米飯於貯藏過程中之老化作用及其抑制方法之研究

Study on the Retrogradation of Cooked Rice during Storage and Methods for Retarding its Development

謝伯東(Po-Tung Hsieh) ； 蔡錫舜(Shi-Sun Tsai) ； 戴芬芝(Fen-Jy Tai)

《化學》 69年2期 (1980/06) Pp. 48-56

https://doi.org/10.6623/chem.1980010

摘要

本研究先探討蓬萊米、在來米及糯米品種間以及新米與舊米之間其炊煮成米飯之性質之差異，再探討以各種米炊煮所得之米飯於貯藏過程中，其澱粉質老化作用(Retrogradation)速率之差異，並比較以油炒或添加食品用之乳化劑或保水劑對於米飯之老化作用之抑制效果，以期所得之結果可供研製食米之加工品尤其是即食米飯罐頭或中式炒飯罐頭等加工產品時之參考。在本研究中爲促進米飯澱粉老化作用之進行以便觀察比較，貯藏溫度定爲5°C，米飯澱粉之老化速率以Glucoamylase對其水解率之變化而測定之。所得之結果可綜合如次：1.糯米與蓬萊米均較在來米易於煮熟糊化，其米飯之老化速率亦較在來米飯爲緩，故蓬萊米與糯米似較適合即食米飯罐頭之加工。2.各種米均顯示同一傾向，即舊米比新米較難糊化，且於貯藏過程中，其米飯之老化速率亦較新米為高。3.由於澱粉質全由Amylopectin所組成之糯米飯於貯藏過程中顯示有老化作用之進行，此項結果可供作各種米飯澱粉中之Amylopectin與Amylose均可參與老化作用之佐證。4.單以食用油脂調製成之炒飯在貯藏過程中之老化速率反較白米飯爲高，此結果顯示單以食用油脂炒飯對於米飯澱粉之老化作用之抑制效果遠較因炒飯過程中部分水分之逸失而促進米飯之老化作用之效果爲小，因此單以食用油脂炒飯對於米飯之老化作用似無抑制效果。5.在炒煮米飯時，如先添加少量(0.05%)食品用乳化劑如Glyceryl monostearate或Sugar ester S-1670等，則對白米飯之老化作用有顯著抑制效果。添加保水劑如Na-alginate對於白米飯之老化作用亦有抑制效果，但對炒飯之老化作用之抑制，其效果較前述之兩種乳化劑稍遜。6.無論白米飯或炒飯於5°C貯藏，其澱粉質之老化度雖已達20%，但經蒸煮10分鐘後，幾能囘復其貯藏前之糊化度。由以上之結果推知，於製備中式炒飯罐頭時，如先於炊煮米飯時添加少量食品用乳化劑及(或)保水劑，再將所得之米飯以食用油脂炒製，則可獲得適口性良好且較耐貯藏之產品。

並列摘要

Attempts have been made to obtain informations which might be useful to the production of the canned cooked rice. The polished rices of three varieties, i.e., glutinous japonica, and indica rices, were cooked and, for accelerating the retrogradation process, stored at 5°C. The changes of the degree of gelatinization and the rate of retrogradation of the cooked rice during storage were determined with its susceptibility to attack by glucoamylase. The results showed that the japonica and glutinous rices were preferred for manufacturing the canned cooked rice, because of their easier gelatinization and lower rate in retrogradation. However, being stored for one year before cooking, the polished rices of the tested varieties showed a tendency to increase their resistance against gelatinization upon cooking. After being cooked, the rate of retrogradation of the cooked stored-rices were also increased. As the starch of cooked glutinous rice, which is composed of amylopectin only, retrograded during storage, it was thus considered that, not only amylose but amylopectin of rice starches also involved in the process of retrogradation. For retarding the development of the retrogradation of cooked rice during storage, some treatments were tried. Frying the cooked rice with edible oil alone to 45-55% moisture content showed likely ineffective. In some cases, the rate of retrogradation of the cooked rice were enhanced by the frying treatment, probably owing to the loss of a portion of its moisture content during frying. By adding a small amount (0.05%) of surfactant, glyceryl monostearate, or water-retention agent, sodium alginate, to rice upon cooking showed the retarding effect significantly. It might be concluded that, for manufacturing the canned Chinese fried-rice with better texture and longer shelf-life, the process involved cooking the rice with added surfactant and/or water-retention agent and followed by frying the cooked rice with edible oil to 45-55% moisture content seemed to be suitable.