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.

中文翻译：

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食品加工过程中玉米中苯酚酸含量的变化

普遍认为，由于食品加工会损失玉米中的许多营养物质和有益的植物化学物质，但酚酸尚未对此进行详细研究。有关整个加工过程中酚酸含量变化的信息非常有价值，因为某些酚酸是与衰老相关的疾病的化学预防剂。尚不清楚何时以及为何加工过程中酚酸含量的这些变化会发生，为什么某些玉米基因型可能比其他基因型更耐加工诱导的酚酸含量的变化，或者加工是否影响基于玉米的酚酸的生物利用度食物产品。对于本研究，开发了实验室规模的处理方案，并用于将整个玉米粒加工成烤玉米片。应用高通量微型实验室湿法分析来确定谷物样品中可溶性和不溶性结合酚酸的浓度，三个中间处理阶段以及从12个前PVP玉米自交系和七个杂种获得的烤玉米片。在谷物中，不溶结合的阿魏酸是最常见的酚酸，其次是不溶结合的对香豆酸和可溶性肉桂酸（酚酸的前体）。值得注意的是，阿魏酸含量约为1950μg/ g，是许多水果和蔬菜浓度的十倍以上。不论基因型如何，加工都会降低酚酸的含量。由于麸皮的去除，大多数变化发生在干磨过程中。由于热胁迫，可生物利用的可溶性阿魏酸和对香豆酸的浓度增加到可以忽略的程度。因此，当前用于制造包括早餐谷物在内的许多基于玉米的食品的基于干磨的加工技术不利于增加加工的玉米食品中生物利用酚的含量。这表明，尽管玉米是酚类的极好来源，但在利用这种营养资源之前必须开发替代或互补的加工方法。