Unravelling the composition and envisaging the formation of sediments in traditional Chinese vinegar

摘要

Sediments will spontaneously form in traditional Chinese vinegars (TCVs), which negatively affect the product acceptability. Here, sediments in Shanxi aged vinegar, a representative TCV, were investigated to unravel the microstructure and composition. Morphologically, crystals, amorphous substances and thalli were three common forms. Composition analysis by confocal laser scanning microscopy manifested starch/polysaccharides and proteins were present. Proteins (~30%), carbohydrates (>10%), crude fats (~17.00%) and metallic elements (~3%) were four main components determined, and polyphenols and flavonoids accounted for about 1% in the sediments. The crystals were recognised as calcium oxalate crystals by micro-area energy-dispersive X-ray and micro-Raman spectrometry, and they were mostly in dihydrate form. This is the first report on the discovery of calcium oxalate crystals in the vinegar. Crystallisation into crystals, self-assembly and polymerisation of polymers, aggregation of particles, as well as interactions between polymers and particles form a basic model of sediments formation in TCV.