(135c) Short-Time Hydrothermal Sterilization of Thermally-Labile Powders

Powdered solid is one of the most important raw materials that attributes for tailoring the functionality and prolonging shelf-life for the food and pharmaceutical industries. With the increasing consumer demand in incorporating added-value functional ingredients to the final dried products, researches have been focusing on the development of effective processes that preserve these heat- and moist-sensitive materials while keeping microbial load within the legal-acceptable range [1, 2]. Suggested technologies cover both thermal and non-thermal processes of bulk powders, however, a technically feasible industrial solution for continuous minimal processing is yet challenging.

Among different food ingredients, starch is the fundamental natural polymer that has a broad application only after modification enzymatically, chemically through cross-linking and/or substitution or by physical means such as high-pressure treatment, annealing (ANN) and heat-moisture treatment (HMT) [3, 4, 5]. In particular, the two hydrothermal treatments, ANN and HMT, have received significant interest for alternating the starch structure and properties but preserving the granular structure that improves heat-, shear-stability and digestibility of starches for further processing. Currently, most heat-moisture treatments are based on lab-scale production which are time- and energy-intensive with treatment time ranges from 15 min to 1 day at temperature range from 50°C to 120°C [6].

Therefore, this investigation focuses on the short-time hydrothermal sterilization in the novel Falling Particle Cloud tubular reactor prototype that was developed in the laboratory. Our previous study validated the decontamination process for model particles based on the promising Vacuum-Steam-Vacuum (VSV) concept which targets efficient heat transfer to the surface of food powders [7]. The application through the reactor prototype is further expanded to hydrothermal treatment of starch and its thermally-labile derivatives. Within 1 s steam treatment time, surface microbial decontamination and hydrothermal modification of the starches can be achieved in the reactor while maintaining powder quality. This research aims to give better understanding on the dynamic process conditions during the short-time hydrothermal sterilization and its effects on granule morphologies and gelatinization behaviors of starch, as well as on the microbial inactivation for powder products. A detailed processing mechanism and device description will be presented together with results from decontamination experiments.

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3. Jayakody, L., Hoover, R. (2008) Effect of annealing on the molecular structure and physicochemical properties of starches from different botanical origins – A review. Carbohydrate Polymers, 74, 691 – 703.

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5. Hoover, R. (2010) The Impact of Heat-Moisture Treatment on Molecular Structures and Properties of Starches Isolated from Different Botanical Sources. Critical Reviews in Food Science and Nutrition, 50, 835 – 847.

6. Chung, H.-J., Liu, Q., Hoover, R. (2009) Impact of annealing and heat-moisture treatment on rapidly digestible, slowly digestible and resistant starch levels in native and gelatinized corn, pea and lentil starches. Carbohydrate Polymers, 75(3), 436 - 447.

7. Hörmansperger, J., Buchmann, L., Merz, S., Schmitt, R., Beyrer, M., Windhab, E. (2016) Microbial decontamination of porous model food powders by Vacuum-Steam-Vacuum treatment. Innovative Food Science & Emerging Technologies, 34, 367 - 375.