Osmotic Dehydration and Freezing as Combined Processes on Apple Preservation

Abstract

Combined processes effects of osmotic dehydration in sucrose solutions and freezing on apple cubes preservation were analysed. Two multifactorial experimental designs, in two levels, were conducted consecutively to quantify the effects of the following factors: temperature, osmotic dehydration time, concentration of the osmotic medium and freezing rate. The response variables considered were: sensory evaluation, colour, texture, water activity ( aw) and reducing and total sugars. The first experimental design selected fast freezing as the best process to preserve texture and colour of the fruit. From the second experimental design, under fast freezing, were obtained the following optimal levels: 55 ºBx for the concentration of the osmotic medium, 35 ºC for the syrup temperature and 60 min for the osmotic dehydration time. A test of acceptability was performed under these conditions with 80 potential consumers on a 7-point hedonic scale, which gave 93% acceptance. Glass transition temperature (Tg') of the maximally cryoconcentrated liquid was –41.89 ºC for the product processed under optimum conditions. Significant correlations ( P= 0.05) were found between sensory and instrumental responses.

Influence of ultrasound pretreatments on diffusion coefficients, texture and colour of osmodehydrated sweet potato (Ipomea batatas)

“…Several works have been carried out on the osmotic dehydration of fruit and vegetables such as pepper (Chenlo, 2006), apple , carrot (Singh et al, 2006), potato (Eren & Kaymak-Ertekin, 2007) and strawberry (Taiwo et al, 2003). It has also been discovered that ultrasound influences the water diffusivity, drying time, water activity and rehydration ratio of fruit and vegetables (C arcel et al, 2007;Kowalski & Szadzi nska, 2014). Ultrasound frequency of 20 kHz and above has an alternative expansion and compression effect on the solid sample which enhances the removal of water from the sample (McClements, 1995;Fernandes et al, 2008).…”

Freezing protocol effect on quality properties of fruit tissue according to the fruit, the variety and the stage of maturity

“…Some authors (Marin, Cano, & Fuster, 1992;Moraga, Martinez-Navarrete, & Chiralt, 2006;Skrede, 1996) have investigated chemical modifications during freezing which are responsible for pH, soluble solid, water content or color changes of frozen/thawed fruits. However, only a few authors have studied physical and chemical changes related to frozen fruit quality after freezing and only for one fruit category at a time: apples (Bunger, Moyano, Vega, Guerrero, & Osorio, 2004), mangoes (Botosoa, Chapleau, & Le-Bail, 2004) and raspberries (González, de Ancos, & Cano, 2002). Moreover, since freezing conditions were generally different and rarely characterized, it was difficult to compare the freezing effects.…”

Freezing time prediction for partially dried papaya puree with infinite cylinder geometry

“…Dermesonlouoglou et al (2007) have shown that the quality of frozen tomato can significantly be improved by osmotic dehydration as a prefreezing treatment. Bunger et al (2004) have considered osmotic dehydration of apple cubes prior to freezing. Dehydrofrozen apple cubes obtained high scores from potential customers.…”