Piiloitävyyteen liittyvän entsyymitoiminnan vaikutuksista ohran laatuominaisuuksiin

Authors

• Ari Orko Alkon Keskuslaboratorio ja Teknillinen Korkeakoulu, Helsinki
• A. J. A. Keränen Alkon Keskuslaboratorio ja Teknillinen Korkeakoulu, Helsinki
• Jyry Tikka Alkon Keskuslaboratorio ja Teknillinen Korkeakoulu, Helsinki

DOI: https://doi.org/10.23986/afsci.71644

Abstract

Samples of two different kinds of barley of the 1962 crop were compared with each other, a perfect high-quality Proctor barley and a poor-quality barley mixture (Pirkka and Balder) harvested under very damp conditions. The two samples were germinated in the laboratory either in the normal way or by double germination in which case all possible rootlets were removed. During normal germination the activity of the amylolytic enzymes increased more markedly in the high-quality barley than in the poor barley mixture. Already before germination the α-amylase activity of the latter was about 3 diastatic units; in the high-quality barley the same activity appeared only after two days’ germination. The original value of the diastatic activity of the high-quality barley was about 20 % less than that of the poor-quality barley, but the diastatic activity of the former increased more sharply and was after 4 days of the same order of magnitude as in the poor-quality mixture. A splitting of the starch caused by the amylolytic enzymes was observed in amylographic investigations after soaking for about 12 h. Paper chromatography revealed that an ungerminated barley mixture of the poor-quality barley contained more maltose than the high-quality barley. The amount of maltose increased markedly after 3 days’ and the amount of glucose after 4 days’ germination. In the high-quality, ungerminated barley the proteolytic activity was barely half of that found in the poor-quality barley, and during the germination the increase of the activity in both samples was about the same. The content of free amino acids increased during germination in conformity with the increased proteolytic activity. At the beginning of germination, during the soaking, the activities of the amylolytic and proteolytic enzymes decreased in both samples of barley; this was confirmed by amylographic determinations. In experiments on double germination it was found that the diastatic activity in the poor-quality barley increased more abruptly during the second germination, and during both germinations the increased activity was more pronounced than in the high-quality barley. The shorter the germination time in the first stage, the sharper the increase of the activity during the second germination. The activities of the amylolytic enzymes were in both samples about twice as high after 3 days in the second germination as after the first germination. The proteolytic activity in the high-quality barley increased during the second germination particularly rapidly compared with that in the poor-quality barley mixture. It has thus been clearly demonstrated that the properties of barley that externally appears to be in perfect condition, may have been changed by enzymatic activity induced by previous exposure to unfavourable moisture conditions.