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A model system of egg albumin and herring oil was studied during storage at 21 "C and -20 "C. Chemical changes in the oil and protein were monitored by determinations of ether-extractable lipid, iodine value, peroxide value, thiobarbituric acid value, ultraviolet absorption of the oil, in vitro digestibility and available lysine. The model system showed greater changes during storage with respect to both protein and oil than did either the albumin or the oil stored separately. Similar determinations were made on a freeze-dried herring meal stored at 21 "C in nitrogen and on a sample of the presscake (from which the meal was made) stored at -20 "C.Available lysine level was a more sensitive criterion of protein alteration during storage than was pepsin-digestibility. The absorption at 233 nm of extractable lipid from both the model and the natural systems was associated with the loss in lysine availability during the storage period. Ultraviolet absorbance of the lipid more closely reflected the rate at which lysine availability declined than did TBA or peroxide values.

Herring meals prepared with and without the addition of 0.025 % of 1,Zdihydro-6-ethoxy-2,2,4-trimethylquinoline (EQ) were stored for ten months at -20 "C and 21 "C. Storage changes in the biologically determined energy and protein values of the meals were monitored and related to changes in the chemical characteristics of the meal. Antioxidant treatment stabilised the meal lipid against oxidative changes resulting in loss of solubility, decline in iodine value and formation of peroxides and malonaldehyde. The effect of storage temperature on the course of oxidation depended upon whether the meal was treated with EQ. Lipid in meals without EQ tended to show greater change early in the storage period at -20 "C. Antioxidant-treated meals showed protection of the protein against changes leading to reduced digestibility and lysine availability. Either antioxidant treatment or storage at -20 "C protected the biological availability of the energy-supplying nutrients present in the meal,

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