Effect of the temperature and drying time on the total anthocyanin concentration and the particle size index of powder extracts from blackberry (Rubus fructicosus), raspberry (Rubus idaeus), and blueberry (Vaccinium corymbosum) crom

Original title: Efecto de la temperatura y tiempo de secado sobre la concentración de antocianinas totales y el tamaño de partícula de extractos en polvo de zarzamora (Rubus fructicosus), frambuesa (Rubus idaeus) y arándano azul (Vaccinium corymbosum)

Berries, also known as wild berries, are fruits of small size, generally sweet and with a very intense pigmentation caused by their anthocyanins. There are a lot of varieties, among the most common are raspberries, blueberries, cherries, cranberries, blackberries, among others. These fruits have many health benefits, mainly known for their great amount of antioxidants, which are substances contained in certain foods and can help to prevent the adverse effects of reactive species on the normal physiological functions of humans. However, this type of fruits have a short shelf life due to its high water activity and moisture content. The objective of this research was to evaluate the effect of the drying time and temperature on the concentration of anthocyanins and the particle size of powders with high content of anthocyanins and an adequate particle size. A coupling of a new device was achieved to obtain the data for the calculation of the percentage of weight loss in of the three fruits during 24-48 hours and at different drying temperatures of 60, 70 and 80 °C. Likewise, anthocyanin extraction was carried out for its quantification by measuring the absorbance at 520 nm using a UV-Vis spectrophotometer. The dehydrated fruits were milled in a knife mill until powders were obtained with adequate particle size, and its characterization was done by the particle size distribution using a sieve separator. The design of experiments was a factorial design of 3x3x4, where the factors evaluated were the temperature and drying time, as well as their interaction. An analysis of variance with a confidence level of 95 % and a multiple comparison analysis of Duncan’s means were made to observe statistical differences between treatments (P<0.05). According to the percentage of weight loss in the three fruits evaluated, it was observed that at a higher temperature the drying time decreased. The drying temperature, the time and its interaction of time and temperature showed very significant effects in the weight loss of the fruits (P<0.0001). The berry that reached a greater moisture loss was the raspberry at 80º C. In the concentration of total anthocyanins it was shown that at higher drying temperature the amount of anthocyanin was increased, being the temperature and time of drying the factors that showed significant statistical effects (P&lt;0.05) according to the data obtained from the analysis of variance, the blueberry was the fruit with the highest concentration of anthocyanin. In the process of milling to obtain the powders of the fruits, the blueberry was the fruit from which on powder was obtained, resulting in a pasty material with inadequate consistency. However, in the case of the raspberry and blackberry, the obtention of a powder material was achieved that could be considered to be use as an additive. In the particle-size distribution (PSD) analyses, it was demonstrated that the number of mesh, the interaction fruit type and number of mesh showed a very significant statistical effect (P<0.0001), and the triple interaction fruit type, temperature, and number of mesh showed significant statistical effects (P<0.05) according to the data obtain from the analysis of variance. On the other hand, the particle-size index (PSI) showed a statistically significant effect (P<0.05).