Corrigendum: Optimization of tomato (Solanum lycopersicum L.) juice fermentation process and analysis of its metabolites during fermentation.

[This corrects the article DOI: 10.3389/fnut.2024.1344117.].

The Use of Ultraviolet Irradiation to Improve the Efficacy of Acids That Are Generally Recognized as Safe for Disinfecting Fresh Produce in the Ready-to-Eat Stage.

Fresh-cut produce is usually produced under standardized disinfection processes, which are unavailable at the ready-to-eat stage. Currently, chemical sanitizers are used for washing, but their disinfection efficacy is limited. In this study, UV-C (1.03 kJ/m2) was combined with organic acids that are generally recognized as safe (GRAS), including citric, malic, acetic, and lactic acids (LAs), to wash lettuce and cherry tomatoes that are contaminated with Escherichia coli O157:H7 and Salmonella Typhimurium. The results showed that LA was the most effective treatment among the single treatments, with a pathogen reduction and cross-contamination incidence of 2.0-2.3 log CFU/g and 28-35%, respectively. After combining with UV-C, the disinfection efficacy and cross-contamination prevention capacity of the four GRAS acids significantly improved. Among the combination treatments, the highest pathogen reduction (2.5-2.7 log CFU/g) and the lowest cross-contamination incidence (11-15%) were achieved by LA-UV. The analyses of ascorbic acid, chlorophyll, lycopene, antioxidant capacity, and ΔE indicated that neither the single nor combination treatments negatively affected the quality properties. These results provide a potential hurdle technology for fresh produce safety improvement at the ready-to-eat stage.

A Novel Strategy for Mixed Jam Evaluation: Apparent Indicator, Sensory, Metabolomic, and GC-IMS Analysis.

Jam is a popular traditional and modern food product for daily consumption. However, the benefits of mixed jams over single-fruit jams have not been thoroughly explored, with analyses limited to superficial indices. In this study, Xinjiang special Morus nigra L. and Prunus domestica L. were used as raw materials to prepare single-fruit and mixed jams, and their differences in antioxidants, organoleptic qualities, pH, texture, and color were analyzed. The dynamics of metabolites before and after thermal processing were assessed using untargeted metabolomics. The results indicate that the main metabolites were flavonoids, terpenoids, amino acids, phenolic acids, and carbohydrates. Flavonoid metabolites changed significantly after thermal processing, with 40 up-regulated and 13 down-regulated. During storage, polyphenols were the prominent differential metabolites, with fifty-four down-regulated and one up-regulated. Volatile aroma components were analyzed using gas chromatography-ion mobility spectrometry (GC-IMS); the aroma components E-2-hexenal, E-2-pentenal, 3-methylbutanal, 1-penten-3-ol, tetrahydro-linalool, 1-penten-3-one, hexyl propionate, isoamyl acetate, α-pinene, and propionic acid in mixed jam were significantly higher than in single-fruit jam. In this study, untargeted metabolomics and GC-IMS were used to provide a more comprehensive and in-depth evaluation system for jam analysis.

Optimization of tomato (Solanum lycopersicum L.) juice fermentation process and analysis of its metabolites during fermentation.

Tomato (Solanum lycopersicum L.) is a nutritious fruit and vegetable. Fermentation can be used to enhance their nutritional value. In this study, the tomato juice was co-fermented with multistrains, optimized by uniform experimental design and response surface methodology. Superoxide dismutase activity reached 496.67 U/g and lycopene content reached 77.12µg/g when P. pentosaceus (53.79%), L. casei (13.17%), L. plantarum (19.87%), L. fermentum (13.17%). To gain insight into the dynamics of metabolites during the tomato fermentation juice process multivariate statistical analysis was performed using the UHPLC-QE-MS/MS method. The main metabolites are peptides, amino acids carbohydrates, organic acids, and phospholipids. Carbohydrates were fully retained at the end of fermentation.The content of galactitol increased from the initial 5.389 to 6.607 while the content of cytarabine decreased by 29% and uridine by 44%. Meanwhile, phospholipids (PS, PE, PC, PG, PI) were all retained by more than 70%. Terpenoids (16-deacetylgairin, (+)-Royleanone, artemisinin) were increased to varying degrees, which gives them good nutritional value and biological activity. Organic acids (malic and citric) were reduced and lactic acid content was increased, changing its original flavor and making it more palatable to the general population. The research results have demonstrated the benefits of lactic acid bacteria fermentation on tomato juice, providing a theoretical basis and reference for the fermentation metabolism process of tomato juice.

Pulsed-control plasma-activated water: An emerging technology to assist ultrasound for fresh-cut produce washing.

In this study, we explored the use of plasma-activated water (PAW) in combination with ultrasound (US) for food disinfection. Our research introduces a novel approach that utilizes a pulsed-control (PC) method to modify the PAW. The resulting PCPAW exhibits significantly higher concentrations of key reactive oxygen and nitrogen species (RONS) compared to conventional PAW. The disinfection efficacy of US-PCPAW against fresh-cut lettuce was compared to that of US-PAW, US, and PCPAW. The combination of US and PCPAW was highly effective in reducing food-borne pathogens, surpassing single treatments in count reduction and minimizing cross-contamination. Furthermore, our study demonstrates that US-PCPAW effectively controls browning appearance without compromising sensory attributes. These findings suggest that PCPAW, as a novel disinfectant, can be a valuable addition to US to enhance the quality and safety of fresh-cut produce.

Effects of adding milk to fermented black mulberry (Morus nigra L.) juice on its antioxidant activity in C2C12 cells and changes in volatile flavor compounds during storage.

This study assessed the impact of milk on the bioactive compounds, physicochemical properties, antioxidant activity, ROS inhibition, and volatile flavor compounds of fermented black mulberry juice (FBMJ). Firstly, the results showed that 25% concentration of milk was the most suitable for preparing FBMJ-Milk. Compared to the control group, the addition of milk significantly increased the SOD activity and antioxidant capacity, as well as enhanced the total phenolic content (TPC) and SOD storage stability. Secondly, HS-SPME-GC-MS combined with OPLS-DA analysis identified 49 compounds in FBMJM, including 12 esters, 6 acids, 1 ketone, 2 aldehydes, 19 alcohols and 9 other compounds. During the storage, the levels of ethyl ester compounds decreased significantly, while the degradation of ester produced some acid and alcohol compounds. The findings revealed that the addition of milk was beneficial for maintaining the antioxidant stability of FBMJM during storage and enhancing the richness of product flavor.

Processing of Fresh-Cut Potato Using Plasma-Activated Water Prepared by Decreasing Discharge Frequency.

As a novel non-thermal processing method, the concentration of active compounds in plasma-activated water (PAW) is usually adjusted by changing the voltage and preparation time. We recently adjusted the discharge frequency and found that the PAW properties were improved. In this study, fresh-cut potato was selected as a model, and PAW was prepared using a frequency of 200 Hz (200 Hz-PAW). Its efficacy was compared with that of PAW prepared using 10 kHz. The results showed that the ozone, hydrogen peroxide, nitrate, and nitrite concentrations in 200 Hz-PAW were 5.00-, 3.62-, 8.05-, and 1.48-fold higher than those of 10 kHz-PAW. PAW inactivated the browning-related enzymes polyphenol oxidase and peroxidase, lowering the browning index and inhibiting browning; 200 Hz-PAW exhibited the lowest of these parameters during storage. In addition, PAW induced PAL to promote phenolic synthesis and increase antioxidant activity to delay malondialdehyde accumulation; 200 Hz-PAW exhibited the highest of these parameters. Moreover, 200 Hz-PAW had the lowest weight loss and electrolyte leakage rates. Furthermore, microbial analysis showed that the lowest aerobic mesophilic, mold, and yeast counts during storage were observed in the 200 Hz-PAW group. These results suggest that frequency-controlled PAW has the potential to treat fresh-cut produce.

Development of fermented sea buckthorn (Hippophae rhamnoides L.) juice and investigation of its antioxidant and antimicrobial activity.

Sea buckthorn (Hippophae rhamnoides L.) is an edible and medicinal plant species. However, due to its sour taste, it is not readily accepted by consumers. To overcome this, fermentation can be used to change its flavor profile. In this study, we used response surface methodology (RSM) to determine the best process for producing fermented sea buckthorn juice (FSBJ) using probiotics. The biological enzyme activity and total flavonoid content (TFC) of sea buckthorn juice (SBJ) increased after fermentation. When the number of bacteria inoculated was 4.08 × 106 CFU/mL and the inoculation ratio was 30% Z. mobilis, 5% L. casei, 13.75% L. plantarum, 31.25% P. acidilactici, 12.5% L. animalis, and 7.5% P. pentosaceus, the amount of sugar was 2.98% (w/v) after 20 h of fermentation at 37°C, and the superoxide dismutase (SOD) activity reached 725.44 U/mL, and the TFC reached 2.38 mg/mL. FSBJ demonstrated strong antimicrobial activity against Escherichia coli, Staphylococcus aureus and Botrytis cinerea. Then, to investigate the antioxidant capacity of FSBJ, we used H2O2 to induce oxidative stress in C2C12 cells and assessed the protection conferred by FSBJ to damaged cells. It was discovered that after 24 h of treatment with FSBJ, not only was there an increase in the activities of intracellular SOD and glutathione peroxidase (GSH-Px), but also a reduction in reactive oxygen species (ROS) content, catalase (CAT) activity, and malondialdehyde (MDA) content. This research lays the theoretical groundwork and provides reference materials for the improved fermentation of sea buckthorn and demonstrates its resulting antioxidant effect.

Study on the preparation process of quinoa anti-hypertensive peptide and its stability.

Quinoa seeds are a food resource rich in protein, vitamins, minerals, and other functional components such as polyphenols, polysaccharides, and saponins. The seeds have become favored by modern consumers due to being gluten-free and featuring a high protein content. This study focused on the preparation of quinoa peptides by short-time enzymatic-assisted fermentation. Quinoa flour (QF) was mixed with water in a certain ratio before being enzymatically digested with 0.5% amylase and 0.1% lipase for 6 h. Then, 16 bacterial taxa were used for fermentation, respectively. The peptide content in the resulting fermentation broths were determined by the biuret method. The dominant taxon was then identified and the peptide content, amino acid distribution, and molecular weight distribution of the prepared quinoa peptides were analyzed. Further, the temperature, pH, metal ions, organic solvents, ion concentration, and anti-enzyme stability of the quinoa anti-hypertensive peptides of different molecular weights after fermentation with the dominant taxon were investigated. Finally, the inhibitory activity of fermented quinoa peptides on bacteria was studied. The results show that the peptide content of the fermentation broth reached 58.72 ± 1.3% at 40 h of fermentation with Lactobacillus paracasei and the molecular weights of the hydrolyzed quinoa peptides were mainly distributed below 2 kDa by polyacrylamide gel. The Angiotensin Converting Enzyme (ACE) inhibition and peptide retention of the 0-3 kDa quinoa peptides were screened to be high and stable. At the same time, the inhibitory activity of quinoa peptide after fermentation on E. coli was obvious. This study provides a theoretical basis for further research on quinoa peptide and its application in industrial production, and also lays a foundation for the later application of polypeptides in new food and chemical products.