Effect of Extraction Method on the Bioactive Composition, Antimicrobial Activity and Phytotoxicity of Pomegranate By-Products

Preparation and characterization of porous corn starch-based antibacterial sustained-release intelligent film

A novel porous corn starch-based antibacterial sustained-release intelligent film was prepared with the porous corn starch as the substrate, purple corn cob anthocyanin (PCA) as the indicator, and tangerine peel essential oil as the antibacterial agent, and its properties were studied. The results showed that the porous corn starch-based antimicrobial sustained-release indicator film had good mechanical strength, surface hydrophobicity and light transmittance. The tensile strength of the sustained-release indicator film (PLSt-12) prepared by porous corn starch with an enzymatic hydrolysis time of 12 h was 14.35 MPa and the elongation at break was 6.55 %. The water contact angle was 89.10°, and the water vapor transmittance was 6.62 × 10-4 g·mm2·s-1·Pa-1. The PLSt-12 was brown at pH 10 and had a sensitive color response. The PLSt-12 reduced the release rate of anthocyanins by 25.01 %, and the sustained-release mechanism was non-Fick diffusion. It showed a significant color change when the pork quality deteriorated, which can be used to monitor the freshness of the pork. This type of antibacterial sustained-release intelligent film had considerable application potential in indicating food freshness.

Preparation and characterization of corn starch-based antimicrobial indicator films containing purple corncob anthocyanin and tangerine peel essential oil for monitoring pork freshness

A novel antibacterial indicator film was prepared by mixing corn starch with tangerine peel essential oil (TEO) Pickering emulsion emulsified by ultrasonic and esterified modified starch (UDSt), and then incorporated with purple corncob anthocyanin (PCA), which was used to monitor the freshness of pork. The results showed that the UDSt can effectively stabilize the TEO emulsion. PCA showed obvious color changes at different pH. With the increase of pH, the color of film changed from red to yellow, and its response to volatile ammonia changed from pink to cyan, showing better response ability. The loading of TEO conferred the film excellent bacteriostatic ability against E. coli and S. aureus. The film also had good ability of light blocking and free radical scavenging. In the process of pork deterioration, the antibacterial indicator film changed from pink to yellow, which was closely related to pork quality and had a good linear indicator correlation. The addition of TEO reduced the release of PCA in the antibacterial indicator film and helped to maintain the functional properties of the film. This type of antibacterial indicator film had considerable application potential in indicating food freshness.

Screening of Chemical Composition, Antimicrobial and Antioxidant Activities in Pomegranate, Quince, and Persimmon Leaf, Peel, and Seed: Valorization of Autumn Fruits By-Products for a One Health Perspective

Antimicrobial resistance is increasing globally and is now one of the major public health problems. Therefore, there is a need to search for new antimicrobial agents. The food industry generates large amounts of by-products that are rich in bioactive compounds, such as phenolic compounds, which are known to have several health benefits, including antioxidant and antimicrobial properties. Thus, we aimed to characterize the phenolic compounds present in pomegranate, quince, and persimmon by-products, as well as their antioxidant and antimicrobial activities. Phenolic compounds were extracted from pomegranate, quince, and persimmon leaves, seeds, and peels using a mixture of ethanol/water (80/20). The polyphenol profile of the extracts was determined by high-performance liquid chromatography. The antioxidant activity of the extracts was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), and cupric reducing antioxidant capacity (CUPRAC) methods. Antimicrobial susceptibility was evaluated using the Kirby-Bauer disk diffusion method. In general, leaves showed higher concentrations of phenolics than the peel and seeds of fruits. In total, 23 phenolic compounds were identified and quantified, with sanguiin and apigenin-3-O-galactoside being present in the highest concentrations. Leaf extracts of pomegranate showed higher antioxidant activities than the other components in all methods used. In general, all extracts had a greater antimicrobial activity against Gram-positive bacteria. Persimmon leaf and seed extracts inhibited a greater number of bacteria, both Gram-positive and -negative. The lowest minimum inhibitory concentration (MIC) detected among Gram-positive and -negative bacteria was 10 mg/mL for pomegranate peel and leaf extracts against Staphylococcus aureus and S. pseudintermedius and for pomegranate leaf extract against Escherichia coli. Our results reinforce the need to value food industry by-products that could be used as food preservatives and antibiotic adjuvants against multiresistant bacteria.

The Potential of Food By-Products: Bioprocessing, Bioactive Compounds Extraction and Functional Ingredients Utilization

Achieving sustainability in the agro-food sector can only be possible with the valorization of food industry waste and side streams, products with an extremely high intrinsic value but often discarded because they are unfit for further processing that meets consumer expectations [...].

Combined Effect of Ultrasound and Microwave Power in Tangerine Juice Processing: Bioactive Compounds, Amino Acids, Minerals, and Pathogens

The inhibition of Escherichia coli ATCC 25922 (E. coli), Staphylococcus aureus ATCC6538 (S. aureus), Salmonella Enteritidis ATCC 13076 (S. Enteritidis), and Listeria monocytogenes DSM12464 (L. monocytogenes) is one of the main aims of the food industry. This study was the first in which the use of ultrasound and microwave power were applied to optimize the values of the bioactive components, amino acids, and mineral compositions of tangerine juice and to inhibit Escherichia coli, Staphylococcus aureus, Salmonella Enteritidis, and Listeria monocytogenes. The response surface methodology (RSM) was used to describe the inactivation kinetics, and the effects of ultrasound treatment time (X1: 12–20 min), ultrasound amplitude (X2:60–100%), microwave treatment time (X3: 30–40 s), and microwave power (X4:200–700 W). The optimum parameters applied to a 5-log reduction in E. coli were determined as ultrasound (12 min, 60%) and microwave (34 s, 700 W). The optimum condition ultrasound–microwave treatment was highly effective in tangerine juice, achieving up to 5.27, 5.12, and 7.19 log reductions for S. aureus, S. Enteritidis, and L. monocytogenes, respectively. Ultrasound–microwave treatment increased the total phenolic compounds and total amino acids. While Cu, K, Mg, and Na contents were increased, Fe and Ca contents were lower in the UM-TJ (ultrasound–microwave-treated tangerine juice) sample. In this case, significant differences were detected in the color values of ultrasound–microwave-treated tangerine juice (UM-TJ) (p < 0.05). The results of this study showed that ultrasound–microwave treatment is a potential alternative processing and preservation technique for tangerine juice, resulting in no significant quality depreciation.

Pomegranate Peels and Seeds as a Source of Phenolic Compounds: Effect of Cultivar, By-Product, and Extraction Solvent

The nutraceutical properties of Punica granatum L. are not restricted to the edible portion of the fruit but also to the peels and seeds, flowers, leaves, and tree bark. The recovery and valorization of the peel and seeds (ca. 50% of the whole fruit), besides the positive environmental impact, can be viewed as a source of natural bioactive compounds. Thus, the bioactive properties of extracts of pomegranate peel and seeds from Acco and Wonderful known cultivars, as well as of the novel Big Full cultivar, were evaluated. The dried and ground pomegranate by-products were submitted to a conventional solid/liquid extraction with ethanol/water mixtures (0%, 25%, 50%, and 75% of EtOH, v/v). The obtained extracts were characterized in terms of total phenolic compounds (TPC), total flavonoids (TF), and antioxidant activity (AA), determined by the DPPH radical scavenging activity and expressed as IC50 (half maximum inhibitory concentration). With the exception of the Acco cultivar, the extraction yield (EY) was higher for peels, whose extracts showed higher TPC, TF, and IC50 (lower AA). The extracts obtained from the by-products of the Big Full cultivar had a statistically higher overall bioactive potential (TPC: 0.36 mg GAE/mg extract; TF: 0.031 mg CATE/mg extract; IC50: 0.51 mg/mL) compared to the other two studied cultivars. Furthermore, the EY was enhanced by solvents richer in ethanol (50-75%), allowing obtaining extracts richer in TPC and TF with higher AA. Finally, it was shown that EY combined with bioactive data allowed a satisfactory principal component unsupervised differentiation of the pomegranate extracts according to the type of by-product used.