Determination of other physical properties of food (3)

4.
Determination of the expansion rate of ice cream

The expansion rate of ice cream refers to the rapid cooling of the mixture material in the cooling stage of the production process, the water forms fine crystals, and the large amount of air mixed in is evenly distributed in the material with tiny bubbles, which expands the volume of the ice cream and gives it Good taste and organization
.

(1) Principle Using the principle of ether reagent defoaming, a certain volume of ice cream sample is thawed and defoamed, and the volume of air contained in the ice cream is measured to calculate the expansion rate of the ice cream
.

(2) Operation steps

①Take a 250mL volumetric flask and a glass funnel, accurately weigh a 50cm3 ice cream sample, use 200mL of 40～50℃ distilled water to transfer all the weighed ice cream samples into the volumetric flask, put it in warm water, and wait for the bubbles to disappear Cool down
.

②Suck 2 mL of ether as defoamer and drop it into the volumetric flask to eliminate foam
.

Add distilled water to the volumetric flask mark, and record the volume (mL) of the added distilled water

(3) Result calculation

In the formula β——the expansion rate of ice cream,%

V ₁ ——the volume of ether added , mL;

V ₂ ——The volume of distilled water added, mL
.

The industry standard requires the expansion rate of ice cream to be 85% to 95%
.

5.

Determination of carbon dioxide in carbonated beverages

The carbon dioxide content in carbonated beverages is a very important quality indicator
.

The detection method specified in GB/T10792-2008 is the pressure reducer method (conventional inspection method) and the same method of distillation titration (arbitration method)

Use a manometer for carbonated beverage sample bottles (cans)
.

(See Figure 2-13) Pierce the needle into the cap and unscrew the exhaust valve.

Figure 2-13 CO ₂ pressure tester in carbonated beverages

According to the measured pressure and temperature, check the carbon dioxide absorption coefficient table (see Table 2-4) to obtain the volume multiple of CO ₂ content
.

Table 2-4 Carbon dioxide absorption coefficient table (partial data)

Note: For more data, see GB/T10792-2008
.

6.

Determination of beer foamability

Foam is one of the important characteristics of beer, and beer is also the only alcohol that uses foam as its main quality indicator
.

(1) Principle Under the same temperature and fixed conditions, use an appliance of the same structure to measure the disappearance speed of beer foam, expressed in s
.

(2) Instruments

①Stopwatch
.

②Colorless and transparent glass: thoroughly clean the oil stains on the surface in advance, and use it after drying
.

Before the test, take the cup out and place it on the test bench for 10 minutes

(3) Operation steps

①Foam shape inspection: Place the glass cup on the base of the iron stand, and fix the iron ring at a distance of 3cm from the mouth of the cup
.

Place the original bottle (can) of beer in a water bath at 15°C, keep it at isothermal temperature, then remove the lid, immediately place the bottle (can) mouth on the iron ring, and pour the beer into the cup at a uniform flow rate along the center line of the cup until the foam height Only when it is aligned with the mouth of the cup

It is strictly forbidden to have air flow during the test, and the sample should avoid shaking before the test
.

②Test of bubble retention: record the time from the beginning of the bubble to the disappearance (or only the 0.
5cm2 wine surface is exposed), expressed in s
.

Observe the condition of the foam hanging cup