THE DISTRIBUTION OF TRYPSIN AND CHYMOTRYPSIN INHIBITORS IN POTATO TUBERS

Potato peel contains trypsin and chymotrypsin inhibitors at levels similar to those in other parts of the tuber. The levels of these inhibitors differ among potato cultivars (P < 0.01). The proteolytic enzyme inhibitors may have to be deactiviated before peel waste can be efficiently utilized by pigs. Key words: Potato steam peel, trypsin, chymotrypsin, proteolytic enzyme inhibitor

DIGESTIBILITY AND ACCEPTABILITY OF POTATO STEAM PEEL BY PIGS

Potato steam peel is a by-product of the production of frozen french fry potatoes. As produced, it typically has 14% dry matter with 15% crude protein and 6% ash (dry matter basis) and a pH of 5.8. The starch is partially denatured and there is no proteolytic enzyme inhibitor activity. The feeding value of steam peel for pigs was evaluated through chemical analyses, a digestibility trial and a feeding trial. Its digestibility (%) by pigs was found to be dry matter 81.1 ± 2.8, crude protein 61.3 ± 3.7, organic matter 82.4 ± 3.0 and energy 76.8 ± 6.0. In the feeding trial carried out on a commercial hog finishing farm, feed consumption was markedly reduced when the steam peel was included at over 30% of the ration dry matter at the start of the trial. The inclusion of steam peel at 15, 20 or 25% of the ration dry matter reduced the average daily gain and feed efficiency (P < 0.05). However, it was concluded that potato steam peel can be used at up to 25% of the diet for growing fattening pigs with little detrimental effect on the level of animal performance. Key words: Potato, steam peel, pigs

In-vitro stability of human alpha-fetoprotein.

We assessed the stability of alpha-fetoprotein (AFP) in clinical specimens in the presence and absence of serum and albumin, at different temperatures and concentrations. We find it depends on both AFP concentration and incubation temperature. Dilution of most specimens with either phosphate buffer or phosphate-buffered saline or by immunoelectrodiffusion resulted in some loss of AFP. Attempts to stabilize AFP during either sample dilution or incubation by use of albumin in concentrations up to 1 g/L did not protect it from inactivation unless normal human serum was also included. Frozen AFP solutions were less stable than solutions stored at 4 degrees C. AFP was most stable when lyophilized and stored desiccated. The AFP-inactivation curves were usually nonlinear. Apparently both polymerization and degradation occur simultaneously as AFP loses its activity. Proteolytic enzyme inhibitor and sulfhydryl reagent not only failed to protect it from inactivation, they appeared to speed it.