EFFECT OF CONVENTIONAL AND FREEZE DRYING METHODS ON SOME QUALITY PROPERTIES OF WATERMELON

Abstract

In this study, water melons dried with two different methods (conventional (70 ^oC) and freeze-drying (66 ^oC-5 mtorr)) were compared by physical, chemical and sensorial properties of them. To determine the effect of drying methods on pH, titration acidity, color, total dry matter, water activity, total carotenoid contents, lycopene, β-carotene, hydroxymethylfurfural (HMF), ascorbic acid and sensorial evolution of dried watermelon samples were carried out. While HMF formation in conventional-dried samples were higher than freeze drying samples, lycopene degradation of freeze-dried samples were higher than conventional dried samples. The color values of L* and Hue* of the freeze-dried samples increased, but a* value decreased. In addition, according to the color values of fresh watermelon sample, the highest color changing (∆E*) was determined for freeze-dried samples. The total carotenoid contents of conventional-dried samples were determined higher (284.33 mg/kg-higher 5.30 times) than freeze-dried samples. While ascorbic acid contents of the conventional-dried samples were decreasing (9.63 mg/kg-lower 3.38 times), the freeze-dried samples were increasing (245.13 mg/kg- higher 7.51 times) according to the fresh watermelon samples. According to sensorial evaluation of dried watermelon samples, the highest color score obtained for conventional-dried, while the highest taste score obtained for freeze-dried.

Keywords

• Dried watermelon,conventional and freeze drying,Lycopene and β-carotene,total carotenoid,HMF,ascorbic acid

KONVEKSİYONEL VE DONDURARAK KURUTMA YÖNTEMLERİNİN KARPUZUN BAZI KALİTE ÖZELLİKLERİNE ETKİSİ

Abstract

Bu araştırmada iki farklı kurutma yöntemi (konveksiyonel (70 ^oC) ve dondurarak kurutma (-66 °C’de 5 mtorr basınçta)  ile kurutulan karpuzların fiziksel, kimyasal ve duyusal özellikleri karşılaştırılmıştır. Üretim yöntemlerinin kurutulmuş karpuz üzerindeki etkisini belirlemek amacıyla pH, titrasyon asitliği, renk, toplam kurumadde, su aktivitesi, toplam karotenoid miktarı, likopen, β-karoten, hidroksimetilfurfural (HMF), askorbik asit içeriği ve duyusal değerlendirilmesi yapılmıştır. Konveksiyonel kurutulmuş karpuzlarda daha fazla HMF oluşurken dondurularak kurutulanlarda ise likopen içeriğinde daha fazla azalmalar tespit edilmiştir. Dondurularak kurutulan örneklerin ölçülen renk değerlerinden L* ve Hue* değerleri artmış, a* değeri azalmış ve tazelerine göre en çok renk değişimi (∆E*) dondurularak kurutulmuş örneklerde görülmüştür.  Konveksiyonel kurutulmuş örneklerin toplam karotenoid içerikleri tazeye göre daha yüksek (284.43 mg/kg-5.30 kat fazla), askorbik asit içerikleri ise tazelerine göre daha az (9.63 mg/kg-3.38 katı azalma) tespit edilmiştir. Dondurularak kurutulmuş örneklerde ise, askorbik asit değeri tazeye göre daha yüksek (245.13 mg/kg-7.51 katı artış) belirlenmiştir. Kurutulmuş karpuzların duyusal değerlendirmesinde renk bakımından konveksiyonel kurutulmuş örnekler yüksek puan alırken, tat bakımından en yüksek beğeniyi dondurularak kurutulan örnekler almıştır. 

Keywords

• Kurutulmuş karpuz,kjonveksiyonel ve dondurarak kurutma,likopen ve β-Karoten,toplam karotenoid,HMF,askorbik asit

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