Chemical and Physicochemical Quality Parameters in Carrots Dehydrated by Power Ultrasound (original) (raw)
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Food Chemistry, 2013
The effect of previous ultrasound and conventional treatments on drying and quality parameters (furosine-as indicator of lysine participation in the Maillard reaction-, carbohydrates, total polyphenols, protein profile, rehydration ratio, microstructure changes) of convective dehydrated carrots has been assessed. The most striking feature was the influence of blanching on the subsequent furosine formation during drying, probably due to changes in the protein structure. The highest values of furosine were found in carrots conventionally blanched with water at 95 ºC for 5 min. However, samples previously treated by ultrasound presented intermediate values of furosine and carbohydrates as compared to the conventionally blanched samples. Dried carrots previously subjected to ultrasound blanching preserved their TPC and showed rehydration properties, which were even better than those of the freeze-dried control sample. The results obtained here underline the usefulness of furosine as an indicator of the damage suffered by carrots during their blanching and subsequent drying.
A novel dehydration technique for carrot slices implementing ultrasound and vacuum drying methods
A novel drying technique using a combination of ultrasound and vacuum dehydration was developed to shorten the drying time and improve the quality of carrot slices. Carrot slices were dried with ultrasonic vacuum (USV) drying and vacuum drying at 65 °C and 75 °C. The drying rate was significantly influenced by the drying techniques and temperatures. Compared with vacuum drying, USV drying resulted in a 41– 53% decrease in the drying time. The drying time for the USV and vacuum drying techniques at 75 °C was determined to be 140 and 340 min for carrot slices, respectively. The rehydration potential, nutritional value (retention of b-carotene and ascorbic acid), color, and textural properties of USV-dried carrot slices are predominately better compared to vacuum-dried carrot slices. Moreover, lower energy consumption was used in the USV technique. The drying data (time versus moisture ratio) were successfully fitted to Wang and Singh model.
European Food Research and Technology, 2012
There is a growing interest in the use of ultrasound (US) as an alternative to conventional processes. Although US have previously been applied as a pretreatment of fruits and vegetables, no investigation has been done on the usefulness of US for carrot blanching, paying special attention to its effect on enzyme inactivation and leaching losses. In the present paper, the influence of US (in bath and with probe) on peroxidase (POD) and pectinmethylesterase (PME) inactivation and on the loss of total soluble solids and carbohydrates by leaching has been evaluated. Results of this preliminary study have also been compared with those obtained after conventional (hot water and steam) blanching of carrots. The highest enzyme inactivation was obtained with the conventional treatments performed at high temperatures and with the US-probe treatments with heat generation. Carrots blanched by US-probe for 10 min at a temperature up to 60ºC, showed similar characteristics than those conventionally treated at 60ºC for 40 min. Although the efficiency of US was limited for total inactivation of POD and PME activity, this treatment resulted to be advantageous in terms of time for blanching at mild temperatures. US-probe treatments could also be considered as an advantageous alternative to low temperature-long time conventional treatments for those applications in which partial inactivation of PME is required for better preservation of carrot structure.
Food Chemistry, 2013
Vitamin C content and sensorial properties have been evaluated in air-dried carrots previously subjected to different ultrasound (US) or conventional blanching pretreatments. In addition, mass spectral fingerprints obtained by the Headspace ChemSensor System have been evaluated for the first time for classification of carrots according to their processing. Conventional blanching treatments at high temperature gave rise to carrots with retention of vitamin C in the range 37.5-85%, whereas carrots blanched conventionally at 60°C and by US-probe at temperatures up to 60 and 70°C showed vitamin C retention values lower than 4%. Regarding sensorial analysis of rehydrated carrots, US-pretreated samples presented acceptable quality, and no statistically significant differences with respect to conventionally blanched carrots, were detected. In spite of this, differentiation of samples processed under comparable intensity conditions and/or with similar composition was possible from their mass spectral fingerprints after chemometric data analysis.
International Journal of Food Science and Technology, 2007
Leaching of soluble solids had a considerable effect on the stability of carrot during drying and storage. Carotenoid destruction and lipid oxidation increased with increased leaching of soluble constituents. Non-enzymic browning and pH changes decreased and rehydration properties improved as the result of leaching of soluble solids. Increased leaching of soluble solids, though favourable for extending the storage life regarding non-enzymic browning, encouraged carotenoid destruction. A maximum storage life of ninety-six days at 37°C was obtained at a leaching loss of 5.7% soluble solids, which is slightly lower than that produced by a water dip treatment after steam blanching of carrot. Optimization of post-blanch treatments is required to maximize storage life and to minimize nutrient losses.
Rehydration Kinetics of Dehydrated Vegetables Pre-Treated By Ohmic-Blanching
Food ScienTech Journal, 2023
Dehydration is an irreversible process resulting in the loss of structural integrity and rehydration capacity (RC) of food products. Pretreatment methods are used to condition the tissue of vegetables for dehydration to reduce its effect on the structural integrity of the products. In this study, we investigated the effect of ohmic blanching as a pretreatment method and compared it with water blanching and microwave blanching. The Peleg model was used to evaluate the rehydration properties through regression analysis. The model was satisfactorily fitted with the data. However, there was a model deviation with water-blanched potato and yam. Dehydrated products pretreated by ohmic blanching compared favorably with microwave-blanching in carrots, potatoes, and yams. The RC ranged between 264.04% to 449%, 141.40% to 274.32%, and 70.46% to 155.54% in ohmic-blanched carrots, potatoes, and yams respectively. The application of ohmic blanching in the pretreatment of vegetables showed the potential of producing dehydrated products with better rehydration properties. We have suggested through this study, an improved method of hot air dehydration which was of lower cost compared to freeze-drying. The design and model of a bench-top ohmic heating device provided a portable, simple, and low-cost alternative to the otherwise more capitalintensive equipment designs.
Applied Sciences, 2021
The purpose of this study was to investigate the effect of pre-treatment in ethyl alcohol for 5, 15, 60 and 180 s with the application of ultrasound on the course of convective drying and properties of carrot tissue directly after the treatment and after the drying process. The treatment in ethanol resulted in loss of mass, increase of dry matter, ethanol conductivity, extractivity of carotenoids with a slight effect on the colour of carrot tissue after the treatment. The utilization of ultrasound during immersion in ethanol contributed to additional increase of conductivity of ethanol, and extractivity of carotenoids. The immersion in ethanol virtually did not affect the drying kinetics, which can be explained by the increase of shrinkage of the tissue in relation to the untreated dried tissue. Despite the lack of the influence on the drying course in the ethanol-immersed carrot, an increase of the carotenoid content (up to 135%) and the rehydration ability (up to 19%) was noted wi...
Ultrasound Pre-Treatment Approach: Convective Drying of Carrot
Latin American Applied Research - An international journal, 2022
In this study, carrot samples that have different slice thicknesses (2 and 4 mm) were dried by applying ultrasound pre-treatment at different time periods (0, 20 and 40 min) and the changes in colour, rehydration, pH and °Brix values were examined. Besides, microstructures of dried samples under different conditions were observed through scanning electron microscopy images. Drying was carried out in a modified oven at temperatures of 60 and 70 °C with an air velocity of 1 m/s. A decrease in b*(green/red) values was observed due to the effect of drying. The highest rehydration ratio (6.930) was found in 2 mm thick carrot samples, which were dried at 60 °C and treated with ultrasound for 40 minutes. It was observed that pH and °Brix values changed from 6.705 to 6.120 and from 68.70 to 6.80, respectively. An increase in the change of product structure was observed as a consequence of the increasing duration of ultrasound pre-treatment. It was emphasized that ultrasound technology m...