Effectiveness of a pomegranate peel extract (PGE) in reducing Listeria monocytogenes in vitro and on fresh-cut pear, apple and melon

Fruit waste: a current perspective for the sustainable production of pharmacological, nutraceutical, and bioactive resources

Fruits are crucial components of a balanced diet and a good source of natural antioxidants, that have proven efficacy in various chronic illnesses. Various kinds of waste generated from fruit industries are considered a global concern. By utilizing this fruit waste, the international goal of "zero waste" can be achieved by sustainable utilization of these waste materials as a rich source of secondary metabolites. Moreover, to overcome this waste burden, research have focused on recovering the bioactive compounds from fruit industries and obtaining a new strategy to combat certain chronic diseases. The separation of high-value substances from fruit waste, including phytochemicals, dietary fibers, and polysaccharides which can then be used as functional ingredients for long-term health benefits. Several novel extraction technologies like ultrasound-assisted extraction (UAE), pressurized liquid extraction (PLE), and supercritical fluid extraction (SFE) could provide an alternative approach for successful extraction of the valuable bioactives from the fruit waste for their utilization as nutraceuticals, therapeutics, and value-added products. Most of these waste-derived secondary metabolites comprise polyphenols, which have been reported to have anti-inflammatory, insulin resistance-treating, cardiovascular disease-maintaining, probiotics-enhancing, or even anti-microbial and anti-viral capabilities. This review summarizes the current knowledge of fruit waste by-products in pharmacological, biological, and probiotic applications and highlights several methods for identifying efficacious bioactive compounds from fruit wastes.

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.

Impact of food-relevant conditions and food matrix on the efficacy of prenylated isoflavonoids glabridin and 6,8-diprenylgenistein as potential natural preservatives against Listeria monocytogenes

Prenylated isoflavonoids can be extracted from plants of the Leguminosae/Fabaceae family and have shown remarkable antimicrobial activity against Gram-positive food-borne pathogens, such as Listeria monocytogenes. Promising candidates from this class of compounds are glabridin and 6,8-diprenylgenistein. This research aimed to investigate the potential of glabridin and 6,8-diprenylgenistein as food preservatives against L. monocytogenes. Their antimicrobial activity was tested in vitro at various conditions relevant for food application, such as different temperatures (from 10 °C to 37 °C), pH (5 and 7.2), and in the presence or absence of oxygen. The minimum inhibitory concentrations of glabridin and 6,8-diprenylgenistein in vitro were between 0.8 and 12.5 μg/mL in all tested conditions. Growth inhibitory activities were similar at 10 °C compared to higher temperatures, although bactericidal activities decreased when the temperature decreased. Notably, lower pH (pH 5) increased the growth inhibitory and bactericidal activity of the compounds, especially for 6,8-diprenylgenistein. Furthermore, similar antimicrobial efficacies were shown anaerobically compared to aerobically at the tested conditions. Glabridin showed a more stable inhibitory and bactericidal activity when the temperature decreased compared to 6,8-diprenylgenistein. Therefore, we further determined the antimicrobial efficacy of glabridin against L. monocytogenes growth on fresh-cut cantaloupe at 10 °C. In these conditions, concentrations of glabridin of 50, 100 and 250 μg/g significantly reduced the growth of L. monocytogenes compared to the control, resulting on average in >1 Log CFU/g difference after 4 days compared to the control. Our results further underscored the importance of considering the food matrix when assessing the activity of novel antimicrobials. Overall, this study highlights the potential of prenylated isoflavonoids as naturally derived food preservatives.

Pomegranate (Punica granatum L.) Peel Extracts as Antimicrobial and Antioxidant Additives Used in Alfalfa Sprouts

Aqueous and ethanolic pomegranate peel extracts (PPE) were studied as a source of phenolic compounds with antimicrobial, anti-quorum sensing, and antioxidant properties. The aqueous extract showed higher total phenolic and flavonoid content (153.43 mg GAE/g and 45.74, respectively) and antioxidant capacity (DPPH radical inhibition: 86.12%, ABTS radical scavenging capacity: 958.21 mg TE/dw) compared to the ethanolic extract. The main phenolic compounds identified by UPLC-DAD were chlorogenic and gallic acids. The aqueous PPE extract showed antimicrobial activity against Listeria monocytogenes, Salmonella Typhimurium, Candida tropicalis (MICs 19–30 mg/mL), and anti-quorum sensing activity expressed as inhibition of Chromobacterium violaceum violacein production (%). The aqueous PPE extracts at 25 mg/mL applied on alfalfa sprouts reduced psychrophilic bacteria (1.12 Log CFU/100 g) and total coliforms (1.23 Log CFU/100 g) and increased the antioxidant capacity of the treated sprouts (55.13 µmol TE/100 g (DPPH) and 126.56 µmol TE/100 g (ABTS)) compared to untreated alfalfa. This study emphasizes PPE’s antioxidant and antimicrobial activities in alfalfa sprouts preservation.

From Pomegranate Byproducts Waste to Worth: A Review of Extraction Techniques and Potential Applications for Their Revalorization

The food industry is quite interested in the use of (techno)-functional bioactive compounds from byproducts to develop ‘clean label’ foods in a circular economy. The aim of this review is to evaluate the state of the knowledge and scientific evidence on the use of green extraction technologies (ultrasound-, microwave-, and enzymatic-assisted) of bioactive compounds from pomegranate peel byproducts, and their potential application via the supplementation/fortification of vegetal matrixes to improve their quality, functional properties, and safety. Most studies are mainly focused on ultrasound extraction, which has been widely developed compared to microwave or enzymatic extractions, which should be studied in depth, including their combinations. After extraction, pomegranate peel byproducts (in the form of powders, liquid extracts, and/or encapsulated, among others) have been incorporated into several food matrixes, as a good tool to preserve ‘clean label’ foods without altering their composition and improving their functional properties. Future studies must clearly evaluate the energy efficiency/consumption, the cost, and the environmental impact leading to the sustainable extraction of the key bio-compounds. Moreover, predictive models are needed to optimize the phytochemical extraction and to help in decision-making along the supply chain.

Antimicrobial activity of essential oils and natural plant extracts against Listeria monocytogenes in a dry-cured ham-based model

BACKGROUND

Listeria monocytogenes is a widespread common contaminant in food production facilities during preparation, storage, and distribution, and minimally processed ready-to-eat products are considered at high risk of contamination by this bacterium. Increased antibiotic resistance has led researchers to search for plant-based natural alternatives to control pathogenic microorganisms. Among these products, essential oils and plant extracts have previously shown antimicrobial activity and are possible alternatives to manage food pathogens. In this study, commercial essential oils (cinnamon, clove, oregano, ginger, and thyme) and plant extracts (pomegranate, acorn, olive, strawberry tree, and dog rose) were tested against L. monocytogenes in a dry-cured ham-based model.

RESULTS

Essential oils and plant extracts were screened by agar diffusion and minimum inhibitory concentration for anti-L. monocytogenes activity. Cinnamon, pomegranate, and strawberry trees returned the strongest results and were therefore evaluated in a dry-cured ham-based medium assay with water activity of 0.93 or 0.95. The 10% essential oil of cinnamon was capable of completely inhibiting bacterial growth, while strawberry tree and pomegranate extract also showed antilisterial activity (P > 0.05). Water activity influenced the bacterial count of L. monocytogenes in a dry-cured ham-based medium.

CONCLUSIONS

There was a reduction in L. monocytogenes with the application of cinnamon essential oil but, because of the negative sensory impact of this particular compound in meat products, we suggest the use of pomegranate or strawberry tree for the biocontrol of Listeria in ready-to-eat products. © 2021 Society of Chemical Industry.

State-of-Art on the Recycling of By-Products from Fruits and Vegetables of Mediterranean Countries to Prolong Food Shelf Life

Annually, 1.3 billion tons of food are wasted and this plays a major role in increasing pollution. Food waste increases domestic greenhouse gas emissions mainly due to the gas emissions associated with its production. Fruit and vegetable industrial by-products occur in the form of leaves, peel, seeds, pulp, as well as a mixture of them and represent the most abundant food waste. The disposal of agricultural by-products costs a large amount of money under certain governmental regulations. However, fruit and vegetable by-products are rich in valuable bioactive compounds, thus justifying their use as food fortifier, active food packaging or as food ingredients to preserve food quality over time. The present review collects the most recent utilization carried out at lab-scale on Mediterranean fruit and vegetable by-products as valid components to prolong food shelf life, providing a detailed picture of the state-of-art of literature on the topic. Bibliographic research was conducted by applying many keywords and filters in the last 10 years. Several scientific findings demonstrate that by-products, and in particular their extracts, are effectively capable of prolonging the shelf life of dairy food, fresh-cut produce, meat and fish-based products, oil, wine, paste and bakery products. All of the studies provide clear advances in terms of food sustainability, highlight the potential of by-products as a source of bioactive compounds, and promote a culture in which foods are intended to receive a second useful life. The same final considerations were also included regarding the current situation, which still limits by-products diffusion. In addition, a conclusion on a future perspective for by-products recycling was provided. The most important efforts have to be conducted by research since only a multidisciplinary approach for an advantageous investigation could be an efficient method to promote the scale up of by-products and encourage their adoption at the industrial level.

Preharvest and Postharvest Applications of a Pomegranate Peel Extract to Control Citrus Fruit Decay During Storage and Shelf Life

Green and blue molds are the most important postharvest diseases affecting citrus in storage. These diseases are commonly controlled with fungicides, but legislative restrictions, consumer concerns, and the development of resistant strains of the pathogens have increasingly led to the search for alternative methods of control. A pomegranate peel extract (PGE) was very effective in controlling Valencia orange and clementine postharvest rot under commercial conditions. After cold storage and 7 days of shelf life, the incidence of decay on oranges sprayed before harvest with PGE at 12, 6, and 3 g/liter was reduced by 78.9, 76.0, and 64.6%, respectively. Similarly, postharvest dipping treatments with PGE reduced rot by 90.2, 84.3, and 77.6%, respectively. Comparable levels of protection were also achieved on clementines. On both oranges and clementines, the extract provided a significantly higher level of protection compared with imazalil, a fungicide commonly used for postharvest treatments. The high level of efficacy and the consistent results on different fruit species (clementines and oranges) and with different application methods (preharvest and postharvest) were evidence of reliability and flexibility. PGE also showed a strong antimicrobial activity against fungi and bacteria, suggesting its possible use in sanitizers to reduce the microbial contamination of recirculated water in packinghouses. The results of the present study encourage the integration of conventional chemical fungicides and sanitizers with PGE to control citrus postharvest rot.

Pomegranate Peel Extracts as Safe Natural Treatments to Control Plant Diseases and Increase the Shelf-Life and Safety of Fresh Fruits and Vegetables

Although the Green Revolution was a milestone in agriculture, it was accompanied by intensive use of synthetic pesticides, which has raised serious concerns due to their impact on human and environmental health. This is increasingly stimulating the search for safer and more eco-friendly alternative means to control plant diseases and prevent food spoilage. Among the proposed alternatives, pomegranate peel extracts (PPEs) are very promising because of their high efficacy. In the present review, we discuss the complex mechanisms of action that include direct antimicrobial activity and induction of resistance in treated plant tissues and highlight the importance of PPE composition in determining their activity. The broad spectrum of activity, wide range of application and high efficiency of PPEs against bacterial, fungal and viral plant pathogens suggest a potential market not only restricted to organic production but also integrated farming systems. Considering that PPEs are non-chemical by-products of the pomegranate industry, they are perceived as safe by the public and may be integrated in circular economy strategies. This will likely encourage agro-pharmaceutical industries to develop commercial formulations and speed up the costly process of registration.