Carbon dots from sour whey to develop a novel antimicrobial packaging for fiordilatte cheese.

In this study, monodispersed and quasi-spherical C-Dots with an average size of 7.2 nm were successfully synthesized from sour whey solution by a hydrothermal method (200 °C for 9 h) for fiordilatte cheese packaging. C-Dots (2500 and 5000 mgL-1) were added to the cheese through an alginate-based coating or directly to the cheese brine. No significant changes in TM4 cell viability were observed at concentrations lower than 10,000 mgL-1. Microbiological and sensory properties of cheese coated and uncoated with C-Dots indicate a substantial preserving effect of the C-Dots. The uncoated control fiordilatte exhibited unacceptable levels of microbial proliferation within 3.5 days. Conversely, the coated cheese remained within acceptable limits, effectively doubling its shelf life compared to the control, primarily due to the coating protection rather than the addition of C-Dots. When compared to the control fiordilatte, the addition of C-Dots in the brine at 5000 mgL-1 resulted in an extension of over 10 days in cheese shelf life. Considering the significance of the sustainable approach in C-Dots synthesis and the exceptional use of C-Dots in the food industry, these findings hold great potential in terms of research and industrial applications.

Introduction to the Special Issue "Scientific Breakthroughs to Fruit and Vegetable By-Product Valorization in the Food Sector".

We are pleased to present this Special Issue, which includes five papers that highlight important research activities in the field of fruit and vegetable by-product valorization [...].

Pomegranate Peel Powder: In Vitro Efficacy and Application to Contaminated Liquid Foods.

In this study the recycling of pomegranate peel powder (PPP) was proposed. In particular, the use of powder loaded in a silk fibroin polymeric matrix to create an active pad was tested. For the sake of comparison, the powder alone was also analysed. Both powder and active pad efficacy was assessed in two different food systems, soymilk (rich in proteins), preliminarily contaminated with Pseudomonas spp. and yeasts, and apple juice (rich in carbohydrates), preliminarily contaminated with Alyciclobacillus acidoterrestris. Three different concentrations of powder alone and powder in the pad were tested (5%, 7.5% and 10% w/v) in both types of beverages. To assess a possible dependence of the efficacy on the powder granulometry, different powder sizes were preliminarily analysed on Pseudomonas spp. and yeasts using an in vitro test. PPP was effective on both Pseudomonas spp. and yeasts. No significant differences appeared among the tested granulometries and therefore in the subsequent tests powder with an average diameter of 250 µm was used. Results recorded with soymilk and apple juice were different. When applied to the soymilk, the activity of PPP in the pad was less effective than that recorded when the powder was directly added to the beverage. With the two highest powder concentrations directly added to food, more than four log cycle reductions in Pseudomonas spp. and yeast cells were recorded, compared to soymilk without any powder. Compared to the control sample, all the soymilk samples either with PPP or with the active pad showed a delayed microbial and fungal growth. When applied to apple juice, both powder and pad were effective at completely inhibiting the proliferation of A. acidoterrestris (<102 CFU/g).

Best Combination of Vegetable By-Products for the Shelf-Life Extension of Fresh Pasta.

A combination of by-products was studied in fresh handmade pasta. Pomegranate peels and olive oil by-products were used in the range 0-6% (w/w) and properly combined in a total of nine combinations with an equal amount of broccoli by-products (10% w/w). The broccoli by-products were added to improve the sensory acceptance, which was compromised when the two above by-products were added to the dough. To verify the synergic effects, among these by-products, on tagliatelle shelf life, microbiological quality based on the main spoilage groups, sensory properties, appearance of visible molds, pH and moisture content were monitored in all the packaged samples stored at 4 °C. In addition to fortified pasta samples, control tagliatelle was also investigated. A mathematical approach was used to fit experimental data and calculate pasta shelf life. In addition, a mathematical model was also proposed to describe the dependence of the shelf life from each by-product percentage added to the formulation. Results showed that while the control fresh pasta lasted about 3 days for the undesired proliferation of yeasts and coliforms, all fortified samples maintained acceptable quality for at least one week. Depending on the by-product combination, shelf-life values could reach more than 13 days. The best combination of by-products calculated based on the mathematical model, that reached the highest shelf life (13.30 days), corresponded to 10% broccoli by-products combined with 6% olive oil by-products and 6% pomegranate peels.

Quality Preservation of Ready-to-Eat Prickly Pears by Peels Recycling.

In the current study, prickly pear peel was advantageously recycled to preserve fruit quality. Specifically, the investigated by-products were transformed into powder and then loaded into an alginate-based solution to be applied as coating to peeled prickly pears, to give an example of sustainable minimally processed fruit. For comparison, uncoated fruit, and coated prickly pears without any powder were also prepared. During storage at refrigerated temperature, coated and uncoated samples were tested for weight loss, microbial and fungal proliferation, as well as for sensory quality acceptance. The results were interesting because great differences were found between coated and uncoated fruit, in that coating the fruit delayed weight loss and spoilage, compared to uncoated fruit. Between the simple coating and the coating with peel powder, slight differences were recorded in favor of the peel-enriched coating. In fact, it allowed the promotion of better fruit preservation, and sensory quality. Therefore, prickly pear peels, that represent abundant by-products during prickly pear processing, could be advantageously recycled to preserve fruit quality.

Introduction to the Special Issue: Advanced Strategies to Preserve Quality and Extend Shelf Life of Foods.

We are pleased to present this Special Issue, which includes 13 papers that highlight the most important research activities in the field of food quality assurance and shelf-life extension [...].

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.

Zero-Waste Approach Applied to Pomegranates for Prolonging Fish Burger Shelf Life.

In this study, the possibility of using whole pomegranate (juice, peel and seeds) according to the zero-waste approach, to prolong fresh fish shelf life, was evaluated. A preliminary antimicrobial in vitro test was carried out with peel and seeds as ground and re-ground powders. Then, the entire fruit, in the right proportions of juice and relative by-products as ground or re-ground powders, was added to fresh fish burger formulation to extend its shelf life. To this aim, a shelf-life test was performed on fortified fish products stored at 4 °C. Control samples were also tested for comparison. Specifically, the pH and microbiological and sensory quality of all the fish burgers were monitored during refrigerated storage for about 1 month. The results from the in vitro test clearly indicate that the peel is abundantly more effective than seeds on selected spoilage bacteria and that the ground peel powder is slightly more antimicrobial than the same re-ground powder. Results from the shelf-life test assessed that the control sample became unacceptable within a few days (about 3 days), while the samples with pomegranate juice and by-products maintained microbial stability for a longer time (2 or 3 weeks) (p < 0.05). The main microbiological problems are the proliferations of mesophilic and psychrotrophic bacteria, Pseudomonas spp. and Shewanella. The addition of pomegranate to the formulation allowed the fish spoilage to be controlled by at least 2 or 3 log cycles. In agreement with findings from the in vitro test, the best results from the microbiological point of view were found in fish burgers with juice, peel and seed ground powders. Furthermore, the addition of pomegranate was also appreciated from the sensorial point of view. In fact, products with pomegranate were prized for about 3 weeks for color, odor, appearance and texture of both raw and cooked products. Therefore, the current study reveals that the incorporation of the entire pomegranate, added in all parts according to the zero-waste concept, could promote a significant shelf-life extension of fish burgers, mainly due to the bioactive compounds present in fruit by-products, without changing the sensory quality.

Silk Fibroin and Pomegranate By-Products to Develop Sustainable Active Pad for Food Packaging Applications.

In this study, a bio-based polymeric system loaded with fruit by-products was developed. It was based on silk fibroin produced by the silkworm Bombyx mori and pomegranate peel powder, selected as active agent. The weight ratio between fibroin and pomegranate powder was 30:70. Pads also contained 20% w/w of glycerol vs. fibroin to induce water insolubility. Control systems, consisting of only fibroin and glycerol, were produced as reference. Both control and active systems were characterized for structural and morphological characterization (Fourier-transform infrared spectroscopy and optical microscope), antioxidant properties and antimicrobial activity against two foodborne spoilage microorganisms. Results demonstrate that under investigated conditions, an active system was obtained. The pad showed a good water stability, with weight loss of about 28% due to the release of the active agent and not to the fibroin loss. In addition, this edible system has interesting antioxidant and antimicrobial properties. In particular, the pad based on fibroin with pomegranate peel recorded an antioxidant activity of the same order of magnitude of that of vitamin C, which is one of the most well-known antioxidant compounds. As regards the antimicrobial properties, results underlined that pomegranate peel in the pad allowed maintaining microbial concentration around the same initial level (104 CFU/mL) for more than 70 h of monitoring, compared to the control system where viable cell concentration increased very rapidly up to 108 CFU/mL.

Improving the Storability of Cod Fish-Burgers According to the Zero-Waste Approach.

This research explored the potential of the zero-waste concept in relation to the storability of fresh food products. In particular, the prickly pear (Opuntia ficus-indica) peel (usually perceived as a by-product) and the pulp were dehydrated, reduced in powder, and used as food additives to slow down the growth of the main spoilage microorganisms of fresh cod fish burgers. The proportion between peel and pulp powder was such as to respect the zero-waste concept. The antibacterial activity of the peel and pulp in proper proportion was first assessed by means of an in vitro test against target microorganisms. Then, the active powder was added at three concentrations (i.e., 2.5 g, 7.5 g, and 12.5 g) to cod fish burgers to assess its effectiveness in slowing down the microbial and sensory quality decay of burgers stored at 4 °C. The results from the in vitro test showed that both the peel and pulp were effective in delaying microbial growth. The subsequent storability test substantially confirmed the in vitro test results. In fact, a significant reduction in growth rate of the main fish spoilage microorganisms (i.e., Pseudomonas spp., psychrotrophic bacteria, and psychrotolerant and heat-labile aerobic bacteria) was observed during 16 days of refrigerated storage. As expected, the antimicrobial effectiveness of powder increased as its concentration increased. Surprisingly, its addition did not affect the sensory quality of fish. Moreover, it was proven that this active powder can improve the fish sensory quality during the storage period.

A New Nanocomposite Packaging Based on LASiS-Generated AgNPs for the Preservation of Apple Juice.

Designing bioactive materials, with controlled metal ion release, exerting a significant biological action and associated to low toxicity for humans, is nowadays one of the most important challenges for our community. The most looked-for nanoantimicrobials are capable of releasing metal species with defined kinetic profiles, either by slowing down or inhibiting bacterial growth and pathogenic microorganism diffusion. In this study, laser ablation synthesis in solution (LASiS) has been used to produce bioactive Ag-based nanocolloids, in isopropyl alcohol, which can be used as water-insoluble nano-reservoirs in composite materials like poly(3-hydroxybutyrate-co-3-hydroxyvalerate). Infrared spectroscopy was used to evaluate the chemical state of pristine polymer and final composite material, thus providing useful information about synthesis processes, as well as storage and processing conditions. Transmission electron microscopy was exploited to study the morphology of nano-colloids, along with UV-Vis for bulk chemical characterization, highlighting the presence of spheroidal particles with average diameter around 12 nm. Electro-thermal atomic absorption spectroscopy was used to investigate metal ion release from Ag-modified products, showing a maximum release around 60 ppb, which ensures an efficient antimicrobial activity, being much lower than what recommended by health institutions. Analytical spectroscopy results were matched with bioactivity tests carried out on target microorganisms of food spoilage.

Pomegranate Peel Powder as a Food Preservative in Fruit Salad: A Sustainable Approach.

This study aimed to assess the potential of pomegranate peel powder as a natural preservative. Its effects were tested on fruit salad quality decay during refrigerated storage. Nectarine and pineapple, equally portioned in polypropylene containers and covered with fructose syrup, were closed using a screw cap in air, with and without the addition of a by-product peel powder. Specifically, amounts of 2.5% and 5% (w/v) of pomegranate peel powder were put into each container. Both the microbiological and sensory qualities of the fruit salad were monitored during storage at 5 °C for 28 days. The results demonstrated that the fruit salad with the by-products showed lower counts of total mesophilic bacteria, total psychrotrophic microorganisms, yeasts, and lactic acid bacteria compared to the control, thus confirming the recognized antimicrobial properties of pomegranate peel. The other interesting finding of this study is that the addition of the investigated by-product in fruit salad did not worsen the main sensory attributes of fresh-cut fruit. Therefore, these preliminary results suggest that pomegranate peel powder has potential applications as a natural preservative in the fresh-cut food sector.

Fiordilatte Cheese Fortified with Inulin from Cichorium intybus or Cynara cardunculus.

The influence of two different types of inulin added to fiordilatte cheese was assessed on product quality during the proper refrigerated storage period. To this aim, the fresh cheese was produced by a pilot plant, adding inulin, either from chicory (low degree of polymerization) or from cardoon (high degree of polymerization), during the stretching phase of the production process. Microbiological stability, sensory acceptability, texture and color changes of fortified dairy food during storage were measured and compared to the control cheese. Results suggest that inulin from different sources, even if characterized by a different degree of polymerization, can keep the texture and color of fiordilatte during storage. Microbiological analyses highlight that inulin seemed to promote a faster Pseudomonas spp. growth; however, the viable cell concentrations were found to be comparable in all the samples after one week. Enterobacteriaceae growth was faster when inulin from chicory was used. Sensory analysis shows that inulin addition to fiordilatte promoted the sensory quality preservation during storage; in fact, the fortified cheese overall quality was found to be always higher (p < 0.05) than that of the control sample, thus suggesting that inulin addition to fiordilatte represents a valid strategy for its fiber fortification.

Pomegranate By-Products as Natural Preservative to Prolong the Shelf Life of Breaded Cod Stick.

This work evaluated the efficacy of pomegranate byproducts, specifically peel powder, as valid preservatives for food quality. Ready-to-cook cod sticks breaded with pomegranate peel powder were prepared. Shelf-life tests were conducted on breaded cod sticks during refrigerated storage (17 days) at 4 °C, monitoring the pH, microbiological and sensory quality. In addition, the nutritional quality of both the breaded and control samples was assessed. The results highlighted that active samples showed higher phenol and flavonoid content and higher antioxidant activity compared to the control fish, suggesting that pomegranate peel powder was responsible for a significant increase in cod stick nutritional quality. Furthermore, the cod stick active breading led to a delay in microbial growth without affecting the sensory properties; rather, it helped slow down the sensory attribute decline during the refrigerated storage. The data suggest that using pomegranate byproducts in breaded cod stick was effective in prolonging its shelf life, as well as improving its nutritional quality. Therefore, pomegranate peel powder can be considered as a potential resource as natural food preservative.

Strategies for fortified sustainable food: the case of watermelon-based candy.

The aim of this research was to design a new product, in particular a watermelon-based jelly candy, without generating waste. The study was divided in two steps: (i) optimization of candy formulation in terms of amount of rind, pulp and juice; (ii) fortification of the jelly candy with different concentrations of orange by-products (albedo and flavedo flours). The fortified jelly samples were assessed for sensory quality and chemical properties, before and after digestion. The new candy product was greatly appreciated. The addition of albedo and flavedo flours significantly improved the chemical composition compared to jelly candy without by-products, before and after digestion. A whole quality index was also calculated to determine the best combination of by-products to be added. Fortification with albedo 1.2% and flavedo ranged between 0.6 and 1.2% allowed recording the most interesting jelly candy.

Food By-Products to Extend Shelf Life: The Case of Cod Sticks Breaded with Dried Olive Paste.

Recently, the interest in recovery bioactive compounds from food industrial by-products is growing abundantly. Olive oil by-products are a source of valuable bioactive compounds with antioxidant and antimicrobial properties. One of the most interesting by-products of olive oil obtained by a two-phase decanter is the olive paste, a wet homogeneous pulp free from residuals of the kernel. To valorize the olive paste, ready-to-cook cod sticks breaded with dried olive oil by-products were developed. Shelf-life tests were carried out on breaded cod sticks and during 15 days of storage at 4 °C pH evolution, microbiological aspects, and sensory properties were also monitored. In addition, the chemical quality of both control and active samples was assessed in terms of total phenols, flavonoids, and antioxidant activity. The enrichment with olive paste increased the total phenols, the flavonoids, and the antioxidant activity of the breaded fish samples compared to the control. Furthermore, the bioactive compounds acted as antimicrobial agents, without compromising the sensory parameters. Therefore, the new products recorded a longer shelf life (12 days) than the control fish sample that remained acceptable for nine days.

Lentil Fortified Spaghetti: Technological Properties and Nutritional Characterization.

Lentil (Lens culinaris), consumed as a part of the diet worldwide, is a functional dietary ingredient that plays a function in human nutrition as a rich source of bioactive nutrients (low quantities of fat, sodium, and vitamin K; high content of potassium, essential amino acids, insoluble dietary fiber, and polyphenols). In this study spaghetti fortified with lentil flours (40% w/w) were developed and characterized. The addition of two different lentil flours significantly affected the sensory attributes and cooking properties of dry spaghetti. Therefore, the addition of carboxymethyl cellulose was adopted as technological option to improve the quality of fortified pasta; specifically, sensory acceptability, cooking loss, swelling index, and water absorption were studied. Chemical results highlighted that the addition of lentil to semolina significantly increased the content of lysine and threonine. It was observed an increase in essential and branched-chain amino acids. Contrary to what was expected, no increase in mono and polyunsaturated fatty acids was observed in fortified spaghetti, due to their loss during cooking, even after the addition of carboxymethyl cellulose.

Characterization and Bio-Accessibility Evaluation of Olive Leaf Extract-Enriched "Taralli".

Olive leaves are rich in many compounds precious for human health. Due to this property, the current study was aimed to valorize the extract from this by-product in a cereal-based food, very popular all around the world, the "taralli". To this aim, ultrasound-assisted extraction was applied to dried olive leaves to obtain the extract, used as "taralli" ingredient, instead of white wine. The "taralli" with and without extract was subjected to in vitro digestion to assess the quantity of polyphenolic compounds released in the gastrointestinal tract to become available for absorption. Total content of phenols and flavonoids, as well as the antioxidant capacity, was measured on both cooked and uncooked samples, before and after digestion. In addition, High-Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD) of the three most abundant polyphenols present in olive leaf extracts, such as oleuropein, hydroxytyrosol, and verbascoside, was carried out at the three stages of the digestion process. The results showed that the substitution of white wine with olive leaf extract increased the total content of polyphenols and flavonoids and the antioxidant capacity. Bio-accessibility of the main phenolic compounds demonstrated that oleuropein resisted slightly after gastric digestion but was almost completely degraded in the intestinal phase, while hydroxytyrosol and verbascoside were not resistant to the digestion process from the gastric phase.

Study on the Influence of Bio-Based Packaging System on Sodium Benzoate Release Kinetics.

The influence of film structure on the release kinetics of sodium benzoate (SB) from polymeric films is addressed in this study. In particular, four film structures were investigated, two monolayer and two multilayer systems. In particular, in one case, the active substance was uniformly distributed into a chitosan-based matrix, and in the other one, it was previously incorporated into alginate beads before dispersion in the chitosan film, thus realizing two types of monolayer films; on the other hand, the same chitosan film with SB encapsulated in alginate beads was used as the inner layer of a multilayer system constituted by two side films of alginate. The two alginate-based layers were made with two different thicknesses, thus producing a total of two multilayer systems. The release of SB from the above-mentioned films in water was studied by means of a UV/VIS spectrophotometer at 227 nm. A first-order kinetics-type equation was used to quantitatively describe the release data. Results suggest that the film structure strongly affected the release kinetics. In fact, monolayer films showed single-stage release kinetics, whereas the two investigated multilayer systems showed two-stage release kinetics. Further, the presence of alginate beads strongly affected the SB release, thus suggesting the potential of encapsulation to control the release mechanism of active compounds.

Sustainable Use of Fruit and Vegetable By-Products to Enhance Food Packaging Performance.

Fruit and vegetable by-products are the most abundant food waste. Industrial processes such as oil, juice, wine or sugar production greatly contribute to this amount. These kinds of residues are generally thrown away in form of leftover and used as feed or composted, but they are a great source of bioactive compounds like polyphenols, vitamins or minerals. The amount of residue with potential utilization after processing has been estimated in millions of tons every year. For this reason, many researchers all around the world are making great efforts to valorize and reuse these valuable resources. Of greatest importance is the by-product potential to enhance the properties of packaging intended for food applications. Therefore, this overview collects the most recent researches dealing with fruit and vegetable by-products used to enhance physical, mechanical, antioxidant and antimicrobial properties of packaging systems. Recent advances on synthetic or bio-based films enriched with by-product components are extensively reviewed, with an emphasis on the role that by-product extracts can play in food packaging materials.