In this study, the effect of addition of water-insoluble dietary fiber (IDF) enzymatically extracted from Auricularia auricula on the acidity and viable bacterial count of fermented milk was explored. One-factor-at-a-time method combined with orthogonal array design was used to optimize the formulation (concentrations of IDF, skim milk powder and sodium carboxymethyl cellulose) of fermented milk with added IDF based on sensory evaluation score. The nutrient composition and texture characteristics of the fermented milk prepared using optimized formulation were determined. The results showed that IDF from Auricularia auricula could promote the proliferation of lactic acid bacteria. The optimum formulation consisted of 7% IDF (converted into 0.78% freeze-dried powder) 1.5% sodium carboxymethylcellulose and 2.0% skim milk powder. The prepared fermented milk contained (3.53 ± 0.08)% protein, (3.12 ± 0.03)% fat, (0.78 ± 0.12)% ash, and (19.35 ± 0.49)% solids. Addition of IDF improved the water-holding capacity, hardness, chewiness and viscosity of fermented milk during storage and at the same time showed a protective effect on the starter culture.

Pectin is a natural polysaccharide present in the cell wall of higher plants, which plays an important role in the textual and nutritional properties of fruit and vegetable-based products. There are two types of pectin: high methoxy pectin (HMP, with methoxy content ≥ 7%) and low methoxy pectin (LMP, with methoxy content < 7%). LMP has good stability, gelling and thickening properties, and is widely used in dairy products since it brings a special flavor to fermented milk and increases the viscosity and stability of the product. However, the yield of LMP is low due to the limitations of production and processing conditions. Therefore, the conversion of plant-derived HMP into LMP through de-esterification can meet the industrial demand for LMP. This review outlines the current status of the application of LMP in the dairy industry and its preparation methods including acid de-esterification, alkaline de-esterification, enzymatic de-esterification and amidation, and discusses the effects of these methods on the structure of pectin. Hopefully, this review will provide a theoretical basis for the industrial production and wide application of LMP.

Functional constipation is a clinically common digestive system syndrome, which can cause a series of diseases. Therefore the prevention and treatment of this disease is of great significance. Bifidobacterium is one of the inherent flora in the human intestinal tract, which has been proved to have a significant alleviating effect on functional constipation. This review discussed the recent progress in understanding the alleviating effect of Bifidobacterium on functional constipation with respect to the relationship between the intestinal microbiota and functional constipation, the mechanism of Bifidobacterium in alleviating constipation and the efficacy of various Bifidobacterium strains, in order to provide research ideas for the in-depth development of functional Bifidobacteria strains and for understanding their mechanism in alleviating constipation.