Citrus fruits are among the most important global crops, with annual production exceeding 160 million tons. Processing produces significant waste, mainly peels, seeds, and pulp, which can make up to fifty percent of the fruit’s mass. This review critically examines innovative ways to valorize these byproducts. Recent research shows that peels, seeds, and pulp can be converted into high-value materials, including biocomposites and biomaterials, marking a shift from traditional uses like animal feed and biogas production. Notable innovations include smart packaging, pectin-based wound dressings, and biodegradable polymers for sustainable electronics. Advanced green extraction methods, such as deep eutectic solvents, have achieved extraction yields over 85% for flavonoids. Additionally, multifunctional biorefineries processing citrus and olive residues have increased biogas yields by 38–42%. The review explores emerging applications in nanotechnology, nutraceuticals, biodegradable polymers, and functional coatings, all aligned with principles of circular economy and green chemistry. These advances suggest that citrus waste can play a significant role in sustainability efforts and new market development. The review also discusses barriers to adoption, including scalability challenges, regulatory limits, and consumer acceptance, from both global and regional viewpoints.

Functional beverages enhance the nutritional value of their ingredients by increasing the levels of bioactive components, such as probiotics. To achieve consumer acceptance, functional beverages must be both palatable and nutritious. This study investigates the fermentation of quinoa and cherimoya at two temperatures (25 °C and 32 °C) using water kefir grains. The aim was to create a fermented mix that is both balanced and appealing to consumers. The response variables measured were the concentrations of lactic acid bacteria (LAB) and yeasts (CFU mL⁻¹), as well as the overall liking (OL). Ten semi-trained panellists evaluated them using a seven-point hedonic scale. All three developed models for LAB and yeast growth, and OL exhibited R² values exceeding 0.8, indicating a strong model fit and simultaneous optimisation considering the three key responses. At a temperature of 25 °C, the mass fractions of the mixes containing quinoa puree (QP) and cherimoya juice (CJ) were 0.13 and 0.87, respectively. Under optimal conditions, the LAB and yeast increased by 4.2 and 4.4 log units, respectively. Moreover, a significant 62% increase in protein levels and a notable 82% decrease in ascorbic acid were observed after 48 h of fermentation, likely caused by the Maillard reaction.

Citrus fruits are among the world's most important crops, with annual production exceeding 160 tons. However, their industrial processing generates substantial amounts of waste (mainly peels, seeds, and pulp), which can represent up to 50% of their total weight. This review examines innovative strategies to valorize these byproducts. Research shows that citrus residues (CR) have great potential for extracting high-value bio composites or converting them into biomaterials, going beyond traditional uses such as animal feed and biogas production. Special attention is paid to emerging applications in nanotechnology, nutraceuticals, biodegradable materials, and functional coatings. In line with the principles of the circular economy and green chemistry, this study highlights the potential of citrus residues to address major sustainability challenges while fostering the development of new market opportunities. The review also critically assesses current limitations related to scalability, regulatory frameworks, and consumer acceptance, with global and regional implications.

Large volumes of orange residues generated by domestic and industrial consumption in Ecuador are commonly discarded, contributing to environmental burdens despite their high content of bioactive antioxidant compounds. This study evaluated the impact of osmotic dehydration (OD) on the physicochemical properties and functional attributes of Ecuadorian Valencia orange (Citrus sinensis) peels. A 2³ factorial design was applied, evaluating blanching time (BT: 5–10 min), sucrose concentration (SC: 50–70 °Brix), and immersion time (IT: 12–24 h). Results revealed highly significant (p < 0.01) non-linear effects of processing variables on mass transfer kinetics. Notably, milder intermediate conditions (50 °Brix, 12 h, 5 min BT) yielded significantly lower water activity (0.70 ± 0.005) and moisture content (11.83% ± 0.12%) compared to severe processing (70 °Brix, 24 h, 5 min BT), which trapped internal water (aw = 0.81 ± 0.009, moisture = 13.77% ± 0.20%), which suggested the occurrence of solute-induced surface case hardening, minimizing subsequent moisture diffusion. Processing induced an extraordinary reduction in total phenolic content (TPC) by 86% to 93% (p < 0.01) from the fresh baseline down to a range of 1.40–2.70 mg GAE/g dw, alongside a critical drop in antioxidant capacity, with post-dehydration ABTS retained at <65% and FRAP at <30% of fresh values due to cellular membrane disruption and subsequent hydrophilic leaching. Conversely, lipophilic total carotenoid content was maximized under severe configurations (10 min BT, 70 °Brix SC, 24 h IT) at 52.92 ± 2.19 µg/g dw (p < 0.01) due to protective sugar matrix encapsulation. Ultimately, these findings demonstrate that while osmotic processing involves an inherent trade-off in soluble antioxidant depletion, it establishes a precise technological process window to stabilize highly perishable citrus by-products into microstructurally stable, value-added dietary fiber matrices, providing a predictable and scalable upcycling strategy for functional ingredient development within the regional circular bioeconomy.