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    Effects of Elevated Temperature and Carbon Dioxide Concentrations on Aromatic Compounds of Stevia rebaudiana
    (Springer India, 2021) Tursun, Ayse Ozlem; Jabran, Khawar; Gurkan, Hacer; Telci, Isa
    A global rise in CO2 concentration and temperature levels can impact the living part of the earth including the plants. Stevia or candy leaf (Stevia rebaudiana Bertoni) is a medicinal aromatic plant that produces several useful chemical compounds. Studies were carried out in a fully automated greenhouse in order to determine the response of aromatic compounds of stevia leaves to different CO2 concentrations and temperature levels. This study had four treatments including (1) 26 +/- 1/16 +/- 1 degrees C day/night temperature plus 400 +/- 50 ppm CO2 concentration [control], (2) 29 +/- 1/19 +/- 1 degrees C day/night temperature plus 600 +/- 50 ppm CO2 concentration, (3) 32 +/- 1/22 +/- 1 degrees C day/night temperature plus 800 +/- 50 ppm CO2 concentration and (4) 35 +/- 1/25 +/- 1 degrees C day/night temperature plus 1000 +/- 50 ppm CO2 concentration. Results of the study showed that yield of total aromatic compounds ranged between 12.65 and 13.65 mu g/g for stevia . Generally, concentrations of the compounds such as ketones, aldehydes and alcohols were decreased with increase in concentration of CO2 and temperature. Terpenes were the compounds whose concentrations were increased with increase in concentration of CO2 and temperature. The climatic conditions did not cause a significant change in the aromatic compounds of stevia.
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    Extraction optimization and microencapsulation of phenolic antioxidant compounds from lemon balm (Melissa officinalis L.): Instant soluble tea production
    (Wiley, 2021) Tulek, Zehra; Alasalvar, Hamza; Basyigit, Bulent; Berktas, Serap; Salum, Pelin; Erbay, Zafer; Telci, Isa
    The purpose of this study was to extract phenolics from lemon balm followed by microencapsulation with spray drying. The optimum extraction conditions were 100 degrees C for the temperature and 120 min for the time with TPC of 6,365 mg GAE/100 g and ABTS radical scavenging activity of 9,196 mg TEAC/100 g. Lemon balm extracts were spray dried using three different air inlet temperatures (130 degrees C, 165 degrees C, and 200 degrees C) of which 165 degrees C was provided better scores than the other points in terms of microencapsulation yield (65.9%), microencapsulation efficiency (99.4%), dry matter (98.3%), and water activity (0.160). The inlet air temperatures had an insignificant (p > .05) effect on the antioxidant capacity of the microcapsules. Phenolic acids in lemon balm were slightly affected by the extraction and spray drying conditions. However, extraction followed by spray drying resulted in significant loss in the amount of volatiles such as geranial, neral, citronellal, and caryophyllene. Practical applications Hot water extracts of the medicinal and aromatic plants are consumed as herbal tea across the world and their biological activity varies depending on the extraction conditions. Furthermore, bioactive compounds are sensitive to environmental conditions when the compounds dissolved in water. The conditions necessary for the effective extraction of bioactive compounds are specific to the target plant and it is a problem for the consumer. Optimization of extraction conditions of lemon balm phenolics could provide useful information for the consumer and food industry. The production of phenolic microcapsules (instant soluble tea) from lemon balm could facilitate herbal tea preparation and reduce the preparation time.