Orphanides A., Goulas V., Gekas V. (2013): Effect of drying method on the phenolic content and antioxidant capacity of spearmint. Czech J. Food Sci., 31: 509-513.The changes in total phenolics, hydroxycinammic acid derivatives, and antioxidant properties of spearmint after five drying treatments (convection oven drying, freeze-drying, microwave drying, and air drying with the sun exposure and without the sun exposure) were investigated. Phenolic composition of dried spearmint was analysed by spectrophotometric assays, while DPPH radical scavenging activity and Ferric reducing/Antioxidant power (FRAP) assay was used to measure the antioxidant properties. The results showed that freeze drying produced dried spearmint that had the highest total phenolics (34.6 ± 1.9 mg/g) content and the most potent antioxidant capacity (126.2 ± 0.4 mg/g for FRAP and 88.1 ± 5.9 mg/g for DPPH, respectively). On the other hand, spearmint that was dried by convection oven and microwave drying presented the lowest amount of phenolic compounds (12.0 ± 0.5 mg/g) and antioxidant potency (49.3 ± 0.7 mg/g for FRAP and 26.9 ± 1.6 mg/g for DPPH, respectively). This might be attributed to the fact that heat-sensitive phenolics were degraded or biotransformed at high temperatures. The loss of phenolic compounds and antioxidant activity reached up to 60% compared to freeze drying.

Herbs are usually marketed as dry due to a consumer demand beyond their seasonality; dehydration leads to a stable, easily moveable product that is available throughout the year. The process of drying, though, leads to modifications in the appearance, composition and quality of the raw material. The extent of these alterations depends on the applied drying methodology and its parameters, rendering the optimization of this process imperative. Numerous studies examining the effect of drying on the main characteristics of herbs have been published in recent years, and this review aims at organizing the available information of the studied herbs, drying methods and measured parameters in a comprehensive manner. Primarily, since aroma is the main characteristic of herbs and the principal aim for the end product is to retain the raw material's character, this review will focus on the most widely studied effect of drying, which is the essential oil yield and composition. Secondly, results from various studies on the influence of drying on biochemical compounds, organoleptic properties of dried herbs are also presented. The most common approach to the study of drying kinetics is also presented. Finally, novel technologies targeting to minimize the magnitude of changes from the raw material are described.

fruits are ingredients of traditional Cypriot sausages. The objective of this study is to evaluate extracts as natural additives to the sausages. First, the phenolic content and antioxidant activity of fruit and leaf extracts were determined. Results revealed that leaves are richer source of polyphenolic antioxidants than fruits, with methanol being the better extraction solvent. In the next step, the antioxidant and antimicrobial effects of methanolic extracts (300 mg/kg) in the pork sausage formulation were investigated. Peroxide, acid and thiobarbituric acid-reactive substance values demonstrated that both fruit and leaf extracts reduced the rate of lipid oxidation of sausages at 4 °C. Total viable count revealed significant differences on the fifth day of storage, with better microbial inhibition by leaf extract. No significant differences between the extracts were observed after the tenth day of storage. Overall, the extracts can be used to prevent lipid oxidation and reduce microbial spoilage during the first days of storage of fresh traditional pork sausages.

Several health claims of olive oil are correlated with phenolic compounds. The objective of this study was to evaluate the effect of different thermal processing methods on phenolic composition and antioxidant properties of heated olive oils. In particular, the phenolic antioxidants of olive oils, which were subjected to frying, baking, boiling and microwave irradiation, were estimated using multispectrophotometric assays approach. Results showed that thermal processing methods affected significantly the phenolic content as well as the antioxidant potency of heated olive oils. The frying and boiling of olive oils caused the highest losses of phenolic compounds that reached up to 75%, whereas a slight decrease in polyphenols was monitored after microwave irradiation. Furthermore, the baked olive oils retained better phenolic antioxidants than olive oils that were subjected to frying and boiling. Overall, our findings suggest baking as the most appropriate thermal method to heat olive oils.

No abstract

Dry spearmint is a commodity widely used in food manufacturing both as an ingredient and a product itself. The objective of this study was to determine the effect of different drying temperatures and air velocities on the quality of dried product in an attempt to recommend the optimum drying conditions. Physicochemical and microbiological properties were evaluated as quality indexes. Results revealed that temperature and air velocity were statistically significant for most of the parameters investigated. Taking into consideration that consumers have a preference towards dried herbs that retain the characteristics of the fresh material, the suggested combination for drying spearmint is at 40C with an air velocity of 3 m/s. This combination has been experimentally demonstrated that can also significantly improve the microbiological quality of the product. Practical Applications Drying process is often applied to preserve and increase self‐life of leafy aromatic plants through decreasing moisture content and water activity. Through the present work the effect of air‐drying on the quality attributes of dried spearmint was investigated. Different combinations of temperature and air velocities were tested in an attempt to determine the most suitable drying parameters that will lead to a high quality product. The application proposed at 40C with an air velocity of 3 m/s can be adopted by manufactures in industrial scale. The aforementioned combination produced dried spearmint with the best physicochemical and microbiological characteristics.