Nutritive value of meat meals II. —influence of raw materials and processing on protein quality

Commercial meat meals have shown low net protein utilisation values with rats of about 32, which is only 40% of the corresponding value for freeze‐dried meat or gut. Biological assays for methionine and tryptophan, based on the weight gains of chicks, have shown a similar inferiority of meat meals despite 81–87% digestibility of their N. It is concluded that the lysine, methionine and tryptophan of the meat meals are approximately 80% available and that dilution of muscle protein with tendon and ossein in the raw material is at least as important as processing damage in reducing the quality of the products. It is argued that previous estimates of only 30% availability of methionine in meat meals are erroneous. Further problems in the use of values for fluorodinitrobenzene‐available lysine and Streptococcus zymogenes ‐ayailable trytophan are discussed.