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.

The food industry is growing significantly every year. Annually, large quantities of fruits and vegetables are grown to meet the population demand. Among them, the orange (Citrus sinensis) production was 70.45 Mt in 2013. After consumption, the remaining orange peel is considered as a waste. From an economic and environmental perspective, the extraction of orange essential oil is a high value-added option for the valorization and use of the orange peel. Therefore, the objective of this study was to determine the experimental conditions where the maximum yield of essential oil of orange peel is obtained by applying a factorial design. The most relevant extraction process factors studied were the grinding time and the operating time. The characterization of the essential oil included FT-IR, GC-FID, high heating value determination and TG analysis. For the processed orange peel, the high heating value was measured, and the SEM-EDS analyses were performed. The maximum experimental yield was achieved with 500 cm³ of solvent, 50 min of extraction time and 2 min of grinding time. The results obtained at these conditions were: a yield of essential oil of 5.23% v/w, with a concentration of 74.43% of limonene, 4.27% of p-myrcene, 3.26% of sabinene, 1.54% of β-pinene, and 1.54 % of linalool. The high heating value of essential oil was 44.25 MJ/kg, and for orange peel was 15.82 MJ/kg. The orange peel elemental composition analysis showed 24.1% oxygen and 73.51% carbon.

The brewing industry generates, as the primary coproduct, brewers’ spent grain (BSG). In Mexicali, Baja California, Mexico, there are 17 companies that generated 282 tons of BSG by 2016. Cattle feeding is the most common type of disposal for this waste. However, it can be valorized for the production of bioenergy or as a source of added-value products. Therefore, the objective of the present work was to assess the physicochemical properties of the brewers’ spent grain from a local craft brewery, to choose the most appropriate exploitation route. Chemical and morphological analyses were carried out by energy dispersive X-ray fluorescence spectroscopy (EDX), scanning electron microscopy, and the higher heating value determination. The results of the proximate analyses were 72.32% moisture, 78.47% volatile matter, 17.48% fixed carbon, and 4.05% ash. The results of the chemical analysis for extractables were 5.23% using organic solvent and 50.25% using hot water. The content determination were 17.13% lignin, 26.80% cellulose, and 37.17% hemicellulose. The results of the ultimate analysis were 43.59% C, 6.18% H, 3.46% N, and 37.22% O. The higher heating value experimentally obtained was 18.70 MJ/kg. Moreover, in the EDX analysis, Ca, P, K, and S were mainly found. It is recommendable to valorize the BSG through the xylitol, bioethanol or biogas production, because of its high moisture, hemicellulose and cellulose content.