Journal of Food Physics 1994, Supplement 2.

Bajúsz-Kabók, K. (et al.): Investigation of the irradiation of whole egg powder

3 INVESTIGATION OF THE IRRADLATION OF WHOLE EGG POWDER K. Bajúsz-Kabók, M. Halász-Fekete, P. Záhonyi-Rács and J. Kispéter College of Food Industry, Mars tér 7, H-6724 Szeged, Hungary Kevwords: colour measurement, egg powder, gamma irradiation, rheology INTRODUCTION Ionizing gamma-radiation has been recently applied in several countries to improve the microbiological and hygienic quality and the preservation of food-industrial row­­materials and mtermediates (spices, vegetables and protein-containing ingredients) [1]. This requires a continuous process control and the qualitative and quantitative detection of the degree of irradiation immediately after the radiation treatment and later during storage. Investigations have proved that physical, Chemical and biological methods can be equally suitable fór the detection of radiation-induced changes. Of these methods the physical ones are very promising [2]. In 1985 Mohr and Wichmann suggested the application of viscosity measurement fór the detection of radiation treatment [3], The changes of reological characteristics of dried vegetables and spices have been discussed in many publications [4,5]. We performed rheological measurements to investigate - the applicability of the investigation of flow characteristics fór the detection of irradi­­ation of egg powder, - the changes occuring during storage. In the case of numerous materials a colour change occurs as a result of the radiation treatment. Therefore we investigated the existence of a correlation between the colour change and absorbed dose fór egg powder. MATERIALS AND METHODS Whole egg powder with a moisture-content of max. 7.5% (produced at the Dairy Plánt in Zalaegerszeg, Hungary) was used in our investigations. The radiation treatment was performed in a continuous “Co gamma radiation source. The absorbed doses were 2, 5 and 10 kGy. Aqeous suspensions of 40 % were produced with an intensive stirring (1 min.) fór the rheological investigations. The foamed sampies were stored in a refrigerator at 10 °C fór 24 hours before measurement. Rheological invesigations were performed with a Rheotest II rotational viscosimeter at 10 ±0.2 °C. The measurement of colour properties of irradiated and control (unirradieted) sampies was carried out with a Hunterlab Spectrocolorimeter Model Labscan II 0/45. The instrument was operated in reflectance mode with a light trap at the reflectance port of 2,5 cm diameter. Powder sampies and aqueous suspensions were placed in an optical clear cylindrical Container (inside diameter and height were 3 and 2 cm, respectively). The bottom of the sampies was viewed at a CIE C 2° Standard Illuminant. The CIE L”, a’ and b‘ readings were converted to hue angle (h*), chroma index (C*) and totál colour difference (AE") according to the formulas given by Hunter [6],

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