Production of grape pekmez by Ohmic heating-assisted vacuum evaporation.

Pekmez is a concentrated syrup-like food conventionally produced by vacuum evaporation process from sugar-rich fruits. In this study, the applicability of grape pekmez production by ohmic heating assisted vacuum evaporation (ΩVE) method was investigated. Conventional vacuum evaporation (CVE) and ΩVE methods were compared in terms of physicochemical properties, HMF (5-hydroxymethylfurfural) contents, rheological properties, and energy consumptions. ΩVE was run at four different voltage gradients (17.5, 20, 22.5, and 25 V/cm). Total process times for grape pekmez production were determined as 57, 28.5, 32, 39, and 50 minutes for CVE, ΩVE (25 V/cm), ΩVE (22.5 V/cm), ΩVE (20 V/cm) and ΩVE (17.5 V/cm), respectively. Energy consumption of CVE method was higher than ΩVE method for all voltage gradients. Energy efficiency increased as the voltage gradient increased. There was no significant difference between CVE and ΩVE methods for HMF contents. The results show that the ΩVE method could be an alternative to the CVE process for grape pekmez production.

Volatile Constituents and Biological Properties of Essential Oils from Aerial Parts of Gentiana gelida BIEB.

This work reports the chemical composition, antimicrobial and antioxidant activities of essential oils from the aerial parts of Gentiana gelida BIEB. for the first time in literature. The oils from the aerial parts (flower, leaf and stem) were obtained by Clevenger-type apparatus and characterized by GC-FID and GC-MS. While tricosane (21.67%) was the main component of flower oil, hexadecanoic acid was the most abundant component of leaf and stem oils in ratios 26.46% and 31.89%, respectively. Additionally, all essential oils of G. gelida were investigated for their antimicrobial activity against eight Gram negative bacteria, four Gram positive bacteria and five fungi, using agar dilution method and antioxidant activities by using 2,2-diphenyl-1-picrylhydrazyl radical scavenging and Folin-Ciocalteu assays. The flower oil of G. gelida showed stronger antimicrobial and antioxidant activities than those of stem and leaf. The amount of total phenolic content and scavenging activity of the flower oil were found 525.35±8.24 mg GAE/L and 49.30±1.25%, respectively.