Luffa Research Report – Producing Sponges from Immature Fruits

Post-harvest Treatments for Producing Sponges from Immature Fruits of Luffa Gourd

Tammy L. Ellington and Todd C. Wehner

Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695-7609

Cucurbit Genetics Cooperative Report 19: 85-86

Luffa gourd (Luffa aegyptiaca Mill) is grown in small areas for the production of sponges for cosmetics and cleaning products. In eastern North Carolina, we usually plant in mid April, and harvest weekly from mid October to mid November. Sponges are produced by harvesting fruits that have turned brown at the end of the season, then removing the seeds and skin from the fruit, and drying the sponge.

Fruits that are green at harvest can be divided into two categories. Fruits that have a dry, leathery skin that is beginning to turn brown will be referred to as mature-green. Those can be used in the same way as fruits that are brown at harvest. Fruits that are still soft and have a bright green skin will be referred to as immature-green. Luffa gourd is of tropical origin and requires a long growing season. As a result, luffa growers may harvest immature-green fruits when frost kills the plants at the end of the season (usually October in eastern North Carolina).

Currently, there are no published data on the handling and processing techniques of immature-green fruits for optimum sponge quality. The objective of this experiment was to determine how to use immature-green fruits.

Methods: In order to evaluate the handling of immature-green fruits, 4 treatments were used: air drying, forced and heated air drying, soaking in water, and soaking in a 10% bleach solution. Those treatments will be hereafter referred to as air, dryer, water, and bleach, respectively. Air involved hanging the sponges on wires in a greenhouse (30 C day/20 C night). Dryer treatment involved putting the sponges in a dryer with heated air (32 C) forced through drying racks. The dryer was designed as a cucumber seed dryer (Wehner and Humphries, 1994). Water treatment involved soaking the sponges in tanks of water, with the water changed daily. Bleach treatment involved soaking the sponges in tanks of 10% chlorine b leach, with the solution changed daily.

The experiment was a randomized complete block design with 2 years, 2 replications, and 1 fruit per treatment combination. The fruits were treated for 1 to 18 days, and evaluations were made 1, 4, 6, 8, 13, 15, and 18 days after harvest. A rating system of 1 to 9 was used for evaluation of skin brownness (1-3 = light green, 4-6 = brownish green, 7-9 = dark brown), peeling ease (1-3 = difficult, 4-6 = intermediate, 7-9 = easy), and sponge quality (1-3 = poor, 4-6 = intermediate, 7-9 = excellent). In the first year, data were not taken on the treatments involving water soaking and bleach soaking after 13 days, because the fruits were disintegrating. In the second year, data were not taken on the fourth day due to scheduling difficulties.

Results: In the first year, skin brownness and ease of peeling generally increased as the treatment time increased (Table 1). Of the 4 treatments tested, air drying for at least 13 days provided the most usable sponges. The data were variable due to the small number of fruits tested.

In the second year, water was consistently the best treatment for ease of peeling (Table 2). Air was the best treatment for promoting skin brownness. Dryer treatment was the best for sponge quality. In general, at least 13 days in the dryer provided the most usable sponge. Once again, the data were variable due to the small number of fruits tested.

The differences between years can be explained by the different stages of immature-green fruits used. In the first year, the immature-green fruit were consistently more mature in development than were those in the second year.

In conclusion, immature-green fruits can be used as sponges if they are air dried for 2 to 3 weeks in a warm, dry location. That treatment will cause the fruit skin to turn brown, and it can then easily be peeled. Care should be taken to avoid the immature-green fruits where the fibrous network has not begun developing, or the dried fruit will not be usable as a sponge. Future studies are needed to evaluate sponges produced from immature-green fruits for strength and usable life relative to mature fruits.

Literature Cited

1. Wehner, T.C. and E.G. Humphries. 1994. A seed dryer for cucumber seeds. Cucurbit Genet. Coop. Rpt. 17:54-56.

Table 1. Sponge usability in 1993 for immature-green fruits of luffa sponge gourd after 4 post-harvest treatments on skin brownness, ease of peeling, and sponge quality 1 to 18 days after fruits were harvested from the vine.z

Days after harvest
Treatment 1 4 6 8 13 15 18
Skin brownness rating
Air 1 1 1 4 9 9 9
Dryer 3 5 2 6 6 5 6
Water 1 2 4 6 6 – –
Bleach 2 2 3 5 5 – –
Ease of peeling
Air 1 7 8 5 8 8 8
Dryer 3 2 6 6 6 6 7
Water 6 6 7 8 8 – –
Bleach 7 6 5 8 6 – –
Sponge quality
Air 1 5 4 5 8 6 6
Dryer 4 3 3 6 5 4 5
Water 5 6 6 6 6 – –
Bleach 2 5 6 6 5 – –

z Data are means of 2 replications of 1 fruit each. LSD (5%) for row-column comparisons = 3.

Table 2. Sponge usability in 1995 for immature-green fruits of luffa sponge gourd after 4 post-harvest treatments on skin brownness, ease of peeling, and sponge quality 1 to 18 days after fruits were harvested from the vine.z

Days after harvest
Treatment 1 4 6 8 13 15 18
Skin brownness rating
Air 1 – 7 5 6 6 6
Dryer 1 – 5 4 5 5 5
Water 2 – 2 3 3 3 3
Bleach 4 – 4 4 6 6 6
Ease of peeling
Air 2 – 5 5 4 5 8
Dryer 2 – 4 4 6 6 6
Water 2 – 6 7 8 8 9
Bleach 2 – 2 4 3 3 4
Sponge quality
Air 2 – 5 6 4 6 8
Dryer 2 – 6 6 6 6 7
Water 2 – 4 5 6 8 8
Bleach 3 – 2 4 4 4 5

z Data are means of 2 replications of 1 fruit each. LSD (5%) for row-column comparisons = 2.