A Novel Extraction Method for Aroma Isolation from Dark Chocolate Based on the Oiling-Out Effect

Abstract

Understanding native aroma of chocolate is important for development of food science and food industry. However, isolation of volatile compounds from chocolate is difficult due to matrix effects of cocoa butter and, so far, done using evaporation, vaporization, and distillation techniques with losing volatile compounds. The aim of this study is to develop an effective method for isolation of the volatile compounds from chocolate under mild conditions and conditions with less matrix effects. In the model study, a big gap among partition coefficients (log Pow value) of cocoa butter and volatile compounds was focused to separate volatile compounds from the matrix. Charging deodorized cocoa butter to a hexane-methanol bilayer solution enabled to perform liquid-liquid extraction and thereby push out volatile compounds into methanol layer. We named this phenomenon, the “oiling-out effect.” As a typical application, volatile compounds in dark chocolate containing 35.3% cocoa butter were extracted using liquid-liquid extraction based on the oiling-out effect. The chocolate extract was prepared under room temperature conditions and then analyzed using gas chromatography-mass spectrometry (GC-MS). Fifty-four volatile compounds from 5 g dark chocolate were identified, comprising acids, alcohols, aldehydes, esters, ketones, lactones, furans, hydrocarbons, pyrazines, pyrroles, sulfur compounds, and thiazoles. Compared with solvent extraction and headspace solid-phase micro extraction (HS-SPME), the present method, named the oiling-out assisted liquid-liquid extraction, enabled the isolation of a wide range of volatile compounds from dark chocolate. In this paper, we demonstrated the oiling-out effect as an efficient extraction method for volatile compounds in high-fat foods.