Optimisation of osmotic dehydration process of guavas by response surface methodology and desirability function

Response surface methodology was used to assess the effects of osmotic solution concentration (40–60°Brix), process temperature (20–40 °C) and vacuum pulse application time (0–20 min) at 100 mbar on water loss (WL), weight reduction (WR), solid gain (SG), water activity (a_w), colour parameters and mechanical properties of guava slices. Optimal process conditions were determined through the desirability function approach and quality characteristics of osmotically dehydrated guavas were analysed. Only models obtained for WL, WR and a_w were suitable to describe the experimental data. The desirability function showed that optimal conditions for osmotic dehydration of guavas were: osmotic solution concentration at 60°Brix, process temperature at 32 °C and 20 min of vacuum pulse application. Under optimal conditions, colour and mechanical properties of treated guavas were similar to fresh fruit, presenting WL of 29.01 g/100 g, WR of 25.91 g/100 g, SG of 3.10 g/100 g and a_w of 0.979.     

Evaluation of Mass Exchange During Osmotic Dehydration of Plum Using Response Surface Methodology

Water loss (WL), solid gain (SG), weight reduction (WR) and shrinkage were quantitatively investigated during osmotic dehydration of plum using response surface methodology with the sucrose concentration (30–60g/100 g sample), temperature of sucrose solution (40–60°C) and immersion time (60–240 min). Experiments were designed according to Central Composite Rotatable Design with these three factors. For each response, second order polynomial models were developed using multiple linear regression analysis. With respect to water loss, solid gain, weight reduction and shrinkage, both linear and quadratic effects of four variables were found to be significant. In most cases, an increase of sucrose concentration, temperature and immersion time increased WL, SG, WR and shrinkage, except the increasing of immersion time for osmotic treatment has no effect on shrinkage. It was found that immersion time and temperature were the most significant factors affecting the WL during osmotic dehydration of plum followed by concentration of sucrose solution. This was also true for WR. Effect of temperature and time were more pronounced for SG than the concentration of sucrose solution.     

Modelling of mass transfer during osmotic dehydration of apple tissue pre-treated by pulsed electric field

The osmotic dehydration mechanism of apple sample pre-treated by pulsed electric field (PEF) was investigated over a range of 44.5-65 ° Brix sucrose concentrations. Apple disks treated by PEF field of 0.90 kV/cm during a constant time were immersed in sucrose solution at ambient temperature with 3:1 syrup to apple ratio (w/w). Increase of the initial solute concentration and the PEF treatment resulted in acceleration of the osmotic dehydration (OD). The PEF-treated samples had a higher water loss (WL) and higher solid gain (SG) than the untreated samples. The osmotic dehydration kinetics was studied on the basis of two approaches: Fick's unsteady state diffusion equation and a two-exponential kinetic model. The coefficients of effective diffusion of water and solute were calculated. Their values were higher for samples pre-treated electrically. The effect of PEF was more pronounced for the WL comparatively to the SG. The two-exponential kinetic model permits evaluating of both convective and diffusion stages of OD. The PEF pre-treatment accelerates the kinetics of water and solute transfer during convective and diffusion stages of OD.     

Osmotic dehydration of the Indian fig (Opuntia ficus indica) with binary and ternary solutions

The objective of this work was to study osmotic dehydration (OD) of the Indian fig with two binary solutions (sucrose/water and glucose/water) and a ternary solution (sucrose/NaCl/water) according to a 2³ factorial design with independent variables: temperature (30–50 °C), immersion time (90–240 min) and concentration (40–60 °Brix). The dependent variables were water loss (WL), solid gain (SG) and dehydration efficiency index. The temperature had greater influence on the WL in the three hypertonic solutions studied; the concentration had greater influence on the SG in the three hypertonic solutions investigated and the best conditions for the OD of the Indian fig were in glucose solution at 40 °Brix, 40 °C and 165 min.     

Centrifugal osmotic dehydration and rehydration of carrot tissue pre-treated by pulsed electric field

This paper studies the centrifugal osmotic dehydration (OD), rehydration and texture of carrot tissue treated by pulsed electric field (PEF). The influence of centrifugal acceleration (0-5430g), salt addition (NaCl/sucrose solutions 0/65, 7/44 and 15/50% w/w), and temperature (20-40 °C) on the OD kinetics was investigated in the presence and absence of PEF (E=0.60 kV/cm, treatment duration t_PEF=0.05 s). The centrifugal OD of samples untreated and treated by PEF was compared with OD under stirring (250 tr/min).Centrifugal force, PEF and salt addition increase the amount of water removed during OD. However, the centrifugal force decreases the intake of solids by the product.The application of PEF enhances both water loss (WL) and solid gain (SG) during OD (under stirring or centrifugation), increases the rehydration capacity of carrot tissue, but somewhat decreases the firmness of rehydrated product.The combination of centrifugal field with PEF and salt addition can be advantageous for reducing the OD duration. The textural study shows that the product obtained with OD is less affected by thermal treatment than the directly dried product.     

Mass transfer kinetics of pulsed vacuum osmotic dehydration of guavas

The effects of vacuum pulse and solution concentration on mass transfer of osmotically dehydrated guava slices were studied. Kinetics of weight reduction (WR), water loss (WL), solid gain (SG) and water activity (a_w) were obtained using sucrose solutions at 40, 50 and 60 °Brix and vacuum pulse of 100 mbar for 0, 10 and 15 min at the process beginning. Higher solution concentrations and the vacuum pulse application caused an increase on WL of osmotically dehydrated guavas and reduced the samples water activity. The SG was reduced by the increase on osmotic solution concentration and favored by vacuum application. Two different models of kinetics diffusion were tested to obtain diffusivity and to compare the accuracy of these models. The effective diffusivity estimated by the hydrodynamic model well reproduced the effects of process variables on mass transfer kinetics and showed a better agreement to the experimental data than the diffusional model.     

Optimisation of vacuum pulse osmotic dehydration of blanched pumpkin

Pulsed vacuum osmotic dehydration (PVOD) is an efficient process for obtaining semi‐dehydrated food. The effects of temperature (30–50°C), solute concentration (NaCl 0–15 kg per 100 kg solution, sucrose, 15–35 kg per 100 kg solution) and vacuum pulse application (50–150 mbar and 5–15 min) on water loss (WL), solid gain (SG), water activity (a_w) and total colour difference (?E) of previously blanched pumpkin slices were assessed through Plackett–Burman experimental design. Temperature was not statistically significant in the process. Later, with the aid of a central composite design (CCD), it was found that concentration of sucrose and NaCl was influent on the WL, SG, a_w and ?E, and the pressure and time of application of vacuum were influent on WL and SG. The optimal conditions of process were stabilised with the desirable function, and the simulated data were similar from the experimental ones.     

Optimisation of the pulsed vacuum osmotic dehydration of cladodes of fodder palm

Fodder palm, a great source of nutrients for human and animals, grows even in arid climates. Pulsed vacuum osmotic dehydration is an efficient process for obtaining semidehydrated food. It was used to slice cladodes of fodder palm. The independent variables used were temperature (30–50 °C), pulsed vacuum pressure (50–150 mbar) and NaCl concentration (5–15 g per 100 g solution). The response variables were water activity (a_w), moisture content (X), colour parameters, water loss (WL), solid gain (SG) and weight reduction (WR). The pulsed vacuum osmotic dehydration process was optimised for minimum values of a_w, X and SG, and maximum values of chroma. The experimental data obtained with the optimum condition (100 mbar; 10 gNaCl per 100 g solution, 44 °C) were near the estimated ones. For example, WL, a_w and ?E, and their error were 8.15 g per 100 g, 11%; 0.985, 0.3% and 6.15, 15.2%, respectively.     

不同小分子糖渗透草莓的传质动力学及对真空冷冻干燥草莓品质的影响

为系统地了解不同小分子糖特别是低聚糖和糖醇对草莓的渗透行为以及不同小分子糖对真空冷冻干燥草莓品质的影响,本研究利用两种数学模型对10 种常见小分子糖（白利度为40 °Brix）的渗透动力学进行拟合,并进一步对渗糖处理后真空冷冻干燥草莓的理化特性进行表征。结果表明,Weibull模型更适用于描述渗糖处理后草莓的可溶性固形物增量（solid gain,SG）,而Peleg模型可以更好地描述草莓的水分去除量（water loss,WL）。经不同糖渗透处理结束后,草莓的SG差异较大,山梨糖醇可以使草莓的SG达到6.84 g/100 g,是低聚异麦芽糖的6.16 倍。此外,渗糖处理的草莓硬度得到普遍提高（94.58%～223.23%）;葡萄糖、果糖、山梨糖醇渗透处理组的脆度分别降低了16.70%、20.74%、41.45%,低聚果糖渗透处理后的草莓质构特性与蔗糖最为接近。综合考虑渗透效率、感官营养品质和生产成本,低聚果糖是蔗糖在果蔬渗透处理方面的一种潜在替代品。     

Optimization of osmotic dehydration of diced green peppers by response surface methodology

Osmotic dehydration of diced green peppers was optimized with respect to temperature (20-40 °C), time (15-600 min), salt (0-10 g/100 g) and sorbitol (0-10 g/100 g) concentrations through response surface methodology. Water loss (WL), solids gain (SG), salt uptake (SA) and sorbitol uptake (SO) were the responses in a 2⁴ central composite rotatable design. Models developed for all responses were significant (p ≤ 0.01) without significant lack of fit. Results suggested that optimum processing conditions of 5.5 g salt/100 g and 6 g sorbitol/100 g at 30 °C after 240 min would result in WL = 23.3%, SG = 4.1%, SA = 8 g/100 g dry pepper and SO = 2.4 g/100 ml extract.     

雪莲果超声波辅助渗透脱水工艺参数的优化

以渗透脱水温度、时间、蔗糖质量分数、超声波功率和处理时间为因素,以失水率(water loss,WL)和固形物增加率(sugar gain,SG)为指标,通过单因素试验,研究雪莲果的渗透脱水工艺参数。以渗透脱水温度、时间、蔗糖质量分数、超声波处理时间为因素,以WL、SG和二者比值(WL/SG)为指标,通过二次回归正交旋转组合试验设计建立雪莲果超声波辅助渗透脱水过程中各响应值(WL、SG和WL/SG)与各因素之间的回归方程,并得到超声波辅助渗透脱水的最优工艺参数。结果表明,超声波辅助处理可显著提高雪莲果渗透脱水效果;影响WL的因素主次顺序是温度＞时间＞蔗糖质量分数＞超声波处理时间;影响SG的因素主次顺序依次是渗透脱水时间＞超声波处理时间＞温度＞蔗糖质量分数;影响SG/WL的因素主次顺序是渗透脱水时间＞蔗糖质量分数＞超声波处理时间＞温度。雪莲果超声波辅助渗透脱水的最佳工艺参数为渗透脱水温度41℃、时间1.7h、蔗糖质量分数60.18%、超声波处理时间35min。在此组合参数条件下,SG/WL平均值为0.059。     

OSMOTIC DEHYDRATION OF APPLES BY IMMERSION IN CONCENTRATED SUCROSE/MALTODEXTRIN SOLUTIONS

The effect of sucrose:maltodextrin (S:M100) ratios on solids gain (SG) and water loss (WL) was investigated during the osmotic dehydration of apple disks. Concentrated solutions were prepared at 40C with 100:0, 90:10, 70:30, 50:50, 30:70 and 10:90 ratios of (S:M100). The highest score in sensory evaluation was achieved with 90:10 ratio of (S:M100). Three stages of osmotic dehydration can be observed by plotting the shrinkage of apple disks vs the moisture content. The result is that a higher maltodextrin concentration favors volume loss and enhances water loss, increasing the duration of stage 2 osmotic dehydration.     

Osmotic dehydration of carrot tissue enhanced by pulsed electric field,salt and centrifugal force

The osmotic dehydration (OD) kinetics of carrot disc untreated and treated by pulsed electric field (PEF) was studied under centrifugation (2400 × g), stirring (250 rpm) and with a salt addition (NaCl/sucrose solutions 0%/65%, 5%/60% and 15%/50%). The PEF intensity was E = 0.60 kV/cm and the treatment duration was t_PEF = 0.05 s (500 rectangular monopolar pulses each of 100 μs). The water loss (WL), solids gain (SG) and water loss/solids gain ratios (WL/SG) were evaluated in the binary (sucrose + water) and ternary (sucrose + salt + water) solutions at the temperature of 20 °C during 4 h. The mass ratio of sample to solution was 1:3. The PEF treatment and salt addition enhanced the OD kinetics. WL and SG were increased under centrifugation (centrifugal OD) and under stirring (static OD). The centrifugal field enhanced the WL, however, decreased the SG comparing to the static OD. Therefore, the static OD has advantages for the higher SG (confectionary adds), while the centrifugal OD is better appropriated if the WL should be increased and the solids (sugar) uptake should be limited (dietetic products).The two-exponential kinetic model fitted well to experimental data for both static and centrifugal OD. The correlation coefficient was R² = 0.982–0.999 and the standard error was 5–10%.     

Comparison of sucrose and fructo-oligosaccharides as osmotic agents in apple

Fructo-oligosaccharides and sucrose were compared as osmotic agents in the osmotic dehydration of apple cv. Idared. Dehydration process of apple cubes (10  10  10 mm) was performed to determine the weight reduction (WR), moisture content (MC), water loss (WL) and solid gain (SG) over a range of osmotic solutions (40–60% w/v), temperature (40–60 °C) and processing time (20–40 min) The effective diffusion coefficient of water and solute was calculated assuming the processes to be governed by Fick's unsteady state diffusion. The effective diffusion coefficients were found to be of the order of 10^− 9 m² s^− 1 and were effected by the type of solute significantly. The WR, MC, WL and SG were predicted as weighted linear combinations of temperature, concentration of solute and time of OD.

Industrial relevance

The use of fructo-oligosaccharides (FOS) in different fruit based products is an efficient way to enrich human diet with functional component, because of the well-known health benefits of FOS. The osmotic behaviour of fructo-oligosaccharides were studied and compared to the conventional used sucrose. In view of the changes of different osmotics regarding to unit parameters of osmotic dehydration the results give possibility to industrial technology planning of products containing FOS, which are available for consumption in every season of the year and are favourable also in processed form e.g. muesli, dairy products.     

Mass transfer kinetics and regressional‐desirability optimisation during osmotic dehydration of pumpkin,kiwi and pear

Mass transfer kinetics and optimisation of osmotic dehydration (OD) of fruits and vegetables with diverse structures were studied. Different concentrations of sucrose (20–60 °Brix) and process times (0–24 h) were used. Magee’s model was appropriate for predicting water loss (WL), while Azuara’s model fitted well solids gain (SG) data and represented more accurately the evolution of the complete process close to equilibrium. Polynomial equations for each kinetic variable [WL, SG and weight reduction (WR) – for pumpkin, kiwi and pear] using multiple linear regression were fitted for a selected range of experimental data (30–240 min, 20–60 °Brix). A complete solution algorithm for desirability function was coded in Matlab^® 7.2 (Mathworks, Natick, MA, USA) with the aim to optimise osmotic dehydration process in terms of WL, SG and WR; optimal conditions were found for each fruit. Besides, an optimal common zone was identified for OD corresponding to process time from 114 to 240 min and sucrose concentration from 54 to 60 °Brix.     

Evaluation of process conditions on osmotic dehydration and quality indexes of pumpkin (Cucurbita moschata) and further polymeric film selection for packaging and refrigerated storage

We studied the influence of composition and concentration of solutions and product size on mass transfer kinetics during Anco pumpkin osmotic dehydration (OD). Once optimal conditions were determined, samples packed in commercial polymeric films were microbiologically analysed during refrigerated storage. The optimal OD time was 3 h, when the efficiency index WL/SG (water loss/solid gain) was stabilised. At this time, 1.0 and 1.5 cm cubes presented the highest index value (about 11) in binary solution (sucrose 55°Bx). WL was higher in 1.0 cm cubes for each dehydrating ternary salt solution tested, and no significant differences in firmness were observed with Calcium Lactate addition. Thus, optimal condition for OD in ternary solutions was 180 min and 55°Bx – 2% NaCl. Microbiological determinations were done for dehydrated (55°Bx without/with 2% NaCl) and untreated samples, packaged in different polymeric films. The combination with lowest mesophilic and psychrophilic counts at day 10 was: samples dehydrated with ternary solution of sucrose-salt packed in Polypropylene film.     

Response surface optimisation of osmotic dehydration of Chinese ginger (Zingiber officinale Roscoe) slices

Response surface methodology (RSM) of Box–Behnken design with 27 experimental runs and the desirability function method were used in the osmotic dehydration process of Chinese ginger (Zingiber officinale Roscoe) slices in ternary solution of water, sucrose and sodium chloride for maximising water loss (WL), rehydration ratio (RR) and total phenolic content (TPC) and minimising solute gain (SG) and hunter colour change (HCC) of dehydrated product. The results indicated that the optimum operating conditions were found to be process duration of 102 min, solution temperature of 30 °C, solution concentration of 50 Brix sucrose + 7.31% sodium chloride and solution to food ratio of 8:1 (w/w). Under this condition, the WL, SG and TPC were 58.8% (wb), 12.56% (wb) and 1.46% (db), while its RR and HCC were 1.59 and 6.55, respectively. The immersion time was the most significant variable for WL, HCC, SG and RR, and for TPC it was temperature (P < 0.05).     

Optimisation of osmotic dehydration process of carrot cubes in mixtures of sucrose and sodium chloride solutions

In the optimisation of the osmotic dehydration process of the carrot cubes in mixtures of sucrose and sodium chloride by response surface methodology, using face-centred central composite design (CCF), it was shown that the independent process variables for osmotic dehydration process were osmotic solution concentrations (5–15% w/v sodium chloride in 50 °Brix sucrose syrup), temperature (35–55 °C) and process duration (120–240 min). Statistical analysis of results showed that the linear terms of all the process variables have a significant effect on all the responses. The optimum osmotic dehydration process conditions for maximum water loss, minimum solute gain, maximum retention of colour, and sensory score were: 50 °Brix + 15% w/v sodium chloride solution, 54.8 °C solution temperature and 120 min process duration.     

Effects of murta (Ugni molinae Turcz) extract on gas and water vapor permeability of carboxymethylcellulose-based edible films

The effect of murta (Ugni molinae Turcz) leaves extract on water vapor permeability (WVP) and gas permeability (GP) of carboxymethylcellulose (CMC)-based films was studied. Two ecotypes of murta leaves “Soloyo Grande” (SG) and “Soloyo Chico” (SC), were analyzed for their composition (HPLC-MS) and SC extract revealed a higher concentration of flavonols than the SG extract. The film forming solution was prepared with 2 g of CMC, 0.4 ml of glycerol and 0.5 ml of sunflower oil in 100 ml of water (Control), 50 ml of water and 50 ml of each exctract (SC50 or SG50) and 100 ml of each extract (SC 100 or SG 100). The addition of murta leaves extract modified the WVP and GP of the films. The WVP decreased significantly (P?0.05) with the incorporation of SG extract in the film but not with the SC extract (P>0.05). The CO₂ and O₂ permeability of the films were influenced by the kind and concentration of murta leaves extract used. The CO₂ permeability, with SG extract was higher than without extract (P?0.05) and with SC extract was not modified. The O₂ permeability with murta leaves extract were lower than without extract. Therefore, it is possible to consider that films with SC acts only as barrier to the oxygen, but with SG the water vapor and gas barrier properties were modified, being more permeable to the CO₂ and acting as barrier to O₂ and water vapor.     

Determination of water effective diffusion coefficient of sardine sheets during vacuum pulse osmotic dehydration

The water effective diffusion coefficient of sardine sheets during vacuum pulse osmotic dehydration was determined. Sardine sheets (20.1×15.0×6.4 mm³) were osmotic dehydrated at brine concentrations between 0.15 and 0.27 g NaCl/g, and temperatures between 32 and 38 °C. The water effective diffusion coefficient ranged approximately from 1.46×10⁻¹⁰ m²/s to 2.41×10⁻¹⁰ m²/s. In general, diffusion coefficient increased with increasing concentration and temperature. Dependence on temperature followed an Arrhenius relationship, regardless of concentration Diffusion coefficient at 0.18 g NaCl/g was found to be the most temperature sensitive (E_a=39.62 kJ/mol) while that at 0.15 g NaCl/g was the least temperature sensitive (E_a=23.67 kJ/mol). The water effective diffusion coefficient was empirically correlated with concentration and temperature of osmotic solution. A high degree of correlation was observed between predicted and experimental values of the water effective diffusion coefficient (R²=0.856).