What does the term 'kimoto' describe in sake brewing?

The term 'kimoto' specifically refers to a traditional method of preparing the yeast starter, known as the 'shubo' in sake brewing. In this process, a mixture of steamed rice, water, and koji mold is allowed to ferment naturally without the addition of commercially cultivated yeast. This method relies on the natural wild yeasts and lactic acid bacteria present in the environment to cultivate the yeast starter. The resulting ferment can produce a sake with a more complex, rich flavor profile due to the influence of these microorganisms.

The other options mention practices that are important in sake brewing but do not accurately define 'kimoto.' For example, the use of koji in fermentation is a key element in sake production but is not specific to the kimoto method. Adding steamed rice is essential during various stages of brewing but does not encapsulate the essence of kimoto, as it specifically pertains to the yeast starter preparation. Lastly, measuring sake flavor involves an entirely different set of techniques and is not linked to the term 'kimoto.' Thus, the definition focused on yeast starter preparation is what makes option B the correct choice.