Ultrasonic Homogenization of Soy Milk
- The challenges of soy milk production lie in the production of a tasty, nutritional high-quality soy-based drink under high efficiency process conditions.
- Ultrasonic homogenization and pasteurization offers the advantages of a healthy soy milk with high nutritional values & shelf-stable properties as well as high mechanical an microbiological stability.
The Production of Soy Milk
The ultrasonic treatment of soy-base and soy milk modifies physicochemical properties (macromolecular changes, enzyme inactivation), gives a uniform, fine-size homogenization and improves the rheological characteristics. Ultrasonic emulsification results in a self stable plant milk, whilst ultrasonic preservation and inactivation of microorganisms ensures microbial stability. Besides the improvements of nutritional values, stability and flavour, sonication convinces by its energy- and time-efficiency. In comparison to conventional methods, the ultrasonic treatment is less energy-consuming and more time-efficient.
Ultrasonic homogenizers cover the full production capacity of soy milk production, result in optimized preservation and allow for a functional versatility of the production line. Ultrasonic inline homogenizers can be adjusted easily to the production targets allowing for the production of various flavour profiles (e.g. beany, non-beany) and product funcionality by simply changing the process parameters.
Soy Flavour
Ultrasonic processing allows to influence the flavour of soybase: Soy milk products can produced with a strong beany flavour, which is appealing to the Asian customer target, whilst western consumers prefer a non-beany, smooth taste. By adapation of the ultrasonic process parameters (amplitude, sonication time, temperature, pressure), either a strong or mild flavour profile can be obtained. This means that the same ultrasonic system can be used to produce selectively various soy flavour profiles in order to manufacture various product types to please different target markets.
Ultrasonic Enzyme Inactivation
The intense soy-bean taste is related mainly to the activity of the lipoxygenase enzyme (LOX). The inactivation of this enzyme LOX is one of the major objectives of modern processing systems.
Manothermosonication (MTS) – the sonication under elevated pressure and temperature conditions – is a proven method to inactivate the lipoxygenase (LOX) enzyme. Lipoxygenase activity causes oxidation of fatty acids and pigments. Intense ultrasound waves cause the inactivation or denaturation of enzymes such as lipoxygenase, peroxidase and polyphenol oxidase.
MTS has been proved to be an efficient tool to inactivate some other enzymes, such as lipoxygenase, peroxidase, and proteases and lipases from psychrophilic bacteria. (Kuldiloke 2002: 2)
- high extraction yield
- pleasant flavour
- mechanical stability
- microbiological stability / preservation
- enzyme inactivation
- energy-efficiency
Ultrasonic homogenization and preservation of soy milk
Microbiological Stability by Ultrasonic Preservation
Ultrasound alone or in combination with heat (thermosonication) or pressure (manosonication) or both heat and pressure (manothermosonication) is known as an effective method to inactivate various food enzymes such as lipoxygenase, peroxidase, and polyphenol oxidase, as well as heat-resistant lipase and protease. Powerful ultrasound waves destruct microorganisms resulting in microbial inactivation and thereby microbial product stability. The inactivation of pathogenic and spoilage microorganisms or enzymes by sonication is mainly caused by physical (caviation, mechanical forces) and/or chemical effects.
Soy Protein
The application of power ultrasound to soy protein isolate (SPI) and soy protein concentrate (SPC) enables for a targeted modification of the soy protein to obtain a highly functional food additive. Manifold new product concepts involve the use of soy proteins as a base and ultrasonically assisted processing allows for the industrial manufacturing of superior quality products such as dairy-free, vegan smoothies, cheese alternatives, soy cream based soups, spreads and creamy dressings.
Sonication with a powerful ultrasonicator (e.g. UIP2000hdT) causes significant changes in conductivity, increases the solubility of soy protein concentrates, increases the specific surface area significantly, which is important for food textures, and increases the values of the emulsion activity index (EAI). Weight mean diameter D and volume–surface average diameter D decrease significantly for soy protein isolates (SPI) and soy protein concentrates (SPC).
In comparison to conventional soy protein treatments, sonication is less energy consuming and significantly more time-efficient.
Ultrasonic Homogenizers
Hielscher Ultrasonics’ food processors are versatile and can be easily installed or retrofitted into existing production lines. High power, reliability and robustness make Hielscher`s ultrasonicators the “work horse” in soybase production.
Hielscher’s industrial ultrasonic processors can deliver very high amplitudes. Amplitudes of up to 200µm can be easily continuously run in 24/7 operation. For even higher amplitudes, customized ultrasonic sonotrodes are available. The robustness of Hielscher’s ultrasonic equipment allows for 24/7 operation at heavy duty and in demanding environments.
The table below gives you an indication of the approximate processing capacity of our ultrasonicators:
| Batch Volume | Flow Rate | Recommended Devices |
|---|---|---|
| 10 to 2000mL | 20 to 400mL/min | UP200Ht, UP400St |
| 0.1 to 20L | 0.2 to 4L/min | UIP2000hdT |
| 10 to 100L | 2 to 10L/min | UIP4000 |
| n.a. | 10 to 100L/min | UIP16000 |
| n.a. | larger | cluster of UIP16000 |
Literature/References
- Berk, Z. (1992): Soymilk and related products. Food and Agriculture Organization of the United Nations, Rome, Italy; Corporate Document Repository: Technology of Production of Edible Flours and Protein Products from Soybeans. Services Bulletin No. 97, Chapter 8. Retrieved 16 January 2017.
- Bourke, P.; Tiwari, B.; O’Donnell, C.; Cullen, P. J. (2010): Effect of ultrasonic processing on food enzymes of industrial importance. Trends in Food Science and Technology, Vol. 21, Issue 7, 2010.
- Mei, Jun ; Feng, Fei; Li, Yunfei (2017): Effective of different homogeneous methods on physicochemical, textural and sensory characteristics of soybean (Glycine max L.) yogurt. CyTA – Journal of Food, 15:1, 2017. 21-26.
- Iswarin, S.J.; Permadi, B. (2012): Coconut Milk’s Fat Breaking by Means of Ultrasound. International Journal of Basic & Applied Sciences IJBAS-IJENS Vol 12, No 01. 2012.
- Kuldiloke, J. (2002): Effect of Ultrasound, Temperature and Pressure Treatments on Enzyme Activity and Quality Indicators of Fruit and Vegetable Juices. Dissertation TU Berlin, 2002.
Facts Worth Knowing
Soy Milk
Soy milk is a beverage, which is produced by extraction from whole soy beans in water. Soy milk is an emulsion of water and soy-derived lipids, which contains water soluble proteins and carbohydrates. For the old-fashioned, traditional way of soy milk preparation, soy beans were soaked, grinded, filtered and cooked. So prepared soy milk offers only a short self life. However, today’s consumers, and the modern lifestyle, request products with a longer shelf-life, which remain safe and stable during the complete storage period. For production of such soy milks and beverages utilization of the UHT technology is obvious. Hereby shelf-life from several months and up to a year can be obtained, depending on the composition of the product. Further, the right choice of emulsifiers and stabilizers is necessary for ensuring a homogeneous product without creaming and sedimentation during the entire shelf-life.
Production of Soy Milk and Soy-Based Drinks
Soy milk is made from whole soybeans or full-fat soy flour. The dry beans are soaked in water overnight or for a minimum of 3 hours or longer. The soaking time is heavily related on the temperature of the water. Afterwards, the soaked beans are ground in a wet-milling process. The water is added to rise the water content as required for the final soy milk product. The final soy drink features generally a protein content of 1–4% and the weight ratio of water to soyabeans 20:1 for a typical soy beverage that appeals to the Western consumers. (Traditional Asian soy milk has a water : soybean weight ratio of as high as 5:1). The milled soy bean slurry is boiled in order to improve flavour properties, digestibility, and microbial stability. The heat treatment inactivates soybean trypsin inhibitors, inactivates lipoxygenase for a milder flavor, and pasteurizes the soy milk. The heat treatment is applied for approx. 15–20 minutes, followed by filtration to remove insoluble residues such as soy pulp fibers / okara. Finally, the soy beverage can be artificially flavoured by adding of sugar, vanilla, chocolate, fruit or other flavours.
Soy Drinks and Yogurt
Soy beans are used to produce various products such as milk substitutes and soy drinks, juice, soy mix drinks (especially in Latinamerica) as well as soy yoghurt. Soy-based drinks and yogurts are widely consumed as dairy alternative by lactose intolerants and vegans, but consumers choose soy products for its health benefits and flavour, too.
Typical soymilk shows the following composition of approx. 3.6% protein, 2% fat, 2.9% carbohydrates and 0.5% ash. Soy beans have a low content of saturated fats, are cholesterol-free and lactose-free. Additionally, they have a high amount of vitamins and minerals make its consumption very health-beneficial.
Manothermosonication
Manothermosonication (MTS) is the synergetic combination of ultrasound with heat and pressure.