Effect of Air Temperature on Drying Kinetics,Vitamin C,Antioxidant Activity,Total Phenolic Content,Non-enzymatic Browning and Firmness of Blueberries Variety O´Neil

Effect of air temperature on drying kinetics, vitamin C, antioxidant capacity, total phenolic content (TPC), colour due to non-enzymatic browning (NEB) and firmness during drying of blueberries was studied. Drying curves were satisfactorily simulated with the Weibull model at 50, 60, 70, 80 and 90°C. The scale parameter (β) decreased as air temperature increased and an activation energy value of 57.85 kJ mol⁻¹ was found. Important losses of vitamin C were reported during drying for all the working temperatures (p < 0.05). Although TPC decreased as air-drying temperature increased (p < 0.05) in comparison to its initial value, the dehydration at high temperatures (e.g., 90°C) presented high values for these antioxidant components. Discoloration due to NEB reaction was observed at all the working temperatures showing a maximum value at 90°C (p < 0.05). The radical scavenging activity showed higher antioxidant activity at high temperatures (80 and 90°C) than at low temperatures (50, 60 and 70°C) (p < 0.05). A tissue firmness reduction was observed with increasing temperature (p < 0.05).     

Mathematical Modeling and Experimental Study on Thin-Layer Vacuum Drying of Ginger (Zingiber Officinale R.) Slices

The vacuum-drying characteristics of ginger (Zingiber officinale R.) slices were investigated. Drying experiments were carried out at a constant chamber pressure of 8 kPa, and at four different drying temperatures (40 °C, 50 °C, 60 °C, and 65 °C).The effects of drying temperature on the drying rate and moisture ratio of the ginger samples were evaluated. Efficient model for describing the vacuum-drying process was chosen by fitting five commonly used drying models and a suggested polynomial was fitted to the experimental data. The effective moisture diffusivity and activation energy were calculated using an infinite series solution of Fick’s diffusion equation. The results showed that increasing drying temperature accelerated the vacuum-drying process. All drying experiments had only falling rate period. The goodness of fit tests indicated that the proposed two-term exponential model gave the best fit to experimental results among the five tested drying models. The average effective diffusivity values varied from 1.859 × 10⁻⁸ to 4.777 × 10⁻⁸ m²/s over the temperature range. The temperature dependence of the effective moisture diffusivity for the vacuum drying of the ginger samples was satisfactorily described by an Arrhenius-type relationship with activation energy value of 35.675 kJ/mol within 40–65 °C temperature range.     

Thin Layer Drying of African Breadfruit (Treculia africana) Seeds: Modeling and Rehydration Capacity

African breadfruit (ABF) seeds are underutilized plant resources, which have been reported to have high potential for novel food and industrial uses. The kinetics of moisture removal during air drying of the whole (WS) and dehulled (DS) seeds was studied at temperatures of 40–70 °C. Five empirical models were tested for predicting the experimental data. Drying of ABF seeds followed an exponential decay pattern, while drying predominantly took place during the falling rate periods. All the drying models predicted the experimental data above 90% accuracy while the Henderson–Pabis model gave the best fit (0.95 < r ² < 0.99) at most of the experimental conditions. Effective moisture diffusivity, D _eff, ranged from 3.65 to 7.15 × 10⁻⁹ m²/s and 3.95 to 6.10 × 10⁻⁹ m²/s for WS and DS, respectively. D _eff showed significant dependence on the moisture content (p < 0.01). Rehydration capacity of DS was not significantly affected by drying temperature while that of WS increased with drying temperature.     

Mass Transfer Modelling During Osmotic Dehydration of Jumbo Squid (Dosidicus gigas): Influence of Temperature on Diffusion Coefficients and Kinetic Parameters

Mathematical modelling was used to study the effect of process temperature on moisture and salt mass transfer during osmotic dehydration (OD) of jumbo squid with 6% (w v ⁻¹) NaCl at 75, 85 and 95 °C. The diffusion coefficients for moisture and salt increased with temperature. Based on an Arrhenius-type equation, activation energy values of 62.45 kJ mol⁻¹ and 52.14 kJ mol⁻¹ for moisture and salt, respectively, were estimated. Simulations of mass transfer for both components were performed according to Newton, Henderson and Pabis, Page, Weibull and logarithmic mathematical expressions. The influence of drying temperature on the kinetic parameters was also studied. Based on statistical tests, the Weibull and logarithmic models were the most suitable to describe the mass transfer phenomena during OD of jumbo squid.     

Characteristics of Convective Drying of Pepino Fruit (Solanum muricatum Ait.): Application of Weibull Distribution

The aim of this research was to study the behaviour of the drying kinetics of pepino fruit (Solanum muricatum Ait.) at five temperatures (50, 60, 70, 80 and 90 °C). In addition, desorption isotherms were determined at 20, 40 and 60 °C over a water activity range from 0.10 to 0.90. The Guggenheim, Anderson and de Boer model was suitable to depict the desorption data. A monolayer moisture content from 0.10 to 0.14 g water g⁻¹ d.m. was reported. The equations of Newton, Henderson–Pabis, Modified Page, Wang–Singh, Modified Henderson–Pabis, Logarithmic as well as standardised Weibull were tested for modelling drying kinetics. Besides, Fick’s second law model was used to calculate the water diffusion coefficient which increased with temperature from 2.55 to 7.29 × 10⁻¹⁰ m² s⁻¹, with estimated activation energy of 27.11 kJ mol⁻¹. The goodness of fit of the models was evaluated using sum squared error and chi-square statistical tests. The comparison of the experimental moisture values with respect to the calculated values showed that the standardised Weibull model presented the best goodness of fit, showing that this equation is very accurate for simulating drying kinetics for further optimisation of drying times.     

Stability and Degradation Kinetics of Bioactive Compounds and Colour in Strawberry Jam during Storage

The effect of storage time and temperature on degradation of bioactive compounds such as ascorbic acid, anthocyanins, total phenols, colour and total antioxidant capacity of strawberry jam were investigated. The results indicated that lightness (L) value decreased significantly (p < 0.05) over 28 days of storage at 4 and 15 °C, with lower values measured at higher temperatures. Anthocyanins, ascorbic acid and colour degradation followed first-order kinetics where the rate constant increased with an increase in the temperature. The reaction rate constant (k) increased from 0.95 × 10⁻² day⁻¹ to 1.71 × 10⁻² day⁻¹ at 4 and 15 °C for anthocyanins. Similarly, k increased from 2.08 × 10⁻² day⁻¹ to 4.54 × 10⁻² day⁻¹ at 4 and 15 °C for ascorbic acid. In general, total antioxidant activity for strawberry jam samples stored for 28 days at 4 and 15 °C exhibited lower values as compared to control (day 0). The results showed greater stability of nutritional parameters at 4 °C compared to 15 °C.     

Water Diffusion and Concentration Profiles During Osmodehydration and Storage of Apple Tissue

The objective of this work was to study the mobility of water and sucrose during osmotic dehydration and storage of apple tissue and to conduct an analysis of the behavior of the effective diffusion coefficients determined from concentration profiles. Osmotic dehydration (OD) of apple was carried out at 40°C for 1 h, and the solution: sample ratio was 20:1 (w/w). Samples of 20-mm diameter were extracted from the dehydrated apple immediately after the OD process and after 4 and 24 h of storage at 25 °C. Moisture of these samples and soluble solids content were analyzed. Our results showed, after 1 h of OD, the outer layer of the apple sample lost 0.37 kg water/kg apple and gained 0.30 kg sucrose/kg apple. These values decreased toward the internal layers of the apple. A fine layer of greatly dehydrated cells was formed on the surface around the sample, which determined the mass transfer rate in the whole tissue. Smaller mass transport rates were observed in the development of concentration profiles during storage. Diffusion coefficients obtained for the outer layer after 1 h of OD were 1.53 × 10⁻¹⁰ and 1.05 × 10⁻¹⁰ m²/s for water and sucrose, respectively. The analysis of compositional profiles developed during osmodehydration was a useful tool to get a better understanding of the changes in the water activity of the outer layer of the apple tissue.     

A Feasibility Study on the Drying of Lime Juice: The Relationship between the Key Operating Parameters of a Small Laboratory Spray Dryer and Product Quality

Concentrated lime juice with 20% total soluble solids was dried using three levels of maltodextrin (40%, 50%, and 60% solid base) and a BüCHI B-190 spray dryer. The drying air temperature and flow rate were 140 °C, 155 °C, and 170 °C and 47.1, 53.5, and 57.8 m³/h, respectively. A total of 27 experiments were conducted (in triplicate) with the feed rate, temperature, and compressed air flow for the atomizer kept constant. Analysis of the data revealed that product recovery increased when the maltodextrin in the feed and drying air flow rate were increased, but the inlet air temperature had no significant (P < 0.05) effect on powder recovery. The moisture content of the powder varied with the maltodextrin level, inlet air temperature, and air flow rate. Using scanning electron microscope images, larger particle size was observed with the increase of maltodextrin concentration. Powder bulk density also increased from 0.41 to 0.68 g/cm³, depending on the level of maltodextrin, whereas the drying air temperature and flow rate were not as effective. The results of this study are beneficial for scaling up the spray drying of lime juice to the food industry.     

Prediction of Drying Characteristics of Pomegranate Arils

The thin-layer drying characteristics of pomegranate arils were investigated at the temperature of 55, 65 and 75°C, and the thin-layer drying models were used to fit the drying data. The increase in drying air temperature resulted in a decrease in drying time. Five different thin-layer drying models were used to predict the drying characteristics. The Midilli et al. model showed a better fit to experimental drying data as compared to other models. Effective moisture diffusivities were calculated based on the diffusion equation for a spherical shape using Fick’s second law, and varied from 9.373 × 10⁻¹¹ to 3.429 × 10⁻¹⁰ m²/s over the temperature range. Moisture diffusivity values increased as air temperature was increased. The dependence of moisture diffusivity on temperature was described by an Arrhenius-type equation. The activation energies of control and pre-treated samples were determined to be 49.7 and 40.1 kJ/mol, respectively.     

Co-production of Lactic Acid and <Emphasis Type="Italic">Lactobacillus rhamnosus</Emphasis> Cells from Whey Permeate with Nutrient Supplements

Lactic acid and cell production from whey permeate by Lactobacillus rhamnosus with different nutrient supplements were investigated in this study. Yeast extract was identified as the most effective nutrient affecting lactic acid production. Increase in inoculum size from 0.05% to 1% (v/v) resulted in a substantial increase in lactic acid productivity from 0.66 to 0.83 g L⁻¹ h⁻¹ (P < 0.001). The optimal temperature for lactic acid production was 37 °C, while the highest cell production was obtained at 42 °C. When whey permeate and yeast extract concentrations were 6.8% (w/v) and 3 g L⁻¹, respectively, lactic acid productivity reached 0.85 g L⁻¹ h⁻¹ after 48-h cultivation, which is 3.40 times of those without nutrient supplements.     

Comparison Between Systems for Synthesis of Fructooligosaccharides from Sucrose Using Free Inulinase from Kluyveromyces marxianus NRRL Y-7571

This work is focused on the synthesis of the fructooligosaccharides (FOS) from sucrose using free inulinase from Kluyveromyces marxianus NRRL Y-7571 in aqueous and aqueous–organic systems. The most significant variables for the aqueous–organic system were identified using a fractional factorial design. The evaluated variables were the temperature, pH, sucrose concentration, inulinase activity, aqueous/organic ratio, and the polyethylene glycol concentration. The use of sequential experimental design methodology was shown to be very useful in the optimization of the FOS synthesis by inulinase either in aqueous or aqueous–organic systems. For the aqueous–organic system, the maximum Y _FOS reached was 16.7 ± 1.1 wt.% with the following operational conditions: temperature of 40 °C, enzyme activity of 4 U mL⁻¹, organic solvent/total system ratio of 25/100, pH of 6.0, and sucrose concentration of 55%. In the aqueous system, the maximum conversion obtained was 12.8 ± 1.0 wt.% under the following conditions: 40 °C, pH 5.0, 55% sucrose, and inulinase activity 4 U mL⁻¹.     

Extraction of Bioactive Compounds from Milled Grape Canes (Vitis vinifera) Using a Pressurized Low-Polarity Water Extractor

Trans-resveratrol and trans-ε-viniferin were extracted from milled grape canes using pressurized low-polarity water. The effects of temperature were significant for both compounds (p ≤ 0.05): extraction at 160 °C resulted in a 40% loss of trans-resveratrol compared to 95 °C while reduction of trans-ε-viniferin at both temperatures remained at 30%. Increasing ethanol concentration from 0% to 25% increased the extraction of total phenolics and trans-ε-viniferin by 44% and 489%, respectively. Solvent flow rate also influenced trans-ε-viniferin extraction. Antioxidant activity showed a strong correlation with total phenolic content of the extracts, and the two target phenolic compounds. Except for the modifier concentration, the extraction parameters studied were not statistically significant with respect to the antioxidant activity of extracts (p > 0.05). Effective diffusivities of trans-resveratrol multiplied from 3.3 × 10⁻¹¹ to 10.4 × 10⁻¹¹ m²/s by three times with increasing temperature. The modified Gompertz equation satisfactorily explained the extraction of the stilbenes investigated.     

Effect of Processing Methods on Physical,Chemical, Rheological,and Sensory Properties of Okra (<Emphasis Type="Italic">Abelmoschus esculentus</Emphasis>)

Effects of freezing/thawing, sun drying, solar drying, and foam-mat drying on physical, chemical, rheological, and sensory attributes of okra were investigated. Average poured bulk and tapped bulk densities of sun-dried, solar-dried, and foam-mat-dried okra were 800 and 950, 715 and 765, 355 and 367 kg/m³, respectively. Minimum and maximum porosity of sun-dried, solar-dried, and foam-mat dried okra were 55.70% and 62.60%, 50.06% and 53.30%, 60.90% and 62.87%, respectively. Sun-dried and solar-dried okra showed higher L*, a*, and chroma values than frozen/thawed and foam-mat-dried okra. Within a temperature range of 80–40 °C, viscosity of fresh, frozen/thawed, foam-mat-dried, solar-dried, and sun-dried okra were 0.055–0.080, 0.055–0.075, 0.050–0.073, 0.005–0.065, and 0.005–0.022 Nsm⁻², respectively. Sensory evaluation showed no significant difference (p < 0.05) between fresh, frozen/thawed, and foam-mat dried okra in color, aroma, and overall acceptability. Sun-dried and solar-dried okra were significantly poorer (p < 0.05) in color, aroma, taste, and overall acceptability.     

Optimization of supercritical CO2 extraction of phytosterol-enriched oil from Kalahari melon seeds

Supercritical carbon dioxide (SC-CO₂) extraction of oil from Kalahari melon seeds was investigated in this study. Response surface methodology was applied to model and optimize the extraction, namely pressure (200–400 bar), temperature (40–80 °C), and supercritical fluid flow rate (10–20 mL/min). Well-fitting models were successfully established for oil recovery (R ² = 0.9672) and phytosterol concentration (milligrams per 100 g; R ² = 0.8150) through multiple linear regressions with backward elimination. The effect of supercritical fluid flow rate was the most significant (P < 0.05) factor that affected oil recovery but this factor had no significant (P > 0.05) effect on phytosterol concentration. The optimal processing conditions for oil recovery and phytosterol concentration were pressure of 300 bar, temperature at 40 °C, and supercritical fluid flow rate of 12 mL/min. These optimal conditions yielded a 76.3% oil recovery and 836.5 mg/100 g of phytosterol concentration. The oil content in the Kalahari melon seeds as estimated by Soxhlet extraction was around 30.5/100 g. The phytosterol concentration in the oil extracted with SC-CO₂ extraction was 94% higher than that obtained with solvent extraction.     

Ohmic heating and pulsed vacuum effect on dehydration processes and polyphenol component retention of osmodehydrated blueberries (cv. Tifblue)

Blueberries are highly perishable fruits; therefore, emerging technologies focus on improving the bioactive compound retention and extending the shelf life. The aim of this study was to evaluate the effect of ohmic heating and vacuum pulses on the dehydration processes and polyphenol compound retention of osmodehydrated blueberries (cv. Tifblue). The treatments were performed using a 65% (w/w) sucrose solution, an electric field of 13 V/cm (100 V) at 30 °C, 40 °C or 50 °C for 300 min, and air drying at 50, 60 or 70 °C to obtain dried blueberries. The moisture content, soluble solids and phenolic compounds were analyzed. The combination of ohmic heating/pulsed vacuum treatments intensifies mass transfer in osmodehydrated blueberries, especially at higher temperatures. Nevertheless, the polyphenol retention was greater at lower temperatures; hence, the application of an intermediate process temperature (40 °C) was selected as a pre-treatment prior to further drying. The treated samples improve the retention of polyphenols after drying compared with untreated samples. Therefore, the results of this research study suggest that the use of a pulsed vacuum and ohmic heating in the osmotic dehydration (PVOD/OH) treatment at 40 °C for 240 min and subsequent drying at 60°C could be the best process for dehydrating blueberries, considering that it improved mass transfer, achieved lower losses of phenolic components and reduced the drying time.Industrial relevanceBlueberries are an important fruit due their high bioactive compound content, especially polyphenols. Studies that involve emerging technologies application could add value to blueberries. Ohmic heating and pulsed vacuum as pre-treatments improve the efficiency of dehydration processes, focused toward bioactive compounds retention and achieving commercial viability. In this work have been applied PVOD/OH treatments at moderated temperatures and subsequently dried at 60 °C, obtaining promissory results.     

Evaluation of Protease-producing Ability of Fish Gut Isolate Bacillus cereus for Aqua Feed

Extracellular protease production by Bacillus cereus isolated from the intestine of fish Mugil cephalus has been investigated in shake-flask experiment using different preparations of tuna-processing waste such as raw fish meat, defatted fish meat, alkali hydrolysate, and acid hydrolysate as nitrogen source. Among the tuna preparations tested, defatted fish meat supported the maximum protease production (134.57 ± 0.47 U ml⁻¹), and 3% concentration of the same was found to be optimum for maximizing the protease production (178.50 ± 0.28 U ml⁻¹). Effect of carbon sources on protease production in the optimized concentration of defatted tuna fish meat revealed that galactose aided the higher protease production (259.83 ± 0.04 U ml^–1) than the other tested carbon sources and a concentration of 1.5% galactose registered as optimum to enhance the protease production (289.40 ± 0.16 U ml⁻¹). The halotolerancy of B. cereus for protease production indicated that 3% of sodium chloride was optimum to yield maximum protease (301.63 ± 0.20 U ml⁻¹). Among the surfactants tested, protease production was high in Triton X 100-added medium (298.63 ± 0.12 U ml⁻¹) when compared to other surfactants, and its optimum concentration recorded was 0.8% (320.57 ± 0.17 U ml⁻¹) for more protease production. Partial characterization of crude enzyme revealed that pH 7.0 (278.90 ± 0.08 U ml⁻¹) and 60°C temperature (332.37 ± 0.18 U ml⁻¹) were optimum for better protease activity by B. cereus.     

Effect of Blanching and Drying Temperature on Polyphenolic Compound Stability and Antioxidant Capacity of Apple Pomace

The effects of blanching and drying treatments on stability, physical properties, and antioxidant activity of apple pomace polyphenols were evaluated. Blanched and unblanched apples were extracted, and the pomace was dried in a cabinet dryer at a speed of 3 m/s at 50 °C, 60 °C, 70 °C, and 80 °C. The color, total phenolics, flavonoids, individual polyphenolic compounds, anthocyanins, and total antioxidant activity were analyzed. The blanching process caused a major retention in color, total polyphenolic content, and total flavonoid content for fresh apple pomace when compared with fresh unblanched pomace. Drying of either fresh blanched or fresh unblanched pomace caused a significant reduction (P < 0.05) in total polyphenol and flavonoid content leading to a reduction in the total antioxidant activity. When compared with the unblanched treatment, drying the blanched pomace at 80 °C resulted in a product with significant amounts of total phenolics, flavonoids, and antioxidant activity. The individual phenolic compounds were significantly increased (P < 0.05) in blanched pomace that was not dried when compared with unblanched samples. Drying blanched apple pomace did not cause a significant change in the concentration of individual polyphenolic compounds, but drying unblanched apple pomace caused a reduction in the concentrations of epicatechin and caffeic acid, with an important reduction in p-coumaric acid at temperatures higher than 60 °C. However, the drying process caused a significant reduction in the antioxidant capacity. Therefore, a combination of blanching and drying processes for apple pomace results in a product that maintains antioxidant capacity.     

Shelf Life of Pretreated Dried Tomato

Determining the shelf life has become a factor of major importance in the development of foods designed to meet consumer demands in terms of quality and safety. The goal of the present study was to investigate the shelf life of vacuum-packed dried tomatoes, stored at both room and refrigeration temperature (4 °C) for a period of 180 days. The following determinations were performed during the storage period studied: microbiological analysis, instrumental color, lycopene, and ascorbic acid. Sorption isotherms were determined at both temperatures (room temperature and 4 °C). The microbiological quality of vacuum-packed dried tomatoes remained unchanged during 180 days for the refrigerated samples and 90 days for the samples stored at room temperature. The rate constant (k) of lycopene degradation of the refrigerated samples and the samples stored at room temperature was 3.209 × 10⁻⁵ and 12.994 × 10⁻⁵/day, respectively. The rate constant (k) of ascorbic acid degradation was 3.339 × 10⁻⁴/day for cold storage and 76.655 × 10⁻⁴/day for storage at room temperature. The tomatoes stored at room temperature were subjected to analysis over 90 days of storage, period after which both the appearance and sensory characteristics of the product fell below the levels of consumer acceptability. As for the tomatoes stored at refrigeration temperature, the original sensory characteristics were maintained throughout the entire storage period of 180 days.     

Review characterization of edible films formulated with sodium alginate and low-methoxyl pectin in osmotic dehydration applications

The aim of this work was to evaluate the behaviour of two edible films (sodium alginate and low-methoxyl pectin) under different osmotic conditions (solutions: sucrose, glucose syrup and maltodextrin; concentrations: 40 °Brix and 60 °Brix; temperature 40 °C and processing times: 0.5, 1 and 2 h). From the experimental water loss and solid uptake kinetics, effective diffusion coefficients and the dehydration performance ratio were obtained. The microstructural characteristics of the osmodehydrated films were also analysed using pear as a food matrix. The results showed that films osmodehydrated with maltodextrin and glucose syrup solutions presented higher dehydration performance ratio values than those osmodehydrated with sucrose. A reduction in the thicknesses of edible coatings was observed. The best formulation was sodium alginate 2% and calcium lactate 5% according to the microstructural analysis and structural integrity for at least up to 16 h of osmotic dehydration.     

Effect of Pre-treatment and Drying Method on Colour Degradation Kinetics of Dried Salak Fruit During Storage

Effect of heat treatment on colour stability of dried salak fruit during storage was investigated by using hot air (40–90 °C), heat pump (isothermal and intermittent modes, 26–37 °C) and freeze-drying. Influence of pre-treatment on the colour property was studied as well by blanching the sample at three levels of temperature (50–70 °C). Total colour change (∆E*) was used to assess the colour degradation kinetics and quantify the degree of browning during processing and storage. It was found that the dried pre-treated sample under heat pump isothermal drying recorded the highest ∆E* value during storage followed by non-pre-treated samples under heat pump intermittent drying, freeze-drying, hot air-drying and heat pump isothermal drying. Weibull model is found to better fit the experimental data as compared with zero-order and first-order kinetics models. Analysis on the kinetics constants reveals that the heat treatment could affect the microstructure, water sorption properties and concentration of reacting species of the dried product. This in turn contributes to the colour changes of the dried product during storage.