Ultrahang alkalmazása húskészítmények minősítésében és gyártástechnológiájában

A szalonnák minősítésében meghatározó a hús-zsírarány, a szalámiknál pedig a kéreg jelenléte és vastagsága, ami a nem megfelelő érlelés és gondatlan tárolás eredménye. A pácolási technológia jellemző paramétere a só diffúziójának növelése, egyenletes sótartalom és állomány kialakítása a húson belül, valamint a kihozatal növelése. Ezért dolgozatomban a hús-zsírarány és a kéregvastagság roncsolásmentes meghatározását tűztem ki célul passzív ultrahanggal, illetve a pácolási technológia innovatív fejlesztését aktív ultrahang alkalmazásával. A passzív ultrahang használatakor meghatároztam az ultrahang terjedési sebességét, csillapodását a vizsgált szalonna minták hús- és zsírrétegeiben, valamint a téliszalámi normál állományú rétegeiben és a kérgében. Továbbá meghatároztam a minták egyes rétegeinek a csillapítási tényezőjét. A minták egyes rétegeinek csillapítását megmértem, majd bizonyítottam a csillapítás additivitását, vagyis azt, hogy az egyes rétegek csillapítását összeadva megkapjuk a teljes minta csillapításértékét. Bizonyítottam, hogy mind a csillapítás additivitását alkalmazva, mind a terjedési sebesség alapján meghatározható a szalonnák hús-zsír aránya, a kéreg vastagsága. Bizonyítottam, hogy az ultrahang terjedési sebessége és csillapodása által meghatározható a nem megfelelő technológiával végzett érlelés és tárolás folyamán keletkező száraz kéreg vastagsága, és nyomon követhető szalámirúdak szárazanyag-tartalmának változása az érlelés során. Az aktív ultrahang pácolási technológiában való alkalmazása során vizsgáltam az ultrahang intenzitásának és a kezelési időnek a hatását a só diffúziós tényezőjére, a sóeloszlásra, a húsok állományára és porhanyósságára. ..

FINITE ELEMENT MODELLING OF WEAR PROCESS OF A PEEK-STEEL SLIDING PAIR AT ELEVATED TEMPERATURE

The operational conditions for polymer-steel sliding pairs frequently produce higher temperature because of the frictional heat generation and/or some environmental sources. To study the wear behaviour an incremental wear simulation technique have been developed, which can consider the temperature- and time-dependent behaviour of polymer materials and evaluate the contact behaviour during the wear process by changing the initial clearance between the pin and disc according to the linear wear equation. The wear simulation technique proposed is applied for a Pin-on-Disk configuration considering creep behaviour of a PEEK material, the frictional heat generation and the thermal expansion. The results illustrate the initial part of the wear process, which involves the edge-like contact and the full contact phases

Utjecaj dodatka mikrobne transglutaminaze na teksturalna svojstva jogurta

Our aim was to determine how 0.5-2 U/g non-inactivated mTG affects the pH development and apparent viscosity during fermentation. Furthermore we wished to examine how the enzyme addition could change protein structure, gel strength and sensory characteristics by healthy low-fat set-type yoghurt product. Therefore commercial mTG enzyme preparation was added in different concentrations (0.5-2.0 U/g, in 0.5 U/g steps) to 1.5 % bovine milk simultaneously with DVS starter culture. Our study revealed that enzyme dosage (0.5-2 U/g protein) had no impact on pH development and apparent viscosity during fermentation when manufacturing low-fat (1.5 %) set-type yoghurt. The addition of mTG contributed to 38 % more whey retention with incorporation of β-casein, and caused 44 % higher gel strength up to a level of 1 U/g protein.Cilj ovog rada bio je utvrditi utjecaj dodatka 0,5-2 U/g mikrobne transglutaminaze (mTG) na pH i viskozitet jogurta tijekom fermentacije, te promjenu strukture proteina, čvrstoću gruša i senzorska svojstva malomasnog jogurta s dodatkom voća. Komercijalna mTG je dodana u nekoliko koncentracija (0,5-2,0 U/g) u mlijeko (1.5 % mliječne masti) zajedno sa DVS kulturom. Istraživanjem je utvrđeno kako dodatak enzima nije imao utjecaj na razvoj pH i viskozitet jogurta tijekom fermentacije, ali je dodatak mTG utjecao na zadržavanje sirutke (do 38 %), dok je čvrstoća gruša bila veća za 44 %

Uht treatment of liquid egg yolk

Egg and its product are easily perishable items because of their high moisture content, although they have a very high amount of nutrients, especially protein. Many efforts have been channelled to increase the shelf-life of these products but heat treatment according to literature is the most promising although egg and its products are heat-sensitive. Thus, a very low temperature is needed or a high temperature for a very short time. Ultra-Heat Treatment (UHT) is one of the known technologies that we used for heat-sensitive products. The aim of the study was to investigate the effect of UHT treatment (approximately 67 °C for 190 seconds) on Liquid Egg Yolk (LEY) and Liquid Egg Yolk with additive (LEYA). During twenty-one days, the pH and colour were measured every seven days for all the samples. Emulsion stability was also studied by the methods of heat stability for mayonnaise. pH and colour measurements were used assess the quality of liquid egg yolks after 21 days of storage. From the results, raw LEY had the shortest shelf life and gave off a foul smell after 14 days of storage with significant colour changes. Addition of citric acid as an additive however improved the shelf life of the LEY with a relatively low pH. UHT treated LEY also showed improved shelf life of the LEY with a relatively constant pH from day 14 until the end of the experiment (day 21). UHT treatment of LEY with addition of addition of citric acid as an additive may help optimise the shelf life of the product

Destruction of Salmonella enteritidis in liquid egg white as the function of treatment temperature and heating rate

In our study we investigated the effect of heat treatment temperature and heating rate on heat resistance of Salmonella enteritidis. The samples were heated from 4 °C to 48,96-56,04 °C by a heating rate 0,76-9,24 °C·min-1 and the changes of the colony counts were determined at given time by plating to XLD agar with overlay. We used Central Composite Rotatable Design (CCRD) in our experiment and Response Surface Method (RSM) was used to evaluate the data. Our results pointed out that beside the temperature of heat treatment the heating rate have also an effect on the heat destruction of Salmonella enteritidis. In case of heating rate 9,24 °C·min-1 the D52,5-value was 2.32 min, however at heating rate 0,76 °C·min-1 the D52,5-value was 19.23 min. In our measurements the samples were heated with linear heating rate in laboratory scale. so further studies are necessary to describe the heat resistance changes of Salmonella enteritidis under parameters which model the industrial heating circumstances