Browsing by Subject "production method"

The breaking of albumen during the mechanical peeling process of cooked eggs causes food waste. The aim of this thesis was to study the effect of housing system, storage temperature and age of hens on the albumen quality and gelation. In addition, the objective was to compare the properties of eggs collected from different quality batches of industrially cooked eggs. Uncooked eggs were collected from different batches before cooking, and the air cell size, albumen pH and dry matter content were measured. Haugh unit score describing the quality of egg was also measured. The same measurements were also made to eggs produced with two different housing systems, to eggs stored at 4°C and 14°C and to eggs from three different age groups of layers once a week during the total storage time of four weeks. The egg size was measured, and shape index, volume and surface area of eggs were calculated. Egg shell thickness was measured, and pore count was determined with stereomicroscope after dyeing the shells with methylene blue. The protein composition was examined with SDS-PAGE. A microwell plate analysis was tested in order to determine the S-ovalbumin content in albumen. Pieces of coagulated egg white were analysed with texture profile analysis and fracture study. The age of the hen had an impact on egg quality. Coagulated egg white samples made of eggs from old hens fractured more easily than samples made of eggs from young hens in all timepoints. The Haugh unit scores were lower in eggs from old hens and dry matter contents increased faster in eggs from young hens compared to the other age groups. Differences between production methods were also noted, and albumen from organic eggs fractured easier than albumen from barn eggs. Haugh unit scores and dry matter contents were lower and pH-values greater in organic eggs compared to barn eggs. Lysotzyme contents based on SDS-PAGE were lower in organic eggs compared to barn eggs. Shells were thinner and pore counts greater in organic eggs compared to barn eggs. Storage temperature had an impact on uncooked egg quality, and eggs stored at 14 °C had lower Haugh unit score and greater pH and dry matter content than eggs stored at 4°C. Textural properties of eggs stored at 14°C were better only in the first two timepoints. Eggs collected from low quality batches of industrially cooked eggs were laid by old layers and had albumen pH more basic and dry matter content and Haugh unit score lower than eggs collected from batches with good quality. Measuring these properties could be helpful when choosing the eggs for the cooking process, because great dry matter content had an positive impact on textural properties of cooked albumen, but the decrease in Haugh unit score over time possible had an negative impact on textural properties.