Compostos voláteis, perfil de aroma, de ácidos graxos e potencial antioxidante de óleo extraído por prensagem a frio de resíduo agroindustrial de açaí (Euterpe oleracea Mart.)

Abstract

The fruit of the açaizeiro (Euterpe oleracea Mart.), is one of the most popular foods of the Amazon Region, and widely consumed in the world. In 2014, the production of açaí pulp and by-products, generated approximately R$ 422 million, guaranteeing employment and income for numerous families in the states of Pará and Amazonas. However, the industrialization of açaí also produces organic waste, which represents another environmental problem for the Amazon region. The objective of the present research was to evaluate the potential of the residues generated by the processing of açaí, for the production of oil destined to culinary and cosmetic applications. Mature açaí fruits were processed in a pilot unit of the Food Technology Department at UFS. The residues generated during the clarification of the pulp, called "açaí grounds", were dried at 9.2% humidity and subjected to cold pressing under 45T for 2 hours. The obtained oil was characterized as relative density, moisture content, and refractive index, acidity, saponification, iodine, fatty acid profile and tocopherols content. The antioxidant capacity of the total and polar fractions of the oil were determined by the DPPH, ABTS and ORAC methods. The volatile compounds present in the headspace of the oil were analyzed in comparison to the processed pulp using SPME technique in DVB/Carboxen/PDMS fiber, HP5MS capillary separation and GC-MS identification (Agilent, Model GC 7890A / 5975C). Isolation conditions were optimized using a DCCR design, with a variation of the adsorption temperature between 35ºC and 65ºC, extraction time between 25 and 60min, and data analysis by Response Surface Methodology and Desirability function. Trained judges, using quantitative descriptive analysis (ADQ), generated the aroma profiles of açaí grounds oil compared to three refined commercial oils: soy, grape and olive oil. Sensory data were analyzed by ANOVA, Tukey (p≤0.05) and Principal Component Analysis (PCA). The lipid content of the dry açaí sludge at 9.2% humidity was 19%, and the extraction of oil by cold pressing presented yield of 37%. The oil had a relative density of 0.92 g.cm-3 , and acid values of 1.79 mg KOH.g-1 , saponification of 195.00 mg KOH.g-1 , and iodine of 75 cgI2.g-1 ; All values within the ranges established by the Codex Alimentarius Commission for edible oils. Oleic acid (C18: 1) was the major oil, representing 63.34% of total fatty acids, followed by palmitic (21.3%) and linoleic (8.45%) acids. The α-tocopherol was identified in the oil with a concentration of 41.17 ± 0.04 mg/100g and by the DPPH method, greater antioxidant capacity was detected in the polar fraction (EC50 = 134.14g of oil / g of DPPH) Than in the total fraction (EC50 = 276.84 g oil / g DPPH) of the acai oil. These results were confirmed by the ORAC method, which revealed 150 μM Trolox / g oil for the polar fraction, and 42.8 μM Trolox / g oil for the total fraction. But by the ABTS method, the total oil fraction showed greater antioxidant capacity (2067.4 μM Trolox / g oil) than the polar fraction (766.7 μM Trolox / g oil). The best conditions for isolation of the volatiles occurred with the fiber exposure at 65ºC for 29 minutes. As aldehydes and alcohols were the majority chemical classes in the processed pulp of açaí, representing respectively 49% and 41% of the total area of the chromatogram, hydrocarbons (~ 74%) and terpenes (15%) were the major chemical classes in the oil. The oil of the açaí grounds presented a very complex aroma, being distinguished from the aroma of the soybean oils, grape and olive oil, for having a greater intensity (p≤ 0,05) of aroma of açaí, sweet, green leaf, fruity, Woody and roasted The extraction of oil from the agro-industrial waste of açaí by cold pressing proved to be viable, generating product of potential application in gourmet cooking and cosmetic industry.