Duanyin Gu

Blanching is a critical postharvest step that influences broccoli color, texture, flavor, and nutritional quality, and may affect the formation of warmed-over flavor (WOF) related volatile compounds under thermal processing. This study compares hot water blanching (HWB, 98 ± 1 °C, 30 to 150 s) and steam blanching (SB, 100 °C, 30 to 150 s) by analyzing color, texture, peroxidase activity, electronic nose, volatile compounds, sulforaphane content, and scanning electron microscopy (SEM) to determine how blanching conditions influence physicochemical attributes, cellular organization, and WOF-related volatile profiles in broccoli. Overall quality retention was superior with SB, particularly at 60 s, as evidenced by lower residual enzyme activity, improved firmness retention, better maintained cellular structure as observed microscopically, and higher sulforaphane retention relative to HWB. Multivariate analysis identified nine key volatile markers (variable importance in projection (VIP) > 1 and relative odor activity value (ROAV) > 1), including the WOF-associated aldehyde pentanal. Broccoli treated by SB for 60 s exhibited markedly lower levels of these aldehydes than samples subjected to HWB. Correlation analysis revealed a positive correlation between sulforaphane and sulfur-containing volatile compounds, including dimethyl disulfide and dimethyl trisulfide. This correlation mainly derived from the superimposed degradation of different precursor pools under thermal action: at high temperatures, dimethyl disulfide is one of the main volatile products generated from the thermal degradation of sulforaphane; meanwhile, during heating, intermediates derived from S-methyl-l-cysteine sulfoxide undergo thermal reactions to form dimethyl disulfide and dimethyl trisulfide. Collectively, these results support SB as an effective strategy to mitigate WOF while maintaining the nutritional quality of broccoli and potentially other cruciferous vegetables.

Objectives: To slow down the chemical fixation of phosphate fertilizer, reduce the risk of active phosphorus leaching, stimulate the inherent phosphorus resource activity of soil, and improve phosphorus supply capacity. Methods: This study utilized a combination of field experiments and indoor chemical analysis. Six types of exogenous organic matter (fulvic acid, biochar, compound microbial fertilizer, high-energy microbial inoculum, pig manure-vermicompost, cow manure-vermicompost) were added based on conventional fertilization. The experiment was conducted under the wheat-maize rotation system in the Huang-Huai-Hai region. Results: Compared with control (CK) without exogenous organic matter (EOM), all the other treatments with EOM had an enhancing effect on the available phosphorus of the cultivated soil. During the maize harvest, the combined application of biochar, pig manure-vermicompost and cow manure-vermicompost treatment significantly increased the content of available phosphorus in 0–20 cm soil by 45.87–56.59% compared with CK. The combined application of fulvic acid, biochar, pig manure-vermicompost and cow manure-vermicompost treatment significantly increased the content of Ca₂-P in 0–20 cm soil by 34.04–65.14%. The content of Ca₁₀-P in each treatment with EOM exhibited a lower level compared to CK. EOM could slow down the fixation of phosphorus to some degree. Correlation analysis revealed significant associations between Ca₂-P, Ca₈-P, Al-P, Fe-P, neutral phosphatase activity, acid phosphatase activity, and the available phosphorus content in the soil. The combined application of fulvic acid, biochar, and cow manure-vermicompost could enhance the activity of neutral and acid phosphatase in topsoil to a certain extent, thereby facilitating the conversion of phosphorus into highly available Ca₂-P. EOM could enhance the soil phosphorus availability and decelerate the conversion of soil phosphorus into O-P and Ca₁₀-P forms with low availability. Among all treatments, biochar exhibited the most pronounced efficiency in mitigating phosphorus leaching downward. Conclusions: All the EOMs had the potential to enhance the conversion of phosphorus into soluble phosphorus (Ca₂-P), thereby mitigating the chemical fixation of soil phosphorus and ameliorating non-point source pollution caused by phosphorus. EOM enhanced the activity of neutral and acid phosphatase, which was beneficial to the conversion of organic phosphorus to inorganic phosphorus and increasing the content of available phosphorus. All EOMs had good effects on the retention of soil effective phosphorus, among which biochar had the best effect on retaining effective phosphorus in the tillage layer and blocking phosphorus leaching downward.