McCleary B V, McCleary B V
Megazyme International Ireland Ltd., Bray, Co. Wicklow.
J AOAC Int. 2000 Jul-Aug;83(4):997-1005.
A study was made of the effect of the activity and purity of enzymes in the assay of total dietary fiber (AOAC Method 985.29) and specific dietary fiber components: resistant starch, fructan, and beta-glucan. In the measurement of total dietary fiber content of resistant starch samples, the concentration of alpha-amylase is critical; however, variations in the level of amyloglucosidase have little effect. Contamination of amyloglucosidase preparations with cellulase can result in significant underestimation of dietary fiber values for samples containing beta-glucan. Pure beta-glucan and cellulase purified from Aspergillus niger amyloglucosidase preparations were used to determine acceptable critical levels of contamination. Sucrose, which interferes with the measurement of inulin and fructooligosaccharides in plant materials and food products, must be removed by hydrolysis of the sucrose to glucose and fructose with a specific enzyme (sucrase) followed by borohydride reduction of the free sugars. Unlike invertase, sucrase has no action on low degree of polymerization (DP) fructooligosaccharides, such as kestose or kestotetraose. Fructan is hydrolyzed to fructose and glucose by the combined action of highly purified exo- and endo-inulinases, and these sugars are measured by the p-hydroxybenzoic acid hydrazide reducing sugar method. Specific measurement of beta-glucan in cereal flour and food extracts requires the use of highly purified endo-1,3:1,4 beta-glucanase and A. niger beta-glucosidase. Beta-glucosidase from almonds does not completely hydrolyze mixed linkage beta-glucooligosaccharides from barley or oat beta-glucan. Contamination of these enzymes with starch, maltosaccharide, or sucrose-hydrolyzing enzymes results in production of free glucose from a source other than beta-glucan, and thus an overestimation of beta-glucan content. The glucose oxidase and peroxidase used in the glucose determination reagent must be essentially devoid of catalase and alpha- and beta-glucosidase.
研究了酶的活性和纯度对总膳食纤维（AOAC方法985.29）以及特定膳食纤维成分（抗性淀粉、果聚糖和β-葡聚糖）测定的影响。在抗性淀粉样品总膳食纤维含量的测定中，α-淀粉酶的浓度至关重要；然而，淀粉葡萄糖苷酶水平的变化影响较小。淀粉葡萄糖苷酶制剂被纤维素酶污染会导致含有β-葡聚糖的样品膳食纤维值被显著低估。使用从黑曲霉淀粉葡萄糖苷酶制剂中纯化得到的纯β-葡聚糖和纤维素酶来确定可接受的临界污染水平。蔗糖会干扰植物材料和食品中菊粉和低聚果糖的测定，必须先用特定的酶（蔗糖酶）将蔗糖水解为葡萄糖和果糖，然后用硼氢化物还原游离糖来去除。与转化酶不同，蔗糖酶对低聚合度（DP）的低聚果糖，如蔗果三糖或蔗果四糖没有作用。果聚糖通过高度纯化的外切和内切菊粉酶的联合作用水解成果糖和葡萄糖，这些糖通过对羟基苯甲酸酰肼还原糖法进行测定。谷物面粉和食品提取物中β-葡聚糖的特异性测定需要使用高度纯化的内切-1,3:1,4-β-葡聚糖酶和黑曲霉β-葡萄糖苷酶。杏仁中的β-葡萄糖苷酶不能完全水解来自大麦或燕麦β-葡聚糖的混合连接β-葡寡糖。这些酶被淀粉、麦芽糖或蔗糖水解酶污染会导致从β-葡聚糖以外的来源产生游离葡萄糖，从而高估β-葡聚糖含量。葡萄糖测定试剂中使用的葡萄糖氧化酶和过氧化物酶必须基本不含过氧化氢酶以及α-和β-葡萄糖苷酶。
