The effects of alternating electric fields on wine
Maturation of wine, also called ageing, is an important process in making premium wine. During this process, many compounds change in concentration, and these changes are responsible for colour and flavour changes that contribute to the complexity of matured wine. However, ageing is an expensive process due to the time taken, frequently years, the cost of which cannot be recovered until sale. Alternating electrical fields have purportedly been shown to accelerate ageing of wine as judged by informal sensory trials, and by limited results in the scientific literature. This research aimed to quantity the changes due to electric fields in terms of sensory and chemical science. Wine ageing machines (WAM) equipped with alternating electric fields were used to treat red wines (Cabernet Merlot, Pinot Noir and Merlot Cabernet Sauvignon) and white wine (Sauvignon Blanc). There were three versions of WAM: a flow-through WAM from the University of Waikato, a flow-through WAM2 (a modified version of the original), and a static WAM. In the first two, the wine flows through glass tubing between the charged plates 1 cm apart. In the static WAM, tubes containing wine are suspended between vertical plates. In the present study, electric fields were adjusted with different frequencies and strengths. The wines were physicochemically analysed by ultraviolet spectrometry, liquid chromatography mass spectrometry (LC-MS) and liquid chromatography mass spectrometry/ mass spectrometry (LC-MS/MS). Further, sensory tests were conducted between control wines and WAM-treated wines. Only flow-through WAM2 treated Sauvignon Blanc appeared to show an absorbance difference in the wavelength range of 230 to 350 nm, but the difference was finally interpreted as artifactual arising from electronic noise in the spectrophotometer. Further, other WAM-treated wines did not show any sensory or colour differences compared with control wines that could not be attributed to noise. In LC-MS (/MS) studies, several compounds were shown to vary with treatment, notably 2-furoic acid in white wine. However, the differences observed were inconsistent and might have been due to statistical variation that can arise in 1 in 20 events by chance alone. It was concluded that these WAMs had no effect on wine ageing in the manner they were applied here.