DSI sterilizer is short for direct steam injection/infusion sterilizer, it is a sterilization method in which materials and heating medium (culinary steam) are directly mixed to rapidly heat materials to a specified sterilization temperature. Both steam infusion and steam injection are direct heating systems, steam injection is where steam is injected into the product to be treated, while steam infusion is where the products and culinary steam will be infused into the sterilization tank at the same time to realize the heat treatment. The steam must be of a good quality culinary grade and free from any off-flavors that could alter the flavor of the product.

Because of the short heating time, high heating efficiency, and fully enclosed operation, DSI sterilization technology is widely used in continuous UHT treatment heat-sensitive low-acid and easy fouling products, such as animal milk, plant-based milk(coconut milk, oat milk, soy milk, almond milk), high value-added juices(NFC juice, fruit nectar), beverages, baby food puree, cream, milkshake, sauce and puddings with aseptic productions.

• Low-temperature milk products: 143-158℃ holding for 0.09S—-Flash cooling—65℃ homogenizing—4℃ milk outlet.
• Normal temperature aseptic products:135-142℃ holding for 4-6S—Flashing cooling—80℃ aseptic homogenizing—25℃ material outlet.
• Heat-sensitive aseptic products: 150-160℃ holding for 0.1-0.9S—Flashing cooling—65℃ aseptic homogenizing—25℃ material outlet.

• Gentle heating with direct steam infusion sterilization minimizes thermal gradients compared to other UHT processes, helping to protect important nutrients such as vitamins, resulting in a high-quality, fresh-tasting product. It provides the sterilization rate necessary for commercial aseptic products and can handle a wide range of viscosities, from light soy milk to thick custards and puddings.
• The cooling jacket on the steam sterilization chamber minimizes product foaming or fouling, and the entire direct steam infusion/injection UHT system is fully closed, with lower CIP cleaning frequency, and longer running time compared to indirect UHT processes, Superior processing speeds and longer cleaning intervals ensure higher productivity.
• High-temperature heating(120-150℃adjustable) for a short period of time(0.2-5S) helps the product maintain its fresh flavor while ensuring a very high sterilization rate, resulting in long shelf life of the product.
• The DSI sterilizer heats up and cools down products quickly, the heating and cooling time of the material is short, so the nutrition and color of the product can be well preserved.
• The infusion type can heat the material to 143℃, and the whole heating time is shorter than Inject type sterilizer; But the direct steam injection sterilizer can heat the material to 162℃ maximumly.
• The Flash cooling process performs in a vacuum evaporation tank to ensure precise control of water drainage so that the product is not diluted or concentrated compared to its original state.
• The whole machine has SIP and CIP functions, usually connect with the aseptic tank, aseptic homogenizer and aseptic filler to produce the aseptic products.
• The whole sterilization process is controlled by PLC, fully automatic, product flow is controlled by the flowmeter, product temperature is controlled by a sensor, and product flowing capacity is frequency control, available from 2 tons/hour to 8 tons/hour.
• The whole machine is made of SUS304 or SUS316L, which is full meets the hygiene requirements in the food and beverage processing field.
• The control system adopts international famous brands, such as Siemens S7 series PLC, Shneider eclectic control parts, Danfoss inverter, Spirax Sacro steam control system, Jumo temperature control system, GEA aseptic valve, etc.

The whole machine is composed of a product balance tank with a level sensor, a product pump with frequency control, a tubular preheating section, steam injection/infusion tank for sterilizing products, a vacuum evaporating tank for flashing cooling, vacuum pump, aseptic product pump,  tubular or plate precooling and final cooling section, acid and alkali addition system, aseptic valves, pipes and fittings, electronic control cabinet, control instrument, etc.

The optional equipment that can be equipped includes an aseptic homogenizer, sterile water system, clean culinary steam generator, rotor or screw pump for high viscosity product transferring.

The DSI sterilizer is automatically controlled by a PLC control system. The control device is programmed for the following functions and can be started by pressing the function key on the operating screen:

− SIP Pre-sterilization: The equipment is sterilized and ready for production. Pre-sterilization is carried out by circulating hot water for about 20 minutes. A temperature sensor is placed on the return pipe after the filler to control the sterilization effect.

− Production: Production starts automatically at the pre-selected recipe temperature and pressure. During the production process, the operation can be interrupted and sterility is maintained. The product enters the balancing tank at a temperature of 65°C. The pump conveys the product from the balancing tank to the preheater, where the product is heated to about 80°C, which is regulated by the steam control valve and controlled by the temperature controller. After preheating, the booster pump conveys the product to the heating chamber, where it is heated to 145°C. The thermal treatment process of infusion is very precise and gentle.

− After reaching the set temperature quickly and accurately, it is equally important to ensure an accurate holding time. Due to the effect of air, non-condensed gases and steam, the product in the tube is kept in a multiphase flow.

− After flash cooling, the product enters the homogenization stage and is homogenized with two-stage homogenization at a pressure of up to 250 bar and finally cooled to about 25°C with cold water

− The homogenized sterile product is now ready for filling and is conveyed to the pre-selected sterile tanks or filling machines

− Aseptic cleaning: During production, it is possible to switch to CIP cleaning at production temperature and then switch directly back to production without pre-sterilization.

− Aseptic water cycle: During production, it is possible to switch to an aseptic water cycle and operate with water instead of product, thus avoiding sterilization. This aseptic water cycle will have a certain impact on the operating time of the equipment.

–CIP cleaning: After production, CIP cleaning must be done, aseptic CIP: 90 minutes at production temperature; normal CIP: 120 minutes at 90-120ºC depending on the product, (NaOH): 2.0 – 2.5%, (HNO3): ≤ 1.5%