Drying Kinetics and Microstructural and SensoryProperties of Black Chokeberry (Aronia melanocarpa) as Affected by Drying Method

Effect of Drying Methods on Chemical and Sensory Properties of Cannabis sativa Leaves

Hemp is used as a source of fiber, oil and bioactive substances including volatile and cannabinoid-containing substances. This paper presents, for the first time, results on the evaluation of drying methods (convective, vacuum-microwave and combined convective pre-drying and vacuum-microwave finishing drying) of hemp leaves on the qualitative and quantitative changes in secondary metabolites, including essential oils, cannabinoids and sterols. A ranking and descriptive test of hemp leaves was also performed. Drying kinetics was presented using three models, including logarithmic, Midilli and modified Page. The SPME-Arrow technique was used to determine 41 volatile compounds, of which caryophyllene, β-myrcene and α-humulene were dominant in dried and fresh leaves. Regarding the essential oils obtained, 64 were identified, with caryophyllene, humulene epoxide II and limonene being the dominant ones. For preserving the highest amount of oils, the best method was the convective pre-drying followed by vacuum-microwave finishing drying (CD60-VMD) combined method, where the retention of volatile compounds was 36.08%, whereas the CD70 and 240-VMD methods resulted in the highest loss of 83%. The predominant cannabinoids in fresh hemp leaves were CBDA 6.05 and CBD 2.19 mg g-1. Drying caused no change in the cannabinoid profile of the plant material. β-Sitosterol, campesterol and lupeol were dominant in the phytosterol and triterpene fractions. No changes in either quality or quantity were observed in any of the variants found.

The Temperature Influence on Drying Kinetics and Physico-Chemical Properties of Pomegranate Peels and Seeds

Pomegranate is a fruit desirable for its nutritional and medicinal properties which has a great industrial potential that is yet under-explored. Notable for its integral use, the peels are used in medicinal infusions and the seeds consumed without restrictions. In this sense, the objective of this work is to determine the drying kinetics of pomegranate peels and seeds in a hot air circulation oven, at temperatures of 50, 60, and 70 °C, adjust mathematical models to experimental data, determine the effective diffusivities and thermodynamic properties of the process and the physicochemical characteristics of peels and seeds of fresh pomegranates and in their flours. Twelve models were used to adjust the drying kinetics, obtaining better results with the Diffusion Approximation model, Verma, and modified Henderson and Pabis. The effective diffusivities were well represented by an Arrhenius equation, with activation energies of 31.39 kJ/mol for seeds and 10.60 kJ/mol for peels. In the drying process, the seeds showed higher values of enthalpy, entropy, and Gibbs free energy concerning peels. Pomegranate peel and seed flours have proximal composition and distinct physicochemical characteristics, with high fiber, carbohydrate, and energy content. In addition, peel flours stand out for their mineral content, and seed flours do for their lipid and protein content.

The role of emerging technologies in the dehydration of berries: Quality, bioactive compounds, and shelf life

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Berries comprise essential nutrients necessary for healthy living.

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Convective, vacuum, microwave, and freeze-drying are the most common methods.

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Pre-treatments improve permeability, accelerate drying, and inactivate oxidation.

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Combined methods are recommended to assure high quality of dehydrated berries.

Berries are among the fruits with the highest nutritional and commercial value. This paper reviews the conventional and emerging dehydration methods most commonly used as postharvest treatment and discusses their efficacy in maintaining and/or improving the nutritional and functional qualities of dried berries. The characteristics of the conventional methods (e.g., convective drying, freeze-drying, spray-drying, osmotic dehydration), their pre-treatments, their combination, and intermittent drying, as well as their potential disadvantages are discussed. The use of emerging dehydration techniques (e.g., electromagnetic radiation drying, explosion puffing drying, heat pump drying, low-pressure superheated steam drying, microwave drying) allows to improve the quality of the dried berries compared to conventional techniques, in addition to reducing drying times, increasing drying speed and energy efficiency. Finally, the use of pre-treatments and the combination of technologies can enhance the quality of the final product as a result of the improvement in the effectiveness of the dehydration process.

Effect of Pulsed Electric Field Pre-Treatment and the Freezing Methods on the Kinetics of the Freeze-Drying Process of Apple and Its Selected Physical Properties

The aim of this study was to investigate the effect of application of pulsed electric field (PEF) and different freezing methods (fast, slow and vacuum freezing) on the drying kinetics as well as selected physical properties of freeze-dried apple. The apples were subjected to PEF treatment with range of pulses from 0 to 160 and the intake energy from 0 to 1327 kJ·g⁻¹. Apples with and without PEF treatment were frozen with different rates and the freeze-dried. The water content, water activity and colour attributes of freeze-dried apples were investigated. Regression analysis and fitting procedures showed that among six different models, the Midilli et al. model the best described the drying curves of all dried samples. The highest value of the parameter L* = 71.54 was obtained for freeze-dried sample prepared without PEF pre-treatment and fast frozen. Application of PEF pre-treatment resulted in increase in browning index of freeze-dried apples (BI). The studies confirmed the positive effect of PEF on the freeze drying rate only in the case of the slow or fast freezing of the material after the application of low-energy PEF treatment. However, the increase in drying rate was also observed after application of slow and vacuum freezing of the material without PEF pre-treatment. These technologies can be recommended for optimization of the freeze drying process of apples. The statement that the freeze drying process with application of appropriately selected PEF processing parameters causing only partial destruction of cell membranes can be considered as an innovative contribution to the development of science about the possibilities of PEF application.

Influence of Drying Temperature on the Different Thermodynamic Parameters during the Indirect Convective Solar Drying of Crocus sativus L. Of Morocco Thin-Layer Solar Drying of Moroccan Saffron

This work deals with the study of the drying kinetics of Crocus sativus L. using convective solar drying. The main objective was to identify the influence of airflow drying temperatures for ambient air temperature ranged between 15.6 and 18.9°C, and a relative humidity between 24.4 and 46.5%. The equilibrium moisture content varies from 0.09 to 0.06 (% d.b), respectively, for drying air temperatures 35-50°C. The airflow velocity was about 0.2 m s-1, which implied establishing a phenomenological diffusion model of the water within the matrix. Empirical models were also determined as well as a polynomial equation (order 3) of the characteristic drying curve. The Midilli-Kucuk model was found to be the best to describe the experimental drying curves of Crocus sativus L. The effective moisture diffusivity ranged between 0.87 and 1.46 10-11 m2 s-1 for airflow temperature 35 and 50°C, while the average activation energy was calculated as 28.76 kJ mol-1. The increase in temperature decreases the total energy consumption which varies, respectively, from 3.211 to 2.681 kWh.

Comparison of Different Drying Methods for Asparagus [Asparagus cochinchinensis (Lour.) Merr.] Root Volatile Compounds as Revealed Using Gas Chromatography Ion Mobility Spectrometry

Asparagus [Asparagus cochinchinensis (Lour.) Merr.] is a traditional herbal medicine plant commonly used to nourish yin, moisten dryness, and clear fire cough symptoms. Drying is an excellent option to conserve food materials, i.e., grains, fruits, vegetables, and herbs, reducing the raw materials volume and weight. This study aims to evaluate different drying approaches that could increase the value of asparagus, particularly as an ingredient in fast foods or as nutraceutical byproducts. The volatile components of asparagus roots were analyzed by using headspace-gas chromatography-ion mobility spectroscopy under different drying conditions, i.e., natural drying (ND) at ambient air temperature in the dark, well-ventilated room, temperature range 28-32°C, blast or oven drying at 50°C, heat pump or hot-air drying at temperature 50°C and air velocity at 1.5 ms-1 and vacuum freeze-drying at the temperature of -45°C and vacuum pressure of 10-30 Pa for 24 h. The findings revealed that the various drying processes had multiple effects on the color, odor index, and volatile compounds of the asparagus roots. As a result of the investigations, multiple characteristics of components, therefore, exploitation and comparison of various flavors; a total of 22 compounds were identified, such as alcohols, ketones, aldehydes, acids, esters, heterocyclic, and terpene. The present findings may help understand the flavor of the processed asparagus roots and find a better option for drying and processing.

The effect of high-power ultrasound pretreatment on drying efficiency and bioactive compounds of chokeberry (Aronia melanocarpa L.)

Chokeberry (aronia) fruit is a rich source of bioactive compounds with various health benefits. However, it has a limited shelf life and a firm (tight) structure that makes it difficult for moisture transfer during drying. Therefore, the aim of the study is to investigate the effects of high-power ultrasound pretreatment (550 W, 30 min) and air drying temperature (65, 70 and 75 °C) on the drying rate and bioactive compounds of chokeberry fruit. Accordingly, chokeberries were dried directly or after ultrasound pretreatment, and the retention rate of bioactive properties, i.e., total phenolic, flavonoid and monomeric anthocyanin contents along with antioxidant capacity values, were examined. The required time for drying as well as the activation energy values were significantly lower in ultrasound treated samples. Logarithmic and Midilli models exhibited the best fit for drying kinetics of samples. The pretreatment led to significantly lower moisture content and a_w values. Compared to fresh sample, the highest retention rate for some bioactive properties was found in ultrasound pretreated sample dried at 75 °C. The ultrasonication also reduced the electricity consumption (kWh) in all temperature levels of drying operations. As a conclusion, the ultrasound pretreatment prior to drying had dual role by facilitating drying kinetics and by providing higher bioactive contents.

Sustainable food processing of selected North American native berries to support agroforestry

Chokeberries, elderberries, blueberries, and blackberries are highly nutritious native fruits in the US Midwest region. Their high moisture content, delicate structure easily leads to fruit loss/waste. This review focuses on different drying methods for whole fruits and juices to preserve their quality and improve their shelf life. Solar drying, hot-air drying, spray drying, freeze-drying, vacuum-drying, electromagnetic drying, and osmotic dehydration are the commonly used dehydrating methods for berries. Berries are photo, heat-sensitive, and rich source of essential nutrients. Texture, flavor, color, water content, phytonutrients, physicochemical properties can be influenced by dryer and processing parameter selection. Drying is a complex dynamic process, due to structural differences among various foods, combined thermal and non-thermal techniques could improve fruit quality. Hence, knowledge of drying behavior and degradation kinetics is vital for optimizing the process parameters to enhance the fruit quality. Freeze drying and spray drying showed better preservation of nutrients. Existing research suggests that chokeberries (Aronia) are underutilized compared to blueberries and blackberries. Aronia fruit has a lot of potentials containing health-promoting compounds and is yet to be explored. Future research suggestions have been put forward for the efficient use of drying techniques and to improve the fruit quality.

The Effect of Plant Additives on the Stability of Polyphenols in Dried Black Chokeberry (Aronia melanocarpa) Fruit

Chokeberry fruit exhibits a high level of pro-health potential, associated with a significant amount of polyphenol content and antioxidant activity. The fruit is easily perishable and therefore needs to be processed in short order to ensure its availability throughout the year. For this purpose, the fruit is dried, which has an impact on the preservation of bioactive components such as polyphenols. In the study, chokeberry fruit was influenced by a suspension of spices, including clove and cinnamon, and subsequently dried using the freeze-drying, convection, and microwave radiation methods. Freeze-drying was concluded to be the most desirable method of drying, which preserves the largest amount of polyphenols while soaking fruit in a suspension of cinnamon or cloves accelerated the loss of anthocyanins during the storage period. The obtained test results may constitute a valuable source of information for manufacturers in designing new products with increased pro-health potential, whose properties result from the high content of polyphenols and other plant additives.

Effects of Different Drying Methods on the Retention of Bioactive Compounds, On-Line Antioxidant Capacity and Color of the Novel Snack from Red-Fleshed Apples

The aim of this study was to determine the effect of different drying methods: convective (at 50, 60, 70 °C), vacuum-microwave (at 120, 240, 360, 480 W and 360 W with reduction to 120 W) and hybrid (convective pre-drying at 50, 60, 70 °C followed by vacuum-microwave drying at 120 W) on the quality parameters of novel red-fleshed apple fruit snacks (RFAs), such as phenolics, on-line antioxidant capacity, water activity and color. Drying kinetics, including a temperature profile of dried material, and modified Page model were determined. Freeze-drying was used as a control method. The highest content of bioactive compounds in the samples was retained following freeze-drying, then hybrid, vacuum-microwave and finally convection drying. The antioxidant capacity measured by on-line 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), identified anthocyanins, flavan-3-ols and phenolic acid as the main compounds responsible for this activity. Unfavorable changes in color, formation of hydroxymethylfurfural (HMF) and degradation of polyphenolics were noted along with increasing drying temperature and magnetron power. The red-fleshed apple snacks are a promising high-quality dehydrated food product belonging to functional foods category.

Comparison of Traditional and Novel Drying Techniques and Its Effect on Quality of Fruits, Vegetables and Aromatic Herbs

Drying is known as the best method to preserve fruits, vegetables, and herbs, decreasing not only the raw material volume but also its weight. This results in cheaper transportation and increments the product shelf life, limiting the food waste. Drying involves the application of energy in order to vaporize and mobilize the moisture content within the porous products. During this process, the heat and mass transfer occurs simultaneously. The quality of dehydrated fruits, vegetables, and aromatic herbs is a key problem closely related to the development and optimization of novel drying techniques. This review reports the weaknesses of common drying methods applied for fruits, vegetables, and aromatic herbs and the possible options to improve the quality of dried products using different drying techniques or their combination. The quality parameters under study include color, bulk density, porosity, shrinkage, phytochemicals, antioxidant capacity, sugars, proteins, volatile compounds, and sensory attributes. In general, drying leads to reduction in all studied parameters. However, the behavior of each plant material is different. On the whole, the optimal drying technique is different for each of the materials studied and specific conditions must be recommended after a proper evaluation of the drying protocols. However, a novel or combined technique must assure a high quality of dried products. Furthermore, the term quality must englobe the energy efficiency and the environmental impact leading to production of sustainable dried products.

Effects of physical and chemical pretreatments on drying and quality properties of blackberry (Rubus spp.) in hot air dryer

This research examines the impact of various pretreatments on effective moisture diffusivity coefficient (Deff ), activation energy (Ea ), specific energy consumption (SEC), color, and shrinkage of blackberry (Rubus spp.). Hot air drying experiments were conducted under three different temperatures (50, 60, and 70°C) and four pretreatments, including thermal pretreatment by hot water blanching at 70, 80, and 90°C, pulse pretreatment with microwave having power of 90, 180, and 360 W, chemical pretreatment using ascorbic acid (1% in distilled water), and mechanical pretreatment using ultrasonic vibration with working frequency of 28 ± 5% kHz for 15, 30, and 45 min. The results show that the highest Deff value, which was 1.00 × 10-8 m2/s, could be achieved by using a microwave pretreatment with power and drying temperature of 360 W and 70°C͘, respectively. Moreover, the lowest Deff value obtained from this similar pretreatment condition was 3.10 × 10-9 m2/s at a drying temperature of 50°C, while Ea ranged from 13.61 to 26.02 kJ/mol. The highest and lowest SECs were 269.91 kW hr/kg for the control sample and 75.63 kW hr/kg for the microwave pretreatment, respectively. Furthermore, the largest color change and shrinkage were detected in ascorbic acid pretreatment and control sample, respectively.

The drying process of Sarcocornia perennis: impact on nutritional and physico-chemical properties

The Sarcocornia genus is an extreme salt-tolerant plant that can be cultivated in saline habitats almost worldwide. To preserve Sarcocornia perennis, convective drying experiments were conducted and their effects on the physico-chemical properties and phenolic content of the plant were studied using conventional and vibrational spectroscopy techniques. The drying process of Sarcocornia perennis at temperatures of 40 °C, 50 °C, 60 °C and 70 °C revealed three periods of convective drying process with drying times ranging between 4.5 and 24.9 h, respectively to higher and lower temperatures. The heating-up period can be neglected as compared with the drying process, and the duration of constant rate period, as a percentage of the total drying time, ranged between 34 and 20% respectively at 40 °C and 70 °C. The Modified Page model was proposed to describe the drying process at the different temperatures. From a nutritional point of view, this halophyte plant may be considered as a good source of fibres, phenolic compounds and natural minerals, such as sodium, potassium, calcium and magnesium. The convective drying, in the temperature range currently used, was found to preserve the colour, nutritional characteristics and phytochemical value of Sarcocornia perennis. These results were confirmed by FTIR-ATR and highlight the potential use of the dried plant in novel food products.

Physicochemical Properties of Dried Apple Slices: Impact of Osmo-Dehydration, Sonication, and Drying Methods

Apple slices of the Elise variety were previously osmo-dehydrated in erythritol, xylitol, and sucrose for 2 h. In some parts of the experiment, 30 min of ultrasound pre-treatment (US) were applied. Afterwards, fruit samples were dried by convective (CD), microwave-vacuum (VM), and a combined method (CD/VM, mix two of them). The main aim of the research was to characterize an impact of osmotic dehydration, sonication pre-treatment, and drying method on the physicochemical properties of the dried apples. The use of sugar alcohols (xylitol, erythritol) in the production of dried apples did not badly affect the taste of the obtained dried products; it enabled a noticeable cooling/refreshing effect felt in the mouth when consuming a snack, and enabled the production of dried snacks with lower calorific value. Polyol residues in the product were at a level that was safe for consumers. The most popular convective drying was long lasting, whereas the VM drying method allowed for the shortest drying time, amounting to 76 min; moreover, additional application of ultrasounds reduced this time to 36 min. The combined drying method allowed the total duration of the process to be reduced 2–4.5 times. Ultrasound applied during osmotic dehydration did not significantly affect attributes of the descriptive sensory analysis for the obtained dried apples. The best hygroscopic properties, ensuring the storage stability of the dried product, showed dried apples previously osmo-dehydrated in erythritol and sucrose solutions.

The Use of a Hybrid Drying Method with Pre-Osmotic Treatment in Strawberry Bio-Snack Technology

The aim of this study was to determine the effect of osmotic pre-treatment on physical and sensory properties of dried strawberry. Frozen strawberries were dehydrated in sucrose solution with/without 5 or 15 % concentrated chokeberry juice. Then, samples were dried in hybrid (convective-microwave-vacuum) and freeze-drying method. The chokeberry juice concentrate addition to the osmotic solutions had no effect on the mass transfer of dehydrated strawberries but changes in sensory properties, also after storage. Initial osmotic treatment in sucrose solution with 5 % of chokeberry juice concentrate resulted in improved colour, when 15 % addition caused the darkening of the dried strawberries. Strawberries dried by hybrid method exhibited greater hardness and brittleness than by freeze-drying, which were slightly higher evaluated in the sensory analysis. Storage for 3 months resulted in an increase in the hardness of the samples, the reduction of colour parameters and sensory quality.

Assessment of the Spatial Distribution of Moisture Content in Granular Material Using Electrical Impedance Tomography

This paper presents a method for the online determination of the spatial distribution of the moisture content in granular material. It might be essential for the monitoring and optimal control of, for example, drying processes. The proposed method utilizes Electrical Impedance Tomography (EIT). As an exemplary material for experimental research, the black chokeberry (Aronia melanocarpa) was used. The relationship between the electrical impedance of the chokeberry and its moisture content was determined for a wide range of frequencies (20 Hz-200 kHz). The EIT research consisted of both simulation and experimental investigation. Experimental studies of the spatial distribution of the moisture content were performed in a cylindrical vessel equipped with 8 electrodes circumferentially arranged. The voltage signal from the electrodes was acquired simultaneously using the data acquisition module. Due to the high impedance of the chokeberries, exceeding 109 Ω for the dried matter, extraordinary instrumentation was necessary to be applied. On the other hand, raw chokeberry was characterized by a several orders of magnitude lower impedance (103-104 Ω), especially for high frequencies. The wide range of the observed impedance was able to be measured owing to its use of the voltage stimulation instead of the current stimulation (which is most common for EIT). The image reconstruction problem was solved using an iterative Gauss-Newton algorithm and the EIDORS (Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software) package. The obtained results showed a satisfactory ability to localize an insufficiently dried part of the material. Prospective ways to improve the imaging quality are also discussed.

The Influence of Drying Method on Volatile Composition and Sensory Profile of Boletus edulis

The objective of this study was to evaluate the influence of different drying methods on aroma and sensory profile of Boletus edulis (cepe). The drying methods tested were convective drying (CD), freeze-drying (FD), vacuum microwave drying (VMD), and a combination of convective predrying and vacuum microwave finish-drying (CPD-VMFD). Fresh and dried cepe volatiles, analyzed by SPME and GC-MS, showed the presence of 53 volatile compounds, most of them present in all dried samples but with quantitative variation. The major volatile compounds in fresh and dried cepe were 1-octen-3-ol (3405 µg 100 g−1·db), 3-octanone (429 µg 100 g−1·db), and hexanal (355 µg 100 g−1·db). The results showed that drying of cepe mushrooms caused major losses of aroma compounds; however, the highest content of volatile compounds and the highest intensity of most of the key positive sensory attributes were found in samples after (i) CD at 80°C (3763 µg 100 g−1·db), (ii) CD at 70°C (3478 µg 100 g−1·db), and (iii) CPD at 60°C and VMFD at 480/240 W (2897 µg 100 g−1·db).

A new setup for the quantitative analysis of drying by the use of gas-phase FTIR-spectroscopy

Drying rates are important for the manufacture of thin films and in specific for the production of electrodes used in electrochemical devices such as fuel cells and electrolyzers. The known procedures to investigate time-dependent sample compositions and selective evaporation rates are insufficient to obtain mean information about the full area instead of a single point analysis. Therefore, a new setup is presented using gas-phase Fourier-transform infrared spectroscopy. This method analyzes the gas-phase composition to recalculate the layer composition in electrode fabrication at any time during drying. According to the golden rule of measurement technology, manufacturer specifications are often overestimated. Therefore, our alternative procedures were used to evaluate the precision of devices used. The calculated measurement precision is confirmed by validation. The expected deviation is quantified to be less than 2% for the common application. Further on, the relative test-retest standard deviation is determined to be 0.3%-0.4%. As a result of the error propagation, the measurement precision is limited by the background gas flow rate precision for common application. At low volume fractions, the influence of the substance flow rate deviations becomes significant. However, further studies will focus on increasing the gas flow rate precision.

Volatile composition and sensory profile of shiitake mushrooms as affected by drying method

BACKGROUND

One of the best preservation method for long-term storage is drying. In this work, the influence of different drying methods on aroma and sensory profile of shiitake mushroom was evaluated. The drying methods tested were: convective drying (CD), freeze-drying (FD), vacuum-microwave drying (VMD), and a combination of convective pre-drying and vacuum-microwave finish-drying (CPD-VMFD).

RESULTS

The volatile composition of fresh and dried shiitake mushrooms was analysed by SPME, GC-MS and GC-FID, and showed the presence of 71 volatile compounds, most of them present in all dried samples but with quantitative variation. The major volatile compounds in fresh shiitake were 1-octen-3-ol (20.2%), 2-octanone (20.7%), 1,2,4-trithiolane (9.8%), and 1,2,3,5,6-pentathiepane (8.2%). Drying of shiitake mushrooms caused significant losses of C8 compounds and cyclic sulfur compounds, such as 1,2,4-trithiolane (V31) and 1,2,4,5-tetrathiane (V57). Samples dried at CD 80 °C implied a relative short drying time (120 min), had the highest contents of total volatiles (1594 μg 100 g^-1 ) and cyclic sulfur compounds (e.g. V57 126 μg 100 g^-1 ), and the highest intensity of most of the key positive sensory attributes, such as inner colour (7.0), fresh shiitake flavour (6.7), and sponginess (6.2).

CONCLUSION

The best dehydration methods, resulting in the highest total concentrations of volatile compounds and high intensity of key sensory attributes were FD (if vacuum and liquid nitrogen facilities are available) and CD at 80 °C (for companies with vacuum and liquid nitrogen facilities). © 2017 Society of Chemical Industry.

The Effect of Selected Fruit Juice Concentrates Used as Osmotic Agents on the Drying Kinetics and Chemical Properties of Vacuum-Microwave Drying of Pumpkin

The study examined the osmotic dehydration of pumpkin slices in chokeberry, flowering quince, and raspberry concentrated juices. Products obtained were subjected to vacuum-microwave finish drying (VMD). The objective of the study was to evaluate the drying kinetics and the chemical properties, that is, total polyphenolics content and antioxidant capacity of the vacuum-microwave-dried pumpkin products. The concentration and temperature of the juices were 40°Brix and 45°C, respectively. The pumpkin slices were pretreated in concentrated juices for 0.5, 1, 2, 3, and 6 hours. Vacuum-microwave finish drying was carried out at the power of magnetrons that ensured the maintenance of the safe temperature (below 90°C) of the slices measured with the use of infrared camera. The results of the study showed that the moisture content of samples during the pretreatment in concentrated juices was decreasing until the equilibrium stage. The logarithmic model was used to describe the drying kinetics of pumpkin during VMD. Osmotic pretreatment resulted in a decrease in colour coordinates, improved the antioxidant activity of dried product, and prolonged the duration of VMD.

The Influence of the Osmotic Dehydration Process on Physicochemical Properties of Osmotic Solution

The osmotic dehydration (OD) process consists of the removal of water from a material during which the solids from the osmotic solution are transported to the material by osmosis. This process is commonly performed in sucrose and salt solutions. Taking into account that a relatively high consumption of those substances might have a negative effect on human health, attempts have been made to search for alternatives that can be used for osmotic dehydration. One of these is an application of chokeberry juice with proven beneficial properties to human health. This study aimed to evaluate the physicochemical properties of the OD solution (chokeberry juice concentrate) before and after the osmotic dehydration of carrot and zucchini. The total polyphenolics content, antioxidant capacity (ABTS, FRAP), dynamic viscosity, density, and water activity were examined in relation to the juice concentration used for the osmotic solution before and after the OD process. During the osmotic dehydration process, the concentration of the chokeberry juice decreased. Compounds with lower molecular weight and lower antioxidant capacity present in concentrated chokeberry juice had a stronger influence on the exchange of compounds during the OD process in carrot and zucchini. The water activity of the osmotic solution increased after the osmotic dehydration process. It was concluded that the osmotic solution after the OD process might be successfully re-used as a product with high quality for i.e. juice production.

Volatile composition and sensory profile of Cantharellus cibarius Fr. as affected by drying method

BACKGROUND

In this work, the influence of different drying methods on the aroma composition and sensory quality of chanterelle mushrooms (Cantharellus cibarius Fr.) was evaluated. The drying methods tested were convective drying (CD), freeze drying (FD), vacuum microwave drying (VMD) and a combination of convective pre-drying and vacuum microwave finish drying (CPD-VMFD).

RESULTS

Analyses of fresh and dried chanterelle samples by HS-SPME and GC/MS and GC-FID showed the presence of 39 volatile compounds at different concentrations. The most abundant compounds in fresh chanterelle were 1-hexanol (33.4 μg per 100 g dry basis (db)), 1-octen-3-ol (80.2 μg per 100 g db) and 2-octen-1-ol (19.3 μg per 100 g db). The results showed that fresh and dried chanterelle contained very low levels of aroma compounds; however, the highest contents of volatile compounds were found in samples after (i) CD at 80 °C (129 μg per 100 g db), (ii) CPD-VMFD at 70 °C-480/240 W (136 μg per 100 g db) and (iii) CPD-VMFD at 80 °C-480/240 W (136 μg per 100 g db).

CONCLUSION

The best dehydration methods, which resulted in high contents of volatile compounds and appropriate sensory quality, according to descriptive sensory analysis and PCA tools, were CD at 70 and 80 °C. Besides, these methods led to spongy dried mushrooms with high intensities of fresh, mushroom ID, with proper color and without intense shrinkage. © 2017 Society of Chemical Industry.

Influence of osmotic dehydration pre-treatment and combined drying method on physico-chemical and sensory properties of pomegranate arils, cultivar Mollar de Elche

"Mollar de Elche" is the most popular Spanish pomegranate cultivar (intense sweetness and easy-to-chew arils); however, arils have pale pink colour and flat sensory profile. "Mollar the Elche" arils first underwent an osmotic dehydration pre-treatment (OD) with concentrated juices: (i) chokeberry, (ii) apple, and/or (iii) pomegranate cultivar "Wonderful", to improve their antioxidant capacity, colour, and sensory profile complexity, and later the arils were dried by a combined method (convective pre-drying+vacuum microwave finish drying). The use of OD provided dried arils with characteristic sweetness, and improved colour and aromatic complexity. The recommended OD methods were those using (i) pomegranate, and (ii) pomegranate with chokeberry juices; they improved the total anthocyanin content (mean of 368mgkg^-1), red colour (a^∗ coordinate 15.6), and antioxidant capacity (e.g. ABTS mean of 5.7mmolTrolox100g^-1). However, further research is still needed because freeze-dried arils had the highest anthocyanin content.

Overall Quality of Fruits and Vegetables Products Affected by the Drying Processes with the Assistance of Vacuum-Microwaves

The seasonality of fruits and vegetables makes it impossible to consume and use them throughout the year, thus numerous processing efforts have been made to offer an alternative to their fresh consumption and application. To prolong their availability on the market, drying has received special attention as currently this method is considered one of the most common ways for obtaining food and pharmaceutical products from natural sources. This paper demonstrates the weakness of common drying methods applied for fruits and vegetables and the possible ways to improve the quality using different drying techniques or their combination with an emphasis on the microwave energy. Particular attention has been drawn to the combined drying with the assistance of vacuum-microwaves. The quality of the dried products was ascribed by chemical properties including the content of polyphenols, antioxidant capacity and volatiles as well as physical parameters such as color, shrinkage, porosity and texture. Both these fields of quality classification were considered taking into account sensory attributes and energy aspects in the perspective of possible industrial applications. In conclusion, the most promising way for improving the quality of dried fruit and vegetable products is hybrid drying consisting of osmotic dehydration in concentrated fruit juices followed by heat pump drying and vacuum-microwave finish drying.

Physicochemical properties of whole fruit plum powders obtained using different drying technologies

Physicochemical quality parameters of plum powders obtained by applying conventional drying methods and their combination devised to process plums were evaluated. The effect of freeze-drying (FD), vacuum drying (VD), convective drying (CD), microwave-vacuum drying (MVD) and combination of convective pre-drying and microwave finish-drying (CPD-MVFD) affected physical (bulk density, porosity, colour, solubility) and chemical (polyphenolic compounds determined by UPLC and antioxidant capacity by TEAC ABTS and FRAP methods) properties of plum powders. The MVD at 1.2 W g(-1) and a novel combination for plum powders production - CPD-MVFD at 70 °C/1.2 W g(-1) allowed the best preservation of phenolic compounds and increased the efficiency of production. Results obtained support the use of MVD and its combination for better quality of dried plum products. The study proved that the determination of the browning index and HMF level (formed via Maillard reaction) might be good tool for monitoring the thermal processing of plum powders.

Bioactive Compounds of Blueberries: Post-Harvest Factors Influencing the Nutritional Value of Products

Blueberries, besides having commonly-recognized taste properties, are also a valuable source of health-promoting bioactive compounds. For several decades, blueberries have gained in popularity all over the world, and recent years have seen not only an increase in fresh consumption, but also in the importance of blueberries for the processing industry. Blueberry processing mostly consists of freezing and juicing. Recently, more attention has been drawn to dewatering and drying, which are promising areas for developing novel blueberry products. Processing affects each biologically-active compound in a different way, and it is still unknown what changes those compounds undergo at the molecular level after the application of different processing technologies. This work presents the most recent state of knowledge about the pre-treatment and processing methods applied to blueberries and their influence on the content of biologically-active compounds. The presentation of methods is preceded by a brief overview of the characteristics of the blueberry species, a description of the chemical composition of the fruit and a short note about the main growing areas, production volumes and the management of fruit crops.