Extração de compostos oriundos dos resíduos agroindustriais de maçã e uva dentro do conceito de biorrefinaria

Abstract

Apple and grape processing industries face difficulties when it comes to the proper disposal of an industrial co-product, pomace. This lignocellulosic residue, obtained after apple pressing or grape fermentation, corresponds to around 25-45% of the weight of the processed fruit. This bagasse contains organic acids, soluble sugars, phenolic compounds and pectin in its composition, which have high added value when recovered. Studies have explored technologies for recovering these compounds, however, the lignocellulosic material remains after the process, and the problem has been partially resolved. Therefore, this thesis aims to investigate and evaluate the potential of apple and grape pomace for recovering high-value compounds, seeking innovative and sustainable technologies that adapt to the concept of bioeconomy and circular economy and with full use of lignocellulosic waste. In Chapter 1, a theoretical approach to the concepts surrounding the thesis was developed based on the available literature based on scientific articles and recent publications. This chapter provides the theoretical basis for the other chapters. In Chapter 2, apple pomace was obtained after pressing apples cv. Gala in full juice. Considering bagasse as a second-generation raw material for a biorefinery, three phases were divided. Phase 1 consisted of the individual extraction of soluble sugars and organic acids (Extract 1), phenolic compounds (Extract 2) and pectin (Extract 3). In Extract 1, glucose (5%),

fructose (21%), sucrose (2%) and malic acid (5 mg/mL) were identified and quantified by high- performance liquid chromatography (HPLC). Analysis of total phenolic compounds (333 mg

EAC/L) and FRAP antioxidant activity (951 μmol/L) were carried out for Extract 2 using spectrophotometric methods. The pectin precipitated in Extract 2 showed a high degree of methoxylation, determined by titration and mid-infrared (IR) spectroscopy. Phase 2 covered the removal of lignin from the remaining lignocellulosic fraction, using a deep eutectic solvent (DES-Choline chloride: Lactic acid, 1:2) with the assistance of ultrasound equipment. Using Box-Behnken factorial design (temperature, solute:solvent ratio and DES concentration), 62% of the lignin can be extracted. Phase 3 completed the use of apple pomace, through the production of cellulose using the oxidative method (1M ammonium persulfate) and characterized by scanning electron microscopy (SEM). Chapter 3 covers the fermentation process of two national grape varieties Vitis labrusca (BRS Carmem, BRS Violeta) and the exploitation of pomace obtained in the industrial vinification of a Vitis vinifera grape variety (Cabernet Sauvignon). Violeta grape juice obtained a 61% yield, while cv. Carmem obtained 52%, by steam dragging, and for fermented products, 67 and 62%, respectively. The cv. Violeta showed a significant difference to the Carmem variety in terms of phenolic compounds (4965 mg EAG/ L), anthocyanins (780 cyanidin-3-glucoside (c3g) mg/L) and antioxidant activity (1709-4729 μmol TE/L) (values referring to the juice). For Part 2, the same biorefinery concept applied in the previous chapter was used as a basis for this chapter, obtaining Extract 1 (290 mg EAG/L) and Extract 2 (1892 mg EAG/L), Extract 3 with precipitation of low methoxylation pectin and cellulose production in micro size. The products recovered and produced from grape fermentation pomace have potential for future studies of their application in the low-calorie beverage industry, as water flavorings, in addition to the smart packaging and hydrogels market. The results obtained in this doctoral thesis propose sustainable solutions for the recovery of high-value compounds that can be applied as second-generation raw materials for innovative materials, through technology transfer between academia and industry.