The effect of drying methods on the concentration of compounds in sage and thyme

Abstract

The aim of the study was to evaluate effects of three drying methods of thyme and sage. Collected herbs were dried: under natural conditions, at temperature of 35 °C/40 °C, and freeze‐dried. The material was tested on the essential oil content using Clevenger apparatus; chemical composition was determined using gas chromatography coupled to mass spectrometry (GC‐MS). Antioxidant activity was analyzed by determining the ability to neutralize the free radical 2,2′‐azino‐bis (3‐ethylbenzothiazoline‐6‐sulphonic acid) (ABTS) with simultaneous measurement of phenolic compounds content. Most oils were isolated from herbs dried at 35 °C, but the largest amount of thymol in thyme and thujone in sage leaves was determined at 40 °C. The highest content of polyphenols for thyme was found at 35 °C and for sage in lyophilized leaves. The lyophilized material was characterized by the largest ability of free radical (ABTS) elimination. Practical applications Drying as a method of preservation of herbal plants, like food preservation, is a necessary process of maintenance, especially in temperate climates. The way in which thyme and sage leaves are dried, has a significant influence on their chemical composition, and thereby the properties of the received raw material. Therefore, there is a possibility of programming their composition according to the needs. Owing to appropriate technological treatment it is possible to obtain the substances which are helpful in the prevention of civilizational diseases. Nowadays thyme and sage are widely used. The presented research results are useful not only in the process of obtaining dried leaves from thyme and sage but also in isolating the essential oil with the desirable chemical composition, for further use and development of functional food.

Spectroscopic Examination and Chemometric Analysis of Essential Oils Obtained from Peppermint Herb (Mentha piperita L.) and Caraway Fruit (Carum carvi L.) Subjected to Pulsed Electric Fields

“…Heating of peppermint above 34 • C may already promote a significant loss of essential oils. Similar observations in the case of sage dried within a comparable temperature range were made by Sellami et al [23], and by Sadowska et al [24] for sage and thyme. The results published by these authors indicate 0.3% to 0.26% loss of oil during convective drying at 45 • C compared to natural drying at a temperature of about 22 • C [23], and increase of said loss at drying temperatures between 35 and 40 • C by 0.23 mL•100 g −1 for sage, and 0.16 mL•100 g −1 for thyme.…”

Influence of Various Drying Conditions on Phytochemical Compounds and Antioxidant Activity of Carrot Peel

“…Particularly, drying temperature directly influences the changes in the physicochemical properties of foods. Current drying methods include: (1) conventional drying, for example hot-air/oven drying [1][2][3][4][5][6], conventional/low temperature-air drying [6][7][8], vacuum/vacuum oven drying [5,6,[9][10][11], sun drying [6,9,12], under shade drying [9,13], heat pump-dehumidified air drying [2], low-pressure superheated steam drying [1], and freeze drying [2,5,9]; (2) radiation drying such as microwave drying [2,6,12,[14][15][16], infrared drying [3,4,6]; and (3) combined drying or novel drying, for instance, microwave-assisted hot-air drying [3], infrared-combined hot air drying [1,4], hot air-assisted radio frequency drying [3], vacuum-microwave drying [10,17], combined infrared-vacuum drying [18], and combined low-pressure superheated steam drying and far-infrared radiation [19]. Among these drying techniques, conventional drying is simpler, has lower production costs, but is less effective (except for freeze drying), while radiation and novel drying are effective but are more complicated, and have higher production costs.…”

Mikro Besin Maddelerinin Humik Asit Koşulları Altındaki Kekik (Thymus vulgaris L.)’in Antioksidan Özelliklerine Etkisi

“…Kruma et al (2008) reported that total phenolic compounds in latvian thyme were 74.96 mg/g. Sadowska et al (2017) evaluate the effects of three drying methods (under natural conditions, at temperature of 35 °C/40 °C, and freeze-dried) of thyme on some biochemical properties. According their result, the highest content of polyphenols for thyme was found at 35 °C drying.…”