**3. From macauba fruit to refined oil: modifications**

#### **3.1 Fruit processing**

The harvest and storage stages of fruits are determinants of the quality of agricultural products. Both the harvest method and the development stage of macauba fruit at the time of harvest directly impact the quality of the oil [16]. The storage time of the fruits before the oil extraction also has a great impact on the product quality, which is determinant in humid tropical countries [37]. In the extractive cultivation system of macauba, the fruits are collected directly from the soil, after the natural fall at the end of the fruiting period, and stored with no controlled humidity and temperature conditions, resulting in low-quality oils and yield [16].

Data have shown an increase in oil content at the end of the maturation period of macauba fruits, thus harvesting bunches at the end of this phase is recommended. However, the proportions of fatty acids and triacylglycerols of both pulp and kernel oils do not vary [48]. A very important peculiarity of the macauba fruit is the additional oil synthesis after abscission, which differentiates it from other palm species, including *E. guineensis*. Studies have shown that such production can reach up to 35% after 40 days of storage under ambient conditions [16]. Therefore, the harvest and postharvest stages of macauba fruits are crucial in the productivity and quality of crude oil, mainly concerning the acidity index and oxidative stability.

The acidity index is a measure of the free fatty acids content in the oil. Oils with acidity levels >5% expressed as free fatty acids compromise the later stages of processing and commercialization [49]. The increase in free fatty acids in the oil from the mesocarp is due to the action of lipases (E.C. 3.1.1.3; glycerol ester hydrolases) that hydrolyze triacylglycerols in the presence of water. These enzymes are produced by plants, animals, and microorganisms [50], and the latter are recognized as potential producers of extracellular lipases [51]. Cavalcanti-Oliveira et al. analyzed the origin of lipases involved in the hydrolysis of macauba pulp oil [52]. The results suggested that the oil from the mesocarp is hydrolyzed by lipases produced by microorganisms that contaminate the fruit when in contact with soil, rather than the action of endogenous lipases. Some authors have reported that macauba fruits harvested directly from the bunch or naturally fallen fruits with no contact with the soil can be stored under ambient conditions for up to 20 days, without exceeding 5% acidity [16, 18, 53]. However, a varied microbiota can be found in the epicarp and mesocarp of macauba fruits without contact with the soil [16].

Thus, efficient harvesting methods and rapid fruit processing are required to slow pulp decomposition and oil acidification [54]. Fresh macauba fruit has high-quality mesocarp oil, even when it is dried immediately after harvest, provided that good harvesting and processing practices are applied [55]. Drying the fruit after harvest decreases the moisture content and reduces the hydrolysis efficiency of lipases in addition to facilitating pulping with simultaneous separation of the peel [56]. The combination of drying and autoclaving processes of macauba fruits allowed the storage of crude oil for 180 days, preserving the original acidity and the triacylglycerol profile [52]. It is worth noting that under good harvesting and storage practices, the acidification process of macauba pulp oil is slower than palm oil [55]. Other methods of treating the fruit immediately after harvest have been used to extend the shelf life of the fruit and the oil quality, including the use of ozone gas, irradiation, and different drying methods [53, 57, 58].

Evaristo et al. [16] reported a significant increase in the oil content of the mesocarp after the fruits were detached from the bunch, suggesting that macauba has climacteric behavior. The authors showed that harvesting macauba fruit directly from the bunch and the immediate storage under controlled humidity and temperature conditions, as well as the treatment with fungicides, resulted in higher fruit quality and therefore longer postharvest shelf life [16].

Improvements in fruit processing steps that positively impact the quantity and quality of the extracted oil can increase productivity and make the macauba more commercially competitive [56].
