Progresses on processing methods of umami substances: A review

Umami taste, which is one of the five basic tastes, refers to the taste expressed by specific chemicals such as glutamic and inosinic acids. Such a taste is known to make the overall taste of food softer, more harmoniously full-bodied; it also helps improve the overall sensory characteristics of food. Umami substances have therefore gained much attention during the past decade. So it is necessary to identify and/or explore effective umami processing technologies to meet the more pressing demands of the food industry. In this review, selected technologies that can be applied to produce or process umami substances, including fermentation, enzymatic hydrolysis, acid hydrolysis, Maillard reaction, water-based extraction, synthesis methods as well as microwave- and ultrasound-assisted processing are described. These methods all have their own advantages in processing umami substances from various raw materials. However, it has proven that composite processing methods in which selected methods are combined can be more effective for processing umami substances. Besides, major types of umami substances, umami raw materials, umami separation technologies and synergistic effect of umami substances are also discussed. It is necessary to consider combined applications of the various reviewed technologies for the processing of umami substances. This can lead to significant improved production efficiency and economy of the whole production process. Some related issues, namely, environmental pollution, cost effectiveness ratio, production efficiency and convenience of process manipulation, should also be taken into consideration in any future studies.