Effects of Sinusoidal Vibrations on Quality Indices of Shell Eggs

In order to assess the effects of the sinusoidal vibrations on indices that characterise the internal quality, five samples of 30 eggs were stressed for 5 h with a constant acceleration of 0·5 g (root mean square value, r.m.s.) at frequency linearly increasing with the time in the 5–20, 20–35, 35–50, 50–65 and 65–80 Hz ranges (one range for each sample). Vibration tests were carried out by means of an electro-dynamical shaker provided by an alveolate surface made of concrete mounted on the vibrating table. After a period of storage, Haugh unit, vitelline membrane strength, yolk index and air cell height were determined. Results showed a significant decrease (23%) of the Haugh unit in the 50–65 Hz range respect the non-vibrated eggs; a low difference in the vitelline membrane strength and the air cell height was observed between the samples vibrated at low and high frequency. In order to determine with more accuracy the frequency with the highest influence on the Haugh unit, the vitelline membrane strength and the air cell height, samples of eggs were also stressed in the 5–10, 10–15, 15–20, 50–55, 55–60 and 60–65 Hz ranges. For the Haugh unit, a very high influence of the vibration was observed in the 50–55 and 60–65 Hz range (44% of maximum decrease with respect to the non-vibrated sample). The vitelline membrane strength in the 50–55 Hz range resulted significantly lower (11%) than in the 15–20 Hz range but the highest difference (13%) was found between the 60–65 and 50–55 Hz range. The highest differences in the air cell (12%) was observed between the 10–15 and 60–65 Hz range.