Rapid Ultrasonic Milk Analyzer for the Indian Market

The high sensitivity of ultrasonic parameters to composition and state of milk and other liquid food products is now well established. Multiple informative ultrasonic parameters can be measured: sound velocity and acoustic impedance, as well as their temperature slope, which are sensitive to compressibility, density, and hydrophobicity of the sample; and ultrasonic absorption and reflection, as well as their frequency slope, which are sensitive to size of the particles and to relaxation processes due to energy losses, aggregation, or conformational transitions. The first application of ultrasound for quality control of milk started about 50 years ago in evaluation of fat content. Currently available commercial ultrasonic devices include measurements of the acoustic properties of milk at different temperatures and therefore require waiting for temperature equilibration of the milk when the sample is heated or cooled and cannot be used for real-time monitoring. In this paper an ultrasonic analyzer that uses radially oscillating PZT piezoceramic tubes, and is applied for monitoring of fat globules, solid-non-fat (SNF), and protein of raw milk in cowsheds is described. This device employs high-intensity standing waves for preliminary separation of the fat globules and SNF by the acoustic radiation forces and employs lowintensity standing waves for compositional analysis. A device based on standing cylindrical waves is far superior to other ultrasonic instrumentation in respect to industrial requirements such as cost, precision, and ease of use in flow-through systems. Preliminary testing of the analyzer was carried out on milk samples from five cows milked twice a day for one month. More than 300 samples of the raw milk were tested. Obtained results demonstrate a possibility of rapid measurements (5-10s) and good correlation with the central certified laboratory for milk quality testing run by the Cattle Breeding Association. Continuous monitoring of milk fat, protein, SNF, which typically have high day-to-day variation, provide a much-needed tool for dairy management and for veterinary diagnostic purposes. It was found that milk production level, stage of lactation, and outside temperature have significant influences on milk composition. The technology can be incorporated in either a hand-held portable device or as an added on-line unit in existing flowthrough systems. This will enable continuous on-line monitoring of the quality of milk, and will facilitate the prediction of mastitis by the determination of the main components with the following accuracy: fat (±0.05%), protein (±0.05%), and SNF (±0.05%). At a later stage the ultrasonic milk analyzer will be applied to compositional analysis and quality control in different liquid milk products.