Analysis of Volatile Organic Compounds in Milk during Heat Treatment Based on E-Nose, E-Tongue and HS-SPME-GC-MS

Volatile organic compounds (VOCs) make up milk flavor and are essential attributes for consumers to evaluate milk quality. In order to investigate the influence of heat treatment on the VOCs of milk, electronic nose (E-nose), electronic tongue (E-tongue) and headspace solid-phase microextraction (HS-SPME)-gas chromatography-mass spectrometry (GC-MS) technology were used to evaluate the changes in VOCs in milk during 65 degrees C heat treatment and 135 degrees C heat treatment. The E-nose revealed differences in the overall flavor of milk, and the overall flavor performance of milk after heat treatment at 65 degrees C for 30 min is similar to that of raw milk, which can maximize the preservation of the original taste of milk. However, both were significantly different to the 135 degrees C-treated milk. The E-tongue results showed that the different processing techniques significantly affected taste presentation. In terms of taste performance, the sweetness of raw milk was more prominent, the saltiness of milk treated at 65 degrees C was more prominent, and the bitterness of milk treated at 135 degrees C was more prominent. The results of HS-SPME-GC-MS showed that a total of 43 VOCs were identified in the three types of milk-5 aldehydes, 8 alcohols, 4 ketones, 3 esters, 13 acids, 8 hydrocarbons, 1 nitrogenous compound, and 1 phenol. The amount of acid compounds was dramatically reduced as the heat treatment temperature rose, while ketones, esters, and hydrocarbons were encouraged to accumulate instead. Furfural, 2-heptanone, 2-undecanone, 2-furanmethanol, pentanoic acid ethyl ester, 5-octanolide, and 4,7-dimethyl-undecane can be used as the characteristic VOCs of milk treated at 135 degrees C. Our study provides new evidence for differences in VOCs produced during milk processing and insights into quality control during milk production.

Automated summary

We investigated the influence of heat treatment on the volatile organic compounds (VOCs) of milk using various technologies. The results showed that heat treatment at 65 degrees C for 30 min preserved the original taste of milk, while treatment at 135 degrees C significantly altered the overall flavor. Different processing techniques also affected taste presentation, with the sweetness, saltiness, and bitterness of the milk being influenced by the temperature of the heat treatment. Additionally, the composition of VOCs in milk changed with heat treatment, with acid compounds decreasing and ketones, esters, and hydrocarbons increasing. Our study provides new evidence for understanding the impact of processing on milk VOCs and insights into quality control during milk production.