Effect Of Oral Processing On The Dynamic Texture And Taste Perception And In Vitro Starch Digestion Of Pumpkin Breads

Oral processing of food studies the series of physicochemical changes that occur from the entrance to the swallowing of food.Along with mastication,food destruction and food-body interactions lead to the perception of dynamic changes in texture and flavor.At the same time,the α-amylase enzyme in saliva promotes the initial digestion of starch when it comes into contact with food.Therefore,oral processing contains two basic functions: sensory experience and initial digestion.Oral processing of food is essential for understanding the taste and digestion of food.Bread,one of the staple foods with complex microstructure and high glycemic index(GI),is a highly open and foamy structure before the mouth and forms sticky boluses after the mouth through tooth breakage and saliva lubrication,which affects the perception of the product through the interaction between food and saliva.In this study,six types of bread(10% juice,15% juice,20% juice,10% puree,15% puree,20% puree)with different pumpkin additions(10%,15%,20% of flour weight)and pumpkin treatments(raw pumpkin juice and cooked pumpkin puree)were used to investigate the effects of the initial characteristics of bread on oral processing and the texture,taste and subsequent gastrointestinal digestion of bread during oral processing.The main findings of the changing patterns of characteristics are as follows:1.The influence of the initial properties of pumpkin bread on the oral processingThe amount of pumpkin added and the pumpkin treatment had significant effects on the physical,chemical,and structural properties of pumpkin bread.The breads with higher pumpkin content(20% pulp,20% puree)had higher moisture content,lower hardness values,and higher surface porosity.At the same pumpkin addition,the pumpkin puree bread was softer and had lower surface porosity than the pumpkin pulp bread.When subjects chewed these six types of pumpkin bread,the breads with soft texture and high moisture content(20% pulp,20% puree)tended to require less chewing times and chewing time;therefore,the hardness and moisture content of the bread were the main reasons affecting the oral processing behavior of people chewing bread.2.Texture characteristics of pumpkin bread during oral processingAs chewing proceeded,the moisture content and saliva impregnation of the boluses gradually increased,the hardness gradually decreased,the stickiness gradually increased,and the proportion of small-area particles became larger.The bread with less pumpkin added(10% pulp,10% puree)had higher salivary impregnation,higher hardness,lower viscosity,and smaller A50 values after chewing.The differences in the texture properties of the six pumpkin breads decreased at the end of chewing compared to the pre-chewing and pre-chewing periods,tending to decrease to similar values.The results suggest that the texture properties during chewing are influenced by the initial characteristics of the breads.When subjects were evaluated for dynamic texture perception,the harder bread(10% pulp,10% puree)was perceived as chewy at the beginning of chewing and the softer textured bread(20% pulp,20% puree)was perceived as soft,but by the end of chewing,all six pumpkin breads were perceived as hydrated,sticky and crumbly.An analysis of the texture characteristics of the boluses in relation to the sensory evaluation of the subjects revealed that the moisture and saliva content,as well as the hardness,chewiness and stickiness values obtained using instrumental analysis,explained the texture perception of the boluses.Thus,the texture properties of the food boluses were highly correlated with the perceived textural attributes during oral processing.3.Taste characteristics of pumpkin bread during oral processingAs chewing proceeded,the p H of the food boluses gradually increased,and the sodium chloride content first decreased and then increased.The five organic acids showed no significant trend throughout oral processing,with the highest concentration of tartaric acid(3326.7-5867.59 mg/kg),followed by oxalic acid(697.3-2417.5 mg/kg),malic acid(424.15-2170.2 mg/kg),succinic acid(486.06-1348.87 mg/kg),and citric acid(146.34-798.24 mg/kg),and TAV>1 for the five organic acids,indicating that organic acids contribute significantly to the taste perception during oral processing of breads.At the same chewing stage,p H was higher in 10% pulp and 10% puree breads,sodium chloride was highest in 15% pulp and 15% puree breads,oxalic,tartaric and malic acids were higher in 20% pulp and 20% puree,and citric and succinic acids were higher in 15% pulp and 15% puree.Dynamic flavor perception assessment of the subjects revealed sweet,sour and savory flavors as the dominant flavors during the oral processing of the bread.Correlation analysis of the taste characteristics of the boluses and the dynamic flavor perception of the subjects indicated that sodium chloride and organic acids were the key flavor compounds in the oral processing of pumpkin breads and they contributed significantly to the flavor perception of the breads.4.In vitro starch digestion characteristics of pumpkin bread after oral processingFood boluses from different chewing stages were collected for subsequent in vitro starch digestion.Kinetic parameters during intestinal digestion indicated that the type of pumpkin bread played a key role in the rate of starch digestion,with 10% pulp having the highest starch hydrolysis rate.HI and e GI values gradually increased with mastication,RDS content gradually increased throughout oral processing,SDS content showed no significant trend and RS content gradually decreased.20% puree bread had the highest RDS content,15% puree bread had the highest SDS content among the six types of pumpkin bread at the same chewing stage,and 10% pulp and 10% puree bread had the highest RS content.In conclusion,the in vitro starch hydrolysis kinetics of the breads were influenced by the type of bread and mastication performance.To further investigate the relationships,partial least squares regression analysis(PLSR)was performed,and the results showed that the physical,chemical,and structural properties of the bread and the corresponding mastication parameters all had an effect on the in vitro starch digestion characteristics of the bread,with the structural and textural properties of the bread being the main determinants of the kinetics of intestinal starch hydrolysis.