岩手大学博士 (農学)doctoral thesi

93275

小舘, 琢磨

Japanese

Iwate University Repository

博士論文要約（Summary）                          平成３０年１０月入学                        連合農学研究科 生物資源科学専攻                        氏  名  小舘 琢磨             タイトル タンパク質含有率を制御した低アミロース米の加工特性及び理化学特性に関する研究 （Research on processing and physicochemical properties of Low amylose content rice with controlled protein content） 第 1 章「緒言」 近年，中食需要の増加とともにおにぎり・弁当向けや冷凍米飯需要が拡大している．それらに対応するには，粘りが強く冷めても硬くなりにくい低アミロース米が最適と考えられるが，栽培面では低収量，加工製造面では米飯成形における 「べたつき」による作業効率の低下が課題として挙げられる．そこで本論文では，以上の課題解決を図るため，岩手県育成の低アミロース水稲品種 「きらほ」を用い，異なる窒素施肥条件が収量性及び米飯物性を含めた食味に与える影響について検討した．更に本論文では，高タンパク質含有率の低アミロース米「きらほ」を用いて，水浸裂傷粒発生率及び吸水特性などの業務用米適性を明らかにするとともに，米飯の低温保存による物性の変化を解明し，生産者と実需者双方のニーズに対応する技術開発に向けた知見を得ることを目的とした．  第 2 章「窒素施肥条件の違いが低アミロース水稲品種 “きらほ” の収量および米飯物性を含めた食味に与える影響」 本章は，異なる窒素施肥条件が収量性および物性を含めた食味に与える影響について検討した．その結果，基肥窒素量が 6g/㎡および 12g/㎡の両試験区とも，幼穂形成期および穂揃期の 2 回の追肥の合計窒素量が 6g/㎡および 12g/㎡の区では，無追肥区と比べ，精玄米重が有意に増加した．また，追肥窒素量の増量により，白米タンパク質含有率は有意に高くなる傾向がみられ，白米アミロース含有率は有意に減少する傾向がみられるものの，差は小さかった．米飯成形時の「べたつき」に関連する炊飯米の物理性についてみると，白米タンパク質含有率は米飯粒表層の硬さとの間に正の相関関係が，また，白米タンパク質含有率と表層の付着性との間に負の相関関係がみられたことから，追肥窒素量の増量により，米飯成形時の「べたつき」低減が推察された．一方で，追肥窒素量の増量による米飯粒全体の硬さへの影響は小さく，食味官能評価における総合評価の低下も小さかった．したがって，低アミロース米 「きらほ」は追肥窒素量を増量することで増収が可能となり，しかも食味を低下させることなく，加工製造時の米飯の「べたつき」による作業効率の低下が抑えられることが示唆された．  第 3 章「高タンパク低アミロース米“きらほ”の水浸裂傷粒発生率と吸水特性」 本章は，窒素追肥技術により，低アミロース米「きらほ」から標準タンパク低アミロース米（無追肥）及び高タンパク低アミロース米（穂揃期に窒素追肥）を栽培・収穫し，その水浸裂傷粒発生率及び吸水特性について測定した．その結果，以下の知見を得た．高タンパク低アミロース米は標準タンパク低アミロース米と比較して，種々の精白米水分及び水浸温度の条件下において水浸裂傷粒発生率が 10 ％以下に大きく減じることが示された．また,高タンパク低アミロース米と標準タンパク低アミロース米との間に吸水速度及び加熱吸水率に差はみられなかった．よって，高タンパク低アミロース米は，水浸裂傷粒の発生率が少なく，吸水特性及び加熱吸水率の観点から，業務用米としての新たな活路が期待できることが示された．  第 4 章「高タンパク低アミロース米“きらほ”米飯の低温保存下における物性変化」 本章は，第３章と同じ材料を用い，窒素追肥技術により低アミロース米「きらほ」から標準タンパク米及び高タンパク米の２試験区と，比較用の主食用「ひとめぼれ」を用い，それらの米飯物性に低温保存温度及び保存時間が与える影響について検討した．その結果，「きらほ」の標準タンパク区及び高タンパク区は，いずれの保存温度及び保存時間においても,「ひとめぼれ」より集団粒としての付着性及び粘りが低下しにくい傾向にあった．特に，5℃保存した場合に，処理開始時と比べ，粘りは「ひとめぼれ」では 24 時間後に 26.3 J/㎡（処理開始時比 59 ％)に低下するのに対し，「きらほ」の標準タンパク区では 48 時間後にそれぞれ 31.3 J/㎡（減少率 59 ％）及び 27.9 J/㎡（58 ％）に低下した．更に, 「きらほ」の高タンパク区は 72 時間後に 23.5 J/㎡（48％）で「ひとめぼれ」及び「きらほ」標準タンパク区より粘りが低下しにくいことが示唆された．その結果，「ひとめぼれ」の 24時間後と「きらほ」標準タンパク区及び高タンパク区の 48 時間後の集団粒の粘りは同じ値を示すとともに,高タンパク化した「きらほ」は「ひとめぼれ」より 48 時間長く, 「きらほ」の標準タンパク区より 24 時間長く，米飯の老化抑制できることを示した．  第 5 章「結言」 本論文は窒素追肥量の増量による多収と高タンパク化により，原料米の低コスト化と炊飯・成形加工製造時の米飯の「べたつき」による作業効率の低下が抑えられることを示した．また，高タンパク化しても，食味は低下しないこと，米飯物性の老化が緩慢になることが示された．このことは持ち帰り弁当やおにぎりなどの冷蔵食品の改善・向上に資する知見である． よって，本論文は低アミロース米を高タンパク化することで，米飯の品質保持・老化抑制が可能であることを初めて示したものである．本研究は，水稲の育種・生産の観点から測定計画を立案し，これを食品科学的に考察したものであり，得られた成果は米飯のみならず米加工・米生産の観点から有益な情報を与えるものである．  [Summary] The demand for cooked rice for rice balls, boxed meals, and frozen rice has been increasing along with the strong demand for ready-made meals. Recently, low amylose content rice has been considered to keep its high tenacity and to have resistance to avoid being hard after cooking and even subjected to cooling condition. However, low amylose content rice has had some problems such as low yield during cultivation and low efficiency such as stickiness during processing and manufacturing. In this study, we investigated the effects of different nitrogen fertilization conditions on yield and eating quality including rice properties, using the low amylose content rice variety "Kiraho" bred in Iwate Prefecture. In addition, the suitability of the rice for commercial use, such as the incidence of water-soaked lacerated grains and water absorption characteristics were clarified by using the high-protein-content low amylose content rice variety "Kiraho". First, low amylose content rice had strong stickiness and was still soft even if it cools. But low yield and lower forming efficiency by "stickiness" of cooked rice in processing were considered as problems. In Chapter 2, we examined the effect of nitrogen application on yield and eating quality of low amylose rice “Kiraho”, which had been developed in Iwate prefecture. The number of husk and the high yielding by the amount of nitrogen for topdressing increased. As for the physicochemical properties of cooked rice related to "stickiness" during forming, there was a positive correlation between the protein content and the hardness of the surface of cooked rice, and a negative correlation between the protein content and the adherence of the surface, suggesting a reduction in "stickiness" during forming, while there was no significant difference between the hardness of high compression rice. On the other hand, there was no significant difference between the hardness of the cooked rice and that of the high compression rice, and the decrease in the overall evaluation in the sensory evaluation of eating quality was small. These results suggested that nitrogen fertilization of low amylose content rice "Kiraho" improved the yield and modified the physicochemical properties of the surface layer of cooked rice by increasing the protein content, and reduced the stickiness of rice in processing, while the effect on the eating quality was small. Therefore, it can be inferred that an increase in the amount of nitrogen in the fertilizer may reduce the stickiness of the rice when it is formed, but the decrease in the overall evaluation in the sensory evaluation of eating quality was small. Therefore, increasing the amount of nitrogen fertilizer applied to low amylose rice "Kiraho" will increase its yield and reduce the work efficiency due to the "stickiness" of rice during processing and manufacturing without decreasing its eating quality. Next, it is said that recently low amylose content has been preferred for industrial use, because it retains its sticky and soft characteristics even after cooking and refrigeration. In Chapter 3, we investigated the low amylose content rice cultivar, “Kiraho”, with either a standard protein content (no fertilizer at the ear stage) or a high protein content (fertilized with nitrogen at the ear stage), and measured the characteristics of the cracked grains after soaking and the water absorbed during soaking. The results showed that the proportion of cracked grains after soaking was lower in high protein than in standard protein low amylose content rice under various conditions of moisture content and water soaking temperature. There was no difference between the low amylose content rice with a high or standard protein content in changes in moisture content during absorption. There was also no difference in the water uptake ratio during the cooking quality test between the high protein and standard protein low amylose content rice. These results indicated that the high protein low amylose content rice is more likely to be suitable for industrial use because of its lower proportion of cracked grains after soaking, and its water absorption and heat absorption rate. In Chapter 4, we studied the affects of low storage temperature and duration on the physicochemical properties of rice, using two test plots of standard protein rice and high protein rice from the low amylose rice variety "Kiraho" using nitrogen fertilization technology, and rice variety "Hitomebore" for comparison. Results showed that the standard and high-protein groups of "Kiraho" tended to be less adhesive and less sticky than those of "Hitomebore" at all storage temperatures and times. In particular, when the grains were stored at 5°C, the stickiness of "Hitomebore" decreased to 26.3 J/㎡ (59% of that at the start of treatment) after 24 hours, while it decreased to 31.3 J/㎡(59% of decrease) and 27.9 J/㎡(58% of decrease) after 48 hours in the standard protein zone of "Kiraho". Furthermore, the high-protein zone of "Kiraho" was 23.5 J/㎡(48%) after 72 hours, suggesting that the stickiness of the "Hitomebore" and "Kiraho" standard protein zones was less likely to decrease. Therefore, the stickiness of the group grains after 24 hours in the "Hitomebore" and after 48 hours in the "Kiraho" standard protein and high-protein groups was the same, and the high-protein "Kiraho" was longer than "Hitomebore" by 48 hours, and longer than the "Kiraho" standard protein group by 24 hours. It was suggested that "Kiraho" with high protein could suppress rice aging 48 hours longer than "Hitomebore" and 24 hours longer than "Kiraho" with standard protein. High yield and high protein by increasing the amount of nitrogen fertilizer can reduce the cost of raw rice and decrease the work efficiency due to "stickiness" of rice during rice cooking and forming process manufacturing. In addition, even with high protein, the taste of the rice is less likely to deteriorate and the aging of the rice properties becomes slower, making it effective for improving and enhancing refrigerated foods such as take-out lunch boxes and rice balls. This dissertation shows had high-protein, low-amylose rice will have a strong feasibility to adapt consumers' and producers' expectations for rice quality after refrigerated and/or frozen treatments as commercial use.  ※注１ 博士論文要約はインターネットの利用により公表されるので、記載内容については十分注意してください。 ※注２ 公表できない「やむを得ない事由」（特許、知的財産等に係る部分）は記載しないでください。 ※注３ 全体で４頁～５頁程度を目処にしてください。 

Research on processing and physicochemical properties of Low amylose content rice with controlled protein content

https://iwate-u.repo.nii.ac.jp/record/15431/files/%28summary%29KODATE-Takuma-2021-A.pdf

Research on processing and physicochemical properties of Low amylose content rice with controlled protein content

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