Modificação de amido de arroz por tratamento térmico de baixa umidade adicionado de óleo de abacate: processo via autoclave versus micro-ondas.

Abstract

The modification of starch is used to overcome some technological limitations and improve the functional and nutritional characteristics, expanding its possibilities of use in the food industry. The objective of this research was to carry out a physical and chemical modification of rice starch by heat-moisture treatment (HMT) in an autoclave and microwave with the addition of avocado oil (AO) for the formation of inclusion complexes and to evaluate physical-chemical parameters and nutritional aspects of modified starches. Starch was extracted from rice flour, characterized and prepared for modification. The HMT process was performed with 30% moisture in the starch with the addition of AO (2, 4 and 8%), in the autoclave at 110 °C for 1 hour and for 3 minutes at 50 °C in the microwave. In modified and native starches, the effects were evaluated by means of X-ray diffraction, differential scanning calorimetry, spectroscopy in the infrared region with Fourier transform, viscoamylographic properties, in vitro digestibility and estimated glycemic index. The final viscosity and the retrogradation gradually decreased as the AO concentration increased, the thermal properties followed the same pattern and there was an increase in the gelatinization temperature. In the FTIR analysis, the starches with AO showed interaction with the lipid. X-ray diffraction showed that native starch has a type A pattern, and those modified with OA showed peaks of a type V pattern, the relative crystallinity of the treatments was reduced. The thermal property of starch showed an increase in digestion after HMT. Even though there is no confirmation of the formation of the inclusion complex between starch and AO, the differences in modification between autoclave and microwave can be clarified. The M8% showed lower digestibility in vitro (p<0.05) and had a reduction in the glycemic index (p>0.05). The modified rice starch via TTBU with OA showed satisfactory results by both processes (autoclave and microwave). The use of microwaves for starch modification is very interesting because it is a fast, safe process, with good energy efficiency, which allows the use of a lower modification temperature, preserving the desirable properties, thus the starch modified by the processes proposed in this work could be applied in food products to increase nutritional functionality.