Change And Mechanism Of Whipping Properties And Qualities Of Whipped Cream

The effects of preparation conditions, protein, oil and emulsifier on quality of whipped cream such as organoleptic properties, overrun, textural properties and stability were investigated systematically in this dissertation. The submicroscopical terms of fat globules size distribution, fat globules partial coalescence rate, protein surface concentration were studied in details, and further related with macroscopical quality. Whipping mechanism of whipped cream was discussed.The results of response surface design for optimization of process conditions of emulsions showed that the homogenization pressure had significant effects on overrun, foam firmness and stability (P<0.0001). The process conditions of homogenization pressure of 39.7 MPa, aging time of 2.98 h, heat treatment temperature of 60.27 oC were best for whipped cream according to the results. Mechanism of effects of homogenization pressure on quality of whipped cream was studied. Big fat globules were broken up into small ones by high homogenization pressure, which resulted in decrease of surface protein concentration, so fat globules coalesced partially more quickly. If homogenization pressure was between 20-40 MPa, quality of cream improved with increase of homogenization pressure. However, quality decreased due to higher pressure that was between 40-60 MPa.Type and concentration of protein had significant influence on quality and whipping properties. Whey protein decreased potential for partial coalescence of fat globules by forming a network on interface of fat globules, which resulted in low stability and overrun of whipped cream. Compared with whey protein, casein was displaced by emulsifier more easily and showed better foamability. The study showed that whipped cream containing 0.70% casein reached their best quality such as overrun of 346%, stability of 2.4h, foam firmness of 303g, good sense of melting in mouth and light greasiness. Whey protein was not suited for whipped cream as a single protein in emulsions due to bad quality.Type and concentration of oil were very important for fat globules partial coalescence rate and surface protein concentration. Melting point of oil had great influence on fat globules partial coalescence, but there was not linear relationship between them. Oil melting point effected partial coalescence rate in the order BL-37> BL-35> BL-41> BL-39. Reducing concentration of protein and emulsifier on interface of fat globules by addition of concentration of oil and fat globules led to lower stability against partial coalescence. Emulsions containing 20-23% BL-41 type oil could be whipped into the best foam. The experiment results showed that foam of 20% BL-41 appeared best quality such as overrun of 349%, stability time of 2.5h, foam firmness of 272g and good organoleptic properties.HLB value and concentration of emulsifier affected greatly quality of whipped cream. High HLB value of emulsifier, which affinity to fat globule interface was strong, displaced less adsorbed protein from the interface. Presence of high concentration with same HLB value led to high partial coalescence rate by displacing more protein. The study indicated that emulsion containing 0.60% emulsifier with HLB value 7 could be whipped into foam of good quality such as overrun of 366%, stability time of 2.4 and the best organoleptic properties.Three stages could be distinguished in process of whipping of whipped cream according to whipping mechanism. During the first stage most of the air incorporated into emulsions existed as big bubbles, which was stabilized by protein with good foamability. Some of big bubbles were broken into smaller ones by further whipping. A few fat globules coalesced partially, but they could not coat bubbles effectively, therefore foam was not stable enough. In the second stage, stability of fat globules against partial coalescence dropped due to rapid substitute of protein by emulsifier. Fat globules coalesced partially and rapidly in the dynamic process of bubble break-up and coalescence, which led to rapid increase in aggregates of fat globules. Bigger bubbles broken into smaller ones were main trend in this stage. Smaller bubbles were coated more coalesced fat globules with comparison to the first stage, hence stability, foam firmness, consistency, cohesiveness and viscosity of the responding foam increased significantly. In the last stage, overrun of foam decreased with too much aggregates of fat globules easily penetrating bubbles, accompanied by rapid increase in foam firmness, and further whipping worsened quality of whipped cream.