稻米礦物元素含量變異及產區判別之研究

Study on variation of mineral contents in rice grains and the determination of production origin

陳姿穎(Tzu-Ying Chen)

指導教授 ： 盧虎生

共同指導教授 ： 張孟基(Men-Chi Chang)

國立臺灣大學/生物資源暨農學院/農藝學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.02260

摘要

隨著國際市場逐漸開放，商品必須具備獨特的特色，才能在市場中拔得頭籌，並且獲得較高的收益。我國在加入國際貿易組織(WTO)之後，國外農產品陸續進入台灣市場，為保護消費者權益，必須建立產區判別技術以玆辨別。又鑒於國人因飲食中營養不均衡而導致健康問題叢生，因此藉由研究栽培環境與品種對穀粒中微量礦物元素含量之影響，期能在未來改善稻米之營養品質，增進附加價值，提升國際競爭力。本論文之試驗目的即為分析台灣本地稻米礦物元素含量，以建立台灣現行栽培稻米的礦物元素含量資料庫，利用元素含量圖譜瞭解環境因子對稻米礦物元素含量之影響，並研究以之進行產地判別之可能性。
試驗結果發現栽培方式、氮肥施用量、榖粒發育時期的溫度以及碾米率，皆會影響稻米的礦物元素含量以及鎂鉀比值(Mg/K)，其中鎂鉀比值的變異可能對稻米口感品質產生影響。例如有機栽培稻米的Mg/K比值較一般栽培者高，而中氮處理會使得台稉九號糙米的Mg/K比值增加，但是高氮處理卻會減少，此外，榖粒發育時期的高溫會造成稉稻的Mg/K比值下降，但是秈稻卻不受影響。碾米率的試驗顯示元素含量在米粒內的分布並不均勻，大部分的礦物元素集中在糠層中。
本試驗亦收集國內外白米、糙米以及國內外品牌之越光白米等樣品，以感應耦合電漿原子發射光譜儀(ICP-AES)測定各樣品中13種礦物元素含量，分別為鋅(Zn)、錳(Mn)、鐵(Fe)、鈣(Ca)、銅(Cu)、鎂(Mg)、鉀(K)、硒(Se)、鉬(Mo)、硼(B)、鋁(Al)、鍶(Sr)以及鋇(Ba)。由結果中發現：同一品種產自不同的地區，因為受到各種環境因素的影響，所以會有相異的元素圖譜，因此有利於產區判別。最後將所有地區稻米的元素含量分析結果，以統計方法之主成分分析(Principle component analysis)以及判別分析法(Discriminant analysis)進行產區判別，結果顯示可區分國內外糙米以及國內外品牌之越光白米，由此確定以稻米內礦物元素含量圖譜判別國內外稻米產區確實具有可行性。

關鍵字

水稻 ； 礦物元素含量 ； 產地

並列摘要

After entered the World Trade Organization (WTO), there have been more agricultural products imported from foreign countries to Taiwan. The products must possess particular characters, such as culture origin and nutrient content, so as to keep competitiveness and generate better profit. The aim of this study was to measure mineral contents of local rice grains, with which to establish a database of mineral contents for Taiwan cultivars. And use this database to understand the effect of environment on mineral contents of rice grains. Ultimately, the present study evaluated the feasibility of determining product origins by the mineral contents profiles.
In the current approach an ICP-AES (Inductively Coupled Plasma – Atom Emission Spectrometry) based protocol was developed to determine element contents including Zn, Mn, Fe, Ca, Cu, Mg, K, Se, Mo, B, Al, Sr and Ba in rice grains. Samples of different cultivars or grown under different temperatures and nitrogen rates were collected to determinant the effects of genotype or environment on mineral content of rice grains. In addition mineral contents for rice grains with different milling rates were also analyzed. To asses the possibility of differentiation of production origins, samples from local and foreign countries were also collected and the mineral content profiles were analyzed.
As revealed by our results in general, method of cultivation, such as the amount of nitrogen applications, temperature during grain-filling period, and milling degree may significantly affect the mineral content profile and Mg/K ratio which relates to the eating-quality of rice grains. For example, rice grains cultivated by organic farming had higher Mg/K ratio than by conventional farming. Application with medium nitrogen rate would increase Mg/K ratio of TK9, whereas application of high nitrogen would decrease the ratio. Moreover, high temperature during grain-filling period decreased Mg/K ratio of tested Japonica rice grains. Furthermore, results from milling degree showed that the distribution of mineral contents in rice grain is not even, and most of the mineral contents are concentrated in the bran or the surface of rice grains.
In the experiment of evaluation for production origin, samples of milled rice, brown rice, and milled rice of cultivar Koshihikari from local and foreign countries were collected to measure 13 elements of Al, B, Ba, Ca, Cu, Fe, K, Mg, Mn, Mo, Se, Sr, and Zn by ICP-AES. The mineral content profiles were further analyzed by utilizing the principle component analysis (PCA) and the discrimination analysis (LDA). The results showed that samples of different production origins could be differentiated by the statistic analysis.
Conclusively, the present results suggest that profile of mineral content of rice grains can be influenced by genetic background, culture environment and milling rate. The resultant mineral content profile of one sample can be used to differentiate its production origin by appropriate statistic analysis.

並列關鍵字

rice ； mineral content ； geographical origin

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