(P09-034-24) Quantifying and Characterizing the Fiber in Hass Avocados During the Ripening Process

Objectives: We aimed to characterize the amount and type of dietary fiber (DF) in Hass avocados and evaluate DF changes during ripening.

Methods: Hass avocados (Persea americana; ~12-d transit time from harvest to receipt) were ripened at 21°C and 24% relative humidity for up to 12 d in our research facility. Avocados were divided into three ripening stages (RS): RS-1=unripe (day 0), RS-2=ripe (day 5), and RS-3=overripe (day 12), with each RS containing 12 avocados. Avocados were freeze-dried and defatted using the Soxhlet method. DF analysis was conducted using an enzymatic-chemical method, which measures DF as the sum of hydrolyzed monosaccharides, cellulose, and lignin. DF was determined on a dry-matter basis (DMB) and converted to an “as-is basis.”

Results: RS-1 contained 3.96g total DF, RS-2 contained 3.68g total DF, and RS-3 contained 3.26g total DF per 100g of “as-is” avocado. The DF in RS-2 was 43.2% (1.59g/3.68g of DF from fresh fruit) soluble dietary fiber (SDF) and 56.8% (2.09g/3.68g of DF from fresh fruit) insoluble dietary fiber (IDF). In RS-2, the main component of the SDF was rhamnogalacturonan-1 and arabinan pectins, as evidenced by the presence of uronic acids, rhamnose, arabinose, and galactose, which represented 60.3%, 24.5%, 6.8% and 2.9%, respectively, of soluble monosaccharides. IDF was predominantly cellulose (56.3%), followed by hemicelluloses (40.3%), including xyloglucan, xylans, and glucomannan. RS-2 avocados contained the greatest amount of DF and SDF on a DMB, followed by RS-1 and RS-3. On an as-is basis, SDF remained highest in RS-2. However, DF tended to decrease with ripening. Pectin was extensively solubilized and depolymerized during ripening, whereas cellulose and hemicellulose remained relatively unchanged.

Conclusions: The total amount of DF in ripe (RS-2) Hass avocados (3.68g/100g) was similar to the mean pooled data from previous reports (3.87g/100g). Novel findings revealed that the types of DF in avocados are predominantly pectin, followed by cellulose and hemicellulose. These findings are important because the chemical structure and physicochemical properties of different fibers underpin health benefits, including intestinal microbial fermentation following consumption.

Funding Sources: Hass Avocado Board