Carotene and protein contents of alfalfa as influenced by variety and certain environmental factors

SAMPLING METHODS AND DRYING CONDITIONS OF ALFALFA are here critically discussed in relation to carotene and protein contents. The preferred sample for variety comparisons is a definite number of culms per plot, with the effect of sample variation minimized by use of replicates.

Hot-water blanching results in loss of dry weight and an apparent increase in carotene content. Steam blanching is therefore preferred. Effective blanching is also possible by placing small samples in a large oven at 130° C.

Drying at 130° C resulted in about 5 per cent more carotene destruction than was obtained by drying in vacuo at 65° C. No significant differences were found in air drying at 65°, 100°, and 130° C; but this probably would not be true with other drying conditions or use of functionally different equipment.

Many varieties were compared. Six standard varieties were studied during six cuttings. No variety was consistently higher than others in either carotene or protein content. Other comparisons between more varieties and strains, but involving fewer cuttings, confirm this similarity. Any differences found could be attributed to differences in leafiness.

Physiological factors are important. As alfalfa matures, carotene content is maximum in the pre-bud stage, decreases rapidly from then until about the 1/10 bloom stage, and less rapidly thereafter. Total dry weight and total carotene per culm increase at a fairly uniform rate until after seed pods are formed and then decrease. The per cent oven dry weight increases and the protein content decreases with increasing maturity. The carotene content of alfalfa cut at the 1/10 bloom stage increased 23 per cent from June to October. Some variation occurs during the day and from day to day.

These data indicate the necessity of sampling at the same stage of maturity for variety comparisons. Seasonal trends are very important for comparisons of carotene contents but not for protein contents.

July, 1953