This study aims to figure out the structure of the microbial community in traditional sourdough and the different flavor components of Chinese steamed bread(CSB) made with it. The sourdough samples were selected from Shanxi, Henan and Shandong provinces. The microbial community composition of the sourdoughs was analyzed by a culture-dependent method and high-throughput sequencing, and the flavor compounds of the steamed breads were determined by the solid-phase micro extraction (SPME) method coupled with gas chromatography/mass spectroscopy (GC/MS). The results showed that: in the 28 samples collected, the pH ranged from 3.50 to 4.91, and the total titratable acid (TTA) values ranged from 2.50 to 7.80 mL of NaOH (1 M), while the total number of lactic acid bacteria (LAB) colonies ranged from 10^4 to 10^7 CFU/mL. Lactobacillus, Lactococcus, and Weissella were the dominant genera, as determined by pyrosequencing. A total of 180 LAB strains were isolated and identified using the 16S rRNA gene; the results indicate that Lactobacillus plantarum, Lactobacillus fermentum, and Weissella confusa were isolated with a relatively high frequency. By GC/MS, a total of 24 volatile compounds were detected, including hydrocarbons, aromatic compounds, alcohols, esters, aldehydes, acids, etc. Benzeneethanol and benzaldehyde were abundant in all five samples detected, while benzene-propoxyethyl was not detected in the control group.The flavor compounds contained in sourdough fermented CSBs, both in terms of quantity and concentration, are higher than those in yeast-fermented CSBs. This study provides a useful base for further exploring the deep connections between microbial communities and food flavors.

Polysaccharides in plants and microorganisms have important application value, and their purification and preparation is a prerequisite for in-depth research. However, there is currently a lack of dedicated separation and purification instruments for polysaccharide substances. In our previous work, a polysaccharide purification instrument (PSPI) was designed using post-column split-flow and post-column derivatization schemes and developed. In this study, the PSPI was applied to separation and preparation of the soybean soluble polysaccharides (SSPSs) and obtained the purified SSPS (SSPS-P). The total carbohydrate content in SSPS-P reached 97.2%, compared to 81.7% in SSPS, and the carbohydrate recovery rate was 86.5%. The composition and structure of SSPS-P have been assessed by HPLC, FT-IR, and NMR. SSPS-P was a polysaccharide with a molecular weight (M_w) of 354 KDa, composed of D-glc, D-gal and L-ara with the molar ratio of 0.02:2.08:1.01. The structure of SSPS-P was mainly →4)-β-galp-(1→unit. The α-L-araf residues were also detected in the form of T-α-L-araf-(1→2)-α-L-araf-(1→, →3)-α-L-araf-(1→ and →3,5)-α-araf-(1→. PSPI could be applied for rapid and precise separation and preparation of polysaccharides.

Natural functional polysaccharides are biodegradable, safe, and bioactive macromolecules that contribute significantly to food security. This review provides a systematic overview of their classification, structural characteristics, and applications in agricultural pest control and grain storage, with emphasis on their mechanisms of action and preparation methods. Key representatives including chitosan, alginate, β-glucan, and pectin function through multiple pathways: direct pest inhibition, induction of plant resistance, bioactive encapsulation, and physical barrier formation. Recent advances in extraction, purification, and advanced nuclear magnetic resonance (NMR) techniques—quantitative NMR (qNMR), diffusion-ordered spectroscopy (DOSY), and pure shift methods—are summarized. Challenges including batch-to-batch variability, high production costs, and regulatory hurdles are discussed and future perspectives on green production, precision structural tailoring, and nano-encapsulation are proposed. This review aims to guide the application of polysaccharide-based materials in insect pest management and food protection.