1. INTRODUCTION
Ice cream is a complex colloidal system, which consists of air bubbles, ice crystals and fat globules. There are many formulation and [processing factors that influence the quality of ice cream. Stabilizer is such a factor, the function of stabilizer is to improve air incorporation, give body and texture, control meltdown of the ice cream(Keeney 1982).The aim of this report describes the procedure of manufacturing ice cream, and discuss what the difference between the two types of ice cream (different stabilizers, one is pectin, the other one is LBG) through the Quality control (QC) tests.
2.2 METHOD
2.2.1 Process
All the equipment was Cleaned, sterilised and rinsed Before starting. First, the measured water was added to the jam pan and heated to 60°C. Then, the milk powder and the sugar was added to the jam pan and heated to 71°C. Emulsifier and Stabiliser(pectin or LBG) was added step by step and the mixture was held at 71oC for 10 minutes. To collect and transform the mixture, stainless steel bucket was used through whole process.
Next, ice cream mixture was homogenized at 4000psi before it was frozen. It is important that keeps homogenizer full during the period and first 200 ml of mix was discarded.
The homogenised ice cream mix was placed through the funnel at the top of the ice cream freezer. At the beginning, the switch was turned to the right, at the same time, the temperature of the ice-cream mixture was monitor until it reached -4°C, then, the switch was turned to the left.
2.2.2 Quality control (QC) tests
Overrun
The overrun measurement was taken per sample by the weight of ice cream mix in a overrun cup. The excess of the cup should be removed and weighted on the overrun scales. Then, the percentage was read on the inner side of the scales.
Density
Each three samples of pectin or LBG were weighted, and the volume of container were measured by 10 times.
Formula:
Density = weight/ mean volume
Texture analysis
Texture Analysis was used to evaluate texture characteristics which is the hardness of ice cream. In this assessment, the sample was transferred from the freezer and tested at room temperature (25º). One measurement was taken per single sample. The conditions for analysis were as follows: a diameter probe penetrated the ice cream to a depth of 4 mm. The analysis used 400 N load cells.
Statistical analysis:
Analysis of variance (ANOVA) was used to find effects of the factor on over-run, density, melting resistance and hardness. The factor was stabilizer (pectin, LBG). If P<0.05, the data were considered significantl different.
Melting
Two samples of each stabilizer was put into oven at 60°C. There was a box put under each of them. The boxes were weighted every minute and wrote down the weight of melting down of ice cream.
3. RESULT AND DISCUSSION
It was a significantly differennce (P<0.05) that the overrun of the ice cream with LBG is higher than the ice cream with pectin (shown in Table 3.1). The main reason is that LBG can create air cell structure smaller and allowed easy incorporation of air into the mix than pectin, so that it increased the number of air cells formation, which means LBG made ice cream include more air(Bahramparvar and Tehrani 2011). It also influnced the density of ice cream, there was a significantly differennce ( P<0.05 ) of the density between ice cream with LBG and the ice cream with pectin (shown in Table 3.2).
