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We compare visual evaluation of yolk colour estimated by the usual method applying La Roche scale with spectrophotometric determination of β-carotene by AOAC method, and by new rapid analyser iCheckTM Egg photometer (BioAnalyt). The eggs under consideration were purchased on a current Czech market. The eggs originated from various countries and various types of breeding including some specialities. The yolk colour varied between the values of 4-13 of La Roche scale. The carotenoid content expressed as β-carotene measured by AOAC method varied between 11-87 mg/kg. The carotenoid content expressed as β-carotene measured with the analyser iCheckTM Egg photometer was lower and varied between 7.5-68.5 mg/kg. The correlation between the colour hue measured visually and the carotenoid content was not proved. Slovak eggs from cages which contained 28.3 mg carotenoids in 1 kg of yolk had the darkest yolks (value 13), Czech bio eggs which contained 20.2 mg carotenoids in 1 kg of yolk had the palest yolks (value 6). The highest content of carotenoids was found in eggs from home hen breeding (72.5 mg carotenoids in 1 kg of yolk) whose colour hue had the value of 10.

The work was targeted on the study of egg white foam forming, including the influence of pH, aluminium ions, xanthan, maltodextrin, and phosphates on the whipping and stability of egg white foams. The whipping was studied with non pasteurised and pasteurised egg white using the blender with planet motion. Both types of egg white formed good foam in the acid area (pH below 4.5) and at neutral pH. Aluminium ions had a positive effect on the foam volume and stability, especially with the non pasteurised egg white. The addition of maltodextrin or saccharose decreased the foam volume but increased the foam stability. The addition of natrium pyrophosphate or natrium hexametaphosphate had a positive effect on the volume, density, and stability of foam. Foams with hexametaphosphate were applied into confectionary products.

During a 15-month period, samples of commercially pasteurised liquid whole egg (LWE) were tested for the presence of spoilage microflora. The total bacterial counts were 2.2 ± 0.6 log CFU/g and total lactic acid bacteria (LAB) counts were 1.9 ± 0.6 log CFU/g. Enterobacteriaceae were detected in 2 samples. Out of the tested samples, 45 LAB were isolated and identified, with 30 strains identified as Enterococcus faecium, 12 as Enterococcus faecalis, and 3 as Lactobacillus paracasei subsp. paracasei. All strains, except 6 strains of E. faecium, possessed lipolytic activity. All the E. faecalis strains and one strain of E. faecium showed a high proteolytic activity, while moderate proteolytic activity was shown by 3 lactobacilli strains. Minimum inhibitory concentration (MIC) of nisin and Micocin X was measured against groups of isolated strains, and ranged from 10.4 µg/ml to 41.7 µg/ml for nisin and from 0.2 mg/ml to 1.6 mg/ml for Micocin X. The LWEs supplemented with 6.25 mg/l of nisin or with 500 mg/ml of Micocin X were pasteurised at 65°C for 2.5 minutes. The shelf life of LWE with the addition of nisin or Micocin X stored under refrigerator conditions was extended by a minimum of 5 weeks.

Many foods are prepared using egg white, most of them being based on the foaming properties of egg white which are due to albumen proteins ability to encapsulate and retain air. Therefore, many scientists aim to find new methods to improve the volume and the stability of egg white foam. This paper is a review of various factors affecting the foaming ability of egg white.