Food or beverage products that contain froth or foam are popular with consumers. For example, both hot and cold beverages, such as cappuccino, milkshakes, fruit-flavored drinks, and the like, may be prepared to have froth or foam. Recently, consumers increasingly prefer instant food and beverage products because of the convenience they provide. Such instant food and beverage products typically include a soluble powdered or granular food product that is dissolvable or dispensable in water or other fluid medium to form food or beverage products that may be consumed.
Recent advances have provided methods and equipment for entrapping pressurized gases within internal voids of the powdered or granular food and beverage products. In this manner, upon dissolving or dispensing the food or beverage product in fluid medium, the pressurized gas is released forming a foam or froth. Thus, a frothy or foamy food or beverage can be prepared from the instant product.
Current methods to prepare such powders may include a base product that has been pretreated to form a powder having internal voids. For example, the base product may be a carbohydrate powder that is prepared using gas-injected spray drying. The powder may be formed by spray drying a solution of the beverage product while injecting small gas bubbles into the solution stream to create a powder with internal voids.
In order to maximize the amount of foam that is created when the food or beverage powder is combined with fluid, the powder can be subjected to a pressurization process to entrap pressurized gas within the internal voids. The base powder substance is first placed into a batch vessel that is capable of withstanding relatively high temperature and pressure variations and the vessel is sealed to the external atmosphere. The vessel is next pressurized and heated by injecting pressurized inert gas into the vessel and applying heat to the walls of the vessel.
After heating, the vessel is usually cooled by cooling the outer walls to slowly decrease the temperature of the powder from the heated temperature to a cooling temperature. The vessel is typically slowly cooled to ensure that it is not damaged due to a rapid change in temperature which could otherwise create thermal stresses in the vessel material. The temperature of the powder is usually held at the cooling temperature for an amount of time so that the powder particles become less permeable to the flow of gas. Once the powder is cooled, while still under pressure, the gas is sealed in the particle voids. Finally, the vessel is de-pressurized.
While previous methods are generally sufficient for forming powdered and granular food and beverage products with entrapped pressurized gas, they do present some shortcomings. For example, the process time for a single batch of powder within a vessel in the prior methods is relatively high due, in part, to the lengthy time required to pressurize, heat, cool, and dc-pressurize the vessel. For the same reason, the energy requirements for each batch is high due to the significant amount of energy consumed each time the vessel is heated and subsequently cooled.