玉(yu)(yu)米(mi)容(rong)(rong)(rong)重(zhong)(zhong)(zhong)(zhong)是(shi)衡量(liang)玉(yu)(yu)米(mi)質(zhi)量(liang)的(de)(de)(de)一(yi)個關(guan)鍵(jian)指(zhi)標。從定(ding)義(yi)上玉(yu)(yu)米(mi)容(rong)(rong)(rong)重(zhong)(zhong)(zhong)(zhong)就(jiu)是(shi)指(zhi)玉(yu)(yu)米(mi)籽粒(li)單位(wei)(wei)容(rong)(rong)(rong)積內(nei)的(de)(de)(de)質(zhi)量(liang)，在我國(guo)其單位(wei)(wei)為g/L。玉(yu)(yu)米(mi)容(rong)(rong)(rong)重(zhong)(zhong)(zhong)(zhong)從某種程度上能(neng)真實地反映出玉(yu)(yu)米(mi)的(de)(de)(de)完整度、均勻度、成(cheng)熟度以及其潛在的(de)(de)(de)營養(yang)價(jia)值(zhi)。一(yi)般情況下(xia)，同一(yi)品種玉(yu)(yu)米(mi)的(de)(de)(de)容(rong)(rong)(rong)重(zhong)(zhong)(zhong)(zhong)值(zhi)越高，其籽粒(li)中所含(han)的(de)(de)(de)營養(yang)物質(zhi)越多。下(xia)文將綜述玉(yu)(yu)米(mi)容(rong)(rong)(rong)重(zhong)(zhong)(zhong)(zhong)差(cha)異的(de)(de)(de)可(ke)能(neng)形(xing)成(cheng)機(ji)制，重(zhong)(zhong)(zhong)(zhong)點分析玉(yu)(yu)米(mi)容(rong)(rong)(rong)重(zhong)(zhong)(zhong)(zhong)參(can)數可(ke)能(neng)蘊藏的(de)(de)(de)飼用營養(yang)價(jia)值(zhi)，以期為正確(que)認識(shi)玉(yu)(yu)米(mi)容(rong)(rong)(rong)重(zhong)(zhong)(zhong)(zhong)參(can)數提供參(can)考。
一、玉米(mi)容重差(cha)異形(xing)成(cheng)機(ji)制分析
1.1測定(ding)方(fang)法對玉(yu)米容重測定(ding)值的影響
研究表明，采取不同取樣方法測定的相同玉米的容重值可相差9g/L(張霞，2005)。所以在測定玉米容重時須按照四分法逐量取樣才能保證測定值誤差在允許范圍之內。具體操作時如發現插片不流暢及受到阻力或震動等都會影響容重的測定結果。另外將排氣砣置于插板下對容重的測定比排氣砣置于插板上可導致容重測定值高約32g/ L(張霞，2005;高清海和呂宏，2011)。實際上，我國1999年發布的玉米容重測定方法測定的容重值比美國相應方法的測定值高出約30 g/L。所以在2009年我國發布了新的玉米容重測定方法。經驗證，修訂后的容重測定方法(GB1353-2009)測定結果與國外方法測定值相差不超過2.5g/L。(即將實施的(de)新標準是(shi) GB1353-2018)
1.2 玉米品種(質地)與容重的關系
張麗(2008)分析(xi)了(le)29 個山東省玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)品種(zhong)容(rong)(rong)重(zhong)(zhong)(zhong)(zhong)的(de)(de)差(cha)異，發(fa)現玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)容(rong)(rong)重(zhong)(zhong)(zhong)(zhong)受到基因型(xing)(xing)(xing)的(de)(de)顯(xian)(xian)著(zhu)影響。受基因型(xing)(xing)(xing)控制的(de)(de)粒(li)型(xing)(xing)(xing)是決定容(rong)(rong)重(zhong)(zhong)(zhong)(zhong)的(de)(de)重(zhong)(zhong)(zhong)(zhong)要(yao)因素，不同粒(li)型(xing)(xing)(xing)之間容(rong)(rong)重(zhong)(zhong)(zhong)(zhong)差(cha)異顯(xian)(xian)著(zhu)，爆裂型(xing)(xing)(xing)玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)容(rong)(rong)重(zhong)(zhong)(zhong)(zhong)值(zhi)高于硬(ying)粒(li)型(xing)(xing)(xing)，硬(ying)粒(li)型(xing)(xing)(xing)玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)容(rong)(rong)重(zhong)(zhong)(zhong)(zhong)普(pu)遍高于馬齒型(xing)(xing)(xing)玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)的(de)(de)容(rong)(rong)重(zhong)(zhong)(zhong)(zhong)。這可能(neng)是因為圓形(xing)(xing)爆裂型(xing)(xing)(xing)玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)在(zai)容(rong)(rong)量筒內排列間隙(xi)小于扁平形(xing)(xing)籽粒(li)，且圓形(xing)(xing)籽粒(li)種(zhong)皮光滑，故圓形(xing)(xing)籽粒(li)比(bi)扁平形(xing)(xing)籽粒(li)容(rong)(rong)重(zhong)(zhong)(zhong)(zhong)高。同時發(fa)現容(rong)(rong)重(zhong)(zhong)(zhong)(zhong)與角(jiao)質(zhi)(zhi)率呈極顯(xian)(xian)著(zhu)正相(xiang)關(guan)，爆裂型(xing)(xing)(xing)玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)基本全部(bu)角(jiao)質(zhi)(zhi)化，硬(ying)粒(li)型(xing)(xing)(xing)的(de)(de)角(jiao)質(zhi)(zhi)率大(da)于馬齒型(xing)(xing)(xing)。這也(ye)是為什么近年來黑龍江(jiang)大(da)量種(zhong)植的(de)(de)膠質(zhi)(zhi)德美亞玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)的(de)(de)容(rong)(rong)重(zhong)(zhong)(zhong)(zhong)普(pu)遍高于普(pu)通東北(bei)玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)的(de)(de)原因。趙(zhao)延明(ming)等(2004)報道玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)胚乳占玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)整粒(li)的(de)(de)80%以上，如(ru)果胚乳出現發(fa)育(yu)不良的(de)(de)情況(kuang)，其籽粒(li)的(de)(de)充實度(du)將差(cha)，玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)子粒(li)容(rong)(rong)重(zhong)(zhong)(zhong)(zhong)將有一(yi)定的(de)(de)降低。玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)子粒(li)容(rong)(rong)重(zhong)(zhong)(zhong)(zhong)的(de)(de)遺(yi)傳(chuan)表(biao)達主要(yao)受到三倍體(ti)胚乳遺(yi)傳(chuan)效(xiao)應影響。這進(jin)一(yi)步說(shuo)明(ming)了(le)玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)胚乳遺(yi)傳(chuan)差(cha)異可能(neng)對(dui)玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)容(rong)(rong)重(zhong)(zhong)(zhong)(zhong)的(de)(de)影響，即玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)品種(zhong)對(dui)玉(yu)(yu)米(mi)(mi)(mi)(mi)(mi)(mi)容(rong)(rong)重(zhong)(zhong)(zhong)(zhong)的(de)(de)影響。
1.3 玉米生(sheng)長發(fa)育與容重的關系
玉(yu)(yu)米(mi)(mi)(mi)(mi)生長發(fa)育(yu)(yu)(yu)主(zhu)要是(shi)胚(pei)(pei)乳(ru)的(de)(de)(de)生長發(fa)育(yu)(yu)(yu)，所以胚(pei)(pei)乳(ru)的(de)(de)(de)發(fa)育(yu)(yu)(yu)情況直接關(guan)系(xi)到(dao)玉(yu)(yu)米(mi)(mi)(mi)(mi)的(de)(de)(de)產量。玉(yu)(yu)米(mi)(mi)(mi)(mi)胚(pei)(pei)乳(ru)的(de)(de)(de)發(fa)育(yu)(yu)(yu)可以概括為兩個(ge)過(guo)(guo)程(cheng)(cheng)，一(yi)是(shi)胚(pei)(pei)乳(ru)細(xi)(xi)胞的(de)(de)(de)分(fen)裂(lie)增殖和(he)(he)生長，在此(ci)過(guo)(guo)程(cheng)(cheng)中淀粉(fen)(fen)粒(li)(li)在胚(pei)(pei)乳(ru)細(xi)(xi)胞中形(xing)成(cheng)(cheng);第二是(shi)淀粉(fen)(fen)的(de)(de)(de)持(chi)(chi)續合成(cheng)(cheng)和(he)(he)積累，在此(ci)過(guo)(guo)程(cheng)(cheng)中胚(pei)(pei)乳(ru)細(xi)(xi)胞中的(de)(de)(de)淀粉(fen)(fen)粒(li)(li)將逐漸膨(peng)大。玉(yu)(yu)米(mi)(mi)(mi)(mi)生長發(fa)育(yu)(yu)(yu)中影(ying)響(xiang)(xiang)以上過(guo)(guo)程(cheng)(cheng)即會影(ying)響(xiang)(xiang)玉(yu)(yu)米(mi)(mi)(mi)(mi)的(de)(de)(de)粒(li)(li)重(zhong)和(he)(he)容(rong)重(zhong)。如溫度(du)影(ying)響(xiang)(xiang)胚(pei)(pei)乳(ru)細(xi)(xi)胞的(de)(de)(de)數(shu)目(mu)和(he)(he)結構，激素能(neng)影(ying)響(xiang)(xiang)胚(pei)(pei)乳(ru)細(xi)(xi)胞和(he)(he)淀粉(fen)(fen)粒(li)(li)的(de)(de)(de)形(xing)成(cheng)(cheng)。同時在玉(yu)(yu)米(mi)(mi)(mi)(mi)胚(pei)(pei)乳(ru)細(xi)(xi)胞分(fen)裂(lie)期，光(guang)照會影(ying)響(xiang)(xiang)光(guang)合作用(yong)進而使(shi)籽(zi)(zi)粒(li)(li)中的(de)(de)(de)糖含量，從而影(ying)響(xiang)(xiang)胚(pei)(pei)乳(ru)細(xi)(xi)胞數(shu)。另外(wai)，缺(que)水(shui)會影(ying)響(xiang)(xiang)胚(pei)(pei)乳(ru)細(xi)(xi)胞分(fen)裂(lie)速(su)率而使(shi)胚(pei)(pei)乳(ru)細(xi)(xi)胞數(shu)減少。長期缺(que)水(shui)會使(shi)得玉(yu)(yu)米(mi)(mi)(mi)(mi)莖稈等儲藏的(de)(de)(de)營(ying)養物質被(bei)分(fen)解，然后運輸到(dao)玉(yu)(yu)米(mi)(mi)(mi)(mi)籽(zi)(zi)粒(li)(li)被(bei)利用(yong)，這將使(shi)得玉(yu)(yu)米(mi)(mi)(mi)(mi)發(fa)育(yu)(yu)(yu)的(de)(de)(de)線性(xing)灌漿持(chi)(chi)續期較短，最終(zhong)導致粒(li)(li)重(zhong)下(xia)降(魏亞萍等，2004)。王(wang)曉燕等(2006)的(de)(de)(de)研究(jiu)結果表明，同一(yi)類型玉(yu)(yu)米(mi)(mi)(mi)(mi)粒(li)(li)重(zhong)與胚(pei)(pei)乳(ru)細(xi)(xi)胞數(shu)呈顯著(zhu)正相(xiang)關(guan)，這也在一(yi)定程(cheng)(cheng)度(du)上說明玉(yu)(yu)米(mi)(mi)(mi)(mi)胚(pei)(pei)乳(ru)細(xi)(xi)胞數(shu)可能(neng)會影(ying)響(xiang)(xiang)玉(yu)(yu)米(mi)(mi)(mi)(mi)容(rong)重(zhong)。
1.4 玉米栽(zai)培環境與容(rong)重的關系(xi)
在玉(yu)(yu)米(mi)(mi)的(de)(de)實際栽培過(guo)程中，溫(wen)度(du)(du)(du)、水分、光照等(deng)環(huan)境(jing)因素和營養元素、密(mi)度(du)(du)(du)、播(bo)期(qi)(qi)等(deng)栽培措施(shi)都可能(neng)(neng)對玉(yu)(yu)米(mi)(mi)容(rong)重(zhong)(zhong)產生影(ying)(ying)響。如李建奇(2004)報道(dao)，增(zeng)加(jia)氮肥能(neng)(neng)提高(gao)(gao)玉(yu)(yu)米(mi)(mi)籽(zi)粒(li)(li)容(rong)重(zhong)(zhong)，提高(gao)(gao)的(de)(de)幅度(du)(du)(du)為(wei)5-26g/L，同時玉(yu)(yu)米(mi)(mi)的(de)(de)淀粉含量提高(gao)(gao)0.48-2.68%。李月華等(deng)(2008)改變(bian)玉(yu)(yu)米(mi)(mi)的(de)(de)收獲期(qi)(qi)，適(shi)當(dang)生長(chang)期(qi)(qi)內的(de)(de)積溫(wen)增(zeng)加(jia)，光照充足，能(neng)(neng)提高(gao)(gao)玉(yu)(yu)米(mi)(mi)的(de)(de)粒(li)(li)重(zhong)(zhong)，玉(yu)(yu)米(mi)(mi)容(rong)重(zhong)(zhong)有一定增(zeng)加(jia)。另外(wai)，玉(yu)(yu)米(mi)(mi)籽(zi)粒(li)(li)容(rong)重(zhong)(zhong)與(yu)玉(yu)(yu)米(mi)(mi)種(zhong)植密(mi)度(du)(du)(du)間可能(neng)(neng)存在負相關，如果玉(yu)(yu)米(mi)(mi)的(de)(de)種(zhong)植密(mi)度(du)(du)(du)增(zeng)加(jia)，玉(yu)(yu)米(mi)(mi)籽(zi)粒(li)(li)容(rong)重(zhong)(zhong)可能(neng)(neng)會降低。另外(wai)，研究(jiu)表明適(shi)當(dang)晚播(bo)有利于提高(gao)(gao)玉(yu)(yu)米(mi)(mi)籽(zi)粒(li)(li)容(rong)重(zhong)(zhong)。因為(wei)播(bo)期(qi)(qi)直接影(ying)(ying)響玉(yu)(yu)米(mi)(mi)的(de)(de)穗分化和灌漿過(guo)程，進而(er)對玉(yu)(yu)米(mi)(mi)容(rong)重(zhong)(zhong)產生影(ying)(ying)響(張(zhang)麗，2008)。
1.5水分與(yu)容(rong)重的關系
郭淑春等(deng)(1996)報道，隨玉(yu)(yu)(yu)米(mi)(mi)籽(zi)粒水(shui)(shui)(shui)分(fen)(fen)(fen)的(de)(de)增加(jia)，其(qi)(qi)容(rong)(rong)重(zhong)(zhong)(zhong)呈下降趨(qu)勢(shi)。在18%水(shui)(shui)(shui)分(fen)(fen)(fen)以(yi)內時，每(mei)增加(jia)1%水(shui)(shui)(shui)分(fen)(fen)(fen)容(rong)(rong)重(zhong)(zhong)(zhong)平均約(yue)減少(shao)3g/L。超(chao)過18%時，每(mei)增加(jia)1%水(shui)(shui)(shui)分(fen)(fen)(fen)容(rong)(rong)重(zhong)(zhong)(zhong)平均減少(shao)約(yue)6g/L。蔡花真等(deng)(2001)也(ye)報道玉(yu)(yu)(yu)米(mi)(mi)水(shui)(shui)(shui)分(fen)(fen)(fen)11-18.8%之間(jian)時容(rong)(rong)重(zhong)(zhong)(zhong)與水(shui)(shui)(shui)分(fen)(fen)(fen)呈顯著(zhu)線(xian)性(xing)相關。玉(yu)(yu)(yu)米(mi)(mi)水(shui)(shui)(shui)分(fen)(fen)(fen)每(mei)增加(jia)1% 其(qi)(qi)容(rong)(rong)重(zhong)(zhong)(zhong)值降低4-6g/ L。其(qi)(qi)主(zhu)要原因(yin)可能是因(yin)為玉(yu)(yu)(yu)米(mi)(mi)比重(zhong)(zhong)(zhong)(1.11-1.25 g/ cm3)大于(yu)水(shui)(shui)(shui)的(de)(de)比重(zhong)(zhong)(zhong)。實際上，隨著(zhu)玉(yu)(yu)(yu)米(mi)(mi)水(shui)(shui)(shui)分(fen)(fen)(fen)增加(jia)，由于(yu)玉(yu)(yu)(yu)米(mi)(mi)子粒膨脹，其(qi)(qi)表面(mian)的(de)(de)摩(mo)擦(ca)系數會有一定(ding)(ding)增加(jia)，那么其(qi)(qi)散落性(xing)將下降，籽(zi)粒間(jian)的(de)(de)空(kong)隙會增加(jia)，所以(yi)最終導致測(ce)(ce)定(ding)(ding)的(de)(de)容(rong)(rong)重(zhong)(zhong)(zhong)值降低。在最新(xin)的(de)(de)玉(yu)(yu)(yu)米(mi)(mi)容(rong)(rong)重(zhong)(zhong)(zhong)測(ce)(ce)定(ding)(ding)方法(GB1353-2009)中(zhong)，考慮到玉(yu)(yu)(yu)米(mi)(mi)產地、品(pin)種等(deng)影(ying)響，隨著(zhu)玉(yu)(yu)(yu)米(mi)(mi)水(shui)(shui)(shui)分(fen)(fen)(fen)變化，其(qi)(qi)測(ce)(ce)定(ding)(ding)的(de)(de)容(rong)(rong)重(zhong)(zhong)(zhong)值規律(lv)性(xing)不(bu)強。特別是對(dui)(dui)于(yu)玉(yu)(yu)(yu)米(mi)(mi)水(shui)(shui)(shui)分(fen)(fen)(fen)超(chao)過23%的(de)(de)樣(yang)品(pin)其(qi)(qi)容(rong)(rong)重(zhong)(zhong)(zhong)測(ce)(ce)定(ding)(ding)值無線(xian)性(xing)關系。對(dui)(dui)于(yu)玉(yu)(yu)(yu)米(mi)(mi)水(shui)(shui)(shui)分(fen)(fen)(fen)大于(yu)18%的(de)(de)容(rong)(rong)重(zhong)(zhong)(zhong)測(ce)(ce)定(ding)(ding)，在新(xin)國標中(zhong)要求通過快速(su)干(gan)燥降水(shui)(shui)(shui)設備和快速(su)水(shui)(shui)(shui)分(fen)(fen)(fen)測(ce)(ce)定(ding)(ding)儀，先將玉(yu)(yu)(yu)米(mi)(mi)水(shui)(shui)(shui)分(fen)(fen)(fen)降到18%以(yi)下，等(deng)玉(yu)(yu)(yu)米(mi)(mi)樣(yang)品(pin)冷卻(que)至室溫(wen)后再按照新(xin)的(de)(de)玉(yu)(yu)(yu)米(mi)(mi)容(rong)(rong)重(zhong)(zhong)(zhong)測(ce)(ce)定(ding)(ding)方法進行測(ce)(ce)定(ding)(ding)(高清(qing)海和呂宏，2011)。
 1.6 雜質(zhi)、破損(sun)粒(li)與容重(zhong)的關系
顧金玲等(2008)測(ce)(ce)定(ding)混入(ru)不同(tong)比(bi)例破(po)(po)碎(sui)粒(li)(li)(li)(li)(li)與(yu)(yu)雜質(zhi)(zhi)(zhi)的(de)(de)(de)(de)玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)樣品容(rong)重(zhong)(zhong)時(shi)(shi)，當破(po)(po)碎(sui)粒(li)(li)(li)(li)(li)與(yu)(yu)雜質(zhi)(zhi)(zhi)的(de)(de)(de)(de)含量低于(yu)9%時(shi)(shi)，容(rong)重(zhong)(zhong)與(yu)(yu)破(po)(po)碎(sui)粒(li)(li)(li)(li)(li)與(yu)(yu)雜質(zhi)(zhi)(zhi)含量存(cun)在(zai)正相(xiang)關，但是(shi)當高于(yu)9%時(shi)(shi)即出現負相(xiang)關。實(shi)際上容(rong)重(zhong)(zhong)測(ce)(ce)定(ding)時(shi)(shi)所測(ce)(ce)定(ding)的(de)(de)(de)(de)玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)必(bi)須(xu)是(shi)3 毫(hao)米(mi)(mi)(mi)(mi)篩層以(yi)上及12 毫(hao)米(mi)(mi)(mi)(mi)篩層以(yi)下玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)。如(ru)果測(ce)(ce)定(ding)玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)樣品去雜質(zhi)(zhi)(zhi)不干(gan)(gan)凈，將影響玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)容(rong)重(zhong)(zhong)的(de)(de)(de)(de)測(ce)(ce)定(ding)值。同(tong)時(shi)(shi)，如(ru)果玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)中混入(ru)的(de)(de)(de)(de)雜質(zhi)(zhi)(zhi)比(bi)重(zhong)(zhong)大(da)于(yu)玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)比(bi)重(zhong)(zhong)，那么玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)的(de)(de)(de)(de)實(shi)際容(rong)重(zhong)(zhong)值將被高估(gu);如(ru)果玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)中雜質(zhi)(zhi)(zhi)的(de)(de)(de)(de)比(bi)重(zhong)(zhong)小于(yu)玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)比(bi)重(zhong)(zhong)，則玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)的(de)(de)(de)(de)實(shi)際容(rong)重(zhong)(zhong)值將被低估(gu)。另外，近(jin)年來(lai)玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)的(de)(de)(de)(de)機械化(hua)收(shou)獲(huo)和烘干(gan)(gan)越(yue)來(lai)越(yue)普(pu)遍，玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)的(de)(de)(de)(de)破(po)(po)損(sun)(sun)(sun)(sun)粒(li)(li)(li)(li)(li)也有不同(tong)程度的(de)(de)(de)(de)增(zeng)(zeng)加，如(ru)2012年收(shou)獲(huo)的(de)(de)(de)(de)東北烘干(gan)(gan)玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)的(de)(de)(de)(de)破(po)(po)損(sun)(sun)(sun)(sun)粒(li)(li)(li)(li)(li)大(da)部分達到10%以(yi)上。根據溫氏(shi)集團技術中心測(ce)(ce)定(ding)的(de)(de)(de)(de)數據來(lai)看，烘干(gan)(gan)玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)的(de)(de)(de)(de)破(po)(po)損(sun)(sun)(sun)(sun)粒(li)(li)(li)(li)(li)增(zeng)(zeng)加10%，其(qi)測(ce)(ce)定(ding)的(de)(de)(de)(de)容(rong)重(zhong)(zhong)值將增(zeng)(zeng)加2-4g/L，這可能與(yu)(yu)破(po)(po)損(sun)(sun)(sun)(sun)玉(yu)(yu)(yu)米(mi)(mi)(mi)(mi)淀(dian)粉被篩入(ru)雜質(zhi)(zhi)(zhi)其(qi)膠質(zhi)(zhi)(zhi)率增(zeng)(zeng)加及破(po)(po)損(sun)(sun)(sun)(sun)顆粒(li)(li)(li)(li)(li)之間的(de)(de)(de)(de)縫(feng)隙變(bian)小有關。
1.7 烘(hong)干方式與容重的關(guan)系
自然溫(wen)度(du)條(tiao)件(jian)下玉(yu)(yu)(yu)(yu)米(mi)籽(zi)粒(li)(li)內部水(shui)(shui)分在揮發的(de)(de)(de)(de)(de)過(guo)程(cheng)(cheng)中(zhong)(zhong)不(bu)會(hui)(hui)(hui)對籽(zi)粒(li)(li)的(de)(de)(de)(de)(de)表(biao)皮光滑度(du)造(zao)成(cheng)損傷，它能反(fan)映出(chu)玉(yu)(yu)(yu)(yu)米(mi)的(de)(de)(de)(de)(de)真實容(rong)(rong)重(zhong)。而利用高溫(wen)烘(hong)干(gan)玉(yu)(yu)(yu)(yu)米(mi)降(jiang)(jiang)(jiang)(jiang)水(shui)(shui)的(de)(de)(de)(de)(de)過(guo)程(cheng)(cheng)中(zhong)(zhong)會(hui)(hui)(hui)出(chu)現(xian)容(rong)(rong)重(zhong)下降(jiang)(jiang)(jiang)(jiang)的(de)(de)(de)(de)(de)現(xian)象(xiang)，即比(bi)(bi)自然降(jiang)(jiang)(jiang)(jiang)水(shui)(shui)玉(yu)(yu)(yu)(yu)米(mi)的(de)(de)(de)(de)(de)容(rong)(rong)重(zhong)低(di)(武強和(he)孫(sun)中(zhong)(zhong)英，2009)。劉昱(yu)鑫(2009)報(bao)道自然溫(wen)度(du)條(tiao)件(jian)下玉(yu)(yu)(yu)(yu)米(mi)水(shui)(shui)分由26-28%降(jiang)(jiang)(jiang)(jiang)至(zhi)14.0%，測定容(rong)(rong)重(zhong)值(zhi)為(wei)740 g/ L。而相同的(de)(de)(de)(de)(de)玉(yu)(yu)(yu)(yu)米(mi)利用烘(hong)干(gan)塔(110℃)烘(hong)干(gan)水(shui)(shui)分至(zhi)14. 0%測定的(de)(de)(de)(de)(de)容(rong)(rong)重(zhong)值(zhi)為(wei)716 g/ L，比(bi)(bi)較可見烘(hong)干(gan)玉(yu)(yu)(yu)(yu)米(mi)的(de)(de)(de)(de)(de)容(rong)(rong)重(zhong)下降(jiang)(jiang)(jiang)(jiang)24 g / L。為(wei)什么會(hui)(hui)(hui)導(dao)致如此大的(de)(de)(de)(de)(de)差(cha)異?從目前的(de)(de)(de)(de)(de)研究(jiu)結果來看(kan)主(zhu)要可能有(you)以下幾方面的(de)(de)(de)(de)(de)原(yuan)因：一是(shi)(shi)在降(jiang)(jiang)(jiang)(jiang)低(di)玉(yu)(yu)(yu)(yu)米(mi)水(shui)(shui)分含(han)量(liang)的(de)(de)(de)(de)(de)過(guo)程(cheng)(cheng)中(zhong)(zhong)，實際上玉(yu)(yu)(yu)(yu)米(mi)表(biao)皮水(shui)(shui)分與胚(pei)和(he)胚(pei)乳(ru)水(shui)(shui)分揮發是(shi)(shi)不(bu)一致，所(suo)以玉(yu)(yu)(yu)(yu)米(mi)籽(zi)粒(li)(li)會(hui)(hui)(hui)出(chu)現(xian)外(wai)硬里軟的(de)(de)(de)(de)(de)現(xian)象(xiang)，使表(biao)皮的(de)(de)(de)(de)(de)粗糙(cao)程(cheng)(cheng)度(du)增加(jia)，籽(zi)粒(li)(li)間的(de)(de)(de)(de)(de)孔(kong)隙度(du)大，有(you)時還會(hui)(hui)(hui)出(chu)現(xian)干(gan)裂、脫皮等現(xian)象(xiang)，所(suo)以導(dao)致測定的(de)(de)(de)(de)(de)容(rong)(rong)重(zhong)值(zhi)下降(jiang)(jiang)(jiang)(jiang)。二是(shi)(shi)玉(yu)(yu)(yu)(yu)米(mi)烘(hong)干(gan)的(de)(de)(de)(de)(de)過(guo)程(cheng)(cheng)是(shi)(shi)急劇降(jiang)(jiang)(jiang)(jiang)水(shui)(shui)的(de)(de)(de)(de)(de)過(guo)程(cheng)(cheng)，溫(wen)度(du)增高的(de)(de)(de)(de)(de)過(guo)程(cheng)(cheng)中(zhong)(zhong)玉(yu)(yu)(yu)(yu)米(mi)籽(zi)粒(li)(li)體積(ji)會(hui)(hui)(hui)膨(peng)脹(zhang)，水(shui)(shui)分降(jiang)(jiang)(jiang)(jiang)低(di)后致使單位(wei)容(rong)(rong)積(ji)內的(de)(de)(de)(de)(de)重(zhong)量(liang)大量(liang)降(jiang)(jiang)(jiang)(jiang)低(di)，致使玉(yu)(yu)(yu)(yu)米(mi)容(rong)(rong)重(zhong)值(zhi)有(you)相應降(jiang)(jiang)(jiang)(jiang)低(di)(宋秀(xiu)娟，2002;楊平和(he)郭景勛，2009)。
二、玉米容(rong)重相關的(de)營養(yang)價(jia)值(zhi)
2.1容重與(yu)能值
關(guan)(guan)于玉(yu)(yu)(yu)米(mi)(mi)(mi)容(rong)重(zhong)(zhong)(zhong)與(yu)(yu)(yu)其(qi)(qi)能(neng)(neng)值的(de)(de)(de)關(guan)(guan)系有較多的(de)(de)(de)報(bao)道。Lilburn和(he)Dale(1989)報(bao)道不同(tong)容(rong)重(zhong)(zhong)(zhong)的(de)(de)(de)玉(yu)(yu)(yu)米(mi)(mi)(mi)對肉(rou)雞的(de)(de)(de)真代謝能(neng)(neng)存(cun)在(zai)(zai)顯著(zhu)(zhu)影響(xiang)。Baidoo等(1991)隨(sui)后(hou)建立了玉(yu)(yu)(yu)米(mi)(mi)(mi)容(rong)重(zhong)(zhong)(zhong)與(yu)(yu)(yu)表觀代謝能(neng)(neng)值的(de)(de)(de)回(hui)歸方(fang)程為(wei)(wei)：y=2929+1.08x，其(qi)(qi)中(zhong)y為(wei)(wei)干(gan)物質(zhi)基礎表觀代謝能(neng)(neng)值(kcal/kg)，x為(wei)(wei)玉(yu)(yu)(yu)米(mi)(mi)(mi)容(rong)重(zhong)(zhong)(zhong)(g/L)。Summers(1993)也(ye)報(bao)道，玉(yu)(yu)(yu)米(mi)(mi)(mi)容(rong)重(zhong)(zhong)(zhong)與(yu)(yu)(yu)代謝能(neng)(neng)之間存(cun)在(zai)(zai)顯著(zhu)(zhu)的(de)(de)(de)線(xian)性關(guan)(guan)系，其(qi)(qi)相關(guan)(guan)系數為(wei)(wei)1.09。由此可見，玉(yu)(yu)(yu)米(mi)(mi)(mi)單位容(rong)重(zhong)(zhong)(zhong)校正(zheng)代謝能(neng)(neng)的(de)(de)(de)系數約(yue)為(wei)(wei)1.0。Dale(1994)也(ye)報(bao)道1992年美國(guo)北部收獲的(de)(de)(de)玉(yu)(yu)(yu)米(mi)(mi)(mi)容(rong)重(zhong)(zhong)(zhong)與(yu)(yu)(yu)其(qi)(qi)真代謝能(neng)(neng)直(zhi)接存(cun)在(zai)(zai)顯著(zhu)(zhu)的(de)(de)(de)相關(guan)(guan)。另外，Johnston(1993)報(bao)道，低(di)(di)容(rong)重(zhong)(zhong)(zhong)玉(yu)(yu)(yu)米(mi)(mi)(mi)飼(si)喂豬的(de)(de)(de)生長試驗(yan)表明，飼(si)喂低(di)(di)容(rong)重(zhong)(zhong)(zhong)玉(yu)(yu)(yu)米(mi)(mi)(mi)組的(de)(de)(de)增重(zhong)(zhong)(zhong)偏低(di)(di)，料比偏高，可能(neng)(neng)與(yu)(yu)(yu)低(di)(di)容(rong)重(zhong)(zhong)(zhong)玉(yu)(yu)(yu)米(mi)(mi)(mi)的(de)(de)(de)能(neng)(neng)值低(di)(di)有關(guan)(guan)。Sarah Muirhead (1995)研(yan)究表明，低(di)(di)容(rong)重(zhong)(zhong)(zhong)玉(yu)(yu)(yu)米(mi)(mi)(mi)添加(jia)油脂(zhi)飼(si)喂豬的(de)(de)(de)效果與(yu)(yu)(yu)正(zheng)常容(rong)重(zhong)(zhong)(zhong)玉(yu)(yu)(yu)米(mi)(mi)(mi)的(de)(de)(de)飼(si)喂效果相當，這進一(yi)步的(de)(de)(de)間接說明低(di)(di)容(rong)重(zhong)(zhong)(zhong)玉(yu)(yu)(yu)米(mi)(mi)(mi)對豬而言其(qi)(qi)能(neng)(neng)值也(ye)偏低(di)(di)。關(guan)(guan)于玉(yu)(yu)(yu)米(mi)(mi)(mi)容(rong)重(zhong)(zhong)(zhong)影響(xiang)其(qi)(qi)能(neng)(neng)值的(de)(de)(de)機(ji)制主(zhu)要可能(neng)(neng)與(yu)(yu)(yu)淀粉(fen)含量(liang)及(ji)組成(直(zhi)鏈淀粉(fen)和(he)支鏈淀粉(fen)含量(liang))等相關(guan)(guan)。下面將進一(yi)步分析(xi)玉(yu)(yu)(yu)米(mi)(mi)(mi)容(rong)重(zhong)(zhong)(zhong)與(yu)(yu)(yu)淀粉(fen)的(de)(de)(de)關(guan)(guan)系。
2.2容重與(yu)淀粉
玉(yu)(yu)米(mi)(mi)(mi)(mi)容(rong)重(zhong)(zhong)(zhong)的(de)(de)(de)(de)(de)(de)差異主(zhu)要可(ke)(ke)能與(yu)(yu)(yu)其淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)含(han)(han)量(liang)差異有關(guan)。Baidoo等(deng)(1991)報道玉(yu)(yu)米(mi)(mi)(mi)(mi)容(rong)重(zhong)(zhong)(zhong)與(yu)(yu)(yu)淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)含(han)(han)量(liang)的(de)(de)(de)(de)(de)(de)相關(guan)性高(gao)(gao)達0.98。張麗(li)等(deng)(2007)研究(jiu)山東(dong)29個玉(yu)(yu)米(mi)(mi)(mi)(mi)樣品的(de)(de)(de)(de)(de)(de)結果也表(biao)明，容(rong)重(zhong)(zhong)(zhong)與(yu)(yu)(yu)淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)含(han)(han)量(liang)的(de)(de)(de)(de)(de)(de)相關(guan)系(xi)數(shu)(shu)高(gao)(gao)達0.72，同(tong)時經過通(tong)徑(jing)分析發現總淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)含(han)(han)量(liang)對(dui)容(rong)重(zhong)(zhong)(zhong)的(de)(de)(de)(de)(de)(de)決(jue)定(ding)(ding)系(xi)數(shu)(shu)接近 70%，可(ke)(ke)見(jian)淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)含(han)(han)量(liang)對(dui)玉(yu)(yu)米(mi)(mi)(mi)(mi)容(rong)重(zhong)(zhong)(zhong)的(de)(de)(de)(de)(de)(de)決(jue)定(ding)(ding)作(zuo)用最大。分析結果表(biao)明玉(yu)(yu)米(mi)(mi)(mi)(mi)中淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)含(han)(han)量(liang)約(yue)為70.8%，且主(zhu)要分布于胚(pei)(pei)乳。對(dui)于高(gao)(gao)淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)的(de)(de)(de)(de)(de)(de)玉(yu)(yu)米(mi)(mi)(mi)(mi)基本(ben)都符合淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)越高(gao)(gao)容(rong)重(zhong)(zhong)(zhong)越大的(de)(de)(de)(de)(de)(de)規律(lv)。另外(wai)張麗(li)(2008)的(de)(de)(de)(de)(de)(de)研究(jiu)表(biao)明，高(gao)(gao)淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)玉(yu)(yu)米(mi)(mi)(mi)(mi)中小于15μm淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)粒占體積百分數(shu)(shu)顯著高(gao)(gao)于普通(tong)玉(yu)(yu)米(mi)(mi)(mi)(mi)，而普通(tong)玉(yu)(yu)米(mi)(mi)(mi)(mi)中大于15μm的(de)(de)(de)(de)(de)(de)大淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)粒所(suo)占的(de)(de)(de)(de)(de)(de)數(shu)(shu)目、體積等(deng)的(de)(de)(de)(de)(de)(de)百分比高(gao)(gao)于高(gao)(gao)淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)玉(yu)(yu)米(mi)(mi)(mi)(mi)。所(suo)以不同(tong)淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)顆粒的(de)(de)(de)(de)(de)(de)數(shu)(shu)量(liang)可(ke)(ke)能也會對(dui)玉(yu)(yu)米(mi)(mi)(mi)(mi)容(rong)重(zhong)(zhong)(zhong)有一定(ding)(ding)的(de)(de)(de)(de)(de)(de)影(ying)響(xiang)。同(tong)時高(gao)(gao)淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)玉(yu)(yu)米(mi)(mi)(mi)(mi)的(de)(de)(de)(de)(de)(de)直鏈淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)積累速率均低于普通(tong)型(xing)玉(yu)(yu)米(mi)(mi)(mi)(mi)，而支鏈淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)和總淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)積累速率較(jiao)高(gao)(gao)。而實際上(shang)在動物上(shang)的(de)(de)(de)(de)(de)(de)研究(jiu)表(biao)明，支鏈淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)的(de)(de)(de)(de)(de)(de)利用率高(gao)(gao)于直鏈淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)(鄭燦，2010)，這也能部分解釋(shi)玉(yu)(yu)米(mi)(mi)(mi)(mi)容(rong)重(zhong)(zhong)(zhong)對(dui)其能值的(de)(de)(de)(de)(de)(de)影(ying)響(xiang)。另外(wai)，還發現玉(yu)(yu)米(mi)(mi)(mi)(mi)胚(pei)(pei)乳橫(heng)斷(duan)面中淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)顆粒的(de)(de)(de)(de)(de)(de)排列緊(jin)密程(cheng)度硬粒型(xing)玉(yu)(yu)米(mi)(mi)(mi)(mi)高(gao)(gao)于高(gao)(gao)淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)型(xing)玉(yu)(yu)米(mi)(mi)(mi)(mi)，高(gao)(gao)淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)型(xing)的(de)(de)(de)(de)(de)(de)玉(yu)(yu)米(mi)(mi)(mi)(mi)高(gao)(gao)于普通(tong)型(xing)玉(yu)(yu)米(mi)(mi)(mi)(mi)，這也說明淀(dian)(dian)(dian)(dian)(dian)(dian)(dian)粉(fen)(fen)(fen)(fen)(fen)的(de)(de)(de)(de)(de)(de)排列方式可(ke)(ke)能與(yu)(yu)(yu)玉(yu)(yu)米(mi)(mi)(mi)(mi)容(rong)重(zhong)(zhong)(zhong)有一定(ding)(ding)關(guan)系(xi)。
2.3容重(zhong)與粗蛋白(bai)等
張麗等(2007)報(bao)道，容(rong)(rong)重(zhong)與蛋(dan)白(bai)質(zhi)(zhi)含量(liang)存在顯著(zhu)的(de)(de)正相關(guan)(r=0.57)，一(yi)般情況(kuang)下，隨著(zhu)玉(yu)(yu)(yu)(yu)米(mi)粗蛋(dan)白(bai)含量(liang)的(de)(de)增加，容(rong)(rong)重(zhong)呈上升(sheng)趨勢。這也是為(wei)什么(me)玉(yu)(yu)(yu)(yu)米(mi)能(neng)是最能(neng)體現玉(yu)(yu)(yu)(yu)米(mi)成熟度的(de)(de)指標，能(neng)夠在一(yi)定程度上反映出玉(yu)(yu)(yu)(yu)米(mi)的(de)(de)內(nei)在品質(zhi)(zhi)。對于富含淀粉的(de)(de)玉(yu)(yu)(yu)(yu)米(mi)而言容(rong)(rong)重(zhong)高(gao)則質(zhi)(zhi)量(liang)優。但是也有特殊的(de)(de)情況(kuang)，如高(gao)蛋(dan)白(bai)、高(gao)油玉(yu)(yu)(yu)(yu)米(mi)的(de)(de)容(rong)(rong)重(zhong)低于一(yi)般玉(yu)(yu)(yu)(yu)米(mi)，其容(rong)(rong)重(zhong)低為(wei)好(hao)。所以對于玉(yu)(yu)(yu)(yu)米(mi)的(de)(de)容(rong)(rong)重(zhong)也要具(ju)體問題具(ju)體分析(車海先和李海玉(yu)(yu)(yu)(yu)，2011)。
三、小結
盡管玉(yu)(yu)米(mi)(mi)的(de)(de)容(rong)(rong)(rong)重(zhong)(zhong)受到諸多(duo)因素的(de)(de)影響，最終導致玉(yu)(yu)米(mi)(mi)的(de)(de)容(rong)(rong)(rong)重(zhong)(zhong)差異(yi)較(jiao)大。目(mu)前畜禽所用的(de)(de)大部分玉(yu)(yu)米(mi)(mi)的(de)(de)容(rong)(rong)(rong)重(zhong)(zhong)與其的(de)(de)營養價值直接相關(guan)。容(rong)(rong)(rong)重(zhong)(zhong)作為一(yi)個測定簡單(dan)快速且(qie)能(neng)衡量玉(yu)(yu)米(mi)(mi)質(zhi)量的(de)(de)指標(biao)，對于選擇優質(zhi)的(de)(de)玉(yu)(yu)米(mi)(mi)用于畜禽飼料配制具有重(zhong)(zhong)要的(de)(de)意義(yi)。在玉(yu)(yu)米(mi)(mi)的(de)(de)采(cai)購和使(shi)用過程中，玉(yu)(yu)米(mi)(mi)容(rong)(rong)(rong)重(zhong)(zhong)是一(yi)個重(zhong)(zhong)要的(de)(de)質(zhi)量標(biao)準。但是目(mu)前關(guan)于容(rong)(rong)(rong)重(zhong)(zhong)差異(yi)形成的(de)(de)機制只有一(yi)個基本的(de)(de)了解，其中蘊含(han)的(de)(de)深層(ceng)次機制還有待進一(yi)步(bu)探究。
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