564. The properties of New Zealand butters and butterfats: IV. Refractive index and density of the butterfat

Abstract

1. The refractive index and density of butterfats were determined for butters forwarded by twenty factories at 8-week intervals over a period of 3 years. The refractive index (n⁴⁰) ranged from 1·4535 to 1·4571, with mean weighted value of 1·45492. The density (D60) ranged from 0·8885 to 0·8916, with mean weighted value of 0·89045.2. Minimum refractive index results were found in the summer butterfats and maximum results in the winter butterfats, i.e. at opposite seasons to the occurrence of the minimum and maximum in Northern European butterfats. Maximum density results were found in late spring butterfats and minimum results in autumn butterfats.3. The mean monthly results for refractive index and for density of North Island and South Island butterfats showed an appreciable divergence only during the winter months.4. The correlations between refractive index and iodine value, between density and saponification value, and between density and Reichert value, on 140 butterfats sampled over 1 year were all highly significant.