Microencapsulação de óleo de chia por spray-drying combinando isolado proteico do soro de leite e maltodextrina e aplicação em cupcakes

Abstract

Chia oil is a source of polyunsaturated fatty acids, with α-linolenic acid being the most abundant. Despite potential health benefits, polyunsaturated fatty acids are susceptible to oxidation. Thus, microencapsulation presents itself as an alternative for its protection. The aim of this study was to produce chia oil microcapsules by combining whey protein isolate (WPI) and maltodextrin (MD) as wall materials and then apply them to cupcakes. Two microcapsule formulations were obtained, MC 1 (10:1 MD:WPI; 0.20 chia oil:solids) and MC 2 (4:1 MD:WPI; 0.08 chia oil:solids). The oil content retained in the microcapsules was determined by cold solvent extraction and the EE% content was determined by quantification of the free (non-encapsulated) oil. MC 2 exhibited a higher retained oil content (95.43%) and a higher EE% (73.11%), demonstrating that the method efficiently encapsulated chia oil when a higher WPI content was used. The α-linolenic acid content of MC 2 and free chia oil was determined by gas chromatography. It was not significantly affected by the encapsulation process, showing levels of 35.08 and 35.44%, respectively. Chia oil exhibited a single thermal event from 345 to 485 °C related to its decomposition in thermogravimetric analysis. However, the microcapsules showed four thermal events related to water evaporation (from 55 to 135 °C), wall materials (245 and 320 °C), and chia oil degradation (410 °C). Despite the higher thermal degradation temperature of chia oil, the total percentage of degraded organic compounds was higher than in microcapsules. A sharp band at 1745 cm-1 was observed in the FTIR-ATR spectrum of chia oil related to the elongation of ester functional groups mainly of fatty acids. This band was also observed in the physical mixture of the blank with chia oil and the microcapsule tests, but to a lesser extent in MC 2, suggesting its greater encapsulation efficiency. Microencapsulated chia oil (MC 2) was incorporated into cupcakes (F2) and its chemical composition and physical-chemical properties were compared to a control formulation (C) and with the addition of free chia oil (F1). The results demonstrated that the addition of MC 2 to the cupcakes influenced the color and texture of the cakes, resulting in a darker crust and greater firmness, adhesiveness, gumminess, and chewiness, in addition to lower water activity during storage for nine days at 18 °C. These results suggest that the WPI and the MD present in MC 2 may have influenced these parameters, by favoring the Maillard reaction and increasing the water retention capacity, respectively. As for the lipid oxidation parameters, after 9 days of storage, the F2 sample exhibited a higher K232 and K270 index, which represent secondary dienes and trienes, respectively, from lipid oxidation. The α-linolenic acid content was higher in samples F1 and F2, respectively, showing a value greater than 600 mg 100 g-1, which indicates that the product has a high content of omega 3, according to the legislation. The omega 3 content did not differ in relation to the initial and final storage time for all tests. The process of microencapsulation of chia oil in WPI and MD by spray-drying proved to be feasible. Free and microencapsulated chia oil made it possible to add omega 3 to the product, remaining stable over the 9 days of storage.