Sour is the definitive book on this unique taste. From cheese to vinegar, throughout the centuries we have deliberately let - and even encouraged - food to go sour to enhance its flavor. Sour foods have never been more fashionable, with the spotlight falling on foodstuffs as disparate as Belgian sour beer and Korean kimchi. But what is it that makes sourness such an enticing, complex element of the eating experience? And what are the best ways...