The purpose of this work was to study the effects of spray-drying conditions on the physicochemical characteristics of blackberry powder using a central composite rotatable design. Inlet air temperature (140-180 C) and maltodextrin concentration (5-25%) were employed as independent variables. Moisture content, hygroscopicity, anthocyanin retention, color, powder morphology, and particle size were analyzed. A higher inlet air temperature significantly increased the hygroscopicity of the powder, decreased its moisture content, and led to the formation of larger particles with smooth surfaces. Powders produced with higher maltodextrin concentrations were less hygroscopic, slightly lighter and less red, and had a lower moisture content. Anthocyanin retention was mainly affected by drying temperature due to the heat sensitivity of the pigment. The optimal processing conditions were an inlet air temperature of 140-150 C and maltodextrin concentration of 5-7%. Overall, these results indicate that good quality powders can be obtained by spray drying, with potential applications for the food industry.

Summary The aim of this work was to study the effect of different carrier agents (maltodextrin, gum arabic or a blend of both carrier agents) on the physicochemical properties of blackberry powder produced by spray drying. Moisture content, anthocyanin retention, antioxidant activity, colour parameters, bulk and absolute density, porosity, wettability, sorption isotherms, particle size and morphology of blackberry powders were evaluated. The use of maltodextrin resulted in less hygroscopic powders with lower moisture content and better reconstitution properties. Powders produced with maltodextrin or a blend of maltodextrin and gum arabic presented the best anthocyanin retention and the highest antioxidant activity. Experimental data of water adsorption were well fitted to GAB model. All the samples exhibited a large number of irregular particles with spherical shapes. However, particles produced with gum arabic were smaller and showed more dented surfaces, which probably contributed to the increase in wettability values and lower pigments retention.

The aim of this work was to evaluate the stability of anthocyanins and antioxidant activity of blackberry powder, obtained by spray drying, using maltodextrin, gum arabic, or a blend of both carrier agents over a period of 5 months. The inlet air temperature was 145 C and the concentration of carrier agent was 7% (w/w). Samples were stored at 25 or 35 C and at relative humidity of 32.8%. Anthocyanin degradation followed the first-order kinetic model. Temperature negatively influenced the stability of anthocyanins, because these pigments are highly thermosensitive. Antioxidant activity increased for the powders stored at 35 C, probably due to the occurrence of the Maillard reaction, leading to the formation of compounds with antioxidant activity. In general, maltodextrin provided greater stability for spray-dried blackberry powder, because particles produced with this carrier agent showed the longest half-life and the lowest anthocyanin degradation rate at 25 C. The use of maltodextrin or the combination of both carrier agents promoted better maintenance of antioxidant potential of blackberry powder. With regard to morphology, all of the samples exhibited a large number of irregular particles with spherical shapes, but powders produced with gum arabic presented the smallest size and shriveled surfaces, which probably affected their stability, resulting in faster anthocyanin degradation during storage.

O objetivo deste trabalho foi avaliar a influência da temperatura do ar de secagem (160 ou 180 ºC) e da concentração de maltodextrina (5, 15 ou 25%) sobre as características físico-químicas do suco de amora-preta em pó, produzido por spray drying. O produto final foi analisado quanto ao teor de umidade e de antocianinas, higroscopicidade, atividade de água, cor, distribuição do tamanho das partículas e microestrutura. Temperaturas de secagem mais altas resultaram na redução da umidade, da atividade de água e do conteúdo de antocianinas dos pós, além da formação de partículas maiores e mais higroscópicas. A temperatura teve um efeito significativo na diminuição dos valores dos parâmetros de cor L* e C* somente nos ensaios realizados com 25% de maltodextrina. Em relação à microestrutura, as partículas produzidas à temperatura de 180 ºC apresentaram superfície lisa e uma maior uniformidade em relação às amostras secas a 160 ºC. O aumento da concentração de maltodextrina resultou na formação de partículas com menor umidade e higroscopicidade. Além disso, esses pós apresentaram menor teor de antocianinas, em função da diluição dos pigmentos da fruta, o que levou ao aumento da luminosidade e à redução do croma e do ângulo de tom das amostras. O ensaio realizado à temperatura de 160 ºC com 5% de maltodextrina foi o mais efetivo na manutenção do teor de antocianinas dos pós, visto que a retenção desses pigmentos foi em torno de 80%.

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