Book Contents
Introduction
- Preface
- Formation of the egg
- Optimum vitamin nutrition of laying hens
- The nutritive value of the egg
- Internal and external egg quality
- The importance of calcium and vitamin D3
- Quality control
- Changes in quality as the egg ages
- Egg quality in the retail store and in the home
- Consumer perceptions of egg quality
- Egg defects
- Nutrient check list
- Glossary
Shell Defects
- Gross cracks
- Hairline cracks
- Star cracks
- Thin-shelled eggs and shell-less eggs
- Sandpaper or rough shells
- Misshapen eggs
- Flat-sided eggs
- Body-checked eggs
- Pimples
- Pinholes
- Mottled or glassy shells
- Cage marks
- Stained eggs
- Fly marks
- Fungus or mildew on shells
Internal Defects
- Blood spots
- Meat spots
- Watery whites
- Pale yolks
- Mottled yolks and discoloured yolks
- Discoloured whites
- Rotten eggs
- Roundworms in eggs
- Off odours and flavours
Watery whites
Description
When an egg broken onto a flat surface has a watery, spread-out white, this usuallyindicates that the egg is stale. The height of the white and the weight of the egg are usedto calculate a value in Haugh units on a scale of 0 to 110; the lower the value, the stalerthe egg.
A minimum Haugh unit measurement of 60 is desirable for whole eggs sold to thedomestic consumer. Most eggs leaving the farm should average between 75 and 85Haugh units.
Incidence
The development of watery whites is chiefly due to the increasing age of the egg. The rateof development is increased by high storage temperature and low humidity (see figure 4).As birds age, the Haugh unit value of their eggs decreases by about 1.5 to 2 units permonth of lay (see figure 3). Some birds consistently produce eggs with watery whites(Haugh units less than 30) later in lay.
| Cause | Control |
|---|---|
| Old eggs | Minimise storage time on the farm by: • increasing the number of pick-ups per week forgrading or delivery to retail outlets.• collecting and packing eggs laid on pick-up days sothat they are consigned on that day. • grading eggs while they are fresh when packing themon the farm. |
| High storage temperature and lowhumidity | Reduce shed temperatures in summer. Collect eggs atleast twice daily and even more frequently in summer.Store eggs in a coolroom at a temperature of lessthan 20 ºC e.g. 12 to 15 ºC (requirements may vary indifferent countries) as soon as possible after collection.If a humidifi er is not fitted to the cooling unit, place anopen tray of water in the coolroom to ensure humidityis kept at 70 to 80%.Oil eggs soon after collection. Use only an oil suchas Caltex Pharma White 15 BP/USP approved for thispurpose by the relevant authorities. |
| Ageing of bird | Keep flock age as low as economically possible. |
| Diseases, e.g. infectious bronchitis andegg drop syndrome | Follow effective vaccination programmes. |
| Fungal toxins | Do not allow feed bins or feed lines to becomecontaminated by stale, wet or mouldy feed. |
| Ammonia | Control ventilation to keep ammonia levels low. |
| Rough handling | Examine egg handling procedures and equipment, andmodify to minimise bumping or shaking of eggs. |
| Incorrect packing | Pack eggs on filler flats with the air cell upwards. |
| Birds which persisently lay eggs withwatery whites | Culling these birds is not practicable, as they are hardto identify. The only way of handling the problem is toremove the eggs at grading (like all eggs with waterywhites, they are distinguished by an enlarged air cell). |
| Strain of bird | Be aware that some strains produce eggs with a highaverage Haugh unit rating. |
Figure 4: Effects of egg age and storage temperature on egg Haugh unit value
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COPYRIGHT NOTICE: OPTIMUM EGG QUALITY - A PRACTICAL APPROACH
© The State of Queensland, Australia (through its Department of Primary Industries and Fisheries) and DSM Nutritional Products Ltd., 2007. No part of this publication may be reproduced, copied or transmitted save with prior written permission of Director, Intellectual Property Commercialisation Unit, Department of Primary Industries and Fisheries, GPO Box 46 Brisbane, Queensland, Australia 4001, and DSM Nutritional Products Ltd.
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