Flavonoid Extracts from Lemon By-Products as a Functional Ingredient for New Foods: A Systematic Review

Recovery, Bioactivity, and Utilization of Bioactive Phenolic Compounds in Citrus Peel

Citrus peels are rich in bioactive phenolic compounds with various health effects including antioxidant, antiobesity, antiinflammatory, antihypertensive, antihypercholesterolemic, antimicrobial, antidiabetic, and anticarcinogenic activities. Both extractable and nonextractable phenolics are present in significant amounts in Citrus peel with diverse bioactivities. While extractable phenolics can be recovered from the fruit peels by conventional extraction methods, nonextractable phenolics remaining in the residues must be released from the cell matrix first by hydrolysis with acid, alkali, or enzymes. Novel processing technologies can help in improvement of extraction efficiency. Extreme process or medium conditions degrade phenolics and their bioactivity where encapsulation can be applied to improve their stability, solubility, and bioactivity. Citrus peel powder including ascorbic acid and dietary fiber besides phenolics or extracts therefrom can be used as functional food ingredients to extend shelf life and provide health benefits. In addition, phenolic extracts can be used as antioxidant and antimicrobial agents in active food packaging applications. Phenolic extracts have also a potential to be used as nutraceuticals and pharmaceuticals. In this review, phenolic compounds in different forms in Citrus peels, their recovery, bioactivity and possible applications for upcycling in the industry are presented.

Response Surface Methodology to Optimize the Extraction of Carotenoids from Horticultural By-Products-A Systematic Review

Response Surface Methodology (RSM) is a widely used mathematical tool for process optimization, setting their main factorial variables. The current research analyzes and summarizes the current knowledge about the RSM in the extraction of carotenoids from fruit and vegetable by-products, following a systematic review protocol (Prisma 2020 Statement). After an identification of manuscripts in Web of Science (September 2023) using inclusion search terms ("carotenoids", "extraction", "response-surface methodology", "ultrasound", "microwave" and "enzyme"), they were screened by titles and abstracts. Finally, 29 manuscripts were selected according to the PRISMA methodology (an evidence-based minimum set of items for reporting in systematic reviews), then, 16 questions related to the quality criteria developed by authors were applied. All studies were classified as having an acceptable level of quality criteria (≤50% "yes answers"), with four of them reaching a moderate level (>50 to ≤70% "yes answers"). No studies were cataloged as complete (>70% "yes answers"). Most studies are mainly focused on ultrasound-assisted extraction, which has been widely developed compared to microwave or enzymatic-assisted extractions. Most evidence shows that it is important to provide information when RSM is applied, such as the rationale for selecting a particular design, the specification of input variables and their potential levels, a discussion on the statistical model's validity, and an explanation of the optimization procedure. In addition, the principles of open science, specifically data availability, should be included in future scientific manuscripts related to RSM and revalorization.