The validity of l-lactic, succinic and d-3-hydroxybutyric acids as indicators of egg freshness and presence of incubator rejects were determined in 120 homogenized farm eggs using the Boehringer-Mannheim enzymic technique and subsequent NIR spectroscopy. Tests were carried out on fresh eggs and eggs held at 4 or 20°C to simulate commercial conditions. The 3 acids proved highly suited as a measure of the eggs' freshness. l-lactic acid content increased considerably during storage, but did not exceed 500 mg/kg DM after 27 days at ambient temp., indicating that the Italian legal limit of 1000 mg/kg DM is set too high. Succinic and d-3-hydroxybutyric acid levels did not rise, but the former gave an indication of the hygienic quality of the eggs, and the latter revealed the presence of incubator egg rejects. NIR spectroscopy proved extremely valuable as a quality control technique, allowing accurate evaluation of the concn. of the 3 indicator acids, as well as providing a means of differentiating between different egg batches.
