Delicious mincemeat sauce and studying fried onion with an FTIR spectrometer

Abstract

My students at the upper secondary school chemistry course have prepared mincemeat sauce and sweet potato mash as a study project for two consecutive years. Half of the students prepared the dish using traditional methods and the other half using molecular gastronomy. At the end of the class we tasted the dishes prepared with different methods and compared them against each other. During cooking, we studied how onion’s large carbohydrates break down to smaller sweet sugars when heated on a low temperature. This sweetening can also be tasted because small molecule carbohydrates are water-soluble and fit in the mouth taste receptors. A sample was taken off the pan once every five minutes and extracted to water. IR spectra were run from the onion-water extract and the received spectra were compared to library sources and references. The aim was not to conduct a thorough analysis of the components formed during cooking, instead the spectra were analysed for indications on whether or not the amount of sugar (sweetness) increases as a function of cooking time. The performed work indicated with sufficient accuracy that sucrose was formed during cooking up to 35 minutes of cooking time, after which the product started to show possible signs of caramelisation and Maillard reaction, and the amount of sugars dropped. The method requires further development in order to find out the ratio of sucrose and glucose formed during heating as compared to their concentration in a raw onion. Preparing (heating) the samples and extracting the sample still require further development in order to present the formation of sugar during heating unambiguously.