Submitted to: Future Foods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2021
Publication Date: N/A
Interpretive Summary: Florida juice processors produced 51,000 metric tons of grapefruit peel, membrane, juice sacs and seeds in the 2018-19 season. Rather than disposing these residues, processors convert them to low cost animal feed and molasses. But there are valuable compounds in these residues that are not being recovered. If these compounds could be recovered, the profitability of these residues could be increased while still avoiding their disposal. Therefore, a method for extracting these compounds from Florida red and white grapefruit juice processing residues was investigated. Specifically, bench scale batch steam explosion was used to identify the conditions to maximize the recovery of pectin, sugars, peel oil, phenolics and flavonoids. Calculations based on the maximum recoveries of these compounds using steam explosion resulted in millions of dollars of potential value that could be garnered in a single season. This information will help inform processors interested in increasing the value from grapefruit juice processing residues.
Technical Abstract: Florida juice processors amassed 51,000 metric tons of grapefruit juice processing residues (GFPR) in the 2018-19 season. GFPR contain valuable compounds such as pectic hydrocolloids, peel oil, sugars, phenolics and flavonoids that are ultimately lost or destroyed when they are converted to low value animal feed and molasses. If these compounds could be isolated from GFPR rather than destroyed, they could be converted to high value products. In this work, red and white GFPR were subjected to steam explosion in a batch system at 130, 150 and 170 °C and 1, 2, 4 and 8 min hold times to identify the conditions for maximum recovery of pectic hydrocolloids, peel oil, sugars, phenolics and flavonoids. Steam explosion at 170 °C and an 8 min hold time resulted in the recovery of 56-85% of total available glucose and fructose and the volatilization of 68-98% of the available peel oil. Of the flavonoids analyzed in this study, 61-62% could be extracted using steam explosion. Maximum recovery pectic hydrocolloids, as estimated by galacturonic acid, was 1.6446 g · 100 g-1 for red GFPR at 130 °C – 8 min and 1.557 g · 100 g-1 for white GFPR at 150 °C – 2 min.