Department of Biological and Agricultural Engineering , University of Arkansas , 4183 Bell Engineering Center , Fayetteville , Arkansas 72701 , United States.
Department of Agronomy and Horticulture , University of Nebraska-Lincoln , 202 Keim Hall , Lincoln , Nebraska 68583 , United States.
J Agric Food Chem. 2018 Apr 4;66(13):3378-3385. doi: 10.1021/acs.jafc.7b05242. Epub 2018 Mar 26.
The notion that many nutrients and beneficial phytochemicals in maize are lost due to food product processing is common, but this has not been studied in detail for the phenolic acids. Information regarding changes in phenolic acid content throughout processing is highly valuable because some phenolic acids are chemopreventive agents of aging-related diseases. It is unknown when and why these changes in phenolic acid content might occur during processing, whether some maize genotypes might be more resistant to processing induced changes in phenolic acid content than other genotypes, or if processing affects the bioavailability of phenolic acids in maize-based food products. For this study, a laboratory-scale processing protocol was developed and used to process whole maize kernels into toasted cornflakes. High-throughput microscale wet-lab analyses were applied to determine the concentrations of soluble and insoluble-bound phenolic acids in samples of grain, three intermediate processing stages, and toasted cornflakes obtained from 12 ex-PVP maize inbreds and seven hybrids. In the grain, insoluble-bound ferulic acid was the most common phenolic acid, followed by insoluble-bound p-coumaric acid and soluble cinnamic acid, a precursor to the phenolic acids. Notably, the ferulic acid content was approximately 1950 μg/g, more than ten-times the concentration of many fruits and vegetables. Processing reduced the content of the phenolic acids regardless of the genotype. Most changes occurred during dry milling due to the removal of the bran. The concentration of bioavailable soluble ferulic and p-coumaric acid increased negligibly due to thermal stresses. Therefore, the current dry milling based processing techniques used to manufacture many maize-based foods, including breakfast cereals, are not conducive for increasing the content of bioavailable phenolics in processed maize food products. This suggests that while maize is an excellent source of phenolics, alternative or complementary processing methods must be developed before this nutritional resource can be utilized.
人们普遍认为，由于食品加工，玉米中的许多营养物质和有益的植物化学物质都会流失，但这一点尚未在酚酸方面进行详细研究。有关酚酸含量在整个加工过程中变化的信息非常有价值，因为一些酚酸是与衰老相关疾病的化学预防剂。目前尚不清楚这些酚酸含量的变化在加工过程中何时以及为何会发生，某些玉米基因型是否比其他基因型更能抵抗加工引起的酚酸含量变化，或者加工是否会影响玉米基食品中酚酸的生物利用度。为此，本研究开发了一种实验室规模的加工方案，并将其用于将整个玉米粒加工成烤玉米片。应用高通量微量湿实验室分析方法来测定来自 12 个前 PVP 玉米自交系和 7 个杂交种的谷物、三个中间加工阶段以及烤玉米片中的可溶性和不可溶性结合酚酸的浓度。在谷物中，不可溶性结合的阿魏酸是最常见的酚酸，其次是不可溶性结合的对香豆酸和可溶性肉桂酸，后者是酚酸的前体。值得注意的是，阿魏酸的含量约为 1950μg/g，是许多水果和蔬菜浓度的十倍以上。无论基因型如何，加工都会降低酚酸的含量。由于去除了麸皮，大部分变化发生在干磨过程中。由于热应力，生物可利用的可溶性阿魏酸和对香豆酸的浓度增加可忽略不计。因此，目前用于制造许多基于玉米的食品（包括早餐麦片）的干磨加工技术不利于增加加工玉米食品中生物可利用酚类的含量。这表明，尽管玉米是酚类物质的极好来源，但在利用这一营养资源之前，必须开发替代或补充的加工方法。
