Effects of pretreatments and drying air temperature on drying behaviour of peach slice

Process modeling and simulation of Gmelina arborea (GmW) and Mansonia altissima (MaW) wood drying

This study simulate the process modeling of drying characteristics of Gmelina arborea (GmW) and Mansonia altissima (MaW) wood under the influence of various process variables such as drying time, drying temperature, and airflow velocity. GmW and MaW moisture desorption isotherms, kinetics, and thermodynamics were also studied. Five (5) thin-layer and desorption isotherm drying models were used to model the moisture ratio and water activity data from the process. According to the anatomical analysis, the GmW sample has an average lumen size of 147.44 m, indicating a high moisture content. The results showed that the Guggenheim, Anderson, and de Boer (GAB) model with the lowest sum of squared error value (0.046) demonstrated the best-fit to the experimental desorption data for GmW samples and the Henderson-P model for MaW samples, while the Demir et al. model emerged as the best kinetics model fit for describing the moisture desorption isotherm and thin-layer drying kinetics. GmW effective diffusivity (Deff) values ranged from 3.671 × 10-8 to 5.378 × 10-8 m2/s and MaW effective diffusivity (Deff) values ranged from 2.923 × 10-8 to 4.678 × 10-8 m2/s. GmW and MaW activation energies were 252.702 kJ/mol and 313.604 kJ/mol, respectively. The thermodynamic studies revealed that the heat and mass transfer coefficients varied linearly with temperature, as the change in enthalpy (ΔH) and change in entropy (ΔS) decreased while the Gibbs free energy (ΔG) increased. The results obtained from this study demonstrated that the proposed drying process modeling and simulation approach could be successfully applied to investigate the wood drying phenomena. The information can be used to reduce the drying costs and improve the wood quality.

Novel insight into the role of sulfur dioxide in fruits and vegetables: Chemical interactions, biological activity, metabolism, applications, and safety

Sulfur dioxide (SO₂) are a category of chemical compounds widely used as additives in food industry. So far, the use of SO₂ in fruit and vegetable industry has been indispensable although its safety concerns have been controversial. This article comprehensively reviews the chemical interactions of SO₂ with the components of fruit and vegetable products, elaborates its mechanism of antimicrobial, anti-browning, and antioxidation, discusses its roles in regulation of sulfur metabolism, reactive oxygen species (ROS)/redox, resistance induction, and quality maintenance in fruits and vegetables, summarizes the application technology of SO₂ and its safety in human (absorption, metabolism, toxicity, regulation), and emphasizes the intrinsic metabolism of SO₂ and its consequences for the postharvest physiology and safety of fresh fruits and vegetables. In order to fully understand the benefits and risks of SO₂, more research is needed to evaluate the molecular mechanisms of SO₂ metabolism in the cells and tissues of fruits and vegetables, and to uncover the interaction mechanisms between SO₂ and the components of fruits and vegetables as well as the efficacy and safety of bound SO₂. This review has important guiding significance for adjusting an applicable definition of maximum residue limit of SO₂ in food.

Methods, mechanisms, models and tail gas emissions of convective drying in sludge: A review

In tandem with the population and economic growth worldwide, the scale of wastewater treatment has been increasing each year. Thus, a large amount of sludge is being produced. If the problem of sludge treatment and disposal cannot be effectively solved, it will cause serious environmental pollution. The premise of sludge drying is that sludge is "harmless" and can be "recycled." Currently, the studies on convective drying focus on the direction of thin-layer drying, fluidized bed drying, spray drying and pneumatic drying. This paper systematically reviews the convective drying technology of sludge. First, the effects of air velocity temperature, relative humidity and particle size on the drying effect are precisely described, as well as the four different drying stages in the drying process, including preheating, constant rate drying, first falling rate drying, and second falling rate drying stages. Second, the research progress of different convective drying treatment technologies and the application of eight mathematical models of thin-layer drying in this field are elaborated. The effects of sludge shrinkage formation mechanisms and sludge viscous resistance generation during the drying process are also discussed in detail. The formation mechanism of sludge shrinkage and the effect of sludge viscosity resistance during drying are also elaborated. Finally, the main dry tail gases and restraining methods are elaborated during the drying process. This paper will provide a structured reference for the related research of sludge convective drying in the future.

Hot-Air Flow Rolling Dry-Blanching Pretreatment Improves the Drying Quality of Acanthopanax sessiliflorus by Increasing the Drying Rate and Inactivating Enzymes

The processing of Acanthopanax sessiliflorus has attracted interest due to its health benefits. In this work, an emerging blanching technology, called hot-air flow rolling dry-blanching (HMRDB), was employed to treat A. sessiliflorus before drying. The effects of varied blanching times (2–8 min) on enzyme inactivation, drying characteristics, bioactive compound retention, and microstructure were examined. The results demonstrated that blanching for 8 min rendered polyphenol oxidase and peroxidase nearly inactive. The blanching process reduced the drying time of samples by up to 57.89% compared to an unblanched sample. The Logarithmic model showed good fitting performance for the drying curves. The total phenolic and flavonoid content of the dried product increased as blanching time increased. The total anthocyanin content of the samples blanched for 6 min was 3.9 times higher than that of the unblanched samples, and 8 min of blanching produced the greatest DPPH• and ABTS• scavenging capabilities. The retention of active compounds in a dried product is a result of the inactivation of enzymes and a reduced drying period. Changes in the porous structure of the blanched samples would be responsible for the accelerated drying rate, according to microstructural analysis. These results indicate that HMRDB enhances the drying process and improves drying quality when applied to A. sessiliflorus before drying.

Recent progress on quality improvement and detection technologies of special foods used for activities in space and aviation: a review

This paper focuses on the development and evolution, quality improvement and research progress in the rapidly emerging area of new detection technologies of special foods for use in space and to some extent aviation. The quality improvement aspects covered in this review ranged from the special food processing technology, sterilization treatment and product packaging to new detection technologies for quality assurance based on DNA microarray technology, sensor, imaging technology, carbon nanotubes and novel probe technology.

Characterization of Key Aroma-Active Compounds in Two Types of Peach Spirits Produced by Distillation and Pervaporation by Means of the Sensomics Approach

As a deep-processed product of peach, the aroma characteristics of peach spirit have not been systematically studied, and there has been no research on improving the aroma quality through process improvement. Pervaporation technology was used for the first time in the production of peach spirit instead of distillation, and its critical aroma compounds were analyzed compared with distilled peach spirit. Compared to the distilled peach spirit, pervaporation produced peach spirit presented stronger fruity, honey, and acidic aromas, and lighter cooked-apple aroma. Sixty-two and 65 aroma-active regions were identified in the distilled and pervaporation produced peach spirits, and 40 and 43 of them were quantified. The concentrations of esters, lactones, and acids were significantly higher in the pervaporation produced peach spirit than those in the distilled peach spirit, while terpenoids showed opposite tendency. Both of the overall aromas of distilled and pervaporation produced peach spirits were reconstituted successfully by the compounds with OAV ≥ 1. The omission tests identified 10 and 18 compounds as important aroma compounds for distilled and pervaporation-produced peach spirits, respectively. The differences in the key aroma compounds between the two types of peach spirits explained the differences in the aroma profiles.

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.

Insight about the biochemical composition, postharvest processing, therapeutic potential of Indian gooseberry (amla), and its utilization in development of functional foods-A comprehensive review

Indian gooseberry/Amla (Emblica officinalis Gaertn. syn. Phyllanthus emblica L) has an amazing nutritional profile and is a reservoir of biologically active compounds which have potential health benefits and are regarded as a remedy for lethal diseases. The unique features of amla, conferred by their bioactive components, have extended future prospects about their usage for useful effects on human nutrition and health globally. With the rapidly growing popularity of this unique therapeutic fruit, it is important to have comprehensive knowledge of this fruit. The current review article presents the nutritional profile, bioactive components, antioxidant and antimicrobial properties, and postharvest processing of amla fruit. Moreover, studies related to therapeutic properties of amla and its utilization in development of functional foods have been presented in this review. E. officinalis is a promising source of bioactive compounds which showed varied potential in the management of a number of human ailments which has been proven through various studies. Therefore, amla should be taken in the regular diet, thereby utilizing its potential health benefits. PRACTICAL APPLICATIONS: Amla (Indian gooseberry), as source of natural bioactive compounds, has a great potential application in improving the status of human nutrition and health. The utilization of amla extract has various biological effects, like antimicrobial, antioxidant, gastroprotective, anticancer, hepatoprotective, cardioprotective, radioprotective, anti-inflammatory, antidiabetic, neuroprotective, and immunomodulatory effect, owing to its bioactive components. The use of amla extract has recently increased in food, pharmaceutical, and cosmetic products to replace synthetic antioxidants which have inherent harmful health effects. The review report will provide information on bioactive components, therapeutic properties, utilization of amla in the development of future functional foods, and postharvest processing of amla, which will provide critical information to researchers all over the world.

Reassessment of Thin-Layer Drying Models for Foods: A Critical Short Communication

Modeling the thin-layer drying of foods is based on describing the moisture ratio versus time data by using a suitable mathematical model or models. Several models were proposed for this purpose and almost all studies were related to the application of these models to the data, a comparison and selecting the best-fitted model. A careful inspection of the existing drying data in literature revealed that there are only a limited number of curves and, therefore, the use of some models, especially the complex ones and the ones that require a transformation of the data, should be avoided. These were listed based on evidence with the use of both synthetic and published drying data. Moreover, the use of some models were encouraged, again based on evidence. Eventually, some suggestions were given to the researchers who plan to use mathematical models for their drying studies. These will help to reduce the time of the analyses and will also avoid the arbitrary usage of the models.

Pengembangan Produk Sambal Andaliman (Zanthoxylum acanthopodium DC) Berkemasan Retort pouch: Studi Karakteristik Fisik, Kimia dan Sensoris

Sambal andaliman (Zanthoxylum acanthopodium DC) adalah sambal khas dari Sumatera Utara, Indonesia. Produk sambal andaliman instan berkemasan retort pouch merupakan produk pangan lokal yang diinovasi agar memiliki masa simpan yang panjang namun masih dalam kualitas yang baik. Perlakuan sterilisasi dan penambahan asam, perlu dilakukan untuk menambah masa simpannya akan tetapi perlu mempertahankan kualitas sensorinya. Penelitian ini bertujuan untuk mengetahui kombinasi lama sterilisasi dan konsentrasi asam sitrat terbaik terhadap karakterisasi sifat fisik, kimia, dan sensoris sambal andaliman. Metode pembuatan produk sambal dilakukan dengan pengukusan cabai, bawang merah, bawang putih, dan tomat yang difinalisasi dengan tahap penghalusan. Hasil penelitian menunjukkan bahwa sambal andaliman terbaik dilihat dari parameter kadar air, pH, aktivitas air, viskositas, dan warna adalah sambal dengan perlakuan: (1) lama sterilisasi 35 menit dan asam sitrat 5% (b/b) dan (2) lama sterilisasi 35 menit dan asam sitrat 3%. Berdasarkan hasil analisis sensoris yang dilakukan pada sambal terpilih bersama dengan sambal kontrol, diketahui bahwa seluruh parameter sensoris menunjukkan hasil yang tidak berbeda nyata, kecuali parameter rasa. Kesimpulannya, sambal terbaik pada penelitian ini adalah sambal dengan lama sterilisasi 35 menit dan asam sitrat 3%. Informasi ini sangat bermanfaat bagi wirausaha dibidang sambal khas untuk dapat memperpanjang masa simpan namun tetap mempertahankan kualitas sensorinya.AbstractAndaliman (Zanthoxylum acanthopodium DC) is traditional chili sauce from North Sumatera, Indonesia. Andaliman chili sauce prepared with retort pouch has known as local food product that was developed to have long shelf life but remaining good quality. Sterilzation and acid fortification were commonly used in manufacture, therefore the purpose of this research was to understand the best combination of sterilization time and citric acid concentration to Andaliman chili sauce’s physical, chemical, and sensory characteristics. Chili sauce was done by steaming fresh chili, onion, garlic, and tomato and followed by grinding. The research showed that the best andaliman chili sauce seeing from several parameter such as moisture content, pH, water activity, viscosity, and color was chili sauce with treatment of: (1) 35-minute sterilization time and 5% (w/w) citric acid concentration; and (2) 35-minute sterilization time and 3% citric acid concentration. Based on sensory analysis in two selected chili sauce and other chili sauce as controls, it has been discovered that all of the sensory parameter showed no significance, except taste parameter. As conclusion, the best andaliman chili sauce in this research was product with combination of 35-minutes sterilization time and 3% citric acid concentration. This information may open the knowledge to chili sauce producer to enhance the shelf life but keep maintaining good quality.

Kinetics, energy efficiency and mathematical modeling of thin layer solar drying of figs (Ficus carica L.)

First convectional thin layer drying of two fig (Ficus carica L.) varieties growing in Moroccan, using partially indirect convective dryer, was performed. The experimental design combined three air temperatures levels (60, 70 and 80 °C) and two air-flow rates (150 and 300 m³/h). Fig drying curve was defined as a third-order polynomial equation linking the sample moisture content to the effective moisture diffusivity. The average activation energy was ranged between 4699.41 and 7502.37 kJ/kg. It raised proportionally with the air flow velocity, and the same pattern were observed for effective moisture diffusivity regarding drying time and velocity. High levels of temperature (80 °C) and velocity (300 m³/h) lead to shorten drying time (200 min) and improve the slices physical quality. Among the nine tested models, Modified Handerson and Pabis exhibited the highest correlation coefficient value with the lowest chi-square for both varieties, and then give the best prediction performance. Energetic investigation of the dryer prototype showed that the total use of energy alongside with the specific energy utilization (13.12 and 44.55 MWh/kg) were inversely proportional to the velocity and drying temperature. Likewise, the energy efficiency was greater (3.98%) higher in drying conditions.

Microwave and Ultrasound Pre-Treatments for Drying of the "Rocha" Pear: Impact on Phytochemical Parameters, Color Changes and Drying Kinetics

The objective of this research was to evaluate the effect of drying temperature and innovative pre-treatments (i.e., microwave and ultrasound) on “Rocha” pear drying behavior and quality characteristics, such as color, total phenolic content and antioxidant activity. Experiments were carried out with pear slabs subjected to microwaves (2450 MHz, 539 W, 4 min, microwave oven) and ultrasounds (35 kHz, 10 min, in an ultrasonic bath) as well as control samples. The drying process was conducted in a tray dryer at three different temperatures (50, 55 and 60 °C) and a fixed air velocity of 0.75 m/s. Microwave technology resulted in a higher quality deterioration in dried pear samples compared to those of controls and ultrasound pre-treated samples. The combined application of ultrasound pre-treatment and the higher drying temperature of 60 °C was characterized by the lowest color changes (ΔE = 3.86 ± 0.23) and higher preservation of nutritional parameters (total phenolic content, TPC = 345.60 ± 8.99; and antioxidant activity, EC₅₀ = 8.80 ± 0.34). The drying characteristics of pear fruits were also analyzed by taking into account empirical models, with the Page model presenting the best prediction of the drying behavior. In conclusion, ultrasound application is a promising technology to obtain healthy/nutritious dried “Rocha” pear snacks as dietary sources for consumers.

Effects of onion bulb processing conditions on drying characteristics, physicochemical and functional properties profile of onion (Allium cepa L.) powder

Onion (Allium cepa L.) is one of the most perishable consuming vegetable in the world as an aromatic seasoning and for its health promoting bioactive compounds. However, drying and blanching are two essential thermal treatments in vegetables processing which lead to considerable changes in their properties. This study investigated the effects of temperature (70, 80, and 90 °C), time (2, 4, 6, and 8 hr), and blanching (100 °C for 5 min) followed by drying at 70 °C for 8 hr on the drying kinetics, physicochemical (Ash and total polyphenol content, pH, and titratable acidity), and functional (water solubility index and particle size) properties of onion powder, as well as compared to local market powders. The variety violet of Galmi was used. The results revealed that the moisture content of non-blanching powder was below 13 ± 0.76 g/100 g with pH under 4. In addition, total polyphenol contents were higher than 512 ± 15.06 mg GAE/100 g DM. These powder showed a small particle size (under 400 µm) and high solubility (≤81.36 ± 2.3 g/100 g DM). Blanching did not affect the powders quality. Local market powders showed a lowest total polyphenol content (386.60 ± 10.02 mg GAE/100 g DM) with large particles (≤800 µm) and a lowest solubility (65.33 ± 1.62 g/100 g DM). Drying at 80 °C for 8 hr without blanching emerge as the best compromise drying conditions resulting in optimal physico-chemical and functional properties (10.8 ± 0.8 g/100 g, 846.6 ±15.09 mg GAE/100 g DM and 88.12 ± 2.31 g/100 g DM of moisture content, total polyphenol content, and water solubility index, respectively. These findings can contribute to reduce postharvest losses in onion and to stimulate the industrialization of onion enriched-powder production in Africa. PRACTICAL APPLICATION: This study provides critical information on onion properties profile during its transformation, on which processor might build on its decision to make an appropriate choice of processing parameters and tools for producing health promoting onion powder meeting modern consumer requirements. In this study, oven-drying at 80 °C for 8 hr without blanching might be the suitable condition to deliver innovative onion powder tailored specifically to functional ingredients of many food formulations.

Effect of cultivars, pretreatment and drying on physicochemical properties of Amla (Emblica officinalis) gratings

Effect of four different cultivars and salt pretreatment on drying of Amla (Emblica officinalis) gratings were studied. Quality attributes namely, ascorbic acid, total phenolic content, antioxidant activity and colour were evaluated for dried (using Cabinet tray dryer at 55 ± 2 °C for 8 h) and stored (refrigerated, ambient and accelerated condition) samples of four cultivars (Krishna, Kanchan, NA-7 and Chakaiya). Salt pretreated dried samples showed better retention of nutrients and colour as compared to untreated. Retention of ascorbic acid, total phenolic content and antioxidant activity (IC₅₀ value) in pretreated dried samples were in the range of 79.51-84.89%, 176.5-220.3 mg GAE/g db and 9.48 to 17.74 mg/µl, respectively. Colour retention was also found to be better in salt pretreated samples. Ambient storage condition resulted in higher retention of ascorbic acid and colour compared to accelerated condition. Taking into consideration, the nutritional value of the fresh Amla, ability to retain nutritional value and color during drying and storage, NA-7 cultivar Amla (pretreated with 1% salt, tray dried at 55 °C for 8 h) is the most suitable for preparation of Amla powder. The method developed in the present work is devoid of blanching step and found to be effective in retaining the nutrients during drying and storage and can be employed also for drying of similar fruits and vegetables.

Influence of microwave-assisted dehydration on morphological integrity and viability of cat ovarian tissues: First steps toward long-term preservation of complex biomaterials at supra-zero temperatures

Ovarian tissue contains large pools of immature oocytes enclosed in primordial follicles, making it an attractive target for fertility preservation in female cancer patients, livestock and wild species. Compared to cryopreservation, desiccation and long-term storage of samples at supra-zero temperatures (using strategies inspired from small organisms to resist extreme environments) would be more cost-effective and convenient. The objective of the study was to characterize the influence of microwave-assisted dehydration on structural and functional properties of living ovarian tissues. While this method allows preservation of single cells (cat oocytes and sperm cells so far) using trehalose as the xeroprotectant, it has not been developed for multicellular tissues yet. Ovarian cortex biopsies were reversibly permeabilized, exposed to various concentrations of trehalose, and dried for different times using a commercial microwave under thermal control. Effective dehydration of samples along with proper trehalose retention were reached within 30 min of microwave drying. Importantly, the process did not affect morphology and DNA integrity of follicles or stromal cells. Moreover, transcriptional activity and survival of follicles were partially maintained following 10 min of drying, which already was compatible with storage at non-cryogenic temperatures. Present data provide critical foundation to develop dry-preservation techniques for long-term storage of living multicellular tissues.

Effect of ultrasound and chemical pretreatment on drying characteristics and quality attributes of hot air dried pineapple slices

Drying of food materials is a time consuming activity making the process cost and energy intensive and hence, several pretreatments are used to improve the drying rate. The present study aims to study the effect of potassium metabisulphite (KMS solution, 0.25% w/v) and ultrasound (20 and 30 min) pretreatment on hot air drying characteristics and quality of pineapple slices. The results indicated that pretreated samples provided higher drying rate, enhanced moisture diffusivity, brighter color and lower hardness than that of untreated dried sample. It was observed that KMS and ultrasound pretreatment for 20 and 30 min reduced the drying time by 23.8%, 19% and 14.3%, respectively. Further, ten thin layer drying models were applied to the experimental drying data and logarithmic model was best fitted to explain the drying behavior of pretreated and untreated samples. Additionally, the effect of shrinkage on moisture transfer mechanism was also studied. Results highlighted that instantaneous moisture diffusivity was increased during drying while shrinkage was not accounted. However, shrinkage consideration reduced the average moisture diffusivity values by 72-83%. Overall color change (13.95 ± 0.92) and browning index (36.02 ± 2.45) were found to be lowest in ultrasound (30 min) pretreated dried sample, highlighting better color stability. Scanning electron microscopy presented noticeable effects of pretreatment on alterations of microstructure of pineapple slices. It can be interpreted that KMS pretreatment was found to be more effective for improvement of drying characteristics of pineapple slices as compared to ultrasound pretreatment.

Comparison of pulsed vacuum and ultrasound osmotic dehydration on drying of Chinese ginger (Zingiber officinale Roscoe): Drying characteristics, antioxidant capacity, and volatile profiles

The effects of pulsed vacuum osmotic dehydration (PVOD) and ultrasound osmotic dehydration (USOD) on drying characteristics and quality attributes of ginger were investigated. PVOD was subjected to pulsed vacuum at 13 kPa for 30 min, and USOD was subjected to ultrasound with the frequency of 40 kHz for 30 min. After PVOD and USOD treatments, the samples were then dried at intermittent microwave & air-drying oven with an output of 700 W and temperature of 60°C to the final moisture content of 0.12 g water/g d.w. The results showed PVOD and USOD treatments could improve the total phenolic contents by -1.8% to 16.4%, total flavonoid content by 7.7%-18.7%, DPPH radical scavenging by 9.5%-12.2%, and ABTS+ antioxidant activity by 17.8%-27.4%, although they prolonged the later stages drying of ginger. Besides, the PVOD- and USOD-pretreated dried samples had less brownings than the untreated-dried samples which could be attributed to the inactivation of polyphenol oxidase (PPO) and peroxidase (POD). The PPO activity was significantly reduced in the PVOD and USOD ginger, whereas POD activity was decreased in USOD ginger but increased in PVOD ginger. Moreover, PVOD pretreatment also led to a better preservation of volatile profiles and cell structure than USOD treatment. Therefore, both PVOD and USOD are effective pretreatments for drying of ginger.

Enhancement of phytochemical content and drying efficiency of onions (Allium cepa L.) through blanching

BACKGROUND

This study investigated the effect of blanching (60, 70 and 80 °C for 1, 3, 5 and 10 min) combined with oven drying at 60 °C on the phenolic compounds, antioxidant activity, colour and drying characteristics (drying time, drying rate constant, effective moisture diffusivity and activation energy) of onion slices.

RESULTS

Blanching of onion slices at 60 °C for 3 min and at 70 °C for 1 min prior to drying increased their bioactive compounds and antioxidant activity compared to the control samples and other treatments. Eighteen drying models were evaluated. The Modified Page and two-term exponential models best represented the drying data. The effective diffusivity ranged from 3.32 × 10^-11 m² s^-1 (control) to 5.27 × 10^-11 m² s^-1 , 5.01 × 10^-11 m² s^-1 , and 4.74 × 10^-11 m² s^-1 for onions blanched at 60 °C, 70 °C and 80 °C, respectively. The higher activation energy was observed for the control (unblanched) sample and slightly lower values were found for 1 min- and 3 min-blanched samples, confirming the higher drying efficiency as a result of the blanching pre-treatment.

CONCLUSION

The use of blanching as a pre-treatment before drying of onions resulted in enhanced phytochemical content and drying efficiency. © 2017 Society of Chemical Industry.

Screening Quality Evaluation Factors of Freeze-Dried Peach (Prunus PersicaL. Batsch) Powders from Different Ripening Time Cultivars

The quality evaluation of processed products is complex. To simplify the quality evaluation process and improve the efficiency, fourteen evaluation factors of freeze-dried powders of seventeen cultivars of peach at different ripening times were analyzed. The most important evaluation indicators and criteria were obtained by analysis of variance (ANOVA), correlation analysis (CA), principal component analysis (PCA), system cluster analysis (SCA), and analytic hierarchy process (AHP). Results showed that the peach powders had the significant differences in quality (P<0.05), and some processing factors were related with some physicochemical and nutritional factors. Five principle components were extracted by PCA and the cumulative contribution achieved was 84.46%. Through the score plot of the first two principal components, a clear differentiation among ripening times was found and three distinct groups were separated according to ripening time. Five characteristic factors were obtained as titratable acid, browning index, hemicellulose, hygroscopicity, and vitamin C by SCA. Their weights of 0.1249, 0.3007, 0.0514, 0.4916, and 0.0315 were obtained by AHP, respectively. The peach cultivars were divided into four evaluation grades by the comprehensive quality score.

Convective drying of hawthorn fruit (Crataegus spp.): Effect of experimental parameters on drying kinetics, color, shrinkage, and rehydration capacity

Thin layer drying characteristics and physicochemical properties of hawthorn fruit (Crataegus spp.) were investigated using a convective dryer at air temperatures 50, 60 and 70°C and air velocities of 0.5, 0.9 and 1.3m/s. The drying process of hawthorn took place in the falling rate period, and the drying time decreased with increasing air temperature and velocity. The experimental data obtained during the drying process were fitted to eleven different mathematical models. The Midilli et al.'s model was found to be the best appropriate model for explaining the drying behavior of hawthorn fruit. Effective moisture diffusion coefficients (Deff) were calculated by Fick's diffusion model and their values varied from 2.34×10(-10)m(2)/s to 2.09×10(-9)m(2)/s. An Arrhenius-type equation was applied to determine the activation energies. While the shrinkage decreased, the rehydration ratio increased with increasing air temperature and air velocity.

Drying Characteristics and Assessment of Physicochemical and Microstructural Properties of Dried Culinary Banana Slices

This study quantifies the drying characteristics and quality attributes of culinary banana at various temperatures (40–70°C) which exhibited falling rate period. Among the different drying models, Wang and Singh model was found the best fitted model with lowest Ӽ2 and highest R2 values. The coefficients of Wang and Singh model were expressed in nonlinear form as a function of temperature and a new model was developed in which moisture ratio is expressed as a function of time and temperature. Effective moisture diffusivity increased with increase in drying temperature. Scanning electron micrographs showed that samples dried at 70°C produced larger pores which resulted in better rehydration ratio and minimum hardness. The nonenzymatic browning occurred faster at 70°C and in addition, the chemical properties were not significantly affected by drying temperatures.

Quality evaluation of yellow peach chips prepared by explosion puffing drying

Nineteen evaluation indicators in 15 yellow peach chips prepared by explosion puffing drying were analyzed, including color, rehydration ratio, texture, and so on. The analysis methods of principle component analysis (PCA), analytic hierarchy process (AHP), K-means cluster (KC) and Discriminate analysis (DA) were used to analyze the comprehensive quality of the yellow peach chips. The dispersed coefficient of variation of the 19 evaluation indicators varied from 3.58 to 852.89 %, suggesting significant differences among yellow peach cultivars. The characteristic evaluation indicators, namely, reducing sugar content, out-put ratio, water content, a value and L value were analyzed by PCA, and their weights 0.0429, 0.1140, 0.4816, 1.1807 and 0.1807 were obtained by AHP. The levels in 15 cultivars effectively were classified by discrimination functions which obtained by KC and DA. The results suggested that three levels of comprehensive quality for yellow peach chips were divided, and the highest synthesis scores was observed in "senggelin" (11.1037), while the lowest synthesis value was found in "goldbaby" (-3.7600).

Mathematical modeling of drying kinetics of untreated and pretreated cocoyam slices

The effect of pretreatment and drying temperature on the drying kinetics and quality of cocoyam was investigated in this study. The best model to predict the drying kinetics was also determined. Cocoyam slices were pretreated by water blanching (WB) and soaking in sodium metabisulphite (SM) and dried in a hot air oven at temperatures of 50, 60 and 70 °C while untreated samples were sun dried. Seventhin layer drying models (Exponential, Generalized Exponential, Page, Logarithmic, Parabolic, Wang and Singh and Two-term) were fitted to the experimental data and selection was done basedon model with highest correlationcoefficient (R(2)), and lowest reduced chi-square (χ (2)), sum square error (SSE) and root mean square error (RMSE) respectively. The Logarithmic and Parabolic model was found to best describe the oven and sun drying of cocoyam respectively. The vitamin C and beta-carotene value of the dried cocoyam slices, which varied from 0.0038 to 0.0075 and 4.1 to 5.888 mg/100 g respectivelygenerally decreased with an increase in drying temperature.

Influence of Citric Acid Pretreatment on Drying of Peach Slices

The effect of citric acid pretreatment on the drying characteristics of peach slices was investigated in a cabinet dryer. The experiments were conducted on peach slices with a thickness of 5 mm at temperatures of 45, 55, 65 and 75°C with an air velocity of 2.0 m/s. The drying time of peach slices pretreated with citric acid solution was shorter than the control ones. The drying data were fitted to five thin-layer drying models. The results show that the Midilli et al. model was the most appropriate model for drying of peach slices. The values of effective moisture diffusivity were found to range between 1.94 × 10−10 and 8.49 × 10−10 m2/s over the temperature range studied. The values of activation energy were calculated as 36.82 and 37.12 kJ/mol for control and pretreated samples, respectively. Superior rehydration was noticed for citric acid pretreated slices dried at 65°C.

Effects of microwave - fluidized bed drying on quality, energy consumption and drying kinetics of soybean kernels

Moisture content of soybean kernel at harvest time is too high for storage, and needs to be reduced. In this research, drying characteristics, quality and energy requirement for microwave-fluidized bed drying of soybean kernels were studied. The results showed that air temperature (80-140 °C), velocity (1.8-4.5 m/s) and microwave power (200-500 W) significantly influenced drying time, moisture diffusivity, rehydration capacity, cracking, and specific energy consumption (P ≤ 0.05). Among the applied models, Page's model has the best performance to estimate the microwave-fluidized bed drying behavior of the soybean kernels. Moisture diffusivity values increased (6.25 × 10(-10) to 42.14 × 10(-10) m(2)/s) as the air velocity decreased and air temperature and microwave power increased. Activation energy was foundto be between 3.33 and 17.70 kJ/mol. Minimum cracking percentage of soybean kernels (12.96 %) was obtained at 80 °C, 1.8 m/s and 200 W treatments. The increase in microwave power and decrease in air velocity level decreased the rehydration capacity. Specific energy consumption varied from 50.94 to 338.76 MJ/kg water and the lowest specific energy consumption were obtained at 80 °C, 4.5 m/s and 500 W.