The new study, published in LWT - Food Science and Technology, reports that the seed kernel of the rambutan (Nephelium lappaceum Linn.) fruit, a product generally considered as a waste material, and obtained in large amounts as a by-product of the fruit canning industry could act be used as a sustainable source of fats.
“The rambutan seed kernels provide a considerable yield of fat and the high arachidic acid content makes the fat highly stable to oxidation,” said the researchers, led by Professor Utai Klinkesorn of Kasetsart University, Thailand.
The authors said that the high levels of arachidic acid found mean that rambutan seed fat is highly stable to oxidation, and could be used as a sustainable source of fats for industry.
“Because of these physical and chemical characteristics, the merit of using rambutan kernel fat in the cosmetic and food industries may be justified,” they added.
However, the researchers said that although roasted rambutan seeds are considered edible in some Asian countries, the safety the kernel fat “must still be evaluated before it is used as an ingredient in the food industry.
The authors said that rambutan is a seasonal fruit that is widely cultivated in Southeast Asian countries. Thailand has become the leading producer and exporter of the fruit.
This fruit is generally consumed fresh, although they are also processed and canned in syrup. During this process the fruits are deseeded, said the authors. They added that the seeds account for around five per cent of the fruit, and as such represent a large waste by-product of the canning industry.
The increasing demand for oils and fats, whether for human consumption or for industrial purposes, necessitates the search for new sources of novel oils and fats.
Klinkesorn noted that research has reported that the rambutan seed possesses a relatively high amount of fat.
“Therefore, the extracted fat from rambutan seed … has a potential to be a source of natural edible fat with possible industrial use,” said the authors.
Fat from rambutan was separated and extracted with solvent extraction, using hexane.
The researcher said that under optimum conditions of extraction, the maximum fat yield was 37.35 grams per 100 grams of kernel.
They reported that the extracted fat was white, and solid at room temperature, whilst the physical and chemical characteristics “compared well with those of conventional fats.”
“The high level of arachidic acid (around 34.3 grams per 100 gram fat) and low iodine value in rambutan kernel fat permits the use of the fat, especially where oxidation may be a concern, without its being subjected to hydrogenation,” concluded the researchers.
Source: LWT - Food Science and Technology
Volume 44, Issue 9, Pages 1946-195, doi: 10.1016/j.lwt.2011.04.011
“Response surface optimization and characteristics of rambutan (Nephelium lappaceum L.) kernel fat by hexane extraction”
Authors: W. Sirisompong, W. Jirapakkul, U. Klinkesorn