Extending the Shelf-Life of Fresh-Cut Green Bean Pods by Ethanol, Ascorbic Acid, and Essential Oils

Linalool Reduces Virulence and Tolerance to Adverse Conditions of Listeria monocytogenes

Listeria monocytogenes, a foodborne pathogen causing listeriosis, poses substantial societal, economic, and public health challenges due to its resistance, persistence, and biofilm formation in the food industry. Exploring subinhibitory concentrations of compounds to target virulence inhibition and increase susceptibility to adverse conditions presents a promising strategy to mitigate its impact of L. monocytogenes and unveils new potential applications. Thus, this study aims to explore the effect of linalool on virulence factors of L. monocytogenes and potential use in the reduction in its tolerance to stressful conditions. This action was analysed considering the use of two sub-inhibitory concentrations of linalool, 0.312 and 0.625 mg/mL. We found that even with the lowest tested concentrations, a 65% inhibition of violacein production by Chromobacterium violaceum, 55% inhibition in biofilm formation by L. monocytogenes and 62% reduction on haemolysis caused by this bacterium were observed. In addition to its impact on virulence factors, linalool diminished the tolerance to osmotic stress (up to 4.3 log reduction after 24 h with 12% NaCl), as well as to high (up to 3.8 log reduction after 15 min at 55 °C) and low temperatures (up to 4.6 log reduction after 84 days with 12% NaCl at 4 °C). Thus, this study paves the way to further investigation into the potential utilization of linalool to mitigate the threat posed by L. monocytogenes in the field of food safety and public health.

Plant Antimicrobials for Food Quality and Safety: Recent Views and Future Challenges

The increasing demand for natural, safe, and sustainable food preservation methods drove research towards the use of plant antimicrobials as an alternative to synthetic preservatives. This review article comprehensively discussed the potential applications of plant extracts, essential oils, and their compounds as antimicrobial agents in the food industry. The antimicrobial properties of several plant-derived substances against foodborne pathogens and spoilage microorganisms, along with their modes of action, factors affecting their efficacy, and potential negative sensory impacts, were presented. The review highlighted the synergistic or additive effects displayed by combinations of plant antimicrobials, as well as the successful integration of plant extracts with food technologies ensuring an improved hurdle effect, which can enhance food safety and shelf life. The review likewise emphasized the need for further research in fields such as mode of action, optimized formulations, sensory properties, safety assessment, regulatory aspects, eco-friendly production methods, and consumer education. By addressing these gaps, plant antimicrobials can pave the way for more effective, safe, and sustainable food preservation strategies in the future.

Bio-Stimulants Extend Shelf Life and Maintain Quality of Okra Pods

Okra (Abelmoschus esculentus L.), a tropical annual crop, is a highly perishable vegetable. Okra pods deteriorate rapidly after harvesting. The pods undergo physical and physiological changes that diminish storability and quality. The purpose of this study was to investigate the effect of bio-stimulants on the storability and quality of okra pods stored at 4 °C and 25 °C for 12 days. Dipping okra pods for 5 min in a solution of 0.5% ascorbic acid, citric acid, or salicylic acid pre-storage significantly extended the shelf life and preserved the quality of the pods compared to the control condition at 4 °C and 25 °C. Citric acid and ascorbic acid were the most effective in preserving most traits. Citric acid reduced the loss in weight, firmness, appearance, and prevented decay at 4 °C and 25 °C. Ascorbic acid decreased the loss of moisture and the degradation of carbohydrates, vitamin C and lycopene at 4 °C and 25 °C. Salicylic acid decreased the degradation of protein at 25 °C. The low temperature was highly effective in decreasing the loss or degradation of most of the studied traits. Taken together, bio-stimulants and storing at 4 °C played a prominent role in extending the shelf life and preserving the quality of okra pods.

Exogenous Proline, Methionine, and Melatonin Stimulate Growth, Quality, and Drought Tolerance in Cauliflower Plants

The impact of proline, methionine, and melatonin on cauliflower plants under drought stress is still unclear in the available publications. So, this research aims to study these biochemical compounds’ effects on cauliflower plants grown under well-irrigated and drought-stressed conditions. The obtained results showed that under drought-stressed conditions, foliar application of proline, methionine, and melatonin significantly (p ≤ 0.05) enhanced leaf area, leaf chlorophyll content, leaf relative water content (RWC), vitamin C, proline, total soluble sugar, reducing sugar, and non-reducing sugar compared to the untreated plants. These treatments also significantly increased curd height, curd diameter, curd freshness, and dry matter compared to untreated plants. Conversely, the phenolic-related enzymes including polyphenol oxidase (PPO), peroxidase (POD), and phenylalanine ammonia-lyase (PAL) were significantly reduced compared to the untreated plants. A similar trend was observed in glucosinolates, abscisic acid (ABA), malondialdehyde (MDA), and total phenols. Eventually, it can be concluded that the foliar application of proline, methionine, and melatonin can be considered a proper strategy for enhancing the growth performance and productivity of cauliflower grown under drought-stressed conditions.

Unravelling the Effect of Triacontanol in Combating Drought Stress by Improving Growth, Productivity, and Physiological Performance in Strawberry Plants

To explore the effects of triacontanol (TR) on drought tolerance of strawberry plants (cv Fertona), two field experiments were carried out to study the effects of three supplementary foliar TR rates (0, 0.5, and 1 ppm) under the following three levels of water irrigation: 11 m³/hectare (40% of water holding capacity (WHC) severe as a drought treatment, 22 m³/hectare (80% of WHC) as moderate drought stress, and normal irrigation with 27 m³/hectare (100% of WHC) server as a control treatment. TR treatments were applied five times after 30 days from transplanting and with 15-day intervals. The results showed that drought stress (40% and 80%) markedly decreased the growth, fruit yield, and chlorophyll reading, as well as the gas exchange parameters (net photosynthetic rate, stomatal conductance, and transpiration rate). Meanwhile, drought stress at a high rate obviously increased antioxidant enzyme activities such as superoxide dismutase (SOD), peroxidase (POX), and catalase (CAT) contents in the leaves of the strawberry plants. The moderate and high drought stress rates enhanced some strawberry fruit quality parameters such as total soluble solids (TSS), vitamin C, and anthocyanin content compared to the control. Additionally, TR increased the activities of SOD, POX, and CAT. TR treatment significantly increased the chlorophyll contents, gas exchange parameters (photosynthetic rate and stomatal conductance), and water use efficiency (WUE). Plant height, fruit weight, and total biomass were increased also via TR application. Total yield per plant was increased 12.7% using 1 ppm of TR compared with the control. In conclusion, our results suggested that TR application could relieve the adverse effects of drought stress on the growth of strawberry plants by enhancing the antioxidant enzymes, photosynthesis rate, and WUE of the leaves.

Nano Coating of Aloe-Gel Incorporation Additives to Maintain the Quality of Freshly Cut Fruits

The edible coating is an environmentally friendly technology that is applied to fresh-cut fruit products. One of the natural ingredients that are potentially applicable is aloe-gel because it contains several functional components. The main advantage of aloe-coating is that additives can be incorporated into the polymer matrix to enhance its properties. Additives tend to improve the safety, nutritional, and sensory attributes of fresh fruits, but in some cases, aloe-coating does not work. Furthermore, particle size determines the effectiveness of the process on fresh-cut fruits. Aloe-gel nano-coating can be used to overcome the difficulty of adhesion on the surface of fresh-cut fruits. However, quality criteria for fresh cut fruit coated with aloe-gel nano-coating must be strictly defined. The fruit to be processed must be of minimal quality so that discoloration, loss of firmness, spoilage ratio, and fruit weight loss can be minimized. This study aims to discuss the use of nano-coating aloe-gel incorporated with additional ingredients to maintain the quality of fresh-cut fruits. It also examined the recent advances in preparation, extraction, stabilization, and application methods in fresh fruits.

Exogenous Postharvest Application of Calcium Chloride and Salicylic Acid to Maintain the Quality of Broccoli Florets

The importance of broccoli (Brassica oleracea var. italica) consumption has increased in recent years due to its significant amount of anticarcinogenic and antioxidant compounds, as well as its many vitamins. However, broccoli florets are a highly perishable product which rapidly senesce and turn yellow after harvest, resulting in losses in nutritional and bioactive compounds. Thus, in this study, we evaluated the effect of postharvest exogenous of salicylic acid (SA) and calcium chloride (CaCl₂) and their combination on the quality of broccoli florets stored at 5 °C for 28 days to minimize the rapid senescence of broccoli florets. Samples treated with 2 mM SA alone or in combination with 2% CaCl₂ showed lower weight loss and lower losses of chlorophyll content, vitamin C, phenolic compounds, carotenoids, flavonoids, and glucosinolates compared with the control samples. Additionally, antioxidant activity was maintained by either SA or SA + CaCl₂ treatments while peroxidase activity was decreased. For higher quality and lower losses in antioxidant compounds of broccoli florets during refrigerated storage at 5 °C, SA + CaCl₂ treatment could be helpful for up to 21 days.

Effect of Titanium and Vanadium on Antioxidants Content and Productivity of Red Cabbage

The present work studied the effect of foliar spray of different concentrations of titanium (Ti, applied as titanium dioxide) and vanadium (V, applied as vanadium pentoxide) on growth, chemical composition, antioxidant contents, antioxidant enzymes, antioxidant capacity, yield and quality criteria of red cabbage plants. For this purpose, 2.0, 4.0 and 6.0 mg L−1 of Ti and V were used to treat red cabbage plants. The control plants were treated with tap water. Our results showed that plants treated with 4.0 mg L−1 of Ti recorded the highest values of plant growth and bioactive compounds, while antioxidant capacity was decreased compared to the other treatments. In addition, plants treated with Ti and V at 2.0 and 4.0 mg L−1, respectively, showed higher values of all of the growth, yield, non-enzymatic antioxidants and antioxidants enzymes’ parameters compared to the untreated plants. Based on the obtained results, it could be concluded that the low concentrations of both Ti and V (2.0 and 4.0 mg L−1) were able to enhance red cabbage growth and yield, as well as the antioxidant contents, enzymes and capacity.

Applications of Essential Oils as Antibacterial Agents in Minimally Processed Fruits and Vegetables—A Review

Microbial foodborne diseases are a major health concern. In this regard, one of the major risk factors is related to consumer preferences for “ready-to-eat” or minimally processed (MP) fruits and vegetables. Essential oil (EO) is a viable alternative used to reduce pathogenic bacteria and increase the shelf-life of MP foods, due to the health risks associated with food chlorine. Indeed, there has been increased interest in using EO in fresh produce. However, more information about EO applications in MP foods is necessary. For instance, although in vitro tests have defined EO as a valuable antimicrobial agent, its practical use in MP foods can be hampered by unrealistic concentrations, as most studies focus on growth reductions instead of bactericidal activity, which, in the case of MP foods, is of utmost importance. The present review focuses on the effects of EO in MP food pathogens, including the more realistic applications. Overall, due to this type of information, EO could be better regarded as an “added value” to the food industry.

Increasing the Storability of Fresh-Cut Green Beans by Using Chitosan as a Carrier for Tea Tree and Peppermint Essential Oils and Ascorbic Acid

The quality of fresh-cut green beans deteriorates rapidly in storage, which contributes to increased food waste and lower perceived customer value. However, chitosan (Cs) and certain plant essential oils show promise in reducing postharvest quality loss during storage. Here, the effect of Cs and the combinations of Cs + tea tree oil (TTO), Cs +x peppermint oil (PMO), and Cs + ascorbic acid (AsA) on the quality of fresh-cut green bean pods (FC-GB) is studied over a 15-d storage period at 5 °C. All four FC-GB treatments reduced weight loss and maintained firmness during storage when compared to uncoated FC-GB. Furthermore, all treatments showed higher total chlorophyll content, AsA, total phenolic compounds, and total sugars compared to the control. The best treatment for reducing microbial growth was a combination of Cs + AsA. Additionally, the combination of Cs with TTO, PMO, or AsA showed a significant reduction in the browning index and increased the antioxidant capacity of FC-GB up to 15 d postharvest.

Effect of Additives on Surface Tension, Viscosity, Transparency and Morphology Structure of Aloe vera Gel-Based Coating

Coating is a new trend for extending shelf-life and reducing postharvest damage to fruits currently. Aloe vera gel-based (AVG) coating is made by adding citric acid, ascorbic acid and potassium sorbate. The additive increases the stability of AVG coating. This research aims to determine the effect of additives on the surface tension, viscosity, transparency and morphology structure of AVG coating. The observation used a completely random design one factor with three replicates. Formulation of AVG coating uses additives involving citric acid, ascorbic acid, potassium sorbate and the mixture of additives, concentrations of 0.15%. Observations are made periodically on days 0, 5, 10 and 15. The type and concentration of additives affect the surface tension, viscosity, transparency and morphology structure of AVG coating. The best formulation of AVG coating for 15 days of storage is a mixture of additives (citric acid, ascorbic acid and potassium sorbate) with a concentration of 0.15% applied on the surface of the fruits. The best numeric value of AVG coating surface tension is 0.122 N/m, acidity 4.22, viscosity 96.03 mPa.s, color L* 19.51 and point of transparency 84.40. The combination of the three additives produced a clear, transparent white coating appearance and the potential to extend the shelf-life of fruit.

Effects of Various Polymeric Films on the Pericarp Microstructure and Storability of Longan (cv. Shixia) Fruit Treated with Propyl Disulfide Essential Oil from the Neem (Azadirachta indica) Plant

Plant extracts represent a rich repository of metabolites with antioxidant and antimicrobial properties. Neem (Azadirachta indica) is a medicinal plant considered the tree of the 21st century. In this study, we investigated the antioxidant and antimicrobial effects of propyl disulfide (PD), a major volatile compound in neem seed, against the pericarp browning (BI), microbial decay incidence (DI), and water loss of longan fruit. Fresh longan cv. Shixia samples were packaged in oriented polypropylene (OPP) and polyethene (PE) packages of different thicknesses (20, 40, and 60 µm). Sterile gauze was fixed inside the packages and 500 uL of PD was placed on them to avoid the direct contact of PD with fruit samples. Packages were sealed immediately to minimize vaporization and stored at 12 ± 1 °C for 18 days. Fruit samples packaged in open net packages served as controls. The results showed that fruit treated with PD in OPP and PE packages significantly prevented losses of water, DI, and BI compared to control treatment. PD also maintained the color, TSS values, TA values, pH values, high peel firmness, high TPC content, and high TFC content, and reduced the activity levels of PPO and POD. Scanning electron microscope (SEM) analysis indicated that the exocarp, mesocarp, and endocarp of longan peel were smooth, uniform, and compact with no free space compared to control, where crakes, a damaged and loose structure, and a lot of fungal mycelia were found. The shortest shelf life of 9 days was observed in control as compared to 18 days in OPP-20 and OPP-40; 15 days in OPP-60, PE-20, and PE-40; and 12 days in PE-60 packaging films. Therefore, PD as a natural antioxidant and antimicrobial agent, in combination with OPP-20 and OPP-40 polymeric films, could successfully be applied commercially to extend the postharvest shelf life of longan.

Pre-Harvest Application of Salicylic Acid, Abscisic Acid, and Methyl Jasmonate Conserve Bioactive Compounds of Strawberry Fruits during Refrigerated Storage

The short shelf-life and loss of bioactive compounds of strawberry fruit are the most important problems during strawberry refrigerated storage. This study was carried out to evaluate the effect of the pre-harvest foliar application of salicylic acid (SA) (2 and 4 mM), abscisic acid (ABA) (0.25 and 0.50 mM), and methyl jasmonate (MeJA) (0.25 and 0.50 mM) three times, 10 d apart, at fruit development and ripening stages on storage ability and bioactive compounds of strawberry fruit (cv. Festival) stored at 4 °C for 12 d. Our results showed that fruit obtained from both concentrations of ABA and 0.25 mM MeJA was firmer and had higher total soluble solids (TSS) than fruit from non-treated plants. However, all previous applications had no significant effect on weight loss, pH, or color. Applications of 4 mM SA and 0.25 mM MeJA conserved fruit from ascorbic acid (AsA) loss compared to control at the end of the storage period. In addition, all pre-harvest applications remained higher in total phenolic compounds (TPC) and anthocyanin contents compared to controls at the last storage period. Hence, the pre-harvest application of SA, ABA, and MeJA could be used to conserve TPC and anthocyanin as well as the quality of strawberry fruits during refrigerated storage.

Global Proteomic Analysis of Listeria monocytogenes' Response to Linalool

Listeria monocytogenes (LM) is one of the most serious foodborne pathogens. Listeriosis, the disease caused by LM infection, has drawn attention worldwide because of its high hospitalization and mortality rates. Linalool is a vital constituent found in many essential oils; our previous studies have proved that linalool exhibits strong anti-Listeria activity. In this study, iTRAQ-based quantitative proteomics analysis was performed to explore the response of LM exposed to linalool, and to unravel the mode of action and drug targets of linalool against LM. A total of 445 differentially expressed proteins (DEPs) were screened out, including 211 up-regulated and 234 down-regulated proteins which participated in different biological functions and pathways. Thirty-one significantly enriched gene ontology (GO) functional categories were obtained, including 12 categories in “Biological Process”, 10 categories in “Cell Component”, and 9 categories in “Molecular Function”. Sixty significantly enriched biological pathways were classified, including 6 pathways in “Cell Process”, 6 pathways in “Environmental Information Processing”, 3 pathways in “Human Disease”, 40 pathways in “Metabolism”, and 2 pathways in “Organic System”. GO and Kyoto Encyclopedia of Genes (KEGG) enrichment analysis together with flow cytometry data implied that cell membranes, cell walls, nucleoids, and ribosomes might be the targets of linalool against LM. Our study provides good evidence for the proteomic analysis of bacteria, especially LM, exposed to antibacterial agents. Further, those drug targets discovered by proteomic analysis can provide theoretical support for the development of new drugs against LM.

Extending Shelf Life and Maintaining Quality of Tomato Fruit by Calcium Chloride, Hydrogen Peroxide, Chitosan, and Ozonated Water

Tomatoes are perishable fruit that makes them deteriorate rapidly during the post-harvest chain. Therefore, the effect of calcium chloride (CaCl2), chitosan, hydrogen peroxide (H2O2), and ozonated water on the storage abil\ity and quality of tomato fruit (Solanumlycopersicum L. cv. 448) stored at 10 °C for 28 d was studied. Weight loss, firmness, fruit color, total soluble solids (TSS), titratable acidity, total carotenoids, and ascorbic acid content (AsA) of treated tomato fruit were recorded. Our results revealed that all tested treatments significantly extended the shelf-life and maintained quality of tomato fruit compared to the control. Chitosan and CaCl2 were the most effective treatments in maintaining quality attributes. Furthermore, a correlation study suggested that AsA and total carotenoids played a vital role in conserving tomato fruit quality during storage. PC1 had strong positive loading for pH, appearance, firmness, AsA, TSS, carotene, fruit color (L* & b*) and a strong negative loading for lycopene content, color (a), weight loss, and color index. PC2 had high positive loading for total acidity and total sugar content.

Improved Shelf-Life and Consumer Acceptance of Fresh-Cut and Fried Potato Strips by an Edible Coating of Garden Cress Seed Mucilage

Coatings that reduce the fat content of fried food are an alternate option to reach both health concerns and consumer demand. Mucilage of garden cress (Lepidium sativum) seed extract (MSE) was modified into an edible coating with or without ascorbic acid (AA) to coat fresh-cut potato strips during cold storage (5 °C and 95% RH for 12 days) and subsequent frying. Physical attributes such as color, weight loss, and texture of potato strips coated with MSE solutions with or without AA showed that coatings efficiently delayed browning, reduced weight loss, and maintained the texture during cold storage. Moreover, MSE with AA provided the most favorable results in terms of reduction in oil uptake. In addition, the total microbial count was lower for MSE-coated samples when compared to the control during the cold storage. MSE coating also performed well on sensory attributes, showing no off flavors or color changes. As a result, the edible coating of garden cress mucilage could be a promising application for extending shelf-life and reducing the oil uptake of fresh-cut potato strips.