TAILIEUCHUNG - Kinetics of nonenzymatic browning reaction in citrus juice concentrates during storage

The kinetics of nonenzymatic browning in citrus juice concentrates (orange, lemon, grapefruit and tangerine) during 8 weeks of storage at 28, 37 and 45 ºC were investigated. Browning development was followed by measuring absorbance at 420 nm (A420) and using CIE-Lab color system. | Turk J Agric For 27 (2003) 353-360 © TÜB‹TAK Kinetics of Nonenzymatic Browning Reaction in Citrus Juice Concentrates during Storage Nuray KOCA, Hande SELEN BURDURLU, Feryal KARADEN‹Z* Ankara University, Faculty of Agriculture, Department of Food Engineering, D›flkap› 06110 Ankara - TURKEY Received: Abstract: The kinetics of nonenzymatic browning in citrus juice concentrates (orange, lemon, grapefruit and tangerine) during 8 weeks of storage at 28, 37 and 45 ºC were investigated. Browning development was followed by measuring absorbance at 420 nm (A420) and using CIE-Lab color system. Analysis of kinetic data from A420 values suggested a zero-order reaction for nonenzymatic browning, while changes in L* and b* parameters followed a first-order reaction. Activation energy for nonenzymatic browning determined by A420 values ranged from to kcal mol-1, while those for L* and b* parameters were kcal mol-1 and kcal mol-1, respectively. Activation energies were higher in orange ( kcal mol-1) and tangerine ( kcal mol-1) juice concentrates than those in grapefruit ( kcal mol-1) and lemon ( kcal mol-1) juice concentrates. The lower activation energies determined for grapefruit and lemon juice concentrates indicated that nonenzymatic browning reactions are favored in these samples. Key Words: Citrus juice concentrate, nonenzymatic browning, color, storage, kinetic Turunçgil Suyu Konsantrelerinin Depolanmas›nda Enzimatik Olmayan Esmerleflme Reaksiyon Kineti¤i Özet: 28, 37 ve 45 °C’de 8 haftal›k bir depolama süresince turunçgil suyu konsantrelerinde (portakal, limon, greypfrut ve mandarin) enzimatik olmayan esmerleflme kineti¤i incelenmifltir. Esmerleflme, 420 nm’de absorbans ölçülerek ve CIE-Lab renk sistemi kullan›larak izlenmifltir. L* ve b* parametrelerindeki de¤iflim birinci dereceden bir reaksiyon izlemekteyken, A420 de¤erlerine ait kinetik veri analizi s›f›r›nc› dereceden bir .

• Nông nghiệp
• Citrus juice concentrate
• Nonenzymatic browning
• CIE Lab color system
• Liquid model systems
• Grapefruit and tangerine