Chemical versus infrared spectroscopic measurements of quality attributes of sun or oven dried fruit leathers from apple, plum and apple-plum mixture

Abstract

This study tested the effect of convective and sun drying on quality parameters of apple, plum and a blend of apple and plum (50:50, w/w) leathers. Moreover, physical, sensory and chemical attributes determined by chemical methods were compared with an infrared spectroscopic method. All products had optimum values of L* (brightness), huge angle and chroma within naturally occurrence range. Convective drying significantly (P < 0.05) caused reduced L* and huge angle and increased chroma, only in plum leather. All products have high general acceptability, while the texture of apple leather was highly preferable. Convective drying lead to significantly decreased dry matter, brix, pH and titratable acidity (TA) and increased aw, total phenolic compound (TPC) and antioxidant capacity (AOC), particularly for plum leather. An overall increase of 10–25% in AOC is found valuable. Peak absorbance values at a band of 1800 to 800 cm−1 in infrared spectra were significantly correlated with TA, pH, TPC and AOC contents. Having compared with chemical methods, infrared spectroscopic method with higher coefficient of determinant, precision and ratio of prediction determinant values as well as lower bias and RMSEP values is recommended for a robust and fast determination of physico-chemical attributes in fruit leather production.