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The efficiency of gas phase plasma at atmospheric pressure by using an electrical discharge in gas argon on the inactivation of microorganisms was examined. The gas phase plasma was applied to suspensions of pure cultures Escherichia coli 3014, Staphylococcus aureus 3048, Salmonella sp. 3064, Listeria monocytogenes ATCC 23074 and Bacillus cereus 30. The experiments were planned and performed according to a statistical experimental design, specifically central composite design, which considered three independent variables: volume (2, 3 and 4 mL), gas flow (0.75, 1 and 1.25 L/min) and treatment time (3, 4 and 5 min). Two studied parameters, volume and treatment time, substantially affected the inactivation. For plasma treatment, the inactivation can be attributed to UV radiation and plasma reactive oxygen species (ROS). It was found that Gram-negative bacteria were more susceptible to the plasma treatment than Gram-positive bacteria, and that the susceptibility of Gram-positive bacteria was remarkably species-dependent. Complete inactivation of Escherichia coli, Salmonella sp., and Listeria monocytogenes was achieved when optimal combination of parameters was applied.

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 wit

Svrha ovog rada je ispitati utjecaj ultrazvuka visokog i niskog intenziteta na reološka i pastozna svojstva suspenzija škroba pšenice. Ispitivane suspenzije sadrže 10 % pšeničnog škroba te su neposredno nakon pripreme procesirane ultrazvukom. Sva ispitivanja provedena su prije i nakon ultrazvučne obrade u ultrazvučnoj kupelji frekvencije 22 kHz, nominalne snage 150 W te ultrazvučnom sondom frekvencije 24 kHz, nominalne snage 100, 300 i 400 W. Vrijeme ultrazvučne obrade svih uzoraka bilo je 15 i 30 minuta. Reološka svojstva određena su primjenom rotacionog reometra Rheometric Scientific RM-180 pri temperaturi od 20 ˚C, a pastozna svojstva škrobnih suspenzija određena su primjenom Micro Visco-Amylo-Graph, Brabender Ohg Duisburg, Njemačka po metodi ICC Standard 126/1. Ultrazvučna obrada uzrokuje mehaničko oštećenje škrobne granule čime njena unutrašnjost postaje dostupnija vodi tijekom zagrijavanja što ima za posljedicu značajne promjene reoloških i pastoznih svojstava škrobnih suspenzija. Reološki parametri pokazuju da sve suspenzije imaju ne-Newtonski karakter, a ultrazvučni tretmen uzrokovao je značajno povećanje koeficijenta konzistencije svih ispitivanih sustava. Ultrazvučnim procesiranjem došlo je do značajnog sniženja temperature želatinizacije kod svih škrobnih suspenzija. Značajno smanjenje početnih temperatura želatinizacije upućuje na raniji stupanj bubrenja granule tijekom zagrijavanja., The aim of this paper was to examine the influence and effect of high and low power ultrasound on rheological and thermophysical properties of wheat starch suspensions. Suspensions containing ten percent of potato starch have been treated with ultrasound. All analysis have been carried out before and after power ultrasound treatment. Ultrasound bath of 22 kHz frequency and nominal power of 150 W has been used, as well as ultrasound probe of 24 kHz frequency and nominal power of 100, 300 and 400 W for 15 and 30 minute treatments. Rheological parameters have been determined with rheometer Rheometric Scientific RM-180 at 20 ºC. Pasting properties have been determined with Micro Visco-Amylo-Graph, Brabender Ohg Duisburg at method ICC Standard 126/1. Ultrasonic treatment caused disrupting of starch granules by mechanical forces and made the granule more permeable to water during the heating step. Because, significant changes of rheological and pasting properties were observed. Rheological parameters showed that all suspensions exhibited non-newtonian (dilatant) character. Also, ultrasonic treatment has affected a significant increase of consistency coefficient of starch suspension. Ultrasonic treatment caused significant lowering of the beginning gelatinization temperatures, which indicated an earlier state of granule swelling during heating.

Ultrazvuk iskazuje frekvenciju zvuka koja se nalazi između 18 i 100 kHz, što je iznad čujnosti ljudskog uha. Ultrazvuk visoke snage znači primjenu intenziteta višeg od I=1Wcm-2(uobičajeno u rasponu od I=10 - 1000Wcm-2). Ultrazvuk visoke snage i niskih frekvencija (f=20 do 100 kHz) smatra se "snažnim ultrazvukom" jer uzrokuje pojavu kavitacije te ima primjenu u prehrambenoj industriji. Primjenjuje se kod odzračivanja tekuće hrane, za induciranje reakcija oksidacije/redukcije, za ekstrakciju enzima i proteina, za inaktivaciju enzima i za indukciju nukleacije kod kristalizacije. Nadalje, ultrazvuk pospješuje prijenos topline, primjenjuje se kod emulgiranja, sterilizacije, ekstrakcije, odzračivanja, filtriranja, sušenja i pojačavanja oksidacije. Konvencionalno sušenje toplim zrakom je energetski veoma zahtjevno i posljedično zahtijeva veća financijska izdvajanja. Primjene različitih predtretmana kao što su osmotska dehidratacija, ultrazvuk i ultrazvukom potpomognuta osmodehidratacija pokazale su različite učinke na voće i povrće. Prolaskom akustičke energije visokog intenziteta kroz čvrsti medij zvučni val uzrokuje serije brzih i sukcesivnih kompresija i opuštanja s brzinama koje ovise o njegovoj frekvenciji. Zbog toga je materijal izložen brzim serijama promjenjivih stezanja i širenja, vrlo nalik neprekidnom stiskanju i opuštanju spužve. Ovaj mehanizam, poznat kao "rektificirana difuzija", vrlo je važan u akustičkom sušenju i migraciji vlage. Primjena ultrazvuka kao prethodne obrade pokazala je velik utjecaj na skraćivanje kasnijeg trajanja sušenja vrućim zrakom, te samim time i ukupna operacija sušenja. Pokazano je da obrada prije provedbe sušenja omogućava bolji prijelaz mase i difuzivnost vode od osmotske dehidratacije. Kvaliteta proizvoda koji se stavlja na sušenje je veća jer se prethodna obrada ultrazvukom primjenjuje pri sobnoj temperaturi čime se smanjuju nepoželjne promjene na strukturi, senzorskim karakteristikama, te gubitci nutritivnih komponenta voća i pov, Ultrasound is a sound frequency in the range between 18 and 100 kHz that is above hearing of the human ear. High power ultrasound means application of intensities higher than 1 W cm–2 (usually in the range between I=10–1000Wcm–2). High power and low frequency ultrasound (f = 20 to 100 kHz) is considered as “power ultrasound” because its application causes cavitation and is applied in the food industry. High power ultrasound is applied for degassing of liquid food, for induction of oxidation/reduction reactions, for extraction of enzymes and proteins, for inactivation of enzymes and induction of nucleation for crystallization. Ultrasound is anticipating heat transfer; it is used for emulsifying, sterilization, extraction, degassing, filtrating, drying and induction of oxidation. Conventional hot air drying is a very energy- and cost-intensive process. Drying is a simultaneous operation of heat and mass exchange that is followed by phase changes. Application of different pretreatments, like osmotic dehydration, ultrasound and ultrasound assisted osmotic dehydration has shown different effects on fruits and vegetables. When the high intensity acoustic energy is passing through solid material, it causes several fast and successive compressions and rarefactions with speeds that depend on the frequency applied. Thus, material is exposed to a series of exchangeable squeezing and relaxations, very like continuous squeezing and releasing of the sponge. This mechanism known as "rectified diffusion" is very important in acoustic drying and migration of water. Application of ultrasound as a pretreatment has shown great influence on reducing afterward hot air drying thereby reducing total drying time. It is also shown that pretreatment before drying facilitates better mass transfer and water diffusivity than osmotic dehydration. Quality of the product after drying is better because ultrasound pretreatment is applied at room temperature thus reducing deteriorating alterations and