Beltsville, MD — Genetic marker analysis of DNA extracted from the seed coat of cacao beans can be used to precisely identify the varietal purity and origin of premium species and earmark adulterant types, according to a study published in the current issue of the American Chemical Society’s Journal of Agricultural and Food Chemistry.
The test would enable suppliers to ensure the integrity of premium cacao across the supply chain and would, in turn, provide strong economic incentives for growers to maintain cacao genetic diversity, rather than cultivating species that are easier to grow.
Because cacao beans are seeds, their seed coat carries the DNA signature of the mother tree. Researchers from the U.S. Dept. of Agriculture/Agriculture Research Services’ Sustainable Perennial Crops Laboratory, the College of Horticulture at the Nanjing Agricultural University and the Cocoa Research Centre at The University of the West Indies extracted DNA from samples of the fine flavor Fortunato No. 4 beans (a Nacional type) and analyzed 48 single nucleotide polymorphism (SNP) markers — the genetic fingerprint — from the seed coat of single fermented beans.
By comparing that SNP panel with those of 30 samples from five varieties of inferior-quality beans grown in the same region, researchers accurately identified the “adulterant” beans. Regarding the test’s predictive value, the authors write: “The chance of sampling identical genotypes from a random mating population would be one out of 100,000. It thus predicts the high statistical power of using this set of SNPs for cacao genotype verification.”
Lyndel Meinhardt, PhD, research leader for the Sustainable Perennial Crops Lab, tells Candy & Snack TODAY the test is still in its early stages: “We’re hoping to develop this test into a broader tool that the industry can use on the manufacturing and supply sides. When you are paying premium prices for the beans, you want to know exactly what you’ve paid for.”
The test can be used to process a large number of samples in a short time with greater accuracy than the current authentication method of having an expert sensory panel taste cacao liquor.
The study was funded by the USDA Agricultural Research Service and a gift from Lindt & Sprüngli AG through the World Cocoa Foundation.