Unique¹ Vacuum Microwave Method Minimizes Drip Loss and Preserves Flavor

Conventional thawing methods such as warm salt water (using approximately 40°C/104°F salt water) and running water often result in uneven thawing, with surfaces thawing quickly while the interior remains frozen. In contrast, the new thawing machine heats the entire food item using microwaves, the same as a household microwave oven, while simultaneously cooling the surface—where heating is most intense—via vacuum cooling, thereby minimizing temperature differences between the interior and exterior. By creating a vacuum, the chamber is depressurized, lowering the boiling point of water and causing surface ice on the food to sublimate directly into vapor without passing through the liquid phase. During sublimation, surrounding heat is absorbed, which lowers the surface temperature of the food. By minimizing the temperature gap between the surface and the interior, the process reduces cell damage that causes loss of umami flavor (drip), enabling more even, higher-quality thawing and better taste.

Temperature Change of Food in Vacuum Microwave Thawing Machine

How Vacuum Microwave Thawing Works

A New Value Proposition of Flavor-Focused Thawing for the Growing Frozen Food Market

Thawing machines using the vacuum microwave method were previously sold by our Group company, Nestor Corporation, from November 2003 through March 2024. However, due to their large size and high price, their adoption was limited. In addition, the product remained largely unchanged in specification for about 20 years.
Hoshizaki has identified growing potential demand for better thawing methods tailored to different types of food, especially as frozen food consumption increases, and is conducting various studies in this area. As part of this initiative, we have independently redeveloped a product that uses this thawing method to meet today’s market needs.
To address customer feedback and the previous model’s size and price constraints, we focused on technological improvements and cost reduction efforts to achieve both superior thawing performance and a practical reduction in size, successfully lowering the price by some 30% compared to the previous model. The shape has been changed from a vertical design to a horizontal one, allowing the top to be used as a table, and a new motor has been adopted for quieter operation. The control interface has been upgraded to a touch panel, making it easy for anyone to use by simply selecting the weight of the item and the desired thawing level.

Touch Panel

Challenges with Current Thawing Methods Include Requiring Skilled Labor and Time

In supermarkets and similar settings, a variety of thawing methods are used depending on the type of food. Proper thawing often requires skill and experience, which leads to variation in thawing quality and limits who can perform the task. Another issue is that for certain foods, thawing can take a considerable amount of time. For example, thawing a block of lean tuna typically involves soaking it in warm saltwater for about 2 to 3 minutes, followed by refrigeration for approximately 60 to 120 minutes.

One Machine Addresses Multiple Customer Challenges: Thawing Quality, Labor Shortages, Food Waste, and Logistics Costs

The new thawing machine offers a range of benefits to customers: