High hydrostatic pressure effect on chemical composition,color, phenolic acids and antioxidant capacity of Cape gooseberry pulp (Physalis peruviana L.)

The aim of this study was to evaluate the effects of high hydrostatic pressure (HHP) at 300, 400 and 500 MPa/1, 3 and 5 min on nutritional and antioxidant properties of Cape gooseberry pulp after immediate application and after 60 days of storage. Proximal analysis, color, phenolic acids content and antioxidant capacity were determined. When analyzing the immediate effect of different treatments, a clear influence of HHP was observed in all the components of the proximal analysis. Regarding color, none of the three chromatic parameters showed significant differences with control leading to a minimum ΔE at 300 MPa/3 min. Changes in bound and free phenolic acids were evidenced after treatments. The maximum levels of TPC as well as antioxidant capacity were observed at 500 MPa/5 min. By the end of storage, all treated samples discolored leading to ΔE = 14.9 at 500 MPa/5 min. The profile of free and bound phenolic acids presented differences compared to Day 0. The antioxidant capacity by means of ORAC increased for treatments above 300 MPa/5 min indicating the effectiveness of these treatments for the production of functional products based on gooseberry pulp. For treatments above 400 MPa/3 min, molds and yeasts were not detected.     

Bioactive phytochemicals, nutritional value, and functional properties of cape gooseberry (Physalis peruviana): An overview

Exotic fruits play an important role in nutrition as an excellent base for low calorie and dietetic products. Highly valued for its unique flavor, texture and color, recent research has shown cape gooseberry (Physalis peruviana) to be high in many beneficial compounds. The diversity of functional applications to which P. peruviana can be put gives this fruit great importance. The food industry has used cape gooseberry in different products including beverages, yogurts and jams. With the rapidly growing popularity of this unique fruit it is important to have a comprehensive reference for its nutritional benefits. This review provides a valuable source for current knowledge on bioactive phytochemicals and further development of P. peruviana for functional foods as well as nutraceutical and pharmaceutical industries.     

Application of power ultrasound on the convective drying of fruits and vegetables: effects on quality

Drying gives rise to products with a long shelf life by reducing the water activity to a level that is sufficiently low to inhibit the growth of microorganisms, enzymatic reactions and other deteriorative reactions. Despite the benefits of this operation, the quality of heat sensitive products is diminished when high temperatures are used. The use of low drying temperatures reduces the heat damage but, because of a longer drying time, oxidation reactions occur and a reduction of the quality is also observed. Thus, drying is a method that lends itself to being intensified. For this reason, alternative techniques are being studied. Power ultrasound is considered as an emerging and promising technology in the food industry. The potential of this technology relies on its ability to accelerate the mass transfer processes in solid–liquid and solid–gas systems. Intensification of the drying process with power ultrasound can be achieved by modifying the product behavior during drying, using pre‐treatments such as soaking in a liquid medium assisted acoustically or, during the drying process itself, by applying power ultrasound in the gaseous medium. This review summarises the effects of the application of the power ultrasound on the quality of different dried products, such as fruits and vegetables, when the acoustic energy is intended to intensify the drying process, either when the application is performed before pretreatment or during the drying process. © 2017 Society of Chemical Industry     

Effect of drying methods on the phenolic constituents of meadowsweet (Filipendula ulmaria) and willow (Salix alba)

The objective of this study was to investigate the effect of drying conditions on the phenolic constituents and colour of extracts of organically grown white willow and meadowsweet for incorporation into a functional beverage with potential anti-inflammatory properties. The herbs were freeze-dried, air-dried, oven or tray-dried at 30 or 70 °C. The drying kinetics of the herbs was first determined. Both drying temperature and method had a significant effect (p ≤ 0.05) on the drying rate, the samples tray-dried had a faster drying rate than those oven-dried. Results show that for meadowsweet and willow, freeze-drying and oven or tray drying at 30 °C had no significant effect on the phenolic constituents (e.g. total phenols, salicylates, quercetin) or the colour of the extracts in comparison to traditional air-drying. Although increasing the drying temperature to 70 °C resulted in an increase in the drying rate of both herbs it also led to the loss of some phenolic compounds. Also, the extracts from both herbs dried at 70 °C were significantly (p ≤ 0.05) redder than the other drying methods. Therefore, tray drying these herbs at low temperatures may reduce drying time without having a significant effect on the phenolic content and colour of the extracts.     

Electrohydrodynamic (EHD) drying of tomato slices (Lycopersicon esculentum)

The drying rate of tomato slices (Early Urbana L.) treated by a high voltage electrostatic field (HVEF) was investigated with an oven-drying and open-room drying sample, under identical conditions. ANOVA showed that the drying methods had a significant effect (P ? 0.01) on decreasing moisture content, surface temperature, and apparent color of tomato slices, but no difference was observed in shrinkage. Average drying rate for 3, 4, and 5 kV cm⁻¹ electrostatic fields over a period of 780 min increased by 1.3, 1.43, and 2 times, respectively, compared to that of the air-dried. Tomato slices dried with EHD⁺, which consumed only 16.5 mJ g⁻¹ of electric power, exhibited a better appearance (lightness and red color) with lower surface temperature than the air-dried and oven drying samples.     

Physalis peruviana Linnaeus, the multiple properties of a highly functional fruit: A review

The main objective of this work is to spread the physicochemical and nutritional characteristics of the Physalis peruviana L. fruit and the relation of their physiologically active components with beneficial effects on human health, through scientifically proven information. It also describes their optical and mechanical properties and presents micrographs of the complex microstructure of P. peruviana L. fruit and studies on the antioxidant capacity of polyphenols present in this fruit.     

Effects of various pretreatments and drying methods on Salmonella resistance and physical properties of cabbage

The combined effects of pretreatment and drying methods on the resistance of Salmonella attached to vegetable surfaces as well as some physical properties, in terms of color and shrinkage, were investigated. Cabbage was used as a test vegetable and Salmonella Anatum was used as a test microorganism. Cabbage leaves were pretreated either by soaking in 0.5% (v/v) acetic acid for 5 min, blanching in hot water for 4 min or blanching with saturated steam for 2 min prior to either hot air drying, vacuum drying (10 kPa) or low-pressure superheated steam drying (10 kPa) at 60 °C. Based on an initial Salmonella contamination level of approximately 6.4 log CFU/g, soaking in acetic acid, hot-water and steam blanching resulted in 1.6, 3.8 and 3.6 log CFU/g reduction in the number of Salmonella, respectively. Drying without pretreatment could not completely eliminate Salmonella attached on the cabbage surfaces, while no Salmonella was detected on the pretreated samples at the end of the drying process. Volumetric shrinkage was not affected by the pretreatment and drying methods. Dried blanched samples exhibited greener and darker color than the dried acetic acid pretreated and untreated samples.     

Effect of hot air drying and sun drying on color values and β-carotene content of apricot (Prunus armenica L.)

In this study, sulphurated and nonsulphurated Hacihaliloglu apricots (Prunus armenica L.) which is the most widely produced cultivar in Turkey were used to study the effects of different hot air drying temperatures (50, 60, 70, and 80 °C) and sun drying on color and β-carotene content of apricot. The time required to obtain the desired final dry matter in hot air drying was lower than sun drying. Sulphuration also decreased drying time at all drying conditions. Color values and β-carotene content of hot air dried samples were favorable in comparison to air drying. β-carotene content in dried apricots at 70 and 80 °C was 7.14, 7.17 mg 100 g⁻¹ dry matter and 6.12, 6.48 mg 100 g⁻¹ dry matter for sulphurated and nonsulphurated apricots, respectively. A good relationship was found between treatments (drying temperatures and drying times) and β-carotene content for sulphurated and nonsulphurated apricots (R²=0.9422 and 0.9129, respectively).     

The characteristics of gelatin extracted from sturgeon (Acipenser baeri) skin using various pretreatments

The physicochemical characteristics of gelatin obtained by different pretreatments of sturgeon (Acipenser baeri) skin with alkaline and/or acidic solutions have been studied. Visual appearance, pH, gel strength, viscosity and amino acid profile of the gelatins were evaluated. Pretreatment with alkaline solutions of Ca(OH)₂ and/or acetic acid (HAC) provided gelatin with a favourable colour. Pretreatment with alkali removed noncollagenous proteins effectively, whilst acid induced some loss of collagenous proteins. Gel strength and viscosity of gelatin pretreated with HAC or alkali followed by HAC were as high as gelatin extracted in the presence of protease inhibitors. Amino acid composition had no significant effect on the gelatin characteristics. The total acid concentration for the highest gel strength was inversely proportional to ionisation strength, and the preferred pH for extracting gelatin with the optimum gel strength was approximately 5.0. The results showed that any available protons, regardless of the type or concentration of the acid, inhibit protease activity, which significantly affects the gelatin characteristics.     

Ethephon‐induced fractional changes of pectic polysaccharides in developing cape gooseberry (Physalis peruviana L) fruits

Pectic polysaccharides extracted from fruit tissue of cape gooseberry (Physalis peruviana L) at different maturity levels were fractionated and analyzed for galacturonic acid backbone molecules. Preharvest spray of the fruits at 7 days old with ethephon resulted in a higher accumulation of water‐soluble and oxalate‐soluble pectic fractions than non‐treated fruits, while this treatment effectively enhanced the polygalacturonase enzyme activity necessary for maintenance of pectin degradation. Treatment with ethephon not only enhanced the solubilization rate but also resulted in a net increase in total pectic polymer content in developing cape gooseberry fruits. Copyright © 2005 Society of Chemical Industry     

Effect of drying temperature on the quality of dried bananas cv. prata and d’água

The effect of drying temperature (60 and 70 °C) on the chemical characterization, sensorial evaluation and microbiological quality of dried bananas obtained in a forced-air drying chamber under constant air flow rate (30 m³/h) was studied. The results showed that drying did not affect the chemical composition and the products were in good sanitary conditions. The sensorial analysis showed that lower drying temperatures produced better-accepted products and that under these conditions products obtained using the banana cv. d’água showed a superior texture to that of the standard.     

Microwave freeze drying of sea cucumber (Stichopus japonicus)

Freeze drying (FD) yields the best quality of dried sea cucumber but at the cost of long drying time and also the overall cost. Air drying (AD) gives an unacceptably poor quality product. To achieve faster drying along with a high quality product a microwave freeze drying (MFD) technique was developed to dry sea cucumbers. The relationship between corona discharge and microwave power at various pressures and initial moisture content conditions was studied to avoid the possibility of corona discharge during MFD. According to the drying characteristics of MFD, a control strategy for the MFD process was also developed. MFD reduced the drying time by about half of conventional FD process and provided a similar good product quality.     

Optimization of the antioxidant capacity of thyme (Thymus vulgaris L.) extracts: Management of the convective drying process assisted by power ultrasound

Food properties change during processing, altering the quality of the final product. Sometimes, the important causal relationships are not well known and thus process management is difficult. This is especially true when chemical changes can occur as in the case of the drying of bioactive materials. The aim of this work was to develop a management tool for the thyme drying process, assisted by power ultrasound, to allow the appropriate values of the operating conditions that maximize the antioxidant capacity (AC) of the dried thyme extracts to be determined. For this proposal, the thyme drying process was analyzed at different drying air temperatures (T) (40–80 °C), drying air velocities (v_a) (1–3 m/s) and levels of power ultrasound (US) (0, 6.2, 12.3, 18.5 kW m⁻³). The essential oil was extracted by means of a supercritical fluid extraction method, and its AC was measured by FRAP. The drying velocity and the AC of the dried thyme extracts were both influenced by the magnitude of the air velocity and temperature, and also by power ultrasound. Artificial neural networks were developed to formulate and solve the optimization problem. The developed management tool allowed the optimal conditions of the process to be established, thereby maximizing the AC values in function of the raw materials, process characteristics and room air conditions.     

Microwave and convective dehydration of ethanol treated and frozen apple – physical properties and drying kinetics

The objective of this study was to examine how the drying kinetics and physical properties of apples are affected by pre-treatment with 95% ethanol or freezing at –18 °C before microwave-assisted air dehydration at 50, 60 and 70 °C. Microwave heating was used to obtain these temperatures in the centre of the apple cubes. After dehydration the shrinkage and rehydration capacity were measured. The texture of dehydrated and rehydrated samples was analysed with a puncture test in a texture analyser. Samples were also analysed with confocal laser scanning microscopy to determine the correlation between physical and microstructural properties. Diffusivity in the different dehydration processes was calculated. Ethanol-treated apples showed both high rehydration and high effective rehydration capacity compared with the other samples. Freezing before dehydration increased the diffusivity and reduced the firmness of rehydrated apples compared with no pre-treatment.     

Effect of chemical pretreatments on the fermentation and ultimate digestibility of bagasse by Phanerochaete chrysosporium

When sugarcane bagasse was pretreated at room temperature with various chemicals singly or in combination, (0.25 m NaOH; 0.5 m H₂SO₄; 2.6 M NH₃;0.14 M Ca(OH)₂+0.12 M Na₂CO₃;4.2 m EDA; and 0.5 M H₂SO₄ or 0.25 M NaOH followed by 4.2 M EDA), increases in in-vitro digestibility range from 28.9 to 48.6% depending on the particular chemicals. With most pretreatments, the hemicellulose content decreased and the cellulose content increased slightly, while lignin levels decreased only with NaOH + EDA pretreatments. Further fermentation of the chemically pretreated bagasse with Phanerochaete chrysosporium gave increased digestibilities, the highest final digestibility (59%) being achieved by pre-treatment with 0.25 M NaOH. Pretreatment with NaOH or Ca(OH)₂+Na₂CO₃ and fermentation gave greatly increased levels of hemi-cellulose and cellulose and substantial decreases in lignin levels. Chemical pretreatments of bagasse together with autoclaving considerably enhanced in-vitro digestibility (up to 75%) and lignin degradation (1.4%). Pretreatment with NaOH, Ca(OH)₂+Na₂CO₃, and EDA plus autoclaving gave large increases in total hemicelluloses and cellulose and marked decreases in lignin. Further fermentation with P. chrysosporium gave only slight increases in digestibility.     

Hot-air drying characteristics of Aloe vera (Aloe barbadensis Miller) and influence of temperature on kinetic parameters

The aim of this research was to study and model the kinetics of the hot-air drying of Aloe vera (Aloe barbadensis Miller) and to evaluate the influence of temperature on the kinetic parameters for the proposed models. A convective dryer was used at 50, 60, 70, 80 and 90 °C with an air flow of 2.0±0.2 m/s. The sorption isotherm of the fresh product was mathematically described by the Guggenheim, Anderson and de Boer (GAB) model, giving as a result monolayer moisture of 0.20 g water/g d.b. The mathematical models evaluated in the kinetic research included five empirical equations (Newton, Henderson-Pabis, Page, modified Page and Fick's diffusional model). The fit quality of the proposed models was evaluated by using the linear regression coefficient (r²), sum square error (SSE), root mean square error (RMSE) and Chi-square statistic (χ²). The diffusivity coefficient increased with the temperature from 5.30 to 17.73×10⁻¹⁰ m²/s, for a range of temperatures between 50 and 90 °C, with an estimated activation energy of 30.37 kJ/mol. When comparing the experimental moisture values with those estimated by the proposed models, the modified Page model provided the best to fit of the data, showing that this equation correctly simulates the Aloe vera drying process and represents an excellent tool for estimating its drying time.     

Analysis of giant pumpkin (Cucurbita maxima) drying kinetics in various technologies of convective drying

The paper analyses the results of the research on drying a variety of giant pumpkin (Justynka – 957). The research involved drying kinetics of pumpkin as well as changes in the volume of 10 mm pumpkin cubes, dried at the temperature of 80 °C, using free (natural) convection and in the forced convection in the tunnel dryer, with the drying factor speed of 1.2 m s⁻¹ and in the fluid bed dryer. Drying kinetics of pumpkin pieces dried in the tunnel dryer, fluid bed dryer and during two-stage initial drying in the tunnel, and in the fluid bed dryer were examined. Measurements results were used to verify the theoretical models of drying kinetics of the first period taking volume shrinkage into consideration, and the second period of the examined processes.     

Effects of pretreatments on colour alterations of litchi during drying and storage

The objective of this research was to study the effect of osmotic pretreatment with combined anti-browning agents (acid, glycerol and/or trehalose) on the colour characteristics of dried litchi after drying and during 5 months of storage compared to samples without pretreatment. The pretreated samples showed good inhibition of polyphenol oxidase activity when compared with the control, while the total phenolic contents in the dried products were not reduced. The results demonstrated that water activity, lightness difference, chroma, degree of browning (DB), and 5-hydroxymethylfurfural values of all pretreated samples increased, while hue angle decreased with storage time. Samples pretreated with glycerol showed the best potential for browning retardation, followed by glycerol combined with trehalose, and trehalose, respectively. In addition, the colour parameters were used to calculate the luminescence values, representing the data in grey scale, which were correlated with a non-enzymatic browning index. The results showed grey value could be adequately used to represent the DB of dried litchi with r ² value of 0.92.     

Effect of high hydrostatic pressure pretreatment on drying kinetics, antioxidant activity, firmness and microstructure of Aloe vera (Aloe barbadensis Miller) gel

The effect of High Hydrostatic Pressure (HHP) and other pretreatments on the drying kinetics, antioxidant activity, firmness and microstructure of Aloe vera gel was investigated during convective drying at 70 °C. The pretreatments analyzed were high hydrostatic pressure, blanching, enzymatic and microwaves. Simulation of drying curves was studied through the application of several mathematical models such as Newton, Henderson and Pabis, Page, Modified Page, Wang and Singh, and Weibull. Among them, the Weibull model provided the best fit for the experimental data. All pretreatments increased the water diffusion coefficient compared to the control sample. Microwaves followed by HHP presented the fastest drying rates. All pretreatments modified the microstructure and hence the texture of the product. HHP and microwaves increased firmness while blanching and enzymatic treatments produced a softer final product. Blanching, microwaves and HHP enhanced A. vera antioxidant activity. However, the HHP pretreated samples showed the highest antioxidant activity compared to the rest. Based on these results, HHP together with convective drying offers the chance of producing dried aloe with high antioxidant attributes.