Businesses involved in butter and cheese production turn milk and cream into dairy products for retail, catering and food manufacturing. Butter makers separate or obtain cream, then churn it to form butter, which is worked, salted where required and packed in blocks, tubs or other formats. Production may include cultured butter, made using bacterial cultures to develop its flavour, as well as unsalted and salted varieties. Cheese producers make cheese by adding cultures and, in many cases, rennet to milk so that it separates into curds and whey. The curds are cut, drained, shaped and often pressed or salted; some cheeses are then matured under controlled conditions, while others are sold fresh. Products can include soft, semi-hard and hard cheeses, blue cheeses and specialist varieties. Producers may also grate, slice or portion products for shops, restaurants and food manufacturers, and handle whey or other by-products from production.