Development of Innovative, Energy-Efficient Processes for the Production of High Quality Herbs and Spices

Herbs and spices have been used throughout the world since antiquity for flavoring and coloring of foods, and additionally, for cosmetic and medicinal purposes. They are natural products, thus carrying a high microbial burden. Spices are mostly produced in tropical and subtropical countries often under poor hygienic conditions. The hot and humid climate, the mostly simple, unpretentious production conditions, and the often inadequate instruction of farmers may result in considerable hygienic and sensory problems causing significant number of food-borne infections and intoxications. Although dried spices are almost nonperishable goods due to their low water activity, microbial populations may grow rapidly upon rehydration of the spices. Furthermore, endogenous enzymes affecting product quality are inhibited only in dry state, but not totally inactivated. Consequently, such enzymes may regain their activity after rehydration of dried foods, thus adversely affecting product quality. Conventional spice powders exhibit poor sensory appearance and are difficult to handle in industrial food processing due to lump and dust formation. Moreover, both drying and cryogenic milling are energy demanding processes leading to high operating costs. Therefore, the present thesis aimed at the development of innovative, energy-efficient processes for the production of high quality herbs and spices.

Compared to conventional dried herbs and spices, the pasty products obtained by this innovative process were characterized by bright colors. This may be ascribed to enhanced chlorophyll retention in parsley pastes partly due to the prevention of magnesium leaching and the early PPO inactivation in celeriac pastes, respectively, as a result of the initial blanching step. Celeriac POD could not be completely inactivated; however, its activities were very low. The apiin levels strongly decreased, while the contents of malonylapiin B significantly increased, when processing parsley and celeriac into pasty products. During cold storage of parsley pastes, the green color was retained for 4 weeks, whereas the products may be stored at -20 °C for several months without color loss. In contrast, storage of celeriac pastes at 4 and -20 °C is possible for several months without browning. Furthermore, crucial enzyme activities were almost disrupted in celeriac pastes and even ceased in parsley pastes during storage for 3 months. However, polyphenol losses could not be prevented during storage of parsley and celeriac pastes.

Compared to conventional spice powders, pasty products are easier to dose, because lumping and dusting are avoided, thus facilitating their easy application in the food processing industry. By omitting drying and cryogenic milling, this process may contribute to save energy and improve energy efficiency in food processing. Due to thermal treatment microbial load of the products is regarded as low, thus their safe application is primarily proposed for sensitive food sectors such as catering of hospitals, schools, and residential homes for the elderly requiring especially high hygiene standards, and for their incorporation into extremely sensitive commodities (e.g. herb butter).