Physicochemical properties and sensory acceptability of beetroot chips pre-treated by osmotic dehydration and ultrasound

Abstract Red beet (or beetroot) is highly nutritious and can be preserved by drying, in order to avoid wastage, to take advantage of crop surpluses, and to add value during the off-season. The objective of this study was to evaluate the effects of osmotic dehydration (OD) and ultrasound (US) pre-treatments on the nutritional quality and sensory characteristics of dried beetroot chips. The kinetics of moisture loss during OD and US were predicted by fitting the experimental data with thin-layer models. The physicochemical parameters (moisture, protein, lipid, carbohydrate, energy, ash, sodium and nitrate) and sensory properties (affective preference-ordering and acceptance test) were determined. Correlations between the treatments and the sensory acceptability evaluated by consumer’s perceptions were performed by applying unsupervised chemometric techniques (Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA)). The two-term exponential model provided the best fit for the experimental drying data. The US treatment promoted a higher drying rate and lower lipid, ash and energy values, while the OD process resulted in higher ash and sodium values. Multivariate analysis revealed that the US and OD treatments improved the sensory properties of the beetroot chips. The US was more efficient pre-treatment for producing beet chips due to its leads a significant reduction on drying time and intermediate level of sensory preference. Resumo A beterraba vermelha é altamente nutritiva e pode ser preservada pela secagem, a fim de evitar desperdícios, aproveitar os excedentes das culturas e agregar valor durante a entressafra. O objetivo deste estudo foi avaliar os efeitos dos pré-tratamentos de desidratação osmótica (DO) e ultrassom (US) na qualidade nutricional e nas características sensoriais de chips de beterraba desidratados. A cinética de perda de umidade durante DO e US foi prevista pelo ajuste dos dados experimentais com modelos de camada fina. Foram determinados parâmetros físico-químicos (umidade, proteína, lipídio, carboidrato, energia, cinzas, sódio e nitrato) e propriedades sensoriais (ordem de preferência afetiva e teste de aceitação). As correlações entre os tratamentos e a aceitabilidade sensorial avaliada pelas percepções do consumidor foram realizadas aplicando técnicas quimiométricas não supervisionadas (Análise de Componentes Principais e Análise de Agrupamento Hierárquico). O modelo exponencial de dois termos forneceu melhor ajust