Taste is an important part of human perception of biological intake energy. The gastrointestinal tract also has taste perception. In this paper, the taste receptors and perception pathway in the gastrointestinal tract and the taste signal transduction mechanism in the gut-brain axis are analyzed. Taste perception in the gastrointestinal tract indicates that there are taste receptors such as taste receptor type 1 member (T1R)1, T1R2 and T1R3 and taste receptors type 2 (T2Rs) in the gastrointestinal tract, and taste substances stimulate the secretion of cholecystokinin (CCK) and peptide YY (PYY) by intestinal endocrine cells, which is related to the transmission of taste signals in the neurons. The umami substance monosodium glutamate present in the intestinal tract significantly activates the neural networks in the habenulae, amygdala and hypothalamus subnuclei of the brain, suggesting that taste perception in the gut-brain axis is under the co-regulation between gastrointestinal receptors and brain-gut peptides, neurons and the central nervous system of the brain. In this context, a hypothesis about the mechanism of taste signaling via the gut-brain axis has been proposed. It states that sweet taste receptor T1R2/T1R3 and umami taste receptor T1R1/T1R3 had similar signal transduction pathways. After taste substances acts on the intestinal tract, they bind to the corresponding taste receptors in the intestinal tract, activates phospholipase C-β2, releases Ca²⁺, causes changes in the intestinal environment, and stimulates intestinal endocrine cells to secrete hormones such as PYY and CCK, which are specifically recognized by intestinal neuron synapses， and transmit taste signals to the nerve center of the brain. However, the metabotropic glutamate receptor 4 (mGluR4) and bitter receptor T2Rs signal transduction pathways reduce the concentration of 3’,5’-cyclic adenylic acid in the cytoplasm by activating phosphodiesterase, thereby relieving the inhibition of cyclic nucleotides and releasing Ca²⁺. Taste preference mediated by the gut-brain axis provides a new direction for the development of new therapeutic drugs and the discovery of new drug targets for patients with changes in taste sensation. Research on the mechanism of taste signal transduction in the gut-brain axis will provide a molecular framework for the neural control of gastrointestinal physiology and accurate control of the physiological response of the human body to taste nutrients, and provide a new theoretical basis for understanding the intake, metabolism and regulation of taste substances in the gut-brain axis and the development of new taste perception pathways.

Erythritol, sorbitol, maltitol, fructooligosaccharide or isomaltulose instead of sucrose was used in lotus paste filling. The effects of different sweeteners on the eating quality of lotus paste filling were investigated by gas chromatography-ion mobility spectrometry (GC-IMS), an electronic tongue, a texture analyzer and sensory evaluation. The results showed that sugar alcohol sweeteners significantly increased the brightness of lotus paste filling, and fructooligosaccharide and isomaltulose deepened the color of lotus paste filling. In addition, the water content of lotus paste filling was negatively correlated with the hardness (r =-0.882, P < 0.01), but positively correlated with the adhesiveness (r =0.620, P < 0.01) and cohesiveness (r =0.622, P < 0.01). All functional sweeteners except erythritol increased the water content and improved the texture quality of lotus paste filling. The results of electronic tongue test showed that the functional sweeteners reduced the sweetness of lotus paste filling and helped to mask undesirable tastes such as bitterness. A total of 32 volatile substances were detected in lotus paste filling by GC-IMS, including aldehydes (53.94%–70.60%), ketones (10.36%–18.63%), alcohols (5.25%–14.25%), acids (1.62%–2.81%), esters (0.22%–0.57%), furans (0.29%–0.72%) and alkanes (0.47%–0.71%). Oligofructose and isomaltose increased the types and contents of aldehydes and ketones and enriched the flavor of lotus paste filling. The flavor of lotus paste filling with sugar alcohols was bland. Isomaltulose and fructooligosaccharide improved the quality of lotus paste filling, and therefore could be used as a substitute for sucrose in the production of low-sugar lotus paste filling.