Background

University of Hawaii researchers developed an efficient, very low cost system to fractionate whole fruit without peeling the skin, damaging the seeds or using expensive, complex, mechanized equipment (). The system was demonstrated on papaya which is widely cultivated in tropical regions throughout the world, and has an estimated 30% to 50% cull rate, generating a proportionate amount of agricultural waste that can be converted into value-added products.

Technology Overview

With the goal of re-purposing culled fruit to minimize agricultural waste and keep equipment and operational costs low, UH researchers streamlined processing steps and reduced costs using inexpensive off-the-shelf equipment. One key benefit of the new system is elimination of the time-and resource-consuming step of peeling the fruit, which utilizes specialized machinery (such as industrial rotary drum scrapers, peeling equipment, or fruit pulping machines). Skipping other processing steps, such as freezing, and not damaging or crushing the seeds, which can each cause unwanted effects in resulting byproducts, generates additional benefits for the production of useful byproducts. This simplified process can be readily adopted by small producers or processors who may not have significant financial resources to establish highly mechanized industrial fruit processing plants such as those for commercial fruit juice puree manufacturing.

Related Publication: RSC Advances 8(49):27963-27972, August 2018

Benefits

Saves significant capital and operating/energy costs by not requiring specialized mechanical equipment.
Requires only simple, low-cost equipment, providing an attractive alternative processing option for small farmers or businesses.
Eliminates certain costly steps and does not damage seeds in the fruit fractionation process.
Generates new uses from culled fruit, including extracted seed oil, puree, and seed meal. For example, sugars and lipids derived from culled fruit waste can be used as feedstock to generate value-added products via chemical, physical, and biological processing.

Applications

For papaya, several useful components were extracted from the seeds alone, including: (1) papaya seed oil essentially free of the inhibitory substance benzyl isothiocyanate (BITC); (2) extract rich in benzyl glucosinate (BG); (3) detoxified/defatted seed meal essentially free of BG; (4) BG-rich crude myrosinase; and (5) papaya seed oil rich in BITC. Crude myrosinase and BITC have potential biofumigation applications, and BITC, a growth inhibitor, is reported to have potent antimicrobial properties.

Plant oils are a source of renewable carbon for microbial fermentation to produce value-added bio-based products. Papaya juice and puree have been used for microbial production or fermentation, but the UH researchers demonstrated that papaya seed oil is also an effective, high yielding carbon substrate for microbial production when using the industrially useful yeast, Yarrowia lipolytica. Papaya seeds, which make up a significant portion of the culled fruit, contain a high percentage of lipids and can also serve as feedstock for carbon and energy sources to grow certain microorganisms to produce single-cell proteins and other high-value recombinant protein products such as fatty acid-based oleochemicals, enzymes, biofuels, biosurfactants, and other recombinant proteins.

Seed meal could be useful as livestock feeds, and papaya seed meal and seed oil contain substances with antimicrobial properties.

The process may be adaptable to other fruits, to re-purpose culled fruit fractions to generate useful byproducts.

Processing Fruit Waste for Value-Added Products

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