Abstract
The citrus by-products pectin and polyphenols were obtained from Citrus x lantifolia residues. The use of acid type, solute-solvent ratio, temperature, and extraction time on pectin yield recovery was evaluated using a factorial design 34; pectin physicochemical characterization, polyphenol profile, and antioxidant activity were also determined. Results indicated a total polyphenol content of 3.92 ± 0.06 mg Galic Acid Equivalents (GAE)/g of citrus waste flour in dry basis (DB), with antioxidant activity of 74%. The presence of neohesperidin (0.96 ± 0.09 mg/g of citrus flour DB), hesperidin (0.27 ± 0.0 mg/g of citrus flour DB), and ellagic acid (0.18 ± 0.03 mg/g of citrus flour DB) as major polyphenols was observed. All of the factors evaluated in pectin recovery presented significant effects (p < 0.05), nevertheless the acid type and solute-solvent ratio showed the greatest effect. The highest yield of pectin recovery (36%) was obtained at 90 °C for 90 min, at a ratio of 1:80 (w/v) using citric acid. The evaluation of pectin used as a food ingredient in cookies elaboration, resulted in a reduction of 10% of fat material without significant texture differences (p < 0.05). The pectin extraction conditions and characterization from these residues allowed us to determine the future applications of these materials for use in several commercial applications.
Highlights
The citrus industry in Mexico represents an important economic and social activity
Previous to polyphenol and pectin extraction the Persian lime Citrus x latifolia waste was oven dried at 65 ◦ C for 48 h; this procedure was performed in order to reduce water content of the residues to favor material preservation
Moisture % of the citrus waste flour is in concordance to the Mexican normativity for flour materials NOM 247-SSAI-2008 [23], which indicates a maximal value of 15%; this is an important parameter to ensure the preservation of the material, reducing the risk of microbial contamination and enzymatic degradation that could reduce polyphenols and pectin yields. pH is related to the acidity presented in citrus residues that could be reduced by the dehydration process due to the salts dissociation as reported by Badillo [22], who obtained pH values of 5.5 for fresh fruits and 3.2 after dehydration
Summary
The citrus industry in Mexico represents an important economic and social activity. Worldwide, Mexico occupies the fifth place in citrus production; lemons represent the second most commonly produced citrus fruit in this country, where Citrus x lantifolia represents 50% of the citrus crop cultivated in Mexico [1]. In order to reduce the environmental impact caused by waste materials from food industry, alternatives to obtain added value products that could be exploited in different areas are necessary; as an example, the extraction of biological molecules from citrus residues is an important part of an integrated system that could finish in bioethanol production with the residues free from compounds as Agriculture 2017, 7, 28; doi:10.3390/agriculture7030028 www.mdpi.com/journal/agriculture. Most of the commercial pectin is extracted from apple and citrus peels by the use of chloride acid, the trend of consumers looking to find products obtained in a more environmentally friendly way, searching for the lowest chemical residues generation as well as integrated citric waste utilization, led to the study of new extraction methods in order to maintain or improve upon recovery yields [2]. The use of pectin as an ingredient in bakery products has been suggested as an effective fat replacer [12]; pectin from Yuja (Citrus junos) pomace has been evaluated as an effective fat replacement (up to 10%) in cakes without volume losses
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