Annually, millions of tons of foods are generated with the purpose to feed the growing world population. One particular eatable is orange, the production of which in 2018 was 75.54 Mt. One way to valorize the orange residue is to produce bioethanol by fermenting the reducing sugars generated from orange peel. Hence, the objective of the present work was to determine the experimental conditions to obtain the maximum yield of reducing sugars from orange peel using a diluted acid hydrolysis process. A proximate and chemical analysis of the orange peel were conducted. For the hydrolysis, two factorial designs were prepared to measure the glucose and fructose concentration with the 3,5-DNS acid method and UV-Visible spectroscopy. The factors were acid concentration, temperature and hydrolysis time. After the hydrolysis, the orange peel samples were subjected to an elemental SEM-EDS analysis. The results for the orange peel were 73.530% of moisture, 99.261% of volatiles, 0.052% of ash, 0.687% of fixed carbon, 19.801% of lignin, 69.096% of cellulose and 9.015% of hemicellulose. The highest concentration of glucose and fructose were 24.585 and 9.709 g/L, respectively. The results highlight that sugar production is increased by decreasing the acid concentration.

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Background. Emerging extraction techniques for bioactive compounds have been cataloged as efficient and cost effective compared to conventional ones. The objective of this research was to define the time and temperature that will guarantee a higher mangiferin content and antioxidant potential in Colombian Criollo mango peel through Ultrasound Assisted Extraction (UAE). Materials and methods. To find the optimal extraction conditions, response surface methodology was used, proposing a 3 2 factorial experimental design having as response variables the content of mangiferin and total phenols, and the antioxidant activity measured through ABTS and ORAC techniques. Results. According to the results obtained, the R 2 values were in accordance with the adjusted R 2 values, showing that the data fit the model well. The results showed that both time and temperature had a significant effect on all the variables evaluated (p < 0.05). The optimization of multiple responses showed that the optimal extraction conditions were 10 min and 54°C; these values were performed experimentally to compare theoretical values, finding percentages of standard residual error of less than 5%. Conclusion. This allows the conclusion that the optimal parameters of temperature and time in ultrasoundassisted extraction were defined in Criollo mango peel. On the other hand, the peel showed a considerable metabolite content and antioxidant activity, suggesting it as a possible functional additive in the production of juices, nectars, and other mango-based products.

1 Introduction