ISO 6477:1988—Cashew Kernels

Cashew fruit (Anacardium occidentale) hanging on tree adhering to cashew kernel process in ISO 6477:1988.

Rich in protein, healthy fats, and antioxidants like polyphenols, cashews offer several health benefits: they lower bad cholesterol and may help prevent heart disease due to their high magnesium content. Truly raw cashews, however, are not safe to eat because they contain a substance known as urushiol, found in poison ivy. Hence, ensuring that this popular tree nut, consumed around the world, undergoes either a roasting, boiling, or streaming process is essential before its consumption. ISO 6477:1988—Cashew Kernels – Specification provides specifications for kernels obtained from the fruits of the cashew nut tree (Anacardium occidentale).

What Do Cashews, Poison Ivy, and Mangos Have in Common?

The anacardiaceae family of trees, sometimes called the cashew family, includes mango, poison ivy, poison oak, sumac, Peruvian pepper, pistachio, and cashews. They all contain urushiol, the oil that causes the skin to erupt in rashes for some people. This oil is found in all parts of the plant, including the leaves, stems, and even the roots. Hence, the harmful part of the cashew, which can also be found in mango plants, is the same ingredient that makes poison ivy poisonous: urushiol.

Is It Safe to Eat Raw Cashews?

Raw cashews contain urushiol, a resin that is toxic and can cause rashes or burns if it contacts the skin. Urushiol is the reason cashews are never sold in the shell. The oil is found on the outer shell (similar to mangos, where it is found on the skin). To remove this substance, cashews must go through a rigorous roasting or steaming process to ensure they are safe to eat, and before this roasting process, cashews are actually green. Toasting the cashews at high temperatures kills any remaining oil that makes its way through to the nut. Although cashew kernels are often sold as “raw” in stores, they have been steamed and as a result the toxins have been removed. ISO 6477:1988 details requirements for cashew kernels.

What Is ISO 6477?

ISO 6477:1988 specifies requirements for kernels obtained from the fruits of the cashew nut tree (Anacardium occidentale Linnaeus) for human consumption. The standard provides a specification of general requirements and of specific requirements, as moisture content, grading, sampling, methods of test, packing, and marking of cashew kernels: a product obtained by roasting, shelling and peeling the fruits of the cashew nut tree.

ISO 6477 Cashew Kernel General Requirements

ISO 6477:1988 provides the following requirements for cashew kernels:

  • Should be reasonably dry
  • Should have the characteristic shape
  • May be either scorched or unscorched; in the form of wholes or pieces
  • Should be completely free from rancid kernels
  • Have a moisture content not greater than 5% (m/m)
  • Determine the moisture content by oven drying method from ISO 1026
  • Should be free from living insects and molds, and from discernible dead insects, mites, insect fragments, rodent contamination and insect damage, visible to the naked eye (corrected, if necessary, for abnormal vision) or with such magnification as may be necessary in any particular case

Cashew Harvesting and Processing

Cashews grow on trees (Anacardium occidentale) so are classified as a tree nut. Further, they protrude from a fruit known as the cashew apple, red or yellow pear-shaped drupes. The cashews themselves grow inside of gray shells on the ends of those fruits; hence, the cashews we eat are the seed. They are ready for harvesting when the cashew apples, edible but highly perishable, fall from the tree and are collected.

The cashew nuts, still in their shell, are removed from the ends of the cashew apple. The nuts may be dried in the sun (depending on the manufacturer’s drying process). These cashews are raw and not sold due to a risk of urushiol exposure. The raw cashews are then roasted at high heat, either by steaming them in a large rotating drum or vat of boiling oil to remove urushiol remnants before they can be shelled, thoroughly dried, and peeled. Since these cashews are free of added flavorings, they are still often labeled as raw cashews. They may be roasted a second time for flavoring purposes if they are being sold as roasted cashews. Another round of roasting may also help ensure any remaining urushiol residue is removed before sale. Commercial cashews are then ready for quality checks, packaging, and sale.

ISO 6477:1988—Cashew Kernels – Specification is available on the ANSI Webstore.

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