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Effect of blanching on the nutritive value and sensorial attributes of dehydrated carrot by convection

AuthorsGamboa-Santos, Juliana ; Montilla, Antonia ; Carrasco Manzano, Juan Atanasio ; Soria, Ana C. ; Pérez-Mateos, Miriam ; Villamiel, Mar
Issue Date2012
CitationANQUE ICCE 2012
AbstractOne of the main reasons for carrot acceptance by the consumers is its high nutritive value and its pleasant flavour, volatiles and sugars being the main compounds that accounts for the distinctively carrot-like flavour (Alalsavar et al., 2001; Rosenfeld et al., 2002). Among the different processes that can be applied to carrot to obtain a product with extended shelf life, dehydration by hot-air is perhaps the most popular. Apart from the drying conditions, other previous and subsequent operations might affect the quality of the final product (Negi and Roy, 2001). In this respect, blanching is one of the most commonly used pre-treatment to inactivate the enzymes responsible for quality deterioration of processed vegetables and it can be carried out under high temperature (Shivhare et al. 2009) or low temperature (Sanjuan et al., 2005) conditions. However, similarly to other thermal processes, blanching and drying have been shown to affect the content of some nutritive and bioactive compounds of vegetable including vitamin C (Sablani, 2006). Both processes, moreover, can also modify the quality of carrot flavour giving rise to a substantial decrease of concentration of important volatiles after these operations (Soria et al. 2008). Alternative blanching methods and/or optimization of drying conditions may result in processed carrots with better flavour, nutritive and bioactive characteristics. Among the different alternative blanching methods, ultrasound pre-treatment has been widely studied in fruits showing a positive effect in the water diffusivity during drying (Fernandes et al., 2011). In the case of carrots, hardly any research has been carried out on the potentiality of US as alternative to conventional pre-treatment. Thus, the aim of this work was to investigate the impact of a blanching by ultrasound and conventional on the degradation of vitamin C and on the sensorial characteristics of carrots dehydrated by convection in a prototype under previously optimized conditions. In addition, a complementary study based on ChemSensor (HS/GC/MS-electronic nose) application based on mass intensity data to classify the different samples in relation to the used processes has been also included. For US treatments, samples were sonicated in an ultrasonic system equipped with a temperature sensor and a tip of 13 mm diameter directly attached to a disruptor horn (20 kHz, 400 W full power). Experiments were carried out with generation of heat: during 10 min at temperature up to 60°C (USP60-10), and for 15 min at temperature up to 70°C, (US70-15)..Carrot samples were also subjected to blanching with steam for 2 min (CS-2), boiling water for 1 min (CB-1), water at 95°C for 5 min (C-95-5) and at 60°C for 40 min (C-60-40) using a hot-plate with control of temperature. Blanched carrot samples were dried at 46°C and 4.9 m/s during 6 hours by convection using a computer controlled air tray dryer
(SBANC, Edibon Technical Teaching Units, Spain). Since all samples were dried under the same conditions, the observed variations in the values of the final content of vitamin C (1.05-18.77 mg/100g DM) were probably due to the different blanching procedures. The highest retention was detected in dehydrated samples previously blanched under the conditions CS-2 and CB-1, due to the highest retention after blanching. However, the corresponding to C95-5 conditions lost most of its content of vitamin C by leaching during blanching and the losses during dehydration were substantially lower. With respect to the other dried samples (C60-40, USP60-10, USP70-15) hardly any presence of vitamin C was detected after drying since the blanching treatment was very severe. Rehydrated carrot samples were analysed by a taste panel of 14 semi-trained judges for their sensorial attributes by means triangle and hedonic tests. In general, the panelists highlight the difficulty of the test since the assayed samples presented similar attributes and overall quality, in agreement with the statistical analyses, since no significant differences (P>0.05) were observed between the samples, with scores between 3.0 (close to “like moderately”) and 3.7 (close to “like slightly”). Therefore, the samples subjected to ultrasound blanching prior to drying by convection presented an acceptable quality, similar than that of samples blanched by different conventional methods. In addition, dehydrated carrot samples were submitted to an analysis by a Headspace ChemSensor System. The chemometric interpretation of obtained data afforded important information on the classification of samples in a precise and fast way. Thus, although no significant differences were detected by the panelists, dehydrated samples previously blanched under the different conditions above mentioned, were separated in different groups, presenting in some cases, significant differences (P<0.05). These results underline the usefulness of ChemSensor as a tool to classify and predict samples subjected to different processing conditions.
DescriptionResumen del póster presentado al ANQUE International Congress of Chemical Engineering (ICCE): "Innovating for the future", celebrado en Sevilla del 24 al 27 de junio de 2012.
Appears in Collections:(CIAL) Comunicaciones congresos
(IQOG) Comunicaciones congresos
(ICTAN) Comunicaciones congresos
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