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- MakaleYalnız künye2026Scopus SJRQ2Drying temperature-dependent changes in grape seed bioactives and oxidative status: integrated HPLC/GC and multivariate analysis
Karaca Sanyürek, Nesrin
Abstract: Drying temperature (40–80 °C) critically influences the stability of bioactive compounds in grape seeds and their functional responses. In this study, we evaluated the vitamin and phytosterol content of Boğazkere grape seeds using high-performance liquid chromatography (HPLC) and the fatty acid content using gas chromatography (GC). Antioxidant capacity was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and the oxidative stress marker, malondialdehyde (MDA). Temperature-dependent and compound-specific alterations were observed: while selected vitamins and phytosterols showed distinct thermal susceptibilities, fatty acid profiles exhibited measurable remodeling. Antioxidant activity revealed non-linear dose- and temperature-dependent patterns, whereas MDA consistently decreased with increasing temperature, reflecting the reduced oxidative metabolism in dehydrated tissues. Multivariate analysis, including principal component analysis (PCA) and heatmap visualization, effectively discriminated temperature treatments and revealed correlations between compositional and functional parameters. The combined use of univariate and multivariate analyses revealed that the drying temperature reshaped not only individual bioactive compounds but also the overall biochemical profile of grape seeds. These findings establish a mechanistic link between thermal processing and bioactive stability, providing a chemical basis for optimizing grape seed valorization in food systems.
- MakaleAçık Erişim2020Determination of Some Aroma Metabolites of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus Isolates from Traditional Yogurt, by HPLC
Yazdiç, Fadime; Akyol, Ismail; Yazdiç, Ferit Can
This study was conducted to determine lactic acid bacteria isolated from Turkish yoghurts produced by traditional methods, amounts of usage of milk lactose in carbohydrate metabolism and formate, pyruvate, 3-hydroxy-2-butanone (acetoin), ethanol and 2,3-butandiol production amounts by HPLC. Two lactic acid bacteria species, widely used in traditional and industrial yoghurt production Streptococcus thermophilus (St. thermophilus) and Lactobacillus delbrueckii subsp. bulgaricus (Lb. bulgaricus) were used from cultural stock. Production potentials of the above mentioned metabolites of 88 pieces of St. thermophilus and 12 pieces of Lb. bulgaricus were researched in different mediums and milk. St. thermophilus isolates were grown in anaerobic SM17, aerobic SM17, LM17 and milk and Lb. bulgaricus isolates were grown in anaerobic MRS (Man, Rogosa and Sharp Broth), aerobic MRS and milk. Amounts of formate, pyruvate, 3-hydroxy-2-butanone, ethanol and 2,3-butandiol determined by HPLC of St. thermophilus isolates were specified respectively as 0.1 +/- 0.0-77.0 +/- 0.2 mg/kg, 0.1 +/- 0.0-90.2 +/- 0.0 mg/kg, 0.1 +/- 0.0-127.0 +/- 8.4 mg/kg, 2.1 +/- 0.0-191.4 +/- 1.1 mg/kg and 1.1 +/- 0.0-130.0 +/- 5.2 mg/kg. Amounts of formate, pyruvate, 3-hydroxy-2-butanone, ethanol and 2,3-butandiol of Lb. bulgaricus isolates were specified respectively as 0.2 +/- 0.0-57.0 +/- 1.0 mg/kg, 0.1 +/- 0.0-3.2 +/- 1.0 mg/kg, 0.1 +/- 0.1-77.0 +/- 2.0 mg/kg, 9.1 +/- 3.09-5.3 +/- 5.0 mg/kg and 6.2 +/- 0.2-98.4 +/- 2.0 mg/kg. Metabolites that determined quantified ranges in study, belong to subcultures of bacteria isolated from yoghurts fermented by traditional methods. These isolates have the potential to be a starter culture for commercial yogurt industry.
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