Physical properties of apple juice treated with high hydrostatic pressure

Cilj ovog rada bio je ispitati utjecaj visokog hidrostatskog tlaka na fizikalna svojstva soka od jabuke. Praćen je utjecaj visokog hidrostatskog tlaka na apsorbanciju, gustoću i raspodjelu veličina čestica pri sljedećim procesnim parametrima: tlak (p = 200, 400, 600 MPa); vrijeme obrade (t = 5, 10, 20, 30 minuta). Ispitivanje je provedeno na dva uzorka soka od jabuke: sok od jabuke dobiven filterom promjera 0,3 mm i sok dobiven filterom promjera 0,5 mm. Rezultati su statistički obrađeni pomoću programskog paketa „Statistica 12“. Stabilnost voćnog soka može se pratiti mjerenjem vrijednosti apsorbancije i izraziti odnosom relativne učestalosti čestica u ovisnosti o njihovom promjeru. Sok dobiven filterom promjera 0,5 mm pokazuje veću stabilnost gdje se vrijednosti ISS (indeks stabilnosti soka) kreću u rasponu od 47 – 224 h, u odnosu na sok dobiven filterom 0,3 mm gdje prevladavaju vrijednosti od oko 30 h.. Na povećanje vrijednosti indeksa stabilnosti soka utječe primijenjeni tlak, dok vrijeme obrade nema utjecaj.Main goal of this research was analysis of the influence of the high hydrostatic pressure on physical properties of apple juice. The influence of high hydrostatic pressure on absorbance, density and particle size distribution was observed under following conditions: pressure (p = 200, 400, 600 MPa); processing time (t = 5, 10, 20, 30 minutes). Research was made on two examples of apple juice: on apple juice made with filter diameter a 0,3 mm and apple juice made with filter diameter a 0,5 mm. Obtained results are processed in the „Statistica 12“ software. The stability of apple juice can be observed by measuring the absorbance and expressed by the ratio of the relative particle frequency depending on their diameter. Apple juice made with filter diameter a 0,5 mm has greater stability where values of the ISS (juice stability index) are in range 47 – 224 h, and for juice made with filter diameter a 0,3 mm this values are around 30 h. Applied pressure affects on increase the value of the juice stability index while processing time has no effect