Osmotic Dehydration Of Pineapple Research Articles

Sucrose syrup reuse during one‐ and multi‐stage osmotic dehydration of pineapple

AbstractMulti‐stage osmotic dehydration of pineapple with sucrose syrups in gradually increasing concentration was experimentally evaluated and compared to the single‐stage dehydration process. Also, osmotic solutions were reused for five osmotic dehydration cycles, without syrup reconditioning treatment. Single‐ and multi‐stage osmotic treatments were carried out for 2 hr at 40°C. Changes in pH, total acidity, and content of soluble solids, water, and ascorbic acid, in fruit and osmotic solutions, were analyzed. Water loss decreased with cycles of syrup reuse in one‐stage treatments and remained almost unchanged in multi‐stage treatments. Dry matter content of pineapple fruit during four‐stage osmotic dehydration cascade (40, 50, 55, and 60 °Bx) was increased respect to one‐stage dehydration at 40 and 60 °Bx. With regard to retention of syrup characteristics, multi‐stage dehydration reached a better performance as compared with the single‐stage dehydration and through the syrup reuse could become a more economical, environmentally friendly process.Practical applicationsOsmotic dehydration allows to reduce the fruit water content with energy saving and conservation of fruit characteristics, but also involves some negative aspects. Syrup management is usually the most important technological problem in the osmotic dehydration process on an industrial scale. Osmotic solution recycling could contribute to the solution of this problem. In this study, the effectiveness of pineapple osmotic dehydration in multi‐stage and single‐stage, with syrup reuse, were compared. The research show: (1) multi‐stage treatment was the most effective for the retention of syrup properties; (2) syrup reuse did not affect the dehydrated pineapple characteristics through multi‐stage dehydration. Thus, results indicated the proposed dehydration operation is of easy implementation, economically and environmentally friendly.

Mechanical and osmotic dehydration behavior of pineapple and retention of Vitamin C

The study was designed to observe the behavior of mechanical and osmotic dehydration of pineapple, retention of vitamin C content during drying and development of jam from fresh and dehydrated pineapple. Osmotic dehydration carried out with pineapples collected from local market of Mymensingh in July 2015 and found that pineapples contained higher moisture content (93.9%,wb) than normal (85-87%,wb) and showed contradictory osmotic behavior due to higher moisture content and hormonal effect. Then the studies were conducted using pineapples of Gaint Kew variety collected from Madhupur without hormone treatment which contained 86.11% moisture, 0.36% ash, 13.89% total solid, 0.54% protein and 17.38mg/100g vitamin C. The osmotic concentration behavior was investigated using sugar and combined sugar-salt solution for 6mm thick pineapple slices and immersion time was 6 hrs. The extent of water loss, solid gain and normalized solid content were strongly influenced by strength of osmotic solution. It was found that K-value (mass transfer coefficient) increases with increasing concentration and was the highest (0.15min-1) for 55/5% sugar/salt solution and lowest (0.07min-1) for 45% sugar solution. Three different temperatures (55, 60 and 65°C) and thicknesses (4, 6 and 8mm) were used to investigate the drying behavior of pineapple slices in a mechanical dryer. Activation energy value of 8.14 Kcal/g-mole was found for fresh pineapple slices. 55/5% sugar/salt osmosed and dried pineapple gave 5.46 times higher dryer throughput compared to nonosmosed dried pineapple. Degradation of vitamin C content of pineapple at different air-dry bulb temperatures (55, 60 and 65°C) of 6mm thickness was investigated and activation energy for degradation of vitamin C was found to be 14.38 Kcal/g-mole. Osmotic dehydration prior to air drying, gave the lower rate of degradation of vitamin C during drying compared to that dried without osmosis. Developed jams were tested for their acceptability by sensory evaluation using 1-9 point hedonic scale and jam made from osmotically dehydrated (55/5% sugar-salt and then dried at 60°C) secured highest score (8.5) and ranked as “like very much”, while the other products were ranked as “like moderately”.

Osmotic Dehydration of Pineapple Stems in Hypertonic Sucrose Solutions

The present study provides the evaluation in the influence of the variables: temperature (T), concentration of the osmotic solution (C) and ratio of fruit and osmotic solution (F:OS) during the osmotic dehydration of slices of pineapple stem variety Perola, on the responses: water loss (WL), mass loss (ML), gain of solids (GS) and ratio of gain of solids and water loss (GS/WL). The centesimal composition was determined both in the raw material and in the dehydrated product. To optmize the process, the studied factors were: temperature (T), with factorial points -1 equal to 30°C and +1 equal to 50°C; concentration of sucrose solution (C), with factorial points -1 equal to 40 g·100 g-1 and +1 equal to 60 g·100 g-1 and ratio of fruit and osmotic dehydration solution (F:OS), with factorial points -1 and +1 equal to 1:20 and 3:20, respectively. In all essays, the dehydration time was 4 hours. The essays showed that F:OS was not significant in any responses; the models adopted were predictive and fitted for WL and ML, and reasonable for GS and GS/WL. The temperature was the most significant variable in the process; the optimized values were: T= 50°C, C = 40 g 100 g-1 e F:OS = 3:20. The product needs a complementary drying to adapt itself to the legislation demands.

Osmotic Dehydration of Pineapple with Sucrose: Mass Transfer Kinetics

Osmotic dehydration of pineapple (Ananas comosus Linn.) slices (6, 9 and 12 mm) was carried out using aqueous solutions of sucrose of different concentrations (40, 50 and 60 % w/w) as osmotic media, at various fruit to solution ratios (1:2, 1:4 and 1:6). Total mass, water loss, solute gain and moisture content were determined for each sample at different time intervals (up to 6 h) of contact with the osmotic media. Regression analysis revealed that the osmotic dehydration kinetics depends strongly on sucrose concentration and slice thickness. The water loss and solute gain are more intensive at higher sucrose concentration and lower slice thickness. The effect of all the process parameters was observed to be significant at 10% level on both water loss and solute gain. Penetration and Magee model was fitted to the experimental data. Magee model was observed to represent water loss and solute gain more accurately as compared to Penetration model.

Osmotic Dehydration of Pineapple with Impregnation of Sucrose, Calcium, and Ascorbic Acid

Mass transfer was evaluated during osmotic dehydration of pineapple in solutions with until four components aiming to investigate the solutes concentration influence on impregnation. In the first step, the experimental trials for optimization of solution concentration were based on 23 factorial design. In the second step, effective diffusion coefficients were determined. Equations representing the influence of the concentration of sucrose, calcium lactate, and ascorbic acid in osmotic solutions on water loss and gains of sucrose, calcium, and vitamin C were found. Results showed that both calcium lactate and sucrose concentration affected calcium and sucrose gain. On the other hand, only vitamin C gain was significantly affected by the ascorbic acid concentration in the studied concentration range. However, when comparing diffusivities in pineapple immersed in sucrose solutions, with and without calcium lactate, with and without ascorbic acid, it was possible to verify that diffusivities of water, sugar, and calcium increased in presence of ascorbic acid in solution. Calcium in solution diminished the water and sucrose diffusivities. High calcium and vitamin C contents were obtained in 1 h immersion in the solutions studied.

Optimization of Osmotic Dehydration Process of Pineapple by Response Surface Methodology

Response Surface Methodology was used for quantitative investigation of water loss, solid gain & weight reduction during osmotic dehydration of pineapple in sugar syrup. Effects of temperature (30, 35, 40, 45 & 50°C), processing time (30, 60, 90, 120 & 150 min), sugar concentration (40, 45, 50, 55 & 60°B) and sample to solution ratio 1:10 (constant) on osmotic dehydration of pineapple were estimated. Quadratic regression equations describing the effects of these factors on the water loss, solid gain & weight reduction were developed. It was found that effects of temperature and sugar concentrations were more significant on the water loss than processing time. For solid gain, processing time & sugar concentration were the most significant factors. The osmotic dehydration process was optimized for water loss, solid gain & weight reduction. The optimum conditions were found to be temperature 38.2°C, processing time 128.7 min and sugar concentration 44.05°B. At these optimum values, water loss, solid gain & weight reduction were found to be 30.0921%, 13.3634% & 20.3772% respectively.

Osmotic dehydration of pineapple as a pre-treatment for further drying

Osmotic dehydration can be used as a pre-treatment for tropical fruits with the final aim of obtaining high quality dried fruit products. This concept was applied to South African grown Cayenne type pineapple pieces. The effect of osmotic dehydration on mass fluxes (water loss, solids gain and weight reduction) was investigated. Pineapple cylinders of 2 cm in diameter and 1 cm thick were immersed in sucrose solutions of 45, 55 and 65 °Brix at 30, 40 and 50 °C for 20, 40, 60, 20, 180 and 240 min. Experiments were conducted at both atmospheric pressure and applying a 200 mbar vacuum pulse during the first 10 min. Water loss and solids gain increased with temperature and concentration. Applying a vacuum pulse facilitated water loss especially at the highest concentration and temperature. Furthermore, the yield was improved by applying a vacuum pulse, as mass loss was less in those cases. Temperature affected mostly the water loss while the concentration of the solution affected mostly the solids gain. Prototypes of high/low water loss and high/low solids gain combinations were selected for quality evaluation.

Mass Transfer During Osmotic Dehydration of Pineapple

The diffusion coefficients of water and solutes are important parameters in the analysis, design and optimisation of an osmotic dehydration process. This work estimated by Fick’s Law the diffusion coefficients of water and sucrose during the osmotic dehydration of slices of pineapple fruit in sucrose solution at different temperatures. In addition, it analysed the effect of the change in thickness (shrinkage) during the process, and the use of higher order terms in the analytical solution. The model results were in good agreement with experimental data of water loss and solid gain. The best fit was found when the shrinkage was considered in a simple model based on the solution of Fick’s Law. The equilibrium water content ranged between 34 and 36% for a 60% w/w sucrose solution and was practically independent of temperature. Equilibrium sugar content increased from 45 to 54% as the temperature rose from 30 to 50°C. Thickness variation was found to be independent of temperature and was only dependent on water content.

Mass transfer during osmotic dehydration of pineapple: considering Fickian diffusion in cubical configuration

Osmotic dehydration kinetics of pineapple cubes (15×15×15 mm 3) was studied over a range of concentration (40–70°B) and temperature (30–50°C) of osmotic solution. The effective diffusion coefficients for water and solute diffusion were determined, considering pineapple as cubical configuration, assuming osmotic dehydration to be governed by Fickian diffusion. The effective diffusion coefficients for water as well as solute were empirically correlated with concentration and temperature of osmotic solution. A high degree of correlation was observed between predicted and experimental values of the effective diffusion coefficients of water ( R 2=0.99) as well as solute ( R 2=0.96).

MULTIVARIATE STATISTICAL ANALYSIS OF VOLATILE COMPOUNDS AS A CRITERION FOR SELECTING TECHNOLOGICAL PARAMETERS IN THE OSMOTIC DEHYDRATION OF PINEAPPLE

ABSTRACTPrincipal component analysis and cluster analysis of volatile compounds were used for selecting technological parameters in the osmotic dehydration of pineapple. Assessment of volatile losses permitted differentiation between samples obtained by different osmotic treatments. Treatments at 30C for 1 h at atmospheric pressure or under vacuum and at 30C or 40C for 1 to 3 h with pulsed vacuum (1 cycle) produce the lowest losses of volatile compounds. Apparently, pulsed vacuum allows higher aromatic volatiles retention than two other pressure modes. It also allows increases in both process temperature and time without an important increase in losses.

Osmotic dehydration of pineapple: kinetics and product quality

Osmotic dehydration as an intermediate step in air or vacuum drying of pineapple was studied. Osmotic dehydration kinetics indicated that both water loss and solids gain increased with increase of syrup temperature and concentration, the former having much more effect for the range of values tested. Equilibrium kinetics was modelled by defining equilibrium constants and in non-equilibrium period water loss and solids gain followed the penetration theory of mass transfer. The colour, flavour and texture of osmo-air dried pineapple indicated that the product was organoleptically acceptable.