A better control of beer properties by predicting acidity of hop iso-α-acids

Of all vegetable derivatives to impart its characteristic flavour to beer and to prevent it from ageing, only hop is now considered to be an essential raw material. Hops and their derivatives offer the industry better control over the properties of beer, such as froth stability, bitterness and scent. In this work, the relationship among structurally similar compounds and their physicochemical properties, such as acidity, has been analysed by using C-13 NMR, UV-spectroscopy and semi-empirical calculations. it has been found that the logarithms of stability constants are essentially linear functions of NMR chemical shift. This will allow an approximate estimation of acid properties in certain hop derivatives such as iso-alpha-acids, which determine beer characteristics such as foam stability. The relationship established would contribute to estimate the aqueous solubility and stability of humulones and their derivates, needed for an effective control of production processes in the brewing industry.