Application of High Pressure in Food Processing

Obrada visokim tlakom podrazumijeva podvrgavanje tekuće ili čvrste hrane, s ambalažom ili bez nje, djelovanju tlaka od 100 do 800 MPa (1200 MPa). Temperatura obrade može se kretati od ispod 0 °C do iznad 100 °C, a vrijeme izloženosti djelovanju tlaka, ovisno o cilju obrade, može varirati od nekoliko sekundi do preko 20 minuta. Zbog djelovanja visokog tlaka dolazi do smanjenja obujma sustava i pospješivanja onih reakcija koje vode smanjenju obujma. Potencijal primjene visokog tlaka u obradi hrane je u inaktivaciji mikroorganizama, modifikaciji funkcionalnih svojstava biopolimera, postizanju funkcionalnosti proizvoda te zadržavanju čimbenika kvalitete (boja, aroma, nutritivni sastav). Komponente odgovorne za specifičnu nutritivnu vrijednost i organoleptičke značajke hrane praktički su neosjetljive na djelovanje tlaka. Cilj rada je, polazeći od teorijskih principa djelovanja visokog tlaka, uzimajući u obzir njegove prednosti i nedostatke, prikazati mogućnosti primjene u postupcima obrade hrane. U radu su također opisani tipovi uređaja za tretiranje visokim tlakom koji se mogu primijeniti u obradi hrane. Osim sposobnosti uništavanja mikroorganizama pri sobnoj temperaturi što ovu tehnologiju čini danas jedinom komercijalno primjenjivom alternativom termičkom tretiranju, u radu su prikazane i specifične mogućnosti primjene visokog tlaka u preradi mlijeka, mesa te voća i povrća. S obzirom na trend rastuće potražnje za hranom bez dodataka koja u velikoj mjeri ima zadržane značajke kvalitete (boja, aroma, nutritivni sastav, tekstura), uz ujedno zajamčenu mikrobiološku stabilnost, može se očekivati da će metoda obrade hrane visokim tlakom u budućnosti naći svoju širu primjenu i to upravo za proizvode koji zahvaljujući svojoj dodanoj vrijednosti imaju istaknuto mjesto na tržištu.In high pressure processing, foods are subjected to pressures generally in the range of 100 – 800 (1200) MPa. The processing temperature during pressure treatments can be adjusted from below 0 °C to above 100 °C, with exposure times ranging from a few seconds to 20 minutes and even longer, depending on process conditions. The effects of high pressure are system volume reduction and acceleration of reactions that lead to volume reduction. The main areas of interest regarding high-pressure processing of food include: inactivation of microorganisms, modification of biopolymers, quality retention (especially in terms of flavour and colour), and changes in product functionality. Food components responsible for the nutritive value and sensory properties of food remain unaffected by high pressure. Based on the theoretical background of high-pressure processing and taking into account its advantages and limitations, this paper aims to show its possible application in food processing. The paper gives an outline of the special equipment used in highpressure processing. Typical high pressure equipment in which pressure can be generated either by direct or indirect compression are presented together with three major types of high pressure food processing: the conventional (batch) system, semicontinuous and continuous systems. In addition to looking at this technology’s ability to inactivate microorganisms at room temperature, which makes it the ultimate alternative to thermal treatments, this paper also explores its application in dairy, meat, fruit and vegetable processing. Here presented are the effects of high-pressure treatment in milk and dairy processing on the inactivation of microorganisms and the modification of milk protein, which has a major impact on rennet coagulation and curd formation properties of treated milk. The possible application of this treatment in controlling cheese manufacture, ripening and safety is discussed. The opportunities for its application within the meat processing sector are also discussed, particularly the specific effects of high pressure on the colour, texture, nutritive value and functional properties of fresh and processed meat. This paper also considers the possibilities of implementing high-pressure technology in fruit and vegetable processing with the aim to maintain microbiological safety, nutritive value, “fresh-like” appearance and antimutagenic properties. The intention of this paper is to broaden the knowledge of experts and technologists regarding implementation possibilities of high pressure, as one of the emerging technologies in the various food-processing sectors. Given the trend of growing consumer preferences for fresh-like, additive-free and microbiologically safe food, high pressure processing is likely to find its future application in food processing for niche products with added value