Ultrasonication and Its Manifold Applications in Food Processing
Power ultrasound offers manifold possibilities for effective and reliable food processing applications. The most common applications in the food industry include mixing & homogenization, emulsification, dispersing, cell disruption and extraction of intra-cellular material, activation or deactivation of enzymes (which is dependent on the ultrasound intensity), preservation, stabilization, dissolving and crystallization, hydrogenation, meat tenderization, maturation, aging and oxidation, as well as degassing and spray drying.
Find below a list of specific applications.
Please click on the applications of your interest to read more about them!
Extraction of Flavours and Active Compounds
Ultrasonication is a well-known and reliable method when it comes to the extraction of intra-cellular matter.
Click here to read more about the ultrasonic lysis
and the examples of ultrasonic extraction of active compound from saffron
Fermentation of Yoghurt
Yogurt is a fermented milk product that can be produced by milk alone or by the addition of bacterial cultures. Bifidobacteria strains (e.g. BB-12, BB-46, B breve) are common probiotics used for yogurt fermentation. Ultrasonic cavitation applied to the bacterial cells can cause their destruction and simultaneously, the release of β-galactosidase. β-galactosidase is an hydrolase enzyme that is heavily used in the milk processing industry. The ultrasonically assisted fermentation is accelerated due to a faster lactose hydrolysis resulting from the ultrasonically induced release of β-galactosidase from the bifidobacteria cells.
The ultrasonic homogenization effects the break of the milk fat globules and a very fine-size distribution.
Ultrasonication can accerlerate the fermentation rate (reduction of total production time of up to 40%) and improve the quality characteristics of yogurt, resulting in higher viscosity, stronger coagulum and superior texture.
Homogenization of Milk
Milk (e.g. cow, buffalo, goat or camel milk) is an emulsion or colloidal system that consists in butterfat globules within a water-based fluid that contains dissolved carbohydrates, proteins and minerals. As fat and water tend to separate into two phases, milk must be homogenized to obtain an even product. Homogenization means the even distribution of the fat molecules in the milk liquid. Ultrasound is a well known method used for various applications in dairy processing. Ultrasonic treatment of milk results in homogenized fat globules, which are even and uniformly distributed. The homogenization by high-power ultrasound is also effective for (vegan/ dairy free) milk substitues derived from plants such as coconut milk or soy milk.
The study of Sfakianakis and Tzia (2012) shows that ultrasonic homogenization reduces the size of milk fat globules (MFG). Low amplitude (150W) had not a satisfactory homogenization effect (Fig.2) ; the MFG size and their distribution were similar to untreated milk (compare fig. 1 and 2). Medium amplitude ultrasound (267.5, 375 W) had a good homogenization effect; MFG average diameter was 2 μm (Fig. 3, 4). Higher amplitude (750W) ultrasound reduced the MFG size crucially (Fig. 6), making them barely visible at the optical microscope (100x magnification); their average diameter size was 0.3 μm.
High power ultrasound is a mild non-thermal homogenization technique. Sfakianakis et al. (2011) show the impressive ultrasonic homogenization effect on milk.
Chandrapala et al. (2012) investigated the effect of ultrasonication on casein and calcium. They applied ultrasonic waves (20kHz) to samples of fresh skim milk, reconstituted micellar casein, and casein powder. They sonicated the samples until the milk fat globules were reduced to approx. 10nm. The analysis of the sonicated milk shows that the size of the casein micelles is unchanged. A small increase in soluble whey protein and a corresponding decrease in viscosity also occurred within the first few minutes of sonication. The study was determined that casein micelles are stable during sonication and the soluble calcium concentration is not affected by the ultrasonic treatment. [Chandrapala et al. 2012]
Sugar Crystallization for Confectionery
Controlled sonication allows to initiate the crystal seeding (creation of nuclei) and to influence the crystal growth. Under ultrasonic irradiation, smaller and thereby more crystals are formed. Ultrasonic assists the crystallization process in two ways: Firstly, power ultrasound is a very effective tool to create an even solution, which is the starting substance for crystallization. In the second stage, ultrasonic supports the formation of a large number of nuclei. Whilst poor nucleation creates a lower number of large crystals, efficient nucleation forms a large amount of small fine-size crystals. In the acoustic field, it becomes even possible to initiate the nucleation of sugars that are normally averse from crystallizing (e.g. D-fructose, sorbitol).
The ultrasonic modification of crystallization is interesting for the formulation of candies, confectionery, spreads, ice cream, whipped cream and chocolate.
Hydrogenation of Edible Oils
The hydrogenation of vegetable oils is an important industrial large scale process. By hydrogenation, liquid vegetable oils are convertetd into solid or semi-solid fats (e.g. margarine). Chemically, the unsaturated fatty acids are converted during the phase transfer catalyzed
reaction of hydrogenation into their corresponding saturated fatty acids by adding hydrogen atoms at the doublebonds. This catalytic process can be accelerated by high-power ultrasonication. A commonly used catalyst is nickel. Hydrogenated fats are used extensively as shortening agents in bakery products. An advantage of saturated fats is their lower tendency to oxidation and thereby a lower risk of rancidity.
Liquefaction of Honey
Ultrasound offers an effective method, crystals in honey to liquefy and destroy the yeast, without affecting the quality of honey.
Click here to learn more!
Stabilization of Juices and Smoothies
Ageing of Wine & Liquor
Ice Cream Freezing
For ice cream production, an ice cream mix is required. This ice cream mix consists of milk, milk powder, cream, butter or vegetable fat, sugar, dry mass, emulsifier, stabilizer as well as additives such as fruits, nuts, flavors and coloring. This special mixture has to be homogenized and pasteurized, then it is stirred slowly during the freeze process to prevent the forming of large ice crystal. Thereby, very small air bubbles are mixed in (so-called aerating process) to froth the ice cream achieving a smoothly textured cold dessert. This is the process step, where ultrasonication can be applied to enhance ice cream’s quality.
During the freezing process, crystals are formed from supercooled water. The morphology of the ice crystals plays an important role regarding the textural and physical properties of frozen and half-frozen food. As size and distribution of the ice crystals are of special importance for the quality of thawed tissue products, for ice cream, smaller ice crystals are preferred because large crystals results in an icy texture. Nucleation is the most important factor to control the crystal size distribution during crystallization. Thereby, the freeze rate is usually the parameter used for controlling size and size distribution of the ice crystals in ice cream. During the whipping and freezing, air is injected to achieve the smooth texture of ice cream. The so-called “over-run”, the amount of air injected, is proportionated – specifically to the particular recipe – proportionally to the combined volume of solids and water. So, the over-run varies due to the different ice cream formulations and the processing streams. Standard ice cream shows an over-run of 100%, which means that the final product consists of an equal volume of ice cream mix and air bubbles.
The use of Hielscher’s high power ultrasound devices
provides a better quality of ice cream by reducing the ice crystal size and avoiding the incrustation of a freezing surface. A better consistency and a more creamy mouth feeling is achieved due to the reduced ice cream crystal size and the enhanced air bubble distribution. Significantly shorter freezing times lead to a higher process capacity and a more energy-efficient production process.
Aeration of Batter
Aerated food products such as sponge cake can be significantly improved by sonication.The application of power ultrasonics during the batter mixing stage improves the quality of sponge cake in terms of lower hardness, and higher cake springiness, cohesiveness and resilience. For the tests, all ingredients have been mixed togetherfollowing the „all-in“ method, which means low protein whole flour, emulsifier, corn starch, sugar, baking powder, salt and fresh whole eggs have been added simultaneous to formulate the batter. Before sonication, the ingredients have been stirred evenly together so that ultrasound is applied to an even batter mixture. The ultrasonically aerated cake showed a lower hardness, lower gumminess and lower chewiness, whilst cake springiness, cohesiveness and resilience were slightly higher than that of the control cake.
Sonication is well known for its extraction capacity. From the cocoa bean, cocoa butter can be released from the cells by ultrasonic milling and extraction.
Ultrasound is an alternative technique to break the sugar crystals in chocolate and provides thereby similar effects as conching.
Tenderization of Meat
The application of powerful ultrasonic waves to meat results in tenderization oft he meat structure. A significant tenderization is achieved by the release of myofibrillar proteins from the muscle cells. Besides the tenderization effect, ultrasound improves the water-binding capacity and the cohesiveness of meat, too.
Sonication in the Kitchen
Chandrapala, Jayani et al. (2012): The effect of ultrasound on casein micelle integrity. Journal of Dairy Science 95/12, 2012. 6882-6890.
Chandrapala, Jayani et al. (2011): Effects of ultrasound on the thermal and structural characteristics of proteins in reconstituted whey protein concentrate. Ultrasonics Sonochemistry 18/5, 2011. 951-957.
Dairy Processing Handbook. Published by Tetra Pak Processing Systems AB, S-221 86 Lund, Sweden. 387.
Feng, Hao; Barbosa-Cánovas, Gustavo V.; Weiss, Jochen (2010): Ultrasound Technologies for Food and Bioprocessing. New York: Springer, 2010.
Huang, B. X.; Zhou, W. B. (2009): Ultrasound Aided Yogurt Fermentation with Probiotics. NUROP Congress, Singapore, 2009.
Keshava Prakash, M. N.; Ramana, K. V. R. (2003): Ultrasound and Its Application in the Food Industry. J. Food Sci Technol. 40/6, 2003. 563-570.
Mortazavi, A.; Tabatabaie, F. (2008): Study of Ice Cream Freezing Process after Treatment with Ultrasound. World Applied Science Journal 4, 2008. 188-190.
Petzold, G. and Aguilera, J. M. (2009): Ice Morphology: Fundamentals and Technological Applications in Foods. Food Biophysics Vol.4, No. 4, 378-396.
Sfakianakis, Panagiotis; Tzia, Constantina (2011): Yogurt from ultrasound treated milk: monitoring of fermentation process and evaluation of product quality characteristics. ICEF 2011.