0139–3006/$ 20.00 © 2016 Akadémiai Kiadó, Budapest Acta Alimentaria, Vol. 45 (1), pp. 119–128 (2016) DOI: 10.1556/066.2016.45.1.15 EFFECT OF COATING CONCENTRATION AND COMBINED OSMOTIC AND HOT-AIR DEHYDRATION ON SOME PHYSICO- CHEMICAL, TEXTURAL AND SENSORY PROPERTIES OF APPLE SLABS M. TAGHIZADEH*, M. FATHI and A.L. SAJJADI Department of Food Science and Technology, Ferdowsi University of Mashhad (FUM), P.O. Box: 91775-1163, Mashhad. Iran (Received: 11 February 2015; accepted: 26 May 2015) In a 120 min osmotic dehydration procedure followed by an air drying process, the effect of carboxy-methyl cellulose (CMC) on some qualitative characteristics of apple slabs including browning index (BI) and rehydration capacity were studied. Moreover, the relation between textural and sensory properties, such as hardness, cohesiveness, springiness, adhesiveness and chewiness, was investigated. Samples containing higher coating concentrations (1– 1.5%) showed higher rehydration capacity and lower browning index compared to those with lower coating concentrations (0.25–0.5%). Weibull distribution model was used to investigate the effect of coating concentration on drying kinetics. The results of sensory tests showed that the overall acceptance of samples is increased with decreasing coating concentration, and an appropriate correlation was found between sensory properties and textural parameters. Keywords: coating, osmotic dehydration, air drying, texture profile analysis, sensory characteristics Osmotic dehydration is based on the fact that the immersion of a product in a hypertonic solution with low water activity and high osmotic pressure leads to the replacement of the inner product water with the surrounding solute (JALAEE et al., 2011). During osmotic dehydration three flows occur, from which two are of more significance. The first one is the moisture flow from sample to osmotic solution and the second one is the flow of solute into sample, which occurs in the opposite direction. The third type of flow, however, is the flow of components, such as vitamins, saccharides, minerals, and flavour agents, into the solution (KHIN et al., 2005). In this study, four different concentrations of carboxy-methyl cellulose (CMC) including 0.25%, 0.5%, 1%, and 1.5% were used as coating material. The effect of CMC concentration on different physico-chemical properties of apple slab, including browning index (BI), rehydration capacity (RC), as well as some textural and sensory properties, were investigated. Furthermore, kinetic of colour change during air drying was taken into account as a function of CMC concentration. * To whom correspondence should be addressed. Phone: +98-38805755; fax: +98-38805755; e-mail: mtaghizadeh@um.ac.ir