How is ice cream produced by refrigeration equipment?

2020-06-17 18:41:32 15
Ice cream is a frozen dairy product. Its physical structure is a complex physicochemical system. Air bubbles are dispersed in a continuous liquid with ice crystals. This liquid contains fat particles, milk proteins, insoluble salts, lactose crystals, and gums. The body stabilizer and sucrose, lactose, soluble salts, such a three-phase system composed of gas phase, liquid phase and solid phase, can be regarded as a partially frozen foam containing 40-50% by volume of air.



The role of refrigeration equipment

The production process of ice cream mainly includes the inspection of raw materials, mixing and sterilization of ingredients, homogenization, cooling and aging, freezing, forming filling, quick freezing, hardening and storage. These technological processes must be completed in accordance with certain technical conditions, otherwise, high-quality products cannot be produced. We know that refrigeration equipment plays a crucial role in the production and storage of ice cream. But which specific processes need refrigeration equipment, and what are the requirements for refrigeration equipment in each process?

Cooling, aging

Aging is to refrigerate the mixture at a low temperature of 2~4℃ for a certain period of time, which is called "mature" or "mature". Its essence lies in the hydration of fat, protein and stabilizer. The stabilizer fully absorbs water to increase the viscosity of the feed liquid, which is beneficial to the increase of the expansion rate during freezing and stirring. The aging time is related to the temperature of the feed liquid, the composition of the raw material and the variety of stabilizer. Generally, it takes 4~24h at 2~4℃. During aging, care must be taken to avoid contamination by miscellaneous bacteria. The aging tank must undergo strict disinfection and sterilization in advance to ensure the sanitary quality of the product.

Ice cream microstructure

The freezing process is the process of freezing the mixture under forced stirring, so that the air is evenly distributed in the entire mixture in the state of tiny bubbles, and part of the water becomes fine crystals of ice: the temperature of the ice cream mixture is reduced by the effect of the refrigerant , The viscosity increases and gradually thickens into a semi-solid state, that is, the frozen state; due to the continuous stirring and cooling of the mixer, the air gradually mixes in during freezing to expand its volume, so that the ice cream reaches a beautiful structure and perfect shape. The freezing temperature is -2~-4℃, the freezing time of the intermittent freezing machine is 15~20 minutes, the discharge temperature of ice cream is generally -3~ -5℃, the continuous freezing machine inlet and outlet are continuous, and the ice cream outlet temperature is -5 ~ -6 ℃, continuous freezing must always check the expansion rate, so as to control the appropriate amount of incoming and outgoing air.

Quick freezing, hardening and storage

The frozen ice cream without hardening is soft ice cream, and if it is hardened after filling into the container, it becomes hard ice cream. Most of the former have stores now in production and sale, while the latter have a larger output.

The purpose of quick freezing and hardening is to quickly freeze the ice cream (-3~-5℃) from the freezing machine at a low temperature (-23℃) to fix the tissue state of the ice cream and complete the process of forming extremely fine ice crystals in the ice cream. Keep its organization to maintain proper hardness, ensure the quality of ice cream, easy to sell and store and transport. For quick freezing and hardening, quick freezing warehouse (-23~-25℃) or quick freezing tunnel (-35~-40℃) can be used.

The general hardening time is 10~12h in the quick freezing training. If the quick freezing tunnel is used, the time will be much shorter, only 30~50 minutes. The conditions that affect hardening include factors such as the shape and size of the packaging container, the temperature of the quick-freezing room and the circulation state of the air, the location of the indoor products, and the composition and expansion rate of the ice cream. The ice cream products after storage and hardening should be kept in a low-temperature freezer before sale, with a temperature of -20°C.