RESUMO
Calcium is one of the essential minerals that enhances various biological activities, including the regulation of blood pressure, the prevention of osteoporosis and colorectal adenomas. Calcium-enriched edible mushrooms can be considered as one of the important daily sources of calcium in foods. Calcium accumulation in edible mushrooms is an effective way to enhance its activities because the organic state of calcium metabolites in edible mushrooms can be formed from the original inorganic calcium. The main calcium sources for calcium-enriched edible mushrooms' cultivation are CaCO3, CaCl2 or Ca(NO3)2. The growth and metabolic process of edible mushrooms are significantly influenced by calcium enrichment. Generally, Ca at low levels is good for the production of edible mushrooms, whereas the reverse phenomenon for the growth of edible mushrooms at high Ca contents is observed. In addition, metabolites, for example, phenolics, flavonoids, polysaccharides, enzymes, minerals, etc., are improved when edible mushrooms are enriched at a moderate level of calcium. This review summarized the literature regarding the influence of calcium enrichment on edible mushrooms' growth and major metabolites. Furthermore, the mechanisms of calcium enrichment in edible mushrooms were highlighted. Understanding calcium-enriched mechanisms in edible mushrooms would not only be beneficial to manipulate the cultivation of edible mushrooms having excellent biological activities and high levels of active Ca, but it would also contribute to the applications of calcium enrichment products in food industries.
RESUMO
Carboxyethyl reaction was used as a pretreatment method before grinding and homogenization to prepare microfibrillated cellulose (MFC). The effect of carboxyethylation on the properties of cellulose materials and prepared MFC samples were investigated. Results showed that cellulose materials with different carboxyethyl content were obtained by controlling the chemical dosage. This reaction increased the water retention value, decreased the degree of polymerization and crystallinity, and changed the crystalline structure of cellulose. After pretreatment, the cellulose fibers were easier to be swelled and fibrillated, which greatly reduces the frequency of grinding. In addition, the diameter of the produced MFC decreased with the increase of carboxyl content. The charge density, suspension stability and transparency of MFC increased obviously due to the presence of carboxyethyl groups. This study provides a comprehensive understanding of carboxyethyl pretreatment for the preparation of MFC, which may help to enrich and promote the preparation and application of MFC.
