Antimicrobial activity of cauliflower (Brassica oleracea var. Botrytis) by-product against Listeria monocytogenes

The impact of Levilactobacillus brevis YSJ3 and Lactiplantibacillus plantarum JLSC2-6 co-culture on gamma-aminobutyric acid yield, volatile and non-volatile metabolites, antioxidant activity, and bacterial community in fermented cauliflower byproducts

Co-culture fermentation is a novel technology for enhancing fermentation quality and promoting gamma-aminobutyric acid (GABA) yield. The purpose of this study was to evaluate the effects of Levilactobacillus brevis YSJ3 and Lactiplantibacillus plantarum JLSC2-6 co-culture on GABA yield, volatile and non-volatile metabolite profiles, and antioxidant activity in cauliflower byproducts. It was found that co-culture had the highest GABA yield (35.00 ± 1.15 mg/L) in fermented cauliflower stems. In total, 111 and 1264 volatile and non-volatile metabolites, respectively, were identified, of which 59 metabolites were significantly upregulated after co-culture fermentation. The results showed that 24 key upregulated metabolites were positively associated with hydroxyl radical-scavenging activity. Notably, Levilactobacills were positively correlated with the yield of GABA and key upregulated metabolites. Thus, these results suggest that Levilactobacillus brevis and Lactiplantibacillus plantarum can improve in key metabolites, GABA yield, and antioxidant activity following co-culture. This study provide a theoretical basis for developing GABA-rich cauliflower byproducts.

ComBase Models Are Valid for Predicting Fate of Listeria monocytogenes on 10 Whole Intact Raw Fruits and Vegetables

ABSTRACT

Listeria monocytogenes was associated with more than 60 produce recalls, including tomato, cherry, broccoli, lemon, and lime, between 2017 and 2020. This study describes the effects of temperature, time, and food substrate as factors influencing L. monocytogenes behavior on whole intact raw fruits and vegetables. Ten intact whole fruit and vegetable commodities were chosen based on data gaps identified in a systematic literature review. Produce investigated belong to major commodity families: Ericaceae (blackberry, raspberry, and blueberry), Rutaceae (lemon and mandarin orange), Roseaceae (sweet cherry), Solanaceae (tomato), Brassaceae (cauliflower and broccoli), and Apiaceae (carrot). A cocktail of five L. monocytogenes strains that included clinical, food, or environmental isolates linked to foodborne outbreaks was used to inoculate intact whole fruits and vegetables. Samples were incubated at 2, 12, 22, 30, and 35°C with relative humidities matched to typical real-world conditions. Foods were sampled (n = 6) for up to 28 days, depending on temperature. Growth and decline rates were estimated using DMFit, an Excel add-in. Growth rates were compared with ComBase modeling predictions for L. monocytogenes. Almost every experiment showed initial growth, followed by subsequent decline. L. monocytogenes was able to grow on the whole intact surface of all produce tested, except for carrot. The 10 produce commodities supported growth of L. monocytogenes at 22 and 35°C. Growth and survival at 2 and 12°C varied by produce commodity. The standard deviation of the square root growth and decline rates showed significantly larger variability in both growth and decline rates within replicates as temperature increased. When L. monocytogenes growth occurred, it was conservatively modeled by ComBase Predictor, and growth was generally followed by decreases in concentration. This research will assist in understanding the risks of foodborne disease outbreaks and recalls associated with L. monocytogenes on fresh whole produce.

HIGHLIGHTS

Phytotherapy and food applications from Brassica genus

Plants of the genus Brassica occupy the top place among vegetables in the world. This genus, which contains a group of six related species of a global economic significance, three of which are diploid: Brassica nigra (L.) K. Koch, Brassica oleracea L., and Brassica rapa L. and three are amphidiploid species: Brassica carinata A. Braun, Brassica juncea (L.) Czern., and Brassica napus L. These varieties are divided into oily, fodder, spice, and vegetable based on their morphological structure, chemical composition, and usefulness of plant organs. The present review provides information about habitat, phytochemical composition, and the bioactive potential of Brassica plants, mainly antioxidant, antimicrobial, anticancer activities, and clinical studies in human. Brassica vegetables are of great economic importance around the world. At present, Brassica plants are grown together with cereals and form the basis of global food supplies. They are distinguished by high nutritional properties from other vegetable plants, such as low fat and protein content and high value of vitamins, fibers along with minerals. In addition, they possess several phenolic compounds and have a unique type of compounds namely glucosinolates that differentiate these crops from other vegetables. These compounds are also responsible for numerous biological activities to the genus Brassica as described in this review.

Valorization of fruits and vegetable wastes and by-products to produce natural pigments

Synthetic pigments from petrochemicals have been extensively used in a wide range of food products. However, these pigments have adverse effects on human health that has rendered it obligatory to the scientific community in order to explore for much safer, natural, and eco-friendly pigments. In this regard, exploiting the potential of agri-food wastes presumes importance, extracted mainly by employing green processing and extraction technologies. Of late, pigments market size is growing rapidly owing to their extensive uses. Hence, there is a need for sustainable production of pigments from renewable bioresources. Valorization of vegetal wastes (fruits and vegetables) and their by-products (e.g. peels, seeds or pomace) can meet the demands of natural pigment production at the industrial levels for potential food, pharmaceuticals, and cosmeceuticals applications. These wastes/by-products are a rich source of natural pigments such as: anthocyanins, betalains, carotenoids, and chlorophylls. It is envisaged that these natural pigments can contribute significantly to the development of functional foods as well as impart rich biotherapeutic potential. With a sustainability approach, we have critically reviewed vital research information and developments made on natural pigments from vegetal wastes, greener extraction and processing technologies, encapsulation techniques and potential bioactivities. Designed with an eco-friendly approach, it is expected that this review will benefit not only the concerned industries but also be of use to health-conscious consumers.

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.

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).

Bioactive potential of fruit and vegetable wastes

Fruits and vegetables are essential for human nutrition, delivering a substantial proportion of vitamins, minerals, and fibers in our daily diet. Unfortunately, half the fruits and vegetables produced worldwide end up as wastes, generating environmental issues caused mainly by microbial degradation. Most wastes are generated by industrial processing, the so-called by-products. These by-products still contain many bioactive compounds post-processing, such as macronutrients (proteins and carbohydrates) and phytochemicals (polyphenols and carotenoids). Recently, the recovery of these bioactive compounds from industry by-products has received significant attention, mainly due to their possible health benefits for humans. This chapter focuses on the bioactive potential of fruit and vegetable by-products with possible applications in the food industry (functional foods) and in the health sector (nutraceuticals).

Effects of low NaNO2 and NaCl concentrations on Listeria monocytogenes growth in emulsion-type sausage

OBJECTIVE

The objective of this study was to evaluate the effect of combinations of NaNO2 and NaCl concentrations on Listeria monocytogenes (L. monocytogenes) growth in emulsion-type sausage.

METHODS

Emulsion-type sausages formulated with different combinations of NaNO2 (0 and 10 ppm) and NaCl (1.00%, 1.25%, and 1.50%) were inoculated with a five-strain L. monocytogenes mixture, and stored at 4°C, 10°C, and 15°C, under aerobic or vacuum conditions. L. monocytogenes cell counts were measured at appropriate intervals, and kinetic parameters such as growth rate and lag phase duration (LPD) were calculated using the modified Gompertz model.

RESULTS

Growth rates increased (0.004 to 0.079 Log colony-forming unit [CFU]/g/h) as storage temperature increased, but LPD decreased (445.11 to 8.35 h) as storage temperature and NaCl concentration increased. The effect of combinations of NaCl and low-NaNO2 on L. monocytogenes growth was not observed at 4°C and 10°C, but it was observed at 15°C, regardless of atmospheric conditions.

CONCLUSION

These results indicate that low concentrations of NaNO2 and NaCl in emulsion-type sausage may not be sufficient to prevent L. monocytogenes growth, regardless of whether they are vacuum-packaged and stored at low temperatures. Therefore, additional techniques are necessary for L. monocytogenes control in the product.