Effects of UV-C and Ultrasound Pre-Treatments on the Quality of Strawberry (Turkish with English Abstract)

Öz

Physicochemical and biological reactions occurring as a result of deterioration of strawberries lead to losses in texture, colour, aroma, flavour and vitamins. For this reason, various pre-treatments are applied to strawberries in order to increase their shelf life. In this study, effects of ultrasound (32 kHz; 20; 50 and 65 ºC) and UV-C (12.36 W/m2) treatments on quality properties of strawberry samples were investigated. Total mesophilic microorganisms count was used to determine microbial effectiveness of each method. UV-C was the most effective alternative method to maintain quality attributes of strawberries such as colour, texture, pH and anthocyanin amount, however it was identified that sufficient microbial inactivation could not be ensured using this technique. Although thermal ultrasonication was effective in microbial inactivation, it was observed that the technique caused colour denaturation and softening in the texture. It was determined that combined use of ultrasonic and thermal treatment, especially at 65 ºC, provided ultrasonic effect in addition to thermal effect on the microbial inactivation. In order to adapt an alternative technology to a commercial application the primary purpose is to ensure the highest degree of safety and to minimize changes in the desirable sensory qualities and nutritional value of the product. Combination of alternative methods may be an option to find the most suitable technique to be used at industrial scale.

Anahtar Kelimeler

• UV-C, ultrasound, strawberry, microbial inactivation　　

UV-C ve Ultrason Önişlemlerinin Çilek Kalitesi Üzetine Etkileri

Öz

Çilekte bozunma sonucu meydana gelen fizikokimyasal ve biyolojik reaksiyonlar doku, renk, aroma, tat ve vitamin kaybına neden olmaktadır. Bu nedenle çileklerin raf ömrünü arttırmak için çeşitli ön işlemler uygulanmaktadır. Bu çalışmada; çilek örneklerine uygulanan ultrason (32 kHz’de 20; 50 ve 65 ºC) ve UV-C (12.36 W/m2) uygulamalarının, çilek kalitesi üzerine etkileri araştırılmıştır. Uygulanan işlemlerin mikrobiyal açıdan etkinliğini saptamak için ise toplam mezofil mikroorganizmaların sayımına bakılmıştır. UV-C uygulamasının renk, doku, pH, antosiyanin miktarı gibi kalite özelliklerinin korunması açısından en etkili alternatif yöntem olduğu, ancak bu tekniğin mikrobiyal açıdan yeterli inaktivasyon sağlayamadığı belirlenmiştir. Isı uygulanarak yapılan ultrason işleminin ise mikrobiyal etkinliğe sahip olmasına rağmen renkte bozulma ve dokuda yumuşamaya neden olduğu gözlenmiştir. Isıtma ve ultrasonun birlikte kullanıldığı işlemin özellikle 65 °C’de, mikrobiyal inaktivasyon üzerine ısıl etkisinin yanı sıra ultrasonik etkisinin de olduğu saptanmıştır. Alternatif bir teknolojinin ticari kullanıma adapte edilebilmesi için temel amaç hem yüksek derecede güvenilirliğe sahip olması hem de duyusal ve besin içeriği açısından daha az değişime neden olmasıdır. Alternatif metotların kombinasyonları endüstriyel ölçekte en uygun tekniğin uygulanmasına olanak sağlayabilir.

Anahtar Kelimeler

• UV-C, ultrason, çilek, kalite, mikrobiyal inaktivasyon　　

Kaynakça

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