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    Comparison of pistachio (Pistacia vera L.) kernel volatile compounds of Siirt, Uzun and Kirmizi grown in Turkey: Effect of traditional and industrial in-shell roasting
    (Wiley, 2022) Guler, Zehra; Dursun, Ahmet; Turkmen, Dilek
    The aim of this study was to compare pistachio (Pistacia vera L.) kernel volatile compounds (VCs) of Siirt, Uzun and Kirmizi cultivars grown in Turkey, and also to determine the effects of traditional and industrial in-shell roasting. The VCs were analyzed by using solid phase microextraction and gas chromatography-mass spectrometry. Regardless of cultivar, a total of 36, 55, and 65 VCs were identified in raw, industrial and traditional roasted pistachios, respectively. Limonene was the major terpene and the most important volatile compound in Siirt and alpha-pinene in raw Kirmizi and Uzun but alpha-terpinolene in their roasted counterparts. The heterocyclic and phenolic compounds reached a maximum in all three cultivars in traditional roasting compared to industrial roasting. Discriminant analysis based on volatile compounds classified the pistachios according to the roasting methods rather than cultivars. Kirmizi may be the most promising cultivar for traditional roasting regarding its highest pyrazine content. Practical Applications The main object of the present study was to determine and compare volatile compounds (VCs) in three different pistachio (Pistacia vera L.) cultivars (Siirt, Uzun and Kirmizi) that are raw (not roasted), industrial and traditional roasted in-shell. They are the main cultivars grown in Turkey. VCs from kernels were analyzed by using solid phase micro-extraction and gas chromatography-mass spectrometry. VC profile and its abundance were dependent on both roasting methods and cultivar. Pyrrole, pyrazine and furan compounds were emerged by the roasting process. Pyrroles were higher than pyrazines in industrial roasting, with exception of Kirmizi but pyrazines were the highest heterocyclic compounds in traditional one, even being the dominant VC group in Siirt and Kirmizi. Roasting process was a crucial factor for pyrazines, pyrroles, furans, phenolic compounds and also terpenes in Siirt, Uzun and Kirmizi pistachios. Kirmizi may be the most promising cultivar for traditional roasting regarding its highest pyrazine content.
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    Different scalding duration in hot whey influencing chemical, biochemical, physical, microstructural, textural and sensorial characteristics of brine-type cheese
    (Elsevier, 2021) Guler, Zehra; Turkmen, Dilek; Dursun, Ahmet
    The effects of curd scalding duration on chemical, biochemical, color, textural, microstructural and sensorial characteristics of a brine-type cheese were examined. The cheeses that were characterized by the scalding of curd in hot whey (60 degrees C) and brining in whey were manufactured from raw cows' milk and the curds were scalded for 10, 20 or 30 min. Regardless of cheese ripening time, increased scalding duration resulted in decreased moisture, titratable acidity, lactic acid, ethanol, whitening index and h degrees values. The images obtained by scanning electron microscopy of the cheeses were clearly different each other. At the end of ripening, cheeses from curds scalded for up to 20 min had the highest water-soluble nitrogen, 2-phenylethyl acetate, acetic acid, chewiness, gumminess and hardness levels, and overall acceptability scores. In conclusion, scalding of curd in whey up to 20 min at 60 degrees C gave satisfactory results in terms of quality parameters of the present cheeses.
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    Effect of harvest maturity on volatile compounds profiling and eating quality of hawthorn (Crataegus azarolus L.) fruit
    (Elsevier, 2021) Dursun, Ahmet; Caliskan, Oguzhan; Guler, Zehra; Bayazit, Safder; Turkmen, Dilek; Gunduz, Kazim
    The effect of maturity stage on fruit quality characteristics, sensory attributes and volatile composition was investigated in the most important hawthorn cultivar (Sultan). The fruit skin color was used as the maturity index for the classification of hawthorn considering their maturity stages as immature (green), mature (green-yellow) and over mature (yellow). The volatile organic compounds (VOCs) of hawthorn fruit at each maturity stage were analyzed by solid-phase micro-extraction (SPME) and gas chromatography-mass spectrometry (GC-MS). The results indicated that the quality traits of the Sultan cultivar were affected by the maturity stage. From immature to over mature stages, firmness and titratable acidity decreased whereas fruit size (weight, diameter and length), edible fruit ratio, pH and esters (butyl and hexyl hexanoates, hexyl and cis-3-hexenyl acetates) increased in Sultan cultivar. The highest amount of esters along with the occurrence of butyl butanoate was observed in over mature fruit in comparison with immature and mature ones. PCA analysis of volatile organic compounds separated successfully hawthorn fruit according to the maturity stages. The results showed that mature and over mature fruit were more preferred by panelists. Those fruit had the highest level of esters being responsible for strong fruit flavor, along with low pH and low fruit firmness compared to immature ones.
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    Influence of chymosin type and brine concentration on chemical composition, texture, microstructural and colour properties of Turkish white cheeses
    (Elsevier Sci Ltd, 2022) Turkmen, Dilek; Guler, Zehra
    The effects of chymosin type and brine concentration on chemical composition, texture, microstructure and colour of white cheese were studied during ripening. The cheeses were manufactured from cows' milk using microbial rennet (Rhizomucor miehei), commercial calf rennet or recombinant chymosin (Kluyveromyces lactis), and ripened in whey brines containing 10% or 12% NaCl. Increasing the brine concentration increased the ratio of salt to moisture, hardness, gumminess, chewiness and whiteness values of cheeses and decreased the moisture, the ratio of moisture to protein and extent of proteolysis. The similar trends were observed in cheeses with microbial rennet compared with those with calf rennet or recombinant chymosin. pH values of all the cheeses unchanged during ripening but their brine pHs increased. A marked effect of rennet type on microstructure of the cheeses was visualised. In microbial rennet cheese brine salt content can be reducible to obtain satisfactory results in terms of quality parameters. (C) 2022 Elsevier Ltd. All rights reserved.