The Effects Of Pre-treatment And Adding Ways Of Bird's Nest On Sensory And Physicochemical Properties Of Ice Cream

Ice cream has long been favored as a delicious frozen dessert by many consumers.To cater to the changing tastes and preferences of the patrons,the addition of solid particles such as nuts and dried fruit into ice cream has become a growing trend among industry players.However,these particles are only confined to food with very low moisture content,high moisture substances in solid form are rarely added to ice cream and relevant research reports are limited.Based on this reasons,this study selected bird's nest as a representative high moisture food to investigate the physicochemical and sensory properties of bird's nest and ice cream following pretreatment approaches of high moisture solid material and its different forms incorporated into ice cream.Firstly,using the consumer testing as a means of sensory evaluation,determined the optimum conditions of the pretreatment process of bird's nest,the sugar type,the added form and amount in ice cream: the dry bird's nest was soaked to 6-6.5 times of its own weight by water;the pretreatment process involved adding 20 times the mass of the 60% sugar solution to the soaked bird's nest then braising it by boiling water bath;the pretreatment sugar was trehalose;the added form was mixed with the freezing ice cream;the added amount was dry weight of bird's nest accounted for 1.0% of the ice cream.The bird's nest ice cream made by this technique has the highest degree of consumer preferences.Descriptive analysis of sensory evaluation methods were used to research the influence of the addition of bird's nest on sensory quality of bird's nest and ice cream.The results showed that the sensory properties of bird's nest,such as hardness,iciness,toughness,elasticity,chewiness and smoothness were different.The iciness was negatively correlated with the preference of bird's nest and had the most obvious effect on preference.The bird's nest with moderate degree of smoothness,elasticity and hardness as well as higher chewiness had higher degree of preference.In the cases of toughness and preference,no obvious correlation between the two was noted.The sensory attributes of ice cream had significant difference in iciness,sweetness,satiny feel,fat feel and hardness.The ice cream with higher consumer preferences had a weak sense of iciness,moderate degree of hardness,but the sense of sweetness,sanity feel and fat feel were much stronger.The results of the physical and chemical properties of bird's nest showed that high concentration of sugar treatment increased the sugar content,viscoelasticity and glass transition temperature,reduced the water content,free water content and melting termination temperature.The differences among physicochemical properties of bird's nest treated by different processes and different sugars were obvious,of which 60% trehalose solution braised bird's nest had moderate viscoelasticity,free water content was only 0.55%,the glasstransition temperature was-28.32? and the melting temperature was-12.14?.Up incorporation of sugar treated bird's nest to ice cream,the sugar content and glass transition temperature of bird's nest were further improved,and the melting temperature of trehalose,maltose,glucose and sorbitol treated bird's nest were slightly increased.The water content and melting termination temperature of bird's nest added to ice cream before freezing were higher than that of those added to ice cream after freezing,but the sugar content and glass transition temperature were lower.With the increase of the added amount of bird's nest,the water content of bird's nest gradually decreased while the sugar content and the glass transition temperature increased first and then decrease.On the contrary,the melting temperature of ice crystal initially diminished before witnessing an increment.The glass transition temperature of the optimally processed bird's nest was further increased to-22.24?while the melting termination temperature changed to-11.79?.In addition,part of the fat in ice cream also infiltrated into bird's nest during the mixing process and decreased gradually from the outer edge to the inner part.The results of the physical and chemical properties of ice cream showed that the migration of the material between the bird's nest and ice cream changed the water content of ice cream.Differently treated bird's nest added to ice cream increased the hardness and slowed the melting rate of the ice cream.High water content of bird's nest led to greater hardness of ice cream,but the increase of water content accelerated the melting rate.The overrun of ice cream due to the addition of bird's nest before freezing was increased from 69.65% to 81.25%,and fat destabilization on the other hand reduced from 37.75% to 29.76%,which accounted for the reduction of hardness and the slow down of melting rate.When the added amount of bird's nest was 1.0%,the hardness and melting rate of this ice cream were close to that of pure ice cream.Further increase of the levels of the bird's nest made the hardness of ice cream lower than the pure ice cream and the melting rate substantial slowdown.