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<p>This study explores the effects of prolonged mild heating on nisin glycation and its structural and functional consequences. Nisin was incubated with glucose, lactose, or dextran at 60&#xa0;°C and 70% relative humidity for seven days to simulate Maillard-type glycation. We hypothesized that covalent sugar attachment would alter nisin’s physicochemical properties, including charge, solubility, and aggregation, leading to reduced antimicrobial efficacy. Structural changes were confirmed by ortho-phthalaldehyde (OPA) assay, UV-Vis, fluorescence spectroscopy, FT-IR, and MALDI-TOF MS. Glycation extent followed the order glucose &gt; lactose &gt; dextran, correlating with sugar size and reactivity. OPA results showed a reduction in free amino groups, while FT-IR and mass spectrometry confirmed sugar conjugation. SDS-PAGE revealed the loss of native monomer bands and increased high-molecular-weight species for glucose and lactose conjugates. Antimicrobial assays demonstrated significantly decreased activity against <i>Staphylococcus aureus</i> and <i>Bacillus cereus</i> in glucose- and lactose-treated samples, with dextran having a lesser effect. These functional impairments are attributed to charge neutralization (via lysine modification), steric interference with membrane binding, and formation of hydrophobic aggregates. Initially, glycation enhanced solubility, but prolonged incubation led to aggregation and reduced solubility due to melanoidin formation. Statistical analysis (ANOVA, Tukey post hoc, <i>p</i> &lt; 0.05) supported these findings. Overall, our results indicate that Maillard glycation under mild thermal conditions can significantly compromise nisin’s structural integrity and antimicrobial performance. These insights highlight the need to consider glycation effects when formulating nisin-containing products in carbohydrate-rich, heat-processed foods.</p>

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Impact of long-term mild heat on nisin structure and function: formation and effects of Maillard reaction products with carbohydrates

  • 期刊论文

  • 发表日期：

    2025年12月24日

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  • Mahdi Hashempour Sadeghian,
  • Milad Faraji,
  • Nasrin Kazemipour,
  • Seyed Shahram Shekarforoush

摘要

This study explores the effects of prolonged mild heating on nisin glycation and its structural and functional consequences. Nisin was incubated with glucose, lactose, or dextran at 60 °C and 70% relative humidity for seven days to simulate Maillard-type glycation. We hypothesized that covalent sugar attachment would alter nisin’s physicochemical properties, including charge, solubility, and aggregation, leading to reduced antimicrobial efficacy. Structural changes were confirmed by ortho-phthalaldehyde (OPA) assay, UV-Vis, fluorescence spectroscopy, FT-IR, and MALDI-TOF MS. Glycation extent followed the order glucose > lactose > dextran, correlating with sugar size and reactivity. OPA results showed a reduction in free amino groups, while FT-IR and mass spectrometry confirmed sugar conjugation. SDS-PAGE revealed the loss of native monomer bands and increased high-molecular-weight species for glucose and lactose conjugates. Antimicrobial assays demonstrated significantly decreased activity against Staphylococcus aureus and Bacillus cereus in glucose- and lactose-treated samples, with dextran having a lesser effect. These functional impairments are attributed to charge neutralization (via lysine modification), steric interference with membrane binding, and formation of hydrophobic aggregates. Initially, glycation enhanced solubility, but prolonged incubation led to aggregation and reduced solubility due to melanoidin formation. Statistical analysis (ANOVA, Tukey post hoc, p < 0.05) supported these findings. Overall, our results indicate that Maillard glycation under mild thermal conditions can significantly compromise nisin’s structural integrity and antimicrobial performance. These insights highlight the need to consider glycation effects when formulating nisin-containing products in carbohydrate-rich, heat-processed foods.