Scientific Study

Background: Walnut (Juglans regia L.) is one of the most widely cultivated nuts. Walnut milk beverage is very popular in China due to its nutritional value. However, adulterated walnut milk ingredients have been detected in the Chinese market. Peanut and soybean are sold at much lower prices than walnut and are reported as common adulterated species in the industrial chain of walnut milk production. Therefore, the purpose of this study is to develop an accurate and efficient method for detecting the authenticity of raw materials of walnut milk beverage. Results: DNA barcoding and high-resolution melting (HRM) analysis were used to identify common adulterated raw ingredients such as peanut and soybean in commercial walnut milk beverage samples. The chloroplast psbA-trnH gene was used for sequencing, and HRM analysis was performed. We also prepared in laboratory experimental mixtures with different quantities of walnut, peanut and soybean. HRM analysis of the experimental mixtures clearly distinguished all of them. Results revealed that most of the walnut milk beverage samples fell in the same cluster of walnut species. Several samples fell in the cluster of peanut, confirming that they were adulterated walnut milk products. Conclusion: The results revealed that HRM analysis based on the psbA-trnH barcode sequence can be used to identify raw ingredients in walnut milk beverages.