Microbiological investigation of peppermint and pumpkin seed kernels drying in batch dryer

Abstract

The goal of this research was to investigate improvement of drying method of peppermint and pumpkin kernels (hull-less pumpkin seed) with the aim to get as best microbiological quality of products as possible. Small and medium scale producers of medicinal plants in most cases perform it in batch dryers, which offer optimal output rate. Disadvantages of this dryer type are slower through-heating of upper layers, with the resulting increase of microbial count. In this paper, results of investigation of drying characteristics in batch dryer expressed through the changes of count of bacteria and microfungi are presented. The drying regime was applied in three different phases, and different material batch heights. Obtained results show that microbial count has increased in the upper layer during process of peppermint drying, while the temperature was less than 45°C for a long period. However, during the final drying phase in this layer, the temperature was also over 45°C, and the final microbial count was almost the same for upper and lower levels. During the treatment of pumpkin kernels in all of cases number of microorganisms indicated that the treated pumpkin grains belonged to the 3B qualitative group or to the 4B for phase drying respectively, and to the 4A for control group according to the Europaean Pharmacopoeia. The results obtained suggest that the treatment of hull-less pumpkin seed with even higher temperatures of drying agents, for example 70°C or 80°C, in the first phase should be investigated. After that phase, the second phase would follow, using temperature of 60°C, and the method with shifting mode should be applied.

Keywords

• drying
• microbiological quality
• peppermint
• pumpkin seed kernel