Silkworm (Bombyx mori) frass as a novel culinary ‘tea’ application in gastronomy: Aroma profile, volatile compounds, and consumer acceptance

Tea is a popular beverage consumed all around the world. Its origins can be traced back to China, where it has been cultivated for thousands of years. A subcategory of tea is referred to as ‘insect tea’; it is produced using the excrement (frass) of insects that consume plants. This study explored the utilisation of silkworm frass, a by-product of silk production, as a novel beverage in the culinary field. It explored optimal preparation methods, and measured physicochemical properties, volatile aroma compounds, the sensory aroma profile, and consumer acceptance. Silkworm frass was collected and roasted at 160 °C for 0, 30, 40, and 50 min. The analysis revealed notable differences in the samples' water activity, moisture content, colour, and pH: Moisture content and water activity decreased, preventing spoilage of the samples, while pH increased, and the colour intensified. The volatile aroma analysis revealed 65 compounds, including alcohols, aldehydes, esters, ethers, ketones, phenols, pyrazines, and hydrocarbons. These compounds exhibited significant variations in concentration depending on the duration of roasting. Sensory evaluation presented distinct attributes associated with each sample, such as earthy and roasted aromas in all samples, and specific aromas of brown herbal aftertaste and tobacco leaves in the 50-min sample, roasted grain aromas in the 40-min sample, and stronger notes of cut hay for both the 30-min and 50-min sample. The hedonic sensory test revealed that the duration of roasting did not influence consumer preferences in terms of the attributes of taste, aroma, colour, texture, and overall acceptance. The novel ‘tea’ demonstrates potential in the gastronomy industry due to its aroma profile and positive consumer acceptance. It is a promising example of an upcycled culinary product that utilizes by-products from silk farms.