Use of Ultrasound in the Distilled Water Pretreament and Convective Drying of Pineapple

Journal of Food Processing and Preservation

Mendonça

2016

The kinetics of water loss (WL), solid gain (SG) and water activity (a w ) of the osmotic dehydration of sweet potato (Ipomoea batatas (L.)) slices were investigated. Three osmotic solutions, sucrose, sorbitol and fructose, were used with two different water activities, 0.900 and 0.940. The diffusivities of both water and solute were evaluated by using Crank's analytical solution to Fick's second law and according to the models of Azuara and Barbosa J unior et al. The shrinkage effect was considered to estimate the water and solid diffusion. A lower a w of the osmotic solutions resulted in higher mass transfer parameters (WL and SG) and a lower a w of the product. Sorbitol promoted higher WL and sorbitol and fructose, higher SG. The shrinkage was directly proportional to moisture reduction. Among the tested mathematical models, the Barbosa J unior et al. presented the best fit. The shrinkage resulted in lower water and solid diffusivity values. PRACTICAL APPLICATIONSBrazil is the largest producer of sweet potatoes (Ipomoea batatas (L.)) in Latin America. This root is considered as the fifth most important crop in developing countries. Like most vegetables, its shelf life is short and its storage is difficult. Therefore, improved techniques for conservation are welcome. Osmotic dehydration is a pretreatment process that provides partial water removal from a food product, with low energy consumption. In the literature, there are few studies on osmotic dehydration with nonionic agents and considering the shrinkage that occurs during the process in sweet potatoes. This study investigates the effects of different osmotic agents and water activities of osmotic solutions on the drying kinetics and effective diffusivities. The mathematical models provide information about the processes. Three different empirical models were employed and one approach investigates the shrinkage that occurs during the process.

Section: Methodsmentioning

confidence: 97%

“…(Corrêa, Rasia et al . )

t^{i}_{1 / n} = \frac{K^{i}_{1}}{K^{i}_{2}} (\sqrt{n} - 1)

where

K_{i}^{1}

and

K_{i}^{2}

are the modified Peleg's parameters (more details see in Barbosa Júnior et al . ).…”

Section: Methodsmentioning

confidence: 99%

Evaluation of the Shrinkage Effect on the Modeling Kinetics of Osmotic Dehydration of Sweet Potato (Ipomoea batatas (L.))

Junqueira

Journal of Food Processing and Preservation

Mendonça

2016

“…On the one hand, drying is a common method for food conservation (Silva and Corrêa ; Corrêa et al . ). On the other hand, exposure to high temperatures for long periods in the drying process decreases prebiotic, nutritional and sensory content in yacon (Lenart and Dabrowska ).…”

Section: Introductionmentioning

confidence: 97%

Mass Transfer Kinetics of the Osmotic Dehydration of Yacon Slices with Polyols

Mendonça

Journal of Food Processing and Preservation

Junqueira

et al. 2016

Osmotic dehydration using different polyols was studied. Yacon slices were immersed in solutions of xylitol, maltitol, erythritol, isomalt and sorbitol. The kinetics of solid gain (SG), water loss (WL) and water activity (aw) were evaluated (0, 10, 30, 45, 60, 90 and 120 min). The effective diffusion coefficients of water (Deffw) and solids (Deffs) were calculated with the models of Fick and Barbosa Júnior et al. At the end of the process, the highest SG was obtained with erythritol solutions; the lowest with sorbitol and maltitol and intermediate values of SG were acquired in osmotic processes with solutions of isomalt and xylitol. The samples treated in sorbitol, xylitol and erythritol solutions presented the highest Deffw and were more effective at increasing WL and reducing aw. The model of Barbosa Júnior et al. presented the best fitness. The Deffw/Deffs ratio showed better results for osmotic processes involving sorbitol and xylitol. Practical Applications Yacon tuber is typical from Latin America. It is considered an important source of fructooligosaccharides (FOS). This class of carbohydrate is employed on the control of diseases such as obesity and diabetes, due its low glycemic index. However, yacon roots are highly perishable and techniques for conservation are required. Osmotic dehydration is a pretreatment process that provides partial water removal from a food product, with low energy consumption. Polyols are widely employed as osmotic agents due their low caloric value. The kinetics of mass transfer on osmotic process are function of process variables, sample matrix characteristics, molecular weight of osmotic agents and others. This study investigate the water loss, solid gain, effective diffusivity and water activity of the OD of yacon with five different polyols and provide information about mass transfer kinetics of osmotic processes using two different empirical models.

“…The use of ultrasound is a promising technique for the purposes of improving mass transport, with its effects depending on the media in which it is propagated. Thus, in liquid media, the main effect is cavitation (Azoubel, Amorim, Oliveira, Maciel, & Rodrigues, 2015;Corrêa et al, 2016). The asymmetric implosions of bubbles produced close to the solid surface can generate microjets in the direction of the surface and intense micro stirring at the interface (Ozuna, Puig, García-Pérez, & Cárcel, 2014b).…”

Section: Introductionmentioning

confidence: 99%

Influence of ultrasound application on both the osmotic pretreatment and subsequent convective drying of pineapple (Ananas comosus)

Innovative Food Science & Emerging Technologies

Rasia

Mulet

et al. 2017

Correa, J.; Rasía, M.; Mulet Pons, A.; Carcel Carrión, JA. (2017). Influence of ultrasound application on both the osmotic pretreatment and subsequent convective drying of pineapple (Ananas comosus). AbstractUltrasound application represents an alternative means of improving heat and mass transfer. This study explored the combined application of ultrasound (US) during both the osmotic dehydration (OD) pretreatment and the convective drying of pineapple. For that purpose, fresh and pretreated samples (20 or 40 min, with (55.5 kW/m 3 , 40 kHz) and without ultrasound application) in an osmotic solution of sucrose (40 % w/w) were dried (40 ºC and 70 ºC) with (21.8 kHz, 31 kW/m 3 ) and without ultrasound application.A diffusion model permitted to quantify the influence of the factors studied (time of pretreatment, ultrasound application during pretreatment, drying temperature and ultrasound application during drying) in drying kinetics. The increase in drying temperature and the application of ultrasound during drying significantly accelerated the drying process by reducing both the internal and the external mass transport resistance.On the contrary, the osmotic pretreatments reduced the drying rate by increasing the external resistance.