Influence of process variables on the drying kinetics and color properties of pear slices (Pyrus communis)

Abstract

In this work, the effect of drying conditions on pear slices' physicochemical properties was determined. The factors investigated were drying temperature, air velocity, and addition of ascorbic acid. An analysis of variance indicated that the factors affected (P ≤ .05) the response variables significantly. The lowest drying time resulted at 60 C, 3 m s −1 , at 0%, and 1% of ascorbic acid concentration. At these drying conditions, the final moisture content in pear samples was 0.14 g H 2 O g d s −1 . The water activity of the pear samples was in the range from 0.27 to 0.39. A low value of 6.36 of color difference was obtained at 50 C, 1 m s −1 , and 0% of ascorbic acid. During the drying process, the lightness in pear samples increases as the air velocity and the drying temperature increases. The highest hue values (from 54.66 to 63.27 ) resulted in dried pear samples without ascorbic acid; therefore, the dried pear slices tended to yellowness. Chroma results ranged from 19.51 to 21.41 and from 14.96 to 19.16 in pear slices with and without ascorbic acid. Therefore, the color of the pear slices resulted in grayish-yellow. An increment in sugar content was observed from an initial value of 18 Brix to values from 37.5 to 48.7 Brix. This behavior is because the sugar core is concentrated in large amounts during the drying process as the residual water content decreases.

Osmotic dehydration of cassava bagasse (Manihot esculenta) and its effect as pretreatment on the efficiency of convective drying

“…All of the above, added to the effects of environmental conditions, and even the experimental error can affect these results to a certain extent (Martínez, 2005;Novales, 2010). Similar results were observed when treating kosia pear slices, even with a greater effect of the concentration of osmotic agent, to such an extent that when they worked with an osmotic concentration of 75 % sucrose, the drying time of the samples was even longer than the time that the control sample required (Taşova et al, 2022;Domínguez-Niño et al, 2021). This is due to the fact that the particles of the osmotic agent adhere to the sample surface, forming a layer that delays the mass transfer during the convective drying operation, resulting in a decrease in the effectiveness of the latter.…”

Effect of osmotic dehydration pre‐treatments on physicochemical and energy parameters of Kosia (Nashi) pear slices dried in a convective oven

“…In these osmotic dehydration pre‐treatments, both sucrose rate and osmotic dehydration durations were at more moderate levels than the others and therefore an effect was observed which reduced the drying time. Domínguez‐Niño et al (2021) dried pear slices subjected to osmotic dehydration in 1% citric acid solution at 50 and 60°C drying temperatures and 1 and 3 m s −1 drying air speeds, and drying pre‐treatments were reported to have similar effects on pear slices.…”

Infrared drying of pear slices: Drying kinetics, energy, and exergy analysis

“…To measure the thickness and diameter of the slices, a Mitutoyo 500-174B digital caliper with a resolution of 0.01 mm (Mitutoyo, São Paulo, Brasil) was used. The thickness of the pear slices was chosen according to some previous studies for several products including some varieties of pear (Domínguez-Niño et al, 2021;Lutovska, Mitrevski, Pavkov, Mijakovski, & Radojcin, 2016;Sadin, Chegini, & Sadin, 2014;Salehi & Satorabi, 2021). The slices were placed in the dryer after it reached the desired temperature.…”