survive the stomach passage. In this study, the influence of consumed foodstuffs on spore survival as well as on cytotoxicity toward colon epithelial cells was investigated. Spore survival of 20 enteropathogenic and apathogenic B. cereus strains during simulated stomach passage was highly strain-specific and did not correlate with the toxic potential. Survival of three tested strains was strain-specifically altered by milk products. Whereas milk, a follow-on formula and rice pudding had only little influence, spores seemed to be protected by milk products with high fat content such as whipped cream and mascarpone. Furthermore, tested milk products decreased the toxic activity of three B. cereus strains toward CaCo-2 cells. Investigating the individual components, lactoferrin, a skim milk powder and vitamins C, B5 and A showed the most inhibiting effects. On the other hand, biotin, vitamin B3 and another skim milk powder even enhanced cytotoxicity. Further studies suggested that these inhibiting effects result only partially from inhibiting cell binding, but rather from blocking the interaction between the single enterotoxin components.

Comparative Phytonutrient Analysis of Broccoli By-Products: The Potentials for Broccoli By-Product Utilization

The phytonutrient concentrations of broccoli (Brassica oleracea var. italica) florets, stems, and leaves were compared to evaluate the value of stem and leaf by-products as a source of valuable nutrients. Primary metabolites, including amino acids, organic acids, and sugars, as well as glucosinolates, carotenoids, chlorophylls, vitamins E and K, essential mineral elements, total phenolic content, antioxidant activity, and expression of glucosinolate biosynthesis and hydrolysis genes were quantified from the different broccoli tissues. Broccoli florets had higher concentrations of amino acids, glucoraphanin, and neoglucobrassicin compared to other tissues, whereas leaves were higher in carotenoids, chlorophylls, vitamins E and K, total phenolic content, and antioxidant activity. Leaves were also good sources of calcium and manganese compared to other tissues. Stems had the lowest nitrile formation from glucosinolate. Each tissue exhibited specific core gene expression profiles supporting glucosinolate metabolism, with different gene homologs expressed in florets, stems, and leaves, which suggests that tissue-specific pathways function to support primary and secondary metabolic pathways in broccoli. This comprehensive nutrient and bioactive compound profile represents a useful resource for the evaluation of broccoli by-product utilization in the human diet, and as feedstocks for bioactive compounds for industry.

S. Typhimurium virulence changes caused by exposure to different non-thermal preservation treatments using C. elegans

The aims of this research study were: (i) to postulate Caenorhabditis elegans (C. elegans) as a useful organism to describe infection by Salmonella enterica serovar Typhimurium (S. Typhimurium), and (ii) to evaluate changes in virulence of S. Typhimurium when subjected repetitively to different antimicrobial treatments. Specifically, cauliflower by-product infusion, High Hydrostatic Pressure (HHP), and Pulsed Electric Fields (PEF). This study was carried out by feeding C. elegans with different microbial populations: E. coli OP50 (optimal conditions), untreated S. Typhimurium, S. Typhimurium treated once and three times with cauliflower by-product infusion, S. Typhimurium treated once and four times with HHP and S. Typhimurium treated once and four times with PEF. Bayesian survival analysis was applied to estimate C. elegans lifespan when fed with the different microbial populations considered. Results showed that C. elegans is a useful organism to describe infection by S. Typhimurium because its lifespan was reduced when it was infected. In addition, the application of antimicrobial treatments repetitively generated different responses: when cauliflower by-product infusion and PEF treatment were applied repetitively the virulence of S. Typhimurium was lower than when the treatment was applied once. In contrast, when HHP treatment was applied repetitively, the virulence of S. Typhimurium was higher than when it was applied once. Nevertheless, in all the populations analyzed treated S. Typhimurium had lower virulence than untreated S. Typhimurium.

Persistence of Indicator and Pathogenic Microorganisms in Broccoli following Manure Spreading and Irrigation with Fecally Contaminated Water: Field Experiment

In 2011 and 2012, trials consisting of experimental plots were carried out to evaluate the presence of pathogenic (Listeria monocytogenes, Salmonella) and prevalence of indicator (Escherichia coli) microorganisms in broccoli fertilized with liquid hog manure or mineral fertilizers and irrigated zero, one, or two times with E. coli-contaminated water. In 2011, results showed that E. coli contamination in broccoli heads was affected by the interval between irrigation and sampling (P = 0.0236), with a significant decrease between the first and third day following irrigation (P = 0.0064). In 2012, irrigation frequency significantly increased E. coli prevalence in broccoli samples (P = 0.0499). In 2012, E. coli counts in the soil were significantly influenced by the type of fertilizer applied, as plots receiving liquid hog manure showed higher bacterial counts (P = 0.0006). L. monocytogenes was recovered in one broccoli sample, but geno-serogrouping differentiated the isolate from those recovered in manure and irrigation water. The L. monocytogenes serogroup IIA, pulsotype 188 strain was found in six soil samples and in irrigation water applied 5 days before soil sampling. This study highlights the link between E. coli levels in irrigation water, irrigation frequency, and interval between irrigation and harvest on produce contamination. It also demonstrates that L. monocytogenes introduced into the soil following irrigation can persist for up to 5 days.