Application of osmotic dehydration to improve the quality of dried goji berry

Three-dimensional mass transfer modeling and phenolic chemistry exploration for ultrasound-assisted and microwave drying of goji berry

Herein, goji berries were pretreated with sodium carbonate (Na2CO3) and then dried via ultrasound-assisted air drying or microwave drying. Water migration and phenolic chemistry of goji berries were studied under drying. A three-dimensional ellipsoid water transport model, accounting for porosity and temperature fluctuations, was established to explore the intricacies of the drying mechanism. Generally, microwave drying promoted interior water transport compared to ultrasound drying. Among all the drying methods, microwave drying at 240 W (MW-240 W) exhibited the highest De (from 7.34 × 10-9 to 9.61 × 10-9 m2/s) and kc (6.78 × 10-4 m/s) values. The goji berries received a considerably high water content gradient between its surface and center within the first 2 s of all the drying treatments. Microwave drying diminished the water content gradient earlier than air drying and ultrasound-assisted air drying treatments. Furthermore, most correlations observed among phenolics, oxidase activity, and cell wall pectin did not align with the established theories, highlighting the highly nonlinear nature of phenolic chemistry during goji berry drying. This study provides a three-dimensional model to study the mass transfer mechanism of goji berries and analyzes the evolution of polyphenols during the drying process.

Modeling Mathematical Relationship with Weight Loss and Texture on Table Grapes of 'Red Globe' and 'Wink' during Cold and Ambient Temperature Storage

Weight loss associated with fruit texture during storage has received numerous reports; however, no research has been conducted on the mathematical relationships between weight loss and textural traits of table grapes stored at cold and ambient temperatures. In this study, it was found that the weight loss of 'Red Globe' was in the range of 0 to 0.0487, 0 to 0.0284 and 0 to 0.0199 compared to 0 to 0.0661, 0 to 0.0301 and 0 to 0.028 of 'Wink' at 13 °C, 3 °C, and 0 °C of storage for 13 days. Stored for 13 days at 13 °C, 3 °C, and 0 °C, the range of the textural traits of failure force, strain and penetration work in 'Red Globe' were 6.274 to 3.765, 6.441 to 3.867, 6.321 to 4.014; 51.931 to 11.114, 51.876 to 13.002, 51.576 to 20.892; 21.524 to 13.225, 21.432 to 14.234, 21.321 to 15.198 in contrast to in 'Wink' of 4.4202 to 2.2292, 4.4197 to 2.653, 4.4371 to 2.8199 and 15.674 to 2.7881, 15.776 to 4.1431, 15.704 to 5.702 and 12.922 to 7.754, 12.909 to 8.021, 12.915 to 8.407. Meanwhile, the weight loss and textural traits of two table grapes were examined using time-dependent and weight loss-dependent modeling at 13 °C, 3 °C, and 0 °C of storage. The Logistic, ExpDec1, and ExpDec2 models, as well as the Boltzmann model, were identified as the best fit for the obtained data. The equations proved to be more effective in characterizing the change in weight loss and texture of 'Red Globe' and 'Wink,' with the best equations suited to the weight loss and textural parameters having an average mean standard error of 2.89%. The viability of the established models was evaluated, and parametric confidence intervals of the equations were proposed to fit different grape cultivars. According to the findings, the weight loss and texture of the two grape cultivars could be accurately predicted by the established models; additionally, the results showed that cold storage is better for the quality of table grapes and that weight loss can predict the textural quality of table grapes. This study provides a theoretical framework for optimum storage temperature together with a significantly convenient and quick approach to measure the texture of grapes for fruit dealers and enterprises.

Effect of Different Drying Techniques on Total Bioactive Compounds and Individual Phenolic Composition in Goji Berries

In recent years, interest in the consumption of dried goji berries has increased due to its high bioactive properties. Alternative drying methods that provide faster drying and better preservation of bioactive properties should be developed. This study aims to investigate the effect of different drying methods on the drying time and quality characteristics of the goji berry; namely, hot-air drying (HAD), ultrasound-assisted vacuum drying (USVD), vacuum drying (VD), freeze-drying (FD), and ultrasound-pretreated freeze-drying (USFD). The drying kinetic, total phenolic content, antioxidant capacity, phenolic profile, carotenoid profile, and color change of the goji berry fruit were determined. The drying times for VD, USVD, and HAD varied between 275–1330 min. USVD treatment showed faster drying behavior than the other two drying methods. The total phenolic content (TPC) value of dry samples varied between 1002.53–1238.59 mg GAE/g DM. USVD treatments exhibited a higher total phenolic content (TPC) value than all other drying methods. DPPH and CUPRAC values varied between 15.70–29.90 mg TE/g DM and 40.98–226.09 mg TE/g DM, respectively. The total color change (ΔE) value ranged between 4.59 and 23.93 and HAD dried samples showed the highest ΔE of all samples. The results of the phenolic profile were consistent with TPC analysis. HAD caused higher phenolic compound degradation than VD, USVD, and FD. The results of this study showed that different drying techniques significantly affected the drying rate and retention of bioactive components of the goji berry fruit, and the USVD and VD methods could be used as an alternative to the HAD method. This study concluded that USVD and FD could be considered as suitable drying methods and could be used as alternatives to HAD in the drying of goji berries.

Study on Ultrasonic Far-Infrared Radiation Drying and Quality Characteristics of Wolfberry (Lycium barbarum L.) under Different Pretreatments

In order to explore the effects of different pretreatment methods on the ultrasonic far-infrared synergistic drying characteristics and quality of wolfberry, the bioactive components (polysaccharide, total phenol, total flavonoids, and antioxidants), the quality characteristics (rehydration ratio, color, vitamin C content, and betaine content), and the microstructure of the dried products were used as evaluation indices to test wolfberry treated by five different pretreatments (hot blanching; candied pretreatment; NaOH solution treatment; NaCl solution treatment; and Na₂CO₃ solution treatment). The results showed that hot blanching pretreatment improved the drying rate and shortened the drying time, and that the vitamin C content of dried products pretreated by hot blanching (92.56 mg/100 g) was higher than that of dried products pretreated by other methods. All five pretreatment methods increased the contents of the total phenols, vitamin C, and betaine of wolfberry. Wolfberry treated by candied pretreatment had lower color differences and higher contents of polysaccharide (0.83 g/g), total phenol (9.26 mg/g), and total flavonoids (2.61 mg/g) than wolfberry treated by the other pretreatment methods. Wolfberry pretreated by NaCl solution had the strongest antioxidant capacity (65.01%). Wolfberry pretreated by Na₂CO₃ solution had the highest betaine content (3.24%). The observation of the microstructure of the dried products revealed that hot blanching caused the most damage to wolfberry, while the candied pretreatment was less destructive to the tissue cells of wolfberry. On the whole, the dried wolfberry products obtained by the candied pretreatment were of a better quality than products obtained by the other pretreatment methods.

Combined effect of pulsed electric field and osmotic dehydration pretreatments on mass transfer and quality of air-dried pumpkin

Pulsed electric field (PEF) and osmotic dehydration (OD) pretreatment can accelerate the time-consuming drying process and minimize its high energy demands. The effect of PEF and OD pre-processing conditions and osmotic solution composition on mass transfer kinetics (water loss, solid gain, water activity) and quality properties (color, texture, total sensory quality) during OD and subsequent air-drying (AD) of pumpkin was studied. Application of PEF (2.0 kV/cm-1500 pulses) significantly enhanced mass transfer during subsequent air-drying (increased effective diffusivity coefficient D_es and drying rate k_drying , respectively). PEF and OD treatments led to a significant reduction of the processing time by 12 and 10%, respectively (p < 0.05). The maximum reduction of processing time by 27% (p < 0.05) (compared to untreated sample) resulted in combined use of PEF and OD as pretreatments prior to AD. When PEF pretreatment was combined with OD prior to AD, the corresponding energy was by 50% less than the respective energy required for nonprocessed samples. PRACTICAL APPLICATION: Pulsed electric fields (PEF) and osmotic dehydration (OD) can be applied for the production of air-dried pumpkin cuts of superior quality (in terms of quality and sensory characteristics) and reduced energy requirements (as a result of total processing time decrease).

Advanced osmotic dehydration techniques combined with emerging drying methods for sustainable food production: Impact on bioactive components, texture, color, and sensory properties of food

The food industries are looking for potential preservation methods for fruits and vegetables. The combination of osmosis and drying has proved the efficient method to improve the food quality. Osmotic dehydration is a mass transfer process in which water molecules from the food move to an osmo-active solution and the solutes from the solution migrate into the food. Advanced osmotic dehydration techniques such as electric field pulse treatment, ultrasonic and microwave-assisted dehydration, pulsed vacuum, and osmodehydrofreezing can improve the nutritional quality (bioactive) and sensory properties (color, texture, aroma, flavor) of fresh and cut-fruits without changing their reliability. Emerging osmotic dehydration technologies can preserve the structure of fruit tissue by forming microscopic channels and increasing effective water diffusivity. However, it is important to analyze the effect of advanced osmotic dehydration techniques on the quality of food products to understand the industrial scalability of these techniques. The present paper discusses the impact of recent osmotic dehydration techniques on bioactive, antioxidant capacity, color, and sensory profile of food.

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 Osmotic Dehydration Pretreatment on the Drying Characteristics and Quality Properties of Semi-Dried (Intermediate) Kumquat (Citrus japonica) Slices by Vacuum Dryer

The effect of osmotic dehydration (OD) pretreatments at different temperatures and immersion times on drying characteristics, total phenolic content (TPC), total antioxidant activity (TAA) (DPPH and CUPRAC methods), and color of kumquat slices dried under vacuum conditions (70 °C-100 mbar) was investigated. The OD pretreatment was performed in a sucrose solution (45 °Bx) at the temperatures of 40 and 50 °C and immersed at times of 30, 60, and 90 min. OD before vacuum drying decreased the total required drying time by up to 70 min compared to the control non-pretreated samples. Page, Modified Page, Henderson Pabis, and Two Terms Exponential models were found to satisfactorily describe the drying behavior of thin layer dried kumquat slices. The minimum and maximum values of effective moisture diffusivity (Deff) for semi-dried kumquat slices were 5.04 × 10⁻⁸ to 7.19 × 10⁻⁸, respectively. OD treatments induced a decline in TPC (5.30–33.92%) and TAA (23.63–59.34% and 4.17–31.67% for DPPH and CUPRAC assays, respectively) of kumquat slices. It was observed that OD pre-treatment can decrease the gross drying time, and make the color and sensorial attributes of dried kumquats better.

Health Benefits and Applications of Goji Berries in Functional Food Products Development: A Review

Goji berries have long been used for their nutritional value and medicinal purposes in Asian countries. In the last two decades, goji berries have become popular around the world and are consumed as a functional food due to wide-range bioactive compounds with health-promoting properties. In addition, they are gaining increased research attention as a source of functional ingredients with potential industrial applications. This review focuses on the antioxidant properties of goji berries, scientific evidence on their health effects based on human interventional studies, safety concerns, goji berry processing technologies, and applications of goji berry-based ingredients in developing functional food products.

Dried Figs Quality Improvement and Process Energy Savings by Combinatory Application of Osmotic Pretreatment and Conventional Air Drying

This study concerns the implementation of osmotic dehydration (OD) as a pre-treatment of air-drying in fig halves, aiming at drying acceleration, energy savings and product quality improvement. The effect of solid/liquid mass ratio, process temperature (25-45 °C) and duration (up to 300 min) on water activity (a_w) and transport phenomena during OD, was modelled. The effective diffusion coefficients, drying time and energy consumption, were also calculated during air-drying at 50-70 °C. At optimum OD conditions (90 min, 45 °C), the highest water loss and solid gain ratio were achieved, while the a_w (equal to an initial value 0.986) was decreased to 0.929. Air-drying time of OD- and control samples was estimated at 12 and 21 h, at 60 °C, respectively, decreasing the required energy by up to 31.1%. Quality of dried figs was systematically monitored during storage. OD-assisted air-drying led to a product of improved quality and extended shelf-life.

Effect of Edible Coating on Antioxidants and Certain Properties of Dried Jerusalem Artichoke

BACKGROUND AND OBJECTIVE

Most food industries try to solve the problem of dried food quality by using optimum pre-treatments before subjecting to hot air drying. The edible coating is considerably extended shelf-life of dried foods. The objectives of this research were to investigate the effect of edible coating agents (modified cassava starch and sodium caseinate) on properties of dried Jerusalem artichoke (JA) slices.

MATERIALS AND METHODS

Pieces of the sample were coated by dipping in the coating solution for 10 min both for atmospheric coating (AC) and vacuum coating (VC). The weight ratio of the sample to the solution was 1:2. The VC was conducted in a closed desiccator connected to a vacuum pump with a residual pressure of 150 m bar controlled during 10 min of dipping.

RESULTS

The coating agents resulted in improvements in product qualities. Browning and shrinkage were reduced significantly (p<0.05). The antioxidant properties were similar between a hot air-dried product and a freeze-dried product. There was no observed benefit of using vacuum pressure rather than atmospheric pressure. Sensory acceptance of coated products was similar to that of an uncoated product.

CONCLUSION

The edible coating with modified cassava starch or sodium caseinate was, therefore, an efficient pre-treatment and could be applied with conventional drying to produce healthy fruit and vegetable snacks by using a simple and inexpensive method.

Gingerols infusion and multi-step process optimization for enhancement of color, sensory and functional profiles of candied mango

Presence of pungent gingerols in ginger oleoresin makes it an ideal natural flavoring candidate for the food industry. The study reports its incorporation for synergistic enhancement of flavor and nutraceutical portfolio of candied mango. The process is systematically optimized at bench-scale for gingerols infusion and subsequent candying treatment in a range of hypo and hypertonic osmotic solutions for critical transport properties. After that, optimization of the drying process and the scale-up study was conducted with a 200 folds increase in the batch size. Collated effects of multistep optimization resulted in 85.6, 76.8, 60.2% retention in β-carotene, total phenolics, Vitamin C, respectively, along with minor color difference and significant improvement in sensory scores over fresh mango. Mass transfer and quality parameters were comparable in both scales, implying excellent repeatability and scalability of the process. Compared with a similar commercial product, substantial improvement in quality characteristics along with 376.7% reduction in overall processing time was achieved.

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.

Evaluation and modelling of osmotic pre-treatment of peach using alternative agents in a multiple-component solution

BACKGROUND

Peach is a perishable fruit of great importance for the Greek food export market which is prone to rapid deterioration after harvesting. Its short shelf life can be substantially prolonged by applying an appropriate osmotic dehydration (OD) pre-treatment, which is a mild, non-thermal procedure. The aim of this study was to describe mass transfer and quality retention induced by the OD process.

RESULTS

Peach pieces were immersed in tertiary solutions of glycerol, erythritol, steviol glucosides and mineral salts at pre-selected OD conditions (25-45 °C for 3-240 min, w_fruit /w_solution = 1:5). Water loss (WL), solid gain (SG), water activity (a_w ) as well as representative quality indices (colour, texture) were measured during OD, showing that osmotically dehydrated peach presented significant a_w reduction (from 0.97 to 0.88) combined with quality retention.

CONCLUSION

This research showed that OD can be an effective pre-processing step in the production of intermediate moisture novel products. A second-degree polynomial model was developed describing adequately the effect of OD time and temperature and glycerol concentration on WL, SG, a_w , colour and texture of osmotically dehydrated peach, and analysis of variance was applied to identify those factors that significantly affect the aforementioned parameters. It was concluded that OD using alternative osmotic agents is an efficient method with respect to product colour and texture retention, allowing for the production of novel products with extended shelf life. © 2018 Society of Chemical Industry.