Kaymaklı yoğurt yüzeylerine sürekli sistemde UV ışık uygulamasının ürün kalitesi üzerine etkilerinin belirlenmesi
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Dosyalar
Tarih
2019
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Ege Üniversitesi, Fen Bilimleri Enstitüsü
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Kaymaklı yoğurt ülkemizde geleneksel olarak üretilen ve sevilerek tüketilen bir süt ürünüdür. Kaymaklı yoğurdun geleneksel üretiminde kaymak tabakasının oluşumu için, sütün yaklaşık 70-80oC'de ambalajlara dolumu gerçekleştirilmekte ve aşılama sıcaklığına kadar ağzı açık olarak bekletilmektedir. Bu aşamada örneklere mikroorganizma bulaşma riski artmakta ve yüzeyde küf gelişimi depolama sırasında daha kısa sürede meydana gelebilmektedir. Küf gelişimini engellemek amacıyla koruyucular yasal olarak kullanılamamaktadır ve son ürün kontaminasyonlarında ısıl işlem uygulanamamaktadır. Bu sebeple, kaymaklı yoğurt üretiminde süre gelen bu problemi engellemek amacıyla kaymaklı yoğurt yüzeylerine özel dizayn edilen sürekli sistemde farklı dozlarda UV-C ışık uygulaması yapılmıştır. UV ışık uygulaması küf inaktivasyonunun yanı sıra ürün kalitesinde bazı değişikliklere sebebiyet verebilmektedir. Çalışma kapsamında, kaymaklı yoğurt yüzeylerine farklı dozlarda sürekli sistemde UV ışık uygulamasının kaymaklı yoğurt yüzeylerinde meydana getirebileceği kalite değişimleri belirlenmiştir. Özel olarak dizayn edilen (UV STR400, UV RND, İzmir, Türkiye) sürekli UV sistemi kullanılarak kaymaklı yoğurt yüzeylerine 7.5 ve 20 cm olmak üzere iki farklı yükseklikten, 0.2,0.4,0.8,1.6,2.4,3.2,4 m/dk olmak üzere yedi farklı bant hızında ve 0.855-26.732 kJ/m2 doz aralığında UV-C ışık uygulanmıştır. UV ışık uygulanmamış olan kontrol gurubu da kullanılmıştır. UV-C ışık uygulamasından sonra örneklerin kurumadde, protein, yağ, kül, sertlik indeksi, pH ve asitlik değerleri, lipid oksidasyon seviyeleri (tiyobarbitürik asit reaktif maddelerin değerleri ve peroksit değeri), renk değerleri ve duyusal özellikleri belirlenmiştir. Yapılan analizler sonucunda UV-C ışık uygulamasının kaymaklı yoğurt örneklerinin bileşimini, sertlik indeksi değerlerini, pH ve asitlik değerlerini etkilemediği tespit edilmiştir. Buna karşın, UV-C ışık dozunun artması, lipid oksidasyon seviyesini arttırmış, renk değerlerinde değişikler meydana getirmiştir. Ayrıca, duyusal değerlendirme sonuçlarına göre, yüksek UV-C dozlarında ( ≥ 4.427 kJ/m2), giderek artan yabancı lezzet tespit edilmiş ve buna bağlı olarak tüm izlenim puanlarında düşüş meydana gelmiştir. 7,5 ve 20 cm yükseklik ve 1.6 m/dk ve daha yavaş bant hızlarında ( ≥ 2.174 kJ/m2) UV ışık uygulamasında kabul edilebilir duyusal özellikler göstermiştir. Bu nedenle, 20 cm yükseklikten, 0.8, 1.6, 2.4 m/dk bant hızlarında ve 1.451, 2.174 ve 4.427 kJ/m2 dozlarında UV ışık uygulanan örnekler ve kontrol grubu örneği 30 gün boyunca depolanmıştır. Depolama süresince örneklerin pH ve titrasyon asitliği değerleri UV uygulamasından bağımsız olarak artmış, yüksek UV dozları uygulanmış örneklerde depolamada lipid oksidasyon düzeyi daha fazla artmıştır. Sertlik indeksi ve renk değerlerinde ise depolama süresince değişim gözlenmemiştir. Ayrıca depolama süresince örnekler izlenmiş ve 14. günden itibaren kontrol örneklerinde küflenmenin meydana geldiği ve depolama süresince küf gelişiminin artmaya devam ettiği belirlenmiştir. Ancak UV uygulanan örneklerde görsel olarak küf gelişimi daha geç gerçekleşmiştir. Çalışma sonucunda UV ışık uygulamasında uygulanan dozun oldukça önemli olduğu ve doza bağlı olarak üründe bazı kalite değişimlerinin meydana gelebileceği belirtilmiştir. Özellikle doz artışına bağlı olarak yabancı lezzet algısı artmakta ve bu da ürünün tüketilebilirliğini azaltmaktadır. UV ışık uygulamasının mikrofloraya olan etkilerinin araştırıldığı çalışmalarda mutlaka kalite özellikleri üzerine olan etkileri de değerlendirilmeli her iki çalışma birlikte yürütülmelidir.
Yoghurt with surface cream is a dairy product that is traditionally produced and mostly consumed in our country. In the traditional production of yoghurt with surface cream, the milk is filled into packages at approximately 70-80oC for the formation of the cream layer and kept open until the inoculation temperature at this stage, the risk of microorganism contamination of the samples increases and mold growth on the surface may occur during storage in a shorter period of time. Preservatives cannot be used legally to prevent mold growth and heat treatment cannot be applied to eliminate the contamination of the end product. For this reason, in order to prevent this problem in the production of yoghurt with surface cream, different doses of UV-C light using continuous system were applied to the surfaces of yogurt with surface cream in this study. However, UV light application can cause some changes in the product quality. Within the scope of this study, it was determined that the quality changes that may occur on the yogurt with surface cream surfaces by applying UV light at different doses to the yogurt with surface cream surfaces. UV-C light was applied to the surface of the yoghurt with surface cream at two different heights of 7.5 and 20 cm, seven different band speeds of 0.2,0.4,0.8, 1.6, 2.4, 4.2, 4 m/min and 0.855-26.732 kJ/m2 in the döşe range by using the specially designed continuous UV system (UV STR400, UV RND, Izmir, Turkey). The control group without treated with UV light was also used. After UV-C light application, dry matter, protein, fat and ash contents, hardness index, pH and acidity values, lipid oxidation levels (thiobarbituric acid reactive substances values and peroxide value), color and sensory properties of the samples were determined. As a result of the analysis, it was found that UV-C light application did not affect the composition, hardness index, pH and acidity values of yoghurt samples. However, increasing UV-C light dose caused an increase in lipid oxidation level and some changes in color values. In addition, according to sensory evaluation results, foreign flavor was perceived at high UV-C doses (≥ 4.427 kJ/m2) resulting in a decrease in total impression scores. UV light applied from 7.5 and 20 cm height and at 1.6 m/min and slower band speeds ( ≥ 2.174 kJ/m2) resulted in acceptable sensory properties. The samples exposed to UV light from 20 cm height, 0.8, 1.6, 2.4 m/min band speeds and 1.451, 2.174, 4.427 kJ/m2 doses and also control samples were stored for 30 days. During storage, pH and titratable acidity values of the samples increased independent of UV light application. The lipid oxidation levels of the samples exposed to high UV light doses increased during storage period. Also, hardness index and color values did not significanlty change during storage. In addition, mold and yeast growth on the surface of samples were observed during storage. Also, samples were monitored during storage and mold growth was observed in control samples starting from the 14th day and mold growth continued to increase during storage However, mold growth was observed later days in UV treated samples. As a result of the study, it is stated that the doses applied in UV light treatment is very important and some quality changes can be occured in the product depending on the applied doses. Particularly, the perception of foreign flavor would increase due to high UV light doses thus resulting a decrease in the acceptibility of the product. In the future, the researches which will be focused on the effects of the UV light on the microflora should be carried out with the quality changes and both microbiological and quality studies should be considered together for the evaluation of light effects.
Yoghurt with surface cream is a dairy product that is traditionally produced and mostly consumed in our country. In the traditional production of yoghurt with surface cream, the milk is filled into packages at approximately 70-80oC for the formation of the cream layer and kept open until the inoculation temperature at this stage, the risk of microorganism contamination of the samples increases and mold growth on the surface may occur during storage in a shorter period of time. Preservatives cannot be used legally to prevent mold growth and heat treatment cannot be applied to eliminate the contamination of the end product. For this reason, in order to prevent this problem in the production of yoghurt with surface cream, different doses of UV-C light using continuous system were applied to the surfaces of yogurt with surface cream in this study. However, UV light application can cause some changes in the product quality. Within the scope of this study, it was determined that the quality changes that may occur on the yogurt with surface cream surfaces by applying UV light at different doses to the yogurt with surface cream surfaces. UV-C light was applied to the surface of the yoghurt with surface cream at two different heights of 7.5 and 20 cm, seven different band speeds of 0.2,0.4,0.8, 1.6, 2.4, 4.2, 4 m/min and 0.855-26.732 kJ/m2 in the döşe range by using the specially designed continuous UV system (UV STR400, UV RND, Izmir, Turkey). The control group without treated with UV light was also used. After UV-C light application, dry matter, protein, fat and ash contents, hardness index, pH and acidity values, lipid oxidation levels (thiobarbituric acid reactive substances values and peroxide value), color and sensory properties of the samples were determined. As a result of the analysis, it was found that UV-C light application did not affect the composition, hardness index, pH and acidity values of yoghurt samples. However, increasing UV-C light dose caused an increase in lipid oxidation level and some changes in color values. In addition, according to sensory evaluation results, foreign flavor was perceived at high UV-C doses (≥ 4.427 kJ/m2) resulting in a decrease in total impression scores. UV light applied from 7.5 and 20 cm height and at 1.6 m/min and slower band speeds ( ≥ 2.174 kJ/m2) resulted in acceptable sensory properties. The samples exposed to UV light from 20 cm height, 0.8, 1.6, 2.4 m/min band speeds and 1.451, 2.174, 4.427 kJ/m2 doses and also control samples were stored for 30 days. During storage, pH and titratable acidity values of the samples increased independent of UV light application. The lipid oxidation levels of the samples exposed to high UV light doses increased during storage period. Also, hardness index and color values did not significanlty change during storage. In addition, mold and yeast growth on the surface of samples were observed during storage. Also, samples were monitored during storage and mold growth was observed in control samples starting from the 14th day and mold growth continued to increase during storage However, mold growth was observed later days in UV treated samples. As a result of the study, it is stated that the doses applied in UV light treatment is very important and some quality changes can be occured in the product depending on the applied doses. Particularly, the perception of foreign flavor would increase due to high UV light doses thus resulting a decrease in the acceptibility of the product. In the future, the researches which will be focused on the effects of the UV light on the microflora should be carried out with the quality changes and both microbiological and quality studies should be considered together for the evaluation of light effects.
Açıklama
Anahtar Kelimeler
UV-C Işık, Kaymaklı Yoğurt, Lipit Oksidasyonu, Duyusal Özellikler, UV-C Light, Yoghurt With Surfacecream, Lipid Oxidation, Sensoryproperties
