Effects of Thermal and Nonthermal Treatments on Kinetics of Mass Transfer and Selected Quality Attributes During Osmotic Dehydration of Seedless Guava (Psidium Guajava L.)

This study evaluated the effect of some process parameters and selected enhancement techniques on the kinetics of mass transfer as well as selected quality attributes for osmotic dehydration of seedless guava. Experimental results revealed that higher values of solution concentration and temperature resulted in higher flows of water (39%) and solids (8%) through the seedless guava. In all cases, Peleg equation adequately (R2>0.92) described the kinetics of mass transfer during osmotic dehydration. Total color difference increased up to 21% while hardness decreased around 32% with increase process variables. A zero order kinetic model was fitted to the experimental data adequately for quality parameters (R2>0.88). The osmotic dehydration process was optimized for maximum water loss, weight reduction and minimum solute gain through response surface methodology. Results suggested optimum processing conditions of 30% w/w sucrose concentration at 33 ºC after 179 min would result in 0.15 gg-1 weight reduction, 0.2 gg-1 water loss and 0.03 gg-1 solid gain. Results showed that at the studied range of process parameters, the values of mass transfer terms were not in accordance with an efficient osmotic dehydration process in which 40–60% water loss and 0.05) changes of optical and textural properties in comparison with traditional blanching. Finally, the influence of ultrasonic wave and centrifugal force as nonthermal treatment on osmotic dehydration process was investigated to overcome the drawbacks of thermal treatment. Application of ultrasonic treatment compared with osmotic dehydration at optimized condition enhanced water loss and solid gain up to 23% and 3.3%, respectively. It improved “L” value without any significant effect (p>0.05) on “a” and “b” values whereas hardness value was significantly (p<0.05) affected. Centrifugal force treatment increased water loss around 34%, however, retarded solid gain. The combination of centrifugal force with osmotic dehydration leads to decrease in hardness of samples (5%) whereas there is no significant (p<0.05) effect on color of samples

Antioxidant activity of spearmint (Mentha spicata L.) leaves extracts by supercritical carbon dioxide (SC-CO2) extraction

In this study, the effects of pressure (100–300 bar), temperature (40–60ºC) and co-solvent flow rate (3–9 g/min) on antioxidant activities of supercritical carbon dioxide (SC-CO²) extracts of spearmint leaves were determined using full factorial in the frame of complete randomize design (CRD). The antioxidant activity of SC-CO² extracts was determined by DPPH radical scavenging method. The results showed that extraction pressure, temperature and co-solvent flow rate had significant effect (P < 0.05) on antioxidant activity of extracts obtained. The highest antioxidant activity (71.00 ± 2.65%) was obtained at 200 bar pressure, 50ºC and 6 g/min co-solvent flow rate. However, all of the extracts obtained in this study had significantly higher antiradical activities varying from 35.62 ± 0.34% to 72 ± 3.17% compared to butylated hydroxytoluene (BHT) as a reference. These results indicated that supercritical carbon dioxide is a promising alternative process for recovering compounds of high antioxidant activities from spearmint leaves

Effect of heat and thermosonication on kinetics of peroxidase inactivation and vitamin C degradation in seedless guava (Psidium guajava L.)

This study aims to evaluate the effect of heat and the simultaneous application of heat (80-95°C) and ultrasonic waves (thermosonication) on the inactivation kinetic of peroxidase and vitamin C degradation in seedless guava. Ultrasonic wave’s amplitudes except 25 and 100% had significant (P<0.05) effect on peroxidase inactivation rate. The thermal and thermosonication inactivation of peroxidase was described well by first-order kinetics (R2>0.98). In the heat blanching process, the peroxidase inactivation rate constant increased from 1.1×10-2 to 4.6×10-2 s-1. However, the inactivation rate of peroxidase was increased by 1.5–3 times in the temperature range 80–95ºC, with the 50 and 75% ultrasonic wave amplitudes, respectively. Decreases in vitamin C contents due to blanching treatments were found. Blanching processes at high temperature and short time resulted in higher vitamin C retention. It was found that thermosonication treatment inactivates seedless guava peroxidase at less severe blanching conditions and consequently retains vitamin C content at higher levels. The present findings will help to design the blanching conditions in order to reduce the severity of conventional thermal treatments and, therefore, improving the quality of the thermally treated product

Mathematical modelling of mass transfer during osmotic dehydration of seedless guava (Pisidium guajava L.) cubes

The present work aimed to study kinetics of osmotic dehydration of seedless guava in terms of solid gain and water loss, which was evaluated at three sucrose concentration levels (30, 40 and 50% w/w), three temperature levels of osmotic solution (30, 40 and 50°C) for 240 min. The experimental data was fitted to different empirical kinetic models including Peleg, Page and Azuara. Determination of coefficient (R 2 ), root mean square error (RMSE) and mean relative deviation modulus (E) were used for determination of the best suitable model. The present work shows that the Peleg empirical model satisfactorily described the dehydration kinetics with the highest R 2 ( > 0.95) and the lowest RMSE ( < 0.003) and E ( < 5.20%). Moreover, the effect of solution concentration and temperature was also studied and it was found that initial water loss and solid gain are related to solution concentration and temperature whereas equilibrium contents are related to sucrose concentration. From the experimental data it is possible to estimate the equilibrium content of water and solid

Physicochemical characteristics of Nigella seed (Nigella sativa L.) oil as affected by different extraction methods.

The physicochemical properties of crude Nigella seed (Nigella sativa L.) oil which was extracted using Soxhlet, Modified Bligh-Dyer and Hexane extraction methods were determined. The effect of different extraction methods which includes different parameters, such as temperature, time and solvent on the extraction yield and the physicochemical properties were investigated. The experimental results showed that temperature, different solvents and extraction time had the most significant effect on the yield of the Nigella oil extracts. The fatty acid (FA) compositions of Nigella seed oil were further analyzed by gas chromatography to compare the extraction methods. The C16:0, C18:1 and C18:2 have been identified to be the dominant fatty acids in the Nigella seed oils. However, the main triacylglycerol (TAG) was LLL followed by OLL and PLL. The FA and TAG content showed that the composition of the Nigella seed oil extracted by different methods was mostly similar, whereas relative concentration of the identified compounds were apparently different according to the extraction methods. The melting and crystallization temperatures of the oil extracted by Soxhlet were -2.54 and -55.76 °C, respectively. The general characteristics of the Nigella seed oil obtained by different extraction methods were further compared. Where the Soxhlet extraction method was considered to be the optimum process for extracting Nigella seed oil with a higher quality with respect to the other two processes

Effect of osmotic dehydration process using sucrose solution at mild temperature on mass transfer and quality attributes of red pitaya (Hylocereus polyrhizusis)

In the current research, osmotic dehydration of red pitaya (Hylocereus polyrhizusis) cubes using sucrose solution at mild temperature (35ºC) was investigated. Sucrose solution (40, 50 and 60% w/w) was employed for osmotic dehydration process. Responses of weight reduction (WR), solid gain (SG), water loss (WL), color (L* , a* and b* ) and texture (hardness) were evaluated. It was found that sucrose concentration significantly (p < 0.05) affected the mass transfer terms during osmosis process. The results obtained revealed an increase in yellowness (b* ), decrease in lightness (L* ) and redness (a* ) as the sucrose concentration increased. Furthermore, osmotically dehydrated samples were considerably softer than untreated samples. Increasing of sucrose concentration and dehydration time caused softer tissue of dehydrated product compared with the fresh red pitaya

Ultrasound-assisted extraction of valuable compounds from winter melon (Benincasa hispida) seeds

Ultrasound-assisted extraction (UAE) was applied for the extraction of bioactive valuable compounds from winter melon (Benincasa hispida) seeds. Effects of amplitude (25-75%), temperature (40-60°C) and sonication time (20-60 min) on crude extraction yield (CEY) and radical scavenging activities (RSA, % inhibition of DPPH˙ and ABTS˙+ free radicals) of extracts were determined using complete randomised design (CRD). The results showed that the CEY and RSA of extracts significantly affected by independent variables. The maximum value of CEY (97.14±0.36 mgg-1), scavenging of DPPH˙ radicals (32.12 ± 0.38%) and scavenging of ABTS˙+ radicals (40.52±0.73%) were obtained at the combined treatment conditions of 75%, 55°C and 40 min. The UAE results obtained were compared with those achieved by using conventional Soxhlet extraction (CSE) method. It was found UAE allowed extraction at lower temperature and the extracts obtained posses higher quality compare with CSE. UAE is a promising environment friendly technique for the extraction of bioactive compounds from winter melon (Benincasa hispida) seeds

Modelling the kinetics of peroxidase inactivation and colour changes of seedless guava (Psidium guajava L.) during thermal treatments

The kinetics of thermal inactivation of peroxidase and colour changes in seedless guava (Psidium guajava L.) due to hot water blanching were studied in the temperature range of 80-95°C. Peroxidase inactivation kinetics followed a first-order Arrhenius model, where the activation energy and rate of the reaction at a reference temperature of 87.5°C were 101.27±3 kJ mol-1 and 0.023±4×10-3s-1, respectively. Colour was quantified using the L, a, b in Hunter system. The results indicated that colour system parameters (L, a, b) followed a first-order Arrhenius kinetics model with activation energies (Ea) of 120.43±3, 86.45±5 and a 100.03±2, kJmol-1, respectively. The zero-order kinetic model was applied to total colour difference (TCD) resulting in activation energies of 111.65±5 kJmol-1. Good agreement was found between estimated and experimental data in all cases (R2>0.91)

Supercritical carbon dioxide (SC-CO2) extraction of catechin, epicatechin, rutin and luteolin from spearmint (Mentha spicata L.) leaves

In this study, supercritical carbon dioxide (SC-CO2) extraction conditions were optimized for the simultaneous separation of four bioactive flavonoids (catechin, CA; epicatechin, EP; rutin, RU; luteolin, LU) contained in spearmint (Mentha spicata L.) leaves. SC-CO2 extraction parameters such as pressure, temperature and dynamic extraction time were optimized by Complete Randomize Design (CRD) full factorial. The optimum condition of SC-CO2 extraction was achieved at 200 bar, 60°C and 60 min (with 60.566 mg/g extraction yield). Extracted yield at optimum condition was then analyzed by high performance liquid chromatography (HPLC) for quantifying bioactive flavonoid compounds. At optimum conditions, four bioactive flavonoids including (+)-catechin, (-)-epicatechin, rutin and luteolin were detected at high concentration. Luteolin (0.657 mg/g) had the highest concentration among the other detected flavonoids. The results indicated that SC-CO2 extraction is a promising and alternative process for recovering the bioactive compounds from spearmint leaves

Characterization of valuable compounds from winter melon (Benincasa hispida (Thunb.) Cogn.) seeds using supercritical carbon dioxide extraction combined with pressure swing technique

In this study, we describe the extraction of different valuable compounds from winter melon seeds using supercritical carbon dioxide extraction combined with pressure swing technique (SCE-PST). The effects of the extraction variables, namely pressure, holding time (HT), and continuous extraction time (CT), were optimized by response surface methodology (RSM) to maximize the crude extraction yield (CEY). The optimal conditions were at pressure of 181.35 bar, HT of 9.93 min, and CT of 50.14 min. Under these conditions, the experimental CEY was 235.70 ± 0.11 mg g−1 with a relatively strong antioxidant activity (64.42 ± 0.21 % inhibition of DPPH· radicals, 67.36 ± 0.34 % inhibition of ABTS·+ radicals) and considerable amount of phenolic compounds (42.77 ± 0.40 mg gallic acid equivalent/g extract). The high-performance liquid chromatography (HPLC) analysis revealed that the bioactive phenolic compounds increased significantly using PST (p < 0.05), where gallic acid had the highest concentration (0.688 ± 0.34 mg g−1). The extract obtained using optimal SCE-PST conditions contained more than 83.65 % total unsaturated fatty acids (UFAs) and linoleic acid accounted for 67.33 ± 0.22 % in the total extract. From the results, the SCE efficiency in terms of extract quantity and quality has been enhanced significantly applying PST. Finally, the results were compared with previous published findings using supercritical carbon dioxide, ultrasound-assisted, and Soxhlet extraction. It was found that higher CEY could be achieved using Soxhlet extraction even through the quality of SCE-PST extracts in terms of antioxidant activity and phenolic compounds was better