Comparative Study of Various Drying Processes at Physical and Chemical Properties of Strawberries (Fragariavarcamarosa) (original) (raw)
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Misr journal of agricultural engineering, 2018
The drying kinetics of strawberry were investigated and optimized. They affected by the strawberry geometries and the drying temperature in addition to the pretreatments including the thermal treatments and osmotic dehydration. Three geometries (whole, halve and quarter), two thermal pretreatments (hot water and microwave), osmotic dehydration (sucrose + calcium chloride and glucose + calcium chloride) and three temperatures (40, 50 and 60°C) were evaluated. The initial moisture content of the fresh strawberry samples was varied between 93.4 and 77 % (w.b). The results indicated that the half that treated by sucrose, Whole that treated by sucrose and hot water (80 °C) for 10 sec and half that treated by glucose, microwave (1100 W) for 10 sec at 40ºC. Also, half that treated by glucose, whole that treated by sucrose and hot water (80 °C) for 10 sec and whole that treated by sucrose, microwave (1100 W) for 10 sec at 50ºC. The optimum conditions at the highest temperature 60 ºC were half that treated by sucrose, whole that treated by sucrose and hot water (80 °C) for 10 sec and whole that treated by sucrose, microwave (1100 W) for 10 sec.
Quality retention in strawberries dried by emerging dehydration methods
Food Research International, 2014
In this study the effectiveness of drying methodsvacuum microwave drying (VMD), hot air drying (AD), convective air drying combined with vacuum microwave drying (AD-VMD) and osmotic dehydration followed by vacuum microwave drying (OD-VMD)and their effects on both physicochemical and structural changes in strawberries are compared. Drying performance was assessed by drying rate, moisture content and water activity, while changes in quality attributes of strawberries were determined by measuring color, texture, microstructure, shrinkage and rehydration ratio. A maximum drying rate of 6.74 × 10 −4 kg water/(kg dry matter s) was found for microwave-assisted drying, which results into a product of intermediate water activity. Combining VMD with osmotic dehydration or air drying did not improve drying efficiency. VMD yields an elastic product of improved mechanical resistance with just a slight loss of color and an appropriate rehydration performance. Preliminary dehydration using hot air or sucrose solution was not able to improve most of the quality attributes of strawberries.
Microwave Drying of Strawberry Slices and the Determination of the Some Quality Parameters
Strawberry slices (Fragaria x ananassa cv. Camarosa) weighing 100 g (±0.04) with a moisture of 11.74 kg (moisture) kg-1 (dry matter) (92.15% wb) were dried using four different microwave output powers: 1000 W, 750 W, 500 W and 350 W. Drying continued until the slices moisture decreased to 0.16 (±0.02) kg (moisture) kg-1 (dry matter) (13.87% (±0.01) wb). Drying periods lasted 4-13.5 min for microwave drying, depending on the microwave output powers. In this study, measured values of moisture were compared with values of predicted obtained from 21l thin-layer equations; the Alibas Model was found to have the best fit. The optimum drying period, color, ascorbic acid and rehydration ratio content were obtained by 500 W.
Effect of Vacuum Microwave Drying on the Quality and Storage Stability of Strawberries
Journal of Food Processing and Preservation, 2015
The aim of this study was to determine how vacuum-assisted microwave drying (VMD, 50C, 6 kPa for 3 h) affects the quality attributes and shelf life of dehydrated strawberries. Changes of quality attributes such as color, texture, and rehydration, shrinkage, polyphenol contents, antioxidant activity, and physicochemical and sensory properties were assessed after VMD. Vacuum packed, dehydrated strawberries were stored at 20C in the dark for 6 months. Decay of anthocyanins, flavonoids and polyphenols, and antioxidant activity was determined and modeled according to first-order kinetics. VMD resulted to minimum color difference. Texture changed by increased mechanical resistance and stiffness, and decreased toughness after VMD. Sensory attributes were between 3.5 and 4.3 on 5-point intensity hedonic scale. Anthocyanins were the most unstable components in strawberries after VMD and storage, assessing the strawberry shelf life to 68 days. Finally, VMD is a promising technology that can be used to maintain fruit quality and extend shelf life. PRACTICAL APPLICATIONS Drying is particularly important for handling and distribution of agricultural products with high moisture content and limited shelf life such as fruits and vegetables. The main objective of drying is to reduce moisture content to a level where microbial spoilage and deteriorative chemical reactions of agricultural products are minimal. However, the degradation of nutrients in food during convective hot air drying results to quality loss. Therefore, new drying equipment and drying techniques have to be designed and studied. Vacuum-assisted microwave drying is an emerging dehydration method that may be efficient to preserve quality characteristics of food and additionally leads to shorten effective drying time. The purpose of this study was to determine the effects of vacuum-assisted microwave drying and subsequent product storage on the quality attributes and shelf life of strawberry fruits. This preservation technique may avoid freezing or refrigeration of fruit.
Journal of Food Research, 2013
Hot air drying (HAD), freeze-drying (FD), and swell-drying (SD, coupling instant controlled pressure drop, DIC, to standard hot air) were applied to strawberries (Fragaria var. Camarosa). The total phenol, total flavonoid, and total anthocyanin contentswere evaluated versusthe drying methods. The correlations between the bioactive compounds and antioxidant activity were investigated. The obtained results showed that the differences in phenol levels were no quite comparing the three drying techniques; however, great variations were reported for anthocyanin and flavonoid content.
Study and comparison of different drying processes for dehydration of raspberries
Drying Technology, 2016
The aim of the present study was to evaluate and compare different drying methods (microwave, hot air + microwave and osmotic dehydration + microwave) in raspberries (cv. Heritage). A portion of raspberries was pretreated with osmotic dehydration (60ºBrix sucrose solution at 20ºC for 360min) and another with hot air drying (HAD) (1.5m/s air speed at 60ºC for 300min). Pretreated raspberries were then dried by microwave and at three different intensities (3.5W/g, 7.5W/g and 11W/g). Physicochemical properties (moisture content, water activity and drying rate) and quality parameters (optical properties, mechanical properties, antioxidant capacity and rehydration capacity) of dried raspberries were evaluated. Results showed that the microwave drying at 7.5W/g (50 min and final temperature of 79± 5.1°C) allowed a high yield of dried raspberries. The combined processes were not efficient to accelerate the decrease of moisture content, due to the low drying rate of the pretreatments. In terms of quality, none of the drying processes allowed a high retention of the antioxidant capacity. However, they allowed an appropriate rehydration performance. The combination of HAD with microwave drying
Determination freeze-drying characteristics of ottoman strawberries
Gazi University Journal of Science
This study was performed to define the kinetic drying model and to define the effective diffusivity coefficient of the fruit, which is called ottoman strawberries in the literature. In the study, strawberries by the weight of 100 g and with a thickness of 5 mm were placed in the drying device, and the data were processed by observing the weight loss every two hours after being subjected to the drying process for 14 hours. 8 different kinetic drying models were applied to the acquired data using the MATLAB program. As a result of the application, the estimated standard errors (RMSE), chi-square (X2), regression coefficients (R2) were calculated, error analysis was performed, R2, X2, and RMSE values were found, as 9,998×10-1, 6,993×10-5 and 0.7242×10-2. According to these results, the model of strawberry was determined that the most suitable model is the Page model. Also, the effective diffusivity coefficients for ottoman strawberries were calculated as 2.73286 × 10-10 m2/s. It was co...
Proceedings of the 22nd International Drying Symposium on Drying Technology - IDS '22
This research investigates and compares the impacts of freezing and dehydrofreezing processes on fruit texture and microstructure after thawing. Freezing at-30 °C occurs on fresh strawberries (9 H2O/g db) and previously differently dehydrated strawberries at 1 and 0.3 g H 2 O/g db water content. Various quality parameters were studied: thawing water exudation TWE, texture, and microstructural characteristics. Results show that the lower the water content, the lower the TWE, and the greater the textural quality of the thawed samples. Moreover, ESEM photomicrographs confirm this behavior and show that an initial drying allowing the initial water content below 1 g H 2 O /g db could improve the preservation of tissues and firmness after the freezing/thawing process.