Propolis is a natural mixture produced by bees from plant resin substances. This study focuses on the general characteristics of five samples of Polish extract propolis originating from agricultural areas. Chemical composition with high performance liquid chromatography‒diode array detector method, total content of flavonoids and polyphenols, and antioxidative activity were determined in the ethanol extracts of propolis (EEP) samples. Minimum inhibitory concentration (MIC), minimum bactericidal/fungicidal concentration (MBC/MFC) and time-kill curves were studied for foodborne pathogens and food spoilage microorganisms. In EEPs the predominant flavonoid compounds were pinocembrin, chrysin, pinobanksin, apigenin, and kaempferol and the predominant phenolic acids were p-coumaric acid, ferulic acid, and caffeic acid. A strong antioxidative action of propolis in vitro was observed (IC50 for DPPH radical was at the level of 0.9–2.1 µg/mL). EEPs had MIC values for bacteria in the range of 1–16 mg/mL, whereas MIC for fungi ranged from 2 to 32 mg/mL. Extract of propolis originating from southern Poland was distinguished by higher content of bioactive components, and stronger antioxidative and antimicrobial activity than EPPs from the remaining areas of Poland. The results indicate the possibility of applying ethanol extracts from Polish propolis to protect food against microbiological spoilage.
Greek oregano and common oregano were compared in respect of the antioxidant and antibacterial activity of the corresponding essential oils and hydroethanolic extracts in relation with their chemical profile. The chemical composition of essential oils was determined by GC-MS and GC-FID, while extracts (phenolic acids and flavonoids fractions) were analyzed by HPLC-DAD. Based on given volatiles, the investigated subspecies represented two chemotypes: a carvacrol/γ-terpinene/p-cymene type in the case of Greek oregano and a sabinyl/cymyl type rich in terpinen-4-ol in common oregano. Within non-volatile phenolic compounds, rosmarinic acid appeared to dominate in both subspecies. Lithospermic acid B, chlorogenic acid and isovitexin were present only in Greek oregano extracts. However, the total content of flavonoids was higher in common oregano extracts. The essential oil and extract of Greek oregano revealed visibly stronger antibacterial activity (expressed as MIC and MBC) than common oregano, whereas the antioxidant potential (determined by DPPH, ABTS and FRAP) of these extracts was almost equal for both subspecies. In the case of Origanum plants, the potential application of essential oils and extracts as antiseptic and antioxidant agents in the food industry should be preceded by subspecies identification followed by recognition of their chemotype concerning both terpene and phenolics composition.
The purpose of the study was to determine the differences between two subspecies: O. vulgare L. subsp. hirtum (Link) Ietswaart (Greek oregano) and O. vulgare L. subsp. vulgare (common oregano) growing in cultivation conditions within temperate climate of Central Europe. The characteristic of the subspecies was undertaken in terms of selected morphological parameters and the quality of the raw material. The herb of both subspecies was evaluated on the content and composition of essential oil by hydrodistillation followed by GC-MS and GC-FID (gas chromatography coupled with mass spectrometry and flame ionization detector), the total content of phenolic acids (according to PP 6th ed.) and the content of rosmarinic acid (by HPLC). The sensory evaluation (QDA) was performed, as well. Greek oregano was distinguished by visibly higher number of glandular trichomes on the leaves (up to 4.85 per 1 mm2) followed by higher content of essential oil in the herb (up to 3.36 g × 100 g−1 DW) in comparison to common oregano. Based on the essential oil composition, Greek oregano was classified as mixed carvacrol/γ-terpinene chemotype, while common oregano as mixed sabinyl/cymyl type rich in sesquiterpenes. Greek oregano was also characterized by higher total content of phenolic acids (up to 6.16 g × 100 g−1 DW) and rosmarinic acid (up to 6787.2 mg × 100 g−1 DW) than common oregano. Essential oil content reached the maximum at the beginning of blooming (common oregano) and at the full blooming stage (Greek oregano). In turn, the amount of phenolic acids followed by rosmarinic acid was the highest at the beginning of seed-setting stage, in the case of both subspecies. The differences between subspecies concerning chemical composition (especially essential oil) were reflected in the sensory attributes, where both odor and taste notes were found at higher level for Greek oregano. Results of our work indicate that Greek oregano is well adapted to grow in the temperate zone conditions. Such adaptation was reflected mainly in the satisfied yield and maintaining characters typical for the Mediterranean plant, e.g., a high essential oil content followed by high carvacrol share, traits the most important from practice viewpoint.
Cherry tomatoes are one of the most popular tomato varieties known for their bioactive compounds and sensory properties. One way to reduce the contamination of tomato is to coat them with natural or antimicrobial substances. In this study, an ethanolic extract of propolis (EEP) was obtained, and its chemical composition was analyzed using high-performance liquid chromatography with diode array detector (HPLC-DAD), and minimum inhibitory concentration (MIC) and the minimum bactericidal/fungicidal concentration (MBC/MFC) were determined using the serial microdilution method. The antimicrobial activity of 5 and 10% EEP and pullulan films containing EEP (5 and 10%) against Listeria monocytogenes, Salmonella Typhimurium, Escherichia coli O157, Penicillium chrysogenum, Fusarium solani, and Botrytis cinerea were compared. The influence of a pullulan coating containing EEP (5 and 10%) on reducing the number of bacteria and molds, physicochemical properties (weight loss (WL), total soluble solids (TSS), titratable acidity (TA), maturity index, pH, and color), and sensory properties (color and brightness of skin, aroma, flavor, overall quality, and general preference) of cherry tomatoes during refrigerated storage was evaluated. Pullulan films with EEP inhibited the growth of microorganisms on cherry tomatoes. These coatings did not affect the TSS and pH values of tomatoes, but a slight decrease in TA and WL was observed. Cherry tomatoes coated with pullulan coatings containing EEP did not show any adverse changes in their sensory properties. It was found that the addition of EEP to the pullulan coatings enriched them with antimicrobial properties and enhanced their action while reducing the WL and maturation time of cherry tomatoes.
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