Yeast protein measurement using near infrared reflectance spectroscopy

The measurement of total protein in yeast cells is useful for fermentation and yeast research as well as for byproduct improvement studies. The protein content of the cell changes with alterations in several fermentation and medium parameters and during the course of the cell cycle. In general, the protein content of the harvested cells is maximised under conditions ideal for yeast growth. Brewers often sell excess yeast as a byproduct and the quality of the yeast, as well as the associated price per unit weight, are often determined by the protein content. Many methods to measure the protein content in yeast cells exist but can be impractical for various reasons or prone to error. In this research, a method was developed to measure the protein content of yeast cells by near infrared reflectance spectroscopy (NIR) - a technique which is finding many applications in brewing and is simple, rapid and amenable to on-line control systems. With this latest application for NIR, it is now possible to measure yeast glycogen, trehalose and protein contents on the same sample in less than 30 minutes including a sample preparation time of 25 minutes.