In new wine regions there is no choice; wine yeasts need time to build up a population and the only ambient strains available are more likely to be harmful than benevolent. With a small but increasing number of exceptions, most New World wines are therefore made by adding specially cultured yeast to the must,which may , if it has been chilled,need warming before fermentation can be persuaded to start.(Once one vat has started,the addition of fermenting must from it will kick-start a second,but some winemakers believe in a deliberate few days’ maceration of red grapes before fermentation as they warm up.)