In oleometer give on technical weights 1,7-1,9 g previously of hashed mayonnaise and place it in boiling water on 10 mines. Then in oleometer pour 18 3 of a sulfuric acid (density 1,5 g/sm3) and 1 sm3 isoamyl spirit. Close by a dry fuse, well stir up, heat up on water bath, with temperature 65-700, periodically stirring up up to complete dissolution of protein substances of mayonnaise, and during 5 mines make centrifugation with speed 1500 ./mines.
Then oleomtre immerse by a fuse downwards on 5 min in water bath with temperature 65-700 and make readout of fat, holding oleometre vertically so that the border of fat was at a level of an eye. By movement of a fuse upwards and downwards establish the bottom border level of fat on the whole division of a scale oleometre and from it count number of divisions up to bottom meniscus of fat level.
The contents of fat (), in percentage expect under the formula:
,where
a- indication of oleometre;
m sample of mayonnaise, ;
- factor of recalculation of the indications oleometre in percents (To = 5).
The divergence between two parallel definitions should be no more than 0,5 %.
Definition of acidity. In conic flask give about 2 gof mayonnaise on technical weights, add 50 sm3 of distilled water. Mix and titrate by a solution of caustic alkali of concentration 0,1n at the presence of the indicator - phenolphtalein before occurrence of weak - pink colouring which is not disappearing during 1 min.
For mayonnaise with sauce "Southern", with tomato - paste the quantity of distilled water is increased up to 100 sm3. For exacter establishment of the end of titration of these mayonnaises near to titrated sample it is necessary to put control flask with same or close to it a sample of mayonnaise in 100 sm3 of distilled water.
Acidity of mayonnaise (X.) count on an acetic acid under the formula:
,where
V - amount of a solution of alkali of concentration 0,1 n, used by titration, sm3;
- amendment to a titer of a solution of alkali of concentration 0,1 n;
0,0006 - factor of recalculation on an acetic acid;
m sample of. mayonnaise,.
The divergence between two parallel definitions should not exceed 0,2 %.
Definition of emulsion stability. The parameter of emulsion stability of mayonnaise is served a quantityof fat allocated from mayonnaise as a result of strong mechanical and thermal influence.
The order of performance of job. Definition of emulsion stability of mayonnaise make in two steps: centrifugal test-tube with divisions by capacity 10 sm3 fill before the top division by mayonnaise, then place test-tube in a centrifuge and centrifugate with speed 1500 ./min, then observe destruction of emulsion. Further that test-tube place in boiling water on 3 min and again centrifugate during 5 min.
Stability of emulsion expect under the formula:
,where
X stability of emulsion, % about.,
V - quantityof the selected fat, sm3;
10 - reduction of volume taken for the analysis to 100 sm3.
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The results of an estimation of quality of mayonnaise on physical-chemical parameters issue as tab. 34.5.
Physical-chemical parameters of quality of mayonnaise
| Parameter | Norms | The fact |
| 1. Moisture content, %, no more 2. Contents of fat, %, not less 3. Acidity in recalculation on an acetic acid, %, no more 4. Stability of emulsion of the allocated fat, %, no more |
The conclusion about quality of mayonnaise __________________
Laboratory job 5
Theme: Estimation of quality of cocoa powder and chocolate.
The purpose of work: make skills and attainments of identification of various kinds of chocolate and definition of quality of cocoa powder and chocolate.
The task
1. Definition of organoleptic indicator of cocoa powder and chocolate.
2. Definition of cocoa powder grinding degree.
3. Definition of fat mass fraction by refractometric method.
4.Draw up report on the work done.
Theoretical part
To get cocoa powder and chocolate the cocoa beans are cleaned and roasted. Then they go trough a machine which cracks them A current of air removes the shells, leaving the edible pieces of cocoa, called nibs.These nibs, containing about 54% fat (cocoa butter), are ground between rollers which free the fat and produce a brown liquor. This liquor is treated in presses which turn it into a hard cake after squeezing out some of the fat. This is next crushed and sifted to produce the familiar brown cocoa powder. In the manufacture of chocolate the roasted nibs are mixed with sugar and roughly ground to a paste.
