Technologies and extraction methods of polyphenolic compounds derived from pomegranate (Punica granatum) peels. a mini review

The interest in using plant by-product extracts as functional ingredients is continuously rising due to environmental and financial prospects. The development of new technologies has led to the achievement of aqueous extracts with high bioactivity that is preferable due to organic solvents nonuse. Recently, widely applied and emerging technologies, such as Simple Stirring, Pressure-Applied Extraction, Enzymatic Extraction, Ultrasound-Assisted Extraction, Pulsed Electric Fields, High Hydrostatic Pressure, Ohmic Heating, Microwave Assistant Extraction and the use of “green” solvents such as the deep eutectic solvents, have been investigated in order to contribute to the minimization of disadvantages on the extraction of bioactive compounds. This review is focused on bioactive compounds derived from pomegranate (Punica granatum) peels and highlighted the most attractive extraction methods. It is believed that these findings could be a useful tool for the pomegranate juices industry to apply an effective and economically viable extraction process, transforming a by-product to a high added value functional product. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Black olives as substrate for Aspergillus parasiticus growth and aflatoxin B1 production

Aflatoxin B1 (AFB1) is a highly toxic and carcinogenic metabolite produced by certain Aspergillus species on agricultural commodities. Molds isolated from black olives are potentially toxigenic and present a potential health hazard. Olive oil originating from contaminated olives with AFB1 might also be contaminated. The aim of this study was to investigate A. parasiticus growth and AFB1 production in black damaged olives inoculated with 100 conidia flask-1 (I) treated with NaOCl 1.25%, (2) autoclaved at 110°C for 2 min, in comparison to the mold growth and AFB1 production into the yeast extract sucrose (YES) medium under the same conditions of incubation and inoculation. AFB1 extracted from cultures or olives and purified with immunoaffinity columns, was derivatized to its hemiacetal AFB2a and then quantitated by HPLC using fluorescence detector. The recoveries and detection limits from YES and olives were 99.2%, 0.02 ng AFB1 ml-1 and 94%, 0.15 ng AFB1 g-1, respectively. Results showed that mycelia growth was not observed in olives during the 15 days of observation. The maximum growth of A. parasiticus on YES medium was shown on the sixth day. The AFB1 production for both treated with NaOCl and autoclaved olives inoculated or not with A. parasiticus was not significantly different. On the other hand, AFB1 levels produced in olives treated with NaOCl were significantly higher as compared with the autoclaved. The range of contamination of all olive samples inoculated or not for the whole period of observation was 0.15-2.3 ng AFB1 g-1. The production of AFB1 in YES medium on the third, the ninth and the 15th day was ∼ 1000-, ∼ 2500- and 10 000-fold higher, respectively, compared with the production in olives thus showing that black damaged olives of Greek origin are not a substrate favorable for AFB1 biosynthesis at hazardous levels. Nevertheless, the production is possible at detectable amounts even after a little contamination that could happen randomly. © 2002 Elsevier Science Ltd. All rights reserved

Chemical properties, fatty-acid composition, and antioxidant activity of Goji berry (Lycium barbarum l. and Lycium Chinense mill.) fruits

In this study, the content composition and antioxidant activity of goji berry fruits from two species (Lycium barbarum and Lycium chinense) were assessed. The total carbohydrate and phenolic contents were evaluated using attenuated total reflection Fourier-transform infrared (ATR-FT-IR) spectroscopy, while the antioxidant activity of fruits was examined with two in vitro methods, which are based on the scavenging activity of the 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and 2,2’-azino-bis(3-ethyl-benzthiazoline-sulfonic acid) (ABTS•+) free radicals. The fatty-acid profile was determined using gas chromatography coupled with mass spectrometry (GC-MS). The results of this study indicate that the fruits of L. barbarum present higher concentrations in carbohydrates and phenolics than L. chinense Mill. fruits. Furthermore, the antioxidant activity based on the half maximal inhibitory concentration (IC50) measurements of DPPH• and ABTS•+ free-radical scavenging was higher in L. barbarum than L. chinense Mill. Also, the GCMS analysis confirms the high levels of linoleic, palmitic, and oleic acids contained in the fruits of both species. Finally, the results of this study clearly show that the concentration of bioactive and antioxidant molecules is higher in L. barbarum than in L. chinense fruits, which was also confirmed by ATR-FT-IR measurements. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

The in vitro antimicrobial activity assessment of ultrasound assisted Lycium barbarum fruit extracts and pomegranate fruit peels

The present study aimed at assessing the antimicrobial properties of a water and ethanol ultrasound-assisted extraction (UAE) of dry goji berries and of lyophilised powdered pomegranate peel in vitro. Minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) methods, turbidity (cell density) measurement, and well diffusion assay were used to determine the antimicrobial activity against several species of foodborne bacteria (Gram – , Escherichia coli, Salmonella typhimurium, Campylobacter jejuni), (Gram + Staphylococcus aureus, Listeria monocytogenes, Clostridium perfringens), yeasts (Yarrowia lipolytica, Metschnikowia fructicola, and Rhodotorula mucilaginosa), and fungi (Penicillium expansum, Aspergillus niger, Fusarium oxysporum, and Rhizoctonia solani). Carbohydrate and phenolic contents were measured, and DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2΄-Azino-bis-(3-ethyl-benzthiazoline-sulphonic acid)) radical scavenging assays were used for the assessment of antioxidant activity. Fourier transform infrared (FTIR) spectrums of all samples were also evaluated in order to determine their chemical profiles. The lyophilised pomegranate peel exhibited the highest antioxidant, antimicrobial, and antifungal activity among all samples, while among the goji berry samples-who had only antibacterial and very little or no antifungal activity—the lyophilised aqueous extract with the lowest content of maltodextrin (2%) and highest phenolic content, had also the highest antioxidant, antimicrobial, and antifungal activity. The antioxidant and antimicrobial bioactivities seemed to be related to the content of polyphenols, the low concentration of maltodextrin in the encapsulated lyophilised samples and the use of optimised ultrasound assisted extraction. Minimum inhibitory concentration or zones of inhibition were in many (but not all) cases lower for the aqueous extracts compared to the ethanol or ethanol/hexane extracts of goji berries. In conclusion, the lyophilized powder of pomegranate peels and the aqueous extracts of goji berries encapsulated with minimal maltodextrin content and high polyphenol content exhibited high antioxidant and antimicrobial activity which could be utilized in food preservation or plant protection. © 2019, Springer Science+Business Media, LLC, part of Springer Nature