Estudo do processamento das sementes de abóbora: qualidade físico-química e estabilidade oxidativa do óleo.

Abstract

The research presented an experimental aspect, both for the characterization of pumpkin seeds and for the analysis of oil from these seeds. The methodology used was subdivided into three parts: the first was to analyze the physical and kinetic properties of drying the seeds to determine particularities of processing and storage. By determining the size and shape of the pumpkin seeds, it was possible to verify that, with the decrease in the water content, the sphericity and circularity values also decreased. As for the drying kinetics curves, it was observed that, when the temperature is increased, the drying time decreases. The Cavalcanti Mata model was the one that best fitted the experimental data for all temperatures studied. The diffusivity values increased with the increase of the drying temperature, presenting values between 1,03 x10-10 to 12,25 x10-10 m²/s. For the activation energy, the results obtained were equal to 42,80, 30,53 and 41,69 kJ.mol-1. The increase in drying temperature promoted an increase in Gibbs free energy and reduced the values of the enthalpy and entropy properties. The second part was based on physicochemical characteristics of pumpkin seeds and the evaluation of the influence of factors: drying temperature and water content, by means of an experimental planning 22 +3 in the extraction process and physical-chemical quality of the oils. Analyzing the results, it was found that pumpkin seeds showed high amounts of proteins (35.13%) and lipids (32.54%), which gives great potential for use in the industry. The maximum extraction yield was 21.7% for seeds dried at 70° C with a water content of 10% on a wet basis, it was observed that for the quality of the extracted oils, drying temperature was the variable of greatest influence in the increase of the acidity, peroxide, and saponification indexes, giving a greater possibility of oxidation to the studied oils. However, the iodine index and fatty acid profile did not change significantly. It was found that the highest oxidative stability, about 6.71 hours, was obtained for oil extracted from dry seeds at 30° C with a water content of 6% on a wet basis. The third part, on the other hand, involved the evaluation of the oxidative stability of pumpkin seed oils, submitted to accelerated storage in an oven at 63° C (schaal test) and in a light chamber. It was observed that, for the oils stored in a greenhouse, acidity indices showed little variability, showing a tendency to stability, for the peroxide indices and specific absorptivity at 232nm, the exposure time at 63° C caused a gradual increase in all oils. For oils exposed to light, it was found that acidity, peroxide and absorptivity rates increased over 12 days of photoxidation for all oils. The most oxidized oil was test 5 (70° C and 10%) and the least oxidized, test 1 (30° C and 6%).