Screening of a High-Affinity Aptamer for Aflatoxin M1 and Development of Its Colorimetric Aptasensor.

Aflatoxin M1 (AFM1), a secondary metabolite of Aspergillus spp., is highly toxic and widely present in food matrices. Therefore, the detection of AFM1 is of great importance for the protection of food safety. In this study, a five-segment sequence was designed as the initial library. Graphene oxide-SELEX (GO-SELEX) was applied to screen AFM1. After seven rounds of repeated screening, affinity and specificity assays showed that aptamer 9 was the best candidate for AFM1. The dissociation constant (Kd) of aptamer 9 was 109.10 ± 6.02 nM. To verify the efficiency and sensitivity aptamer for the detection of AFM1, a colorimetric sensor based on the aptamer was constructed. The biosensor showed good linearity in the range of AFM1 concentration of 0.5-500.0 ng/mL with a detection limit of 0.50 ng/mL. This colorimetric method was successfully used for the detection of AFM1 in milk powder samples. Its detection recovery was 92.8-105.2%. This study was conducted to provide a reference for the detection of AFM1 in food.

Effects of radio-frequency energy on peroxidase inactivation and physiochemical properties of stem lettuce and the underlying cell-morphology mechanism.

This paper investigated the effects of radio-frequency (RF) energy and conventional hot-water blanching (95 °C for 2 min) on the peroxidase (POD) activity, physiochemical properties, and changes in the cellular morphology of stem lettuce. The relative residual POD activity significantly decreased (P < 0.05) from 66.03% to 6.46% with increased RF heating temperature (65 °C-85 °C). The weight loss (3.06%-7.64%), color, texture, relative electrolyte leakage (23.45%-67.90%), and residual vitamin C content (72.22%-16.67%) significantly changed (P < 0.05) with increased RF heating temperature (65 °C-85 °C). Micrographs indicated that the changes in physiochemical property can be attributed to the destruction of cell membranes, loss of cell turgor, reduced rigidity of cell walls, and loose adhesion between adjacent cells. Samples treated by RF heating at 75 °C showed lesser cell damage and better nutrient retention than those treated by hot-water blanching at a similar level of POD inactivation.