Application of Ultrasound and High Hydrostatic Pressures on Variation of Fat Globule Size and Chemical Composition of Cow Milk

Abstract

Nove tehnologije, danas popularno nazvane netoplinske (primjena visokog hidrostatskog tlaka, pulsirajućih električnih polja, i ultrazvuka visokog intenziteta) imaju svojstvo da tijekom obrade ne utječu na značajno povišenje temperature čime u većini ostaju nepromijenjena teksturna i senzorička svojstva uzoraka koji se obrađuju. Vrijeme obrade uzoraka traje od nekoliko sekundi do 30 minuta. Konvencionalne postupke homogenizacije mlijeka moguće je unaprijediti novim metodama obrade. Cilj rada je pokazati prednosti utjecaja ultrazvuka visokog intenziteta u diskontinuiranom (maksimalna nominalna snaga 100W) i kontinuiranom postavu (maksimalna nominalna snaga 1000W sa protočnom ćelijom) kao i utjecaj visokog hidrostatskog tlaka (do 600 MPa) na raspodjelu veličine masnih globula. Budući da je homogenizacija mlijeka provedena pri optimalnim procesnim parametrima koji statistički značajno utječu na promjenu raspodjele veličine masnih globula mlijeka (stupanj homogenizacije), ispitan je i utjecaj ultrazvuka i visokog tlaka na promjenu kemijskog sastava kravljeg mlijeka. Optimalna raspodjela veličine globula masti u intervalu 0,3 – 6 μm dobiva se u oba postava. Smanjenje vrijednosti medijana postiže se primjenom tlakova od 200MPa. Kemijska analiza provedena ultrazvukom niskih intenziteta pokazala je da diskontinuirani postav ultrazvuka i visoki hidrostatski tlak nemaju statistički značajan utjecaj na promjenu kemijskog sastava mlijeka. Ultrazvučni kontinuirani postav ima utjecaja na promjenu sastava pepela (mineralnih tvari) pri nižim vrijednostima volumnih protoka.Main common property of novel food processing technologies, such as high hydrostatic pressure, pulsed light and high intensity ultrasound is non-thermal treatment. Such technologies input minimal amount of heat energy in food, which is low enough to preserve bioactive compounds, textural and other organoleptic properties of processed food. High pressure processing and ultrasonics also utilize relatively short processing times, ranging from a few seconds up to 30 minutes. Main goals of this research are to improve conventional milk homogenization technology, show advantages of application of high intensity ultrasound in the batch (maximal power 100 W) and continuous setup (maximal power of 1000 W, with flow cell), as well as investigate influence of high pressure processing (up to 600 MPa) on particle size distribution of fat globules. Milk homogenization is conducted under optimal processing parameters, which have statistically significant influence on changes in the size distribution of milk fat globules (degree of homogenization). Influence of high intensity ultrasound and high pressure processing on changes in chemical composition of cow milk is also investigated. Optimal globule size distribution in interval between 0.3 and 6 μm is achieved using both setups. Median value decrease is achieved processing with 200 MPa pressure. Chemical analysis counducted with low intensity ultrasound indicate that batch ultrasound processing and high hydrostatic pressure processing of milk have minimal or no statistically significant influence on chemical composition of milk. Continuous ultrasonic processing at lower volume flows have small but statistically significant influence on ash composition