The updated sixth edition of her New Zealand Crockpot and Slow Cooker Cookbook (Longacre) has just been released. The fifth was published only last year, although she finished writing a year earlier.
However, it was necessary to update it because some slow cookers have become faster, and as a result of more vigorous cooking, they do not form a vapour seal around the lid, so liquid evaporates, she said.
Some of her friends who bought her book were delighted with the recipes, but others told her they were having problems with the cooking times.
"I was staggered and I started asking around and borrowing slow cookers and retesting, and found there was a problem with some recent slow cookers," she said.
The early crockpots were very slow and gentle, then slow cookers appeared which cooked faster than crockpots. In 2006 she updated her book with dual cooking times for the two different types of cooker.
The newest edition of her book has three cooking times - for crockpots, for slow cookers, and for what she calls "speedy" slow cookers.
She and her friend and fellow food writer Mary Browne retested her recipes with new slow cookers and found some were "speedy" and others were not.
The problem is, when you are buying a slow cooker there is no way of telling whether it will be a "speedy" one that cooks a meal in three or four hours, or one that takes seven to nine hours and so allows you to prepare your meal before going to work, so it's ready when you come home. You need to experiment with the slow cooker you have bought and see how it cooks, according to the times she gives. You may find you have one that you need to go home at lunch time to turn on - which defeats the purpose of putting on your meal before going to work.
Some writers, such as Alison Holst and Allyson Gofton, in their slow-cooker books suggest going by the wattage, but Mrs Bishop says she has tested numerous old and new slow cookers and found wattage was not a reliable guide to how fast or slow they cooked. Some of the lowest-wattage cookers still cooked very fast.
