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Progress in Agricultural Engineering Sciences
Authors: Karina Ilona Hidas, Csaba Németh, Anna Visy, Adrienn Tóth, László Ferenc Friedrich, and Ildikó Csilla Nyulas-Zeke

Abstract

Eggs are commonly used in the food industry because of their excellent nutrient value and also for their coagulating, foaming, emulsifying, colouring and flavouring properties. Manufacturers substitute shell eggs with processed egg products, such as liquid whole egg, liquid egg yolk or albumin. They have a shelf life of a few weeks, but freezing can increase it to 1 year. However, freezing causes gelation in case of egg yolk. This process is highly dependent on the conditions of freezing and thawing.

In our study, raw liquid egg yolk was frozen and stored for 14 days at −18 °C. On days 1, 7 and 14 samples were thawed by two different methods. Denaturation temperature and enthalpy were investigated by differential scanning calorimetry. Besides, rheological properties were examined at 20 °C, Herschel–Bulkley model was fitted to flow curves of the examined samples. The dry matter content was also recorded during the experiment. Two-way ANOVA was used to analyse data.

The results of the study showed that method of thawing had no significant effect on calorimetric and rheological properties and dry matter content. In contrast, freezing and frozen storage had a significant effect on denaturation enthalpy and rheological properties.

Open access
Progress in Agricultural Engineering Sciences
Authors: Anna Visy, Karina Ilona Hidas, József Surányi, Gábor Jónás, and László Friedrich

Abstract

Excessive consumption of salt causes many diseases, including high blood pressure and cardiovascular system disease. In most countries, salt intake is above the WHO guideline daily intake. In Hungary, the average salt intake is more than double the recommended value. Based on these, significant changes are needed in food technology and recipes. To avoid excessive salt intake Hungary has joined the European Union's community program for salt reduction.

The aim of this study was to compare the salt content in different areas of Mangalitsa ham during the dry salting, and compare the average salt content with the regulations of the Codex Alimentarius Hungaricus. The ham was dry salted with 10% by weight of the meat and placed in a controlled atmosphere storage room. The curing took 21 days. The NaCl uptake was measured with Mohr method. The ham was cut at 3 points Cushion (C), Fore Cushion (FC) and Butt End (BE). The salt content of BE was generally higher than the other two areas (C, FC). The differences can be explained by the difference in the thickness of the pieces of meat and fat. The average salt content of the different areas did not exceed the threshold limit in the Codex Alimentarius Hungaricus. At the beginning of the experiment, the salt content of each meat layer was very different, the absorbed salt was concentrated in the surface layer. Over time, as the ham lost a lot of water and due to the lack of outer salt, a significant increase in salt content began in the meat centrum. By day 80, the salt content of the meat centrum exceeded the salt content of both the fat and the surface layer.

Open access
Progress in Agricultural Engineering Sciences
Authors: Karina Ilona Hidas, Csaba Németh, Lien Phuong Le Nguyen, Anna Visy, Adrienn Tóth, László Friedrich, and Ildikó Csilla Nyulas-Zeke

Abstract

Freezing can enhance the storage time of liquid egg products, but egg yolk undergoes an irreversible textural and structural change when it is cooled to –6 °C. In this study, the effects of different salt concentrations on the physical properties of frozen-thawed egg yolk were investigated.

The pasteurised liquid egg yolk (LEY) was treated with 4, 5, and 6% of NaCl before freezing and it was stored at –18 °C for 4 weeks. The colour, pH, and rheological characteristics (firmness, consistency, cohesiveness, and index of viscosity) of yolk samples were evaluated before and after freezing.

Salt treatment resulted in preventing gelation, with decreasing firmness, consistency and viscosity compared to control samples. The pH of all yolk samples increased during frozen storage. The lightness value decreased in treated samples and increased in the control sample after freezing.

The results indicated that the applied salt concentrations could inhibit protein aggregation of LEY induced by freezing during the storage period. At least 5% salt concentration could reduce effectively the changes in rheological properties.

Open access
Progress in Agricultural Engineering Sciences
Authors: Anna Visy, Karina Ilona Hidas, Annamária Barkó, Lien Le Phuong Nguyen, László Friedrich, and Gábor Jónás

Abstract

Consuming enough protein is a very important part of a balanced and healthy diet. Complete proteins are those in which all essential amino acids are present. In meat products, like hams, many different reactions occur during ageing and storage. For example, the production of free amino acids or the production of biogenic amines is formed by decarboxylation. In this study, the presence of these amino acids and biogenic amines, as well as the quality properties of cured hams during curing and ageing, were investigated.

The meat samples were immersed into 100 g L−1 NaCl brine. The curing took 20 days, followed by smoking and ageing for 35 days (12 °C, 75% RH). The wet-cured ham samples were analysed for changes in NaCl concentration (at 3 parts: surface, core, bottom layer). Moreover, color, water activity, denaturation temperature and enthalpy (Differential Scanning Calorimetry), free amino acids (FAAs) and biogenic amines (BAs) were also evaluated.

Open access
Progress in Agricultural Engineering Sciences
Authors: Emna Ayari, Csaba Németh, Karina Ilona Hidas, Adrienn Tóth, Dávid Láng, and László Friedrich

Abstract

Starting from mechanical revolution, each day new methods and new equipment have emerged. Today, the Ultra Heat Treatment (UHT) is one of the important technologies that permits to the industry to reduce processing time while maintaining the same quality of the products. Egg and egg products are known as heat-sensitive products, so the UHT enables us to preserve their qualities after a heat treatment.

Our aim is to study the effect of UHT treatment (approximately 67 °C for 190 s) on the Liquid Egg Yolk (LEY). For twenty-one days, the color and the apparent viscosity were measured every seven days, we also studied the damage of protein using DSC (Differential Scanning Calorimetry).

Comparing the two graphs of DSC, the denaturation of protein is distinct. The endothermic peak decreased. This could be seen also on the rheological curves. The apparent viscosity is diminished from 231 mPa.s on the 1st day of storage to 224 mPa.s on 21st day. However, the treated LEY could be stored for longer period than the raw LEY.

Open access