Laboratory work #5. Features assess the quality of certain types of cereals Theoretical part

Party are considered the blocks of one designation, manufactured by enterprise for one change, with the mass not of more than 1 t. Of each party they select all-level sample - not less than 0,5 kg - by the groove of articles of 5 places in an equal quantity. 10-15 blocks are separated from the all-level sample for the physic chemical analysis.

The number of pieces of blocks in 1 kg determine on the all-level sample, color, smell, taste and exterior view - organoleptically. Blocks must have the form, provided by technological instructions. Brittleness is set to breaking not less than two blocks from the represented model.

The determination of a quantity of scrap and crackers of the reduced size

The blocks of all designations, except vanilla, creamy and amateurish, pour out of the box to the table; select the blocks of smaller size, which are adjacent to the crusts, and separately blocks - scrap. Crackers vanilla, creamy and amateurish shift from the box to the table by hand. A quantity of blocks of the reduced size and blocks - scrap is determined by the demand of user by the dissection of 1-2 boxes from each party and is calculated in the percentages to the overall mass of blocks in the box.

Quantity the crackers reduced size, that are adjacent to the crusts, there must not exceed 8%, scrap in the weight blocks it is not allowed not more than 5%, in packed - 1 block in one to packing.

The determination of swelling

Two crackers prick by long awl either knitting needle from the end part to the depth, which ensures the retention of crackers in the water in the vertical position, or hold crackers in this position by crucible tongs. Both crackers lower in the water with the temperature of 60ºC simultaneously (children's and road on 2 min, rest on 1 min).

The crackers, which do not have the by feel the touch condensed sections, with exception of sections near the impression or the place, stopped up by crucible tongs, are considered swollen.

The determination of moisture content

Of the average model select not less than two slide crackers and grind them on the grater, in the mortar or by knife before obtaining 40-50 g of crumb. Crumb thoroughly is intermixed and from it immediately is taken hinge quantity for determining of humidity and acidity.

Determination of moisture content by desiccation in the cabinets СЭШ. According to the instruction of the committee of standards, measures and meters with the determination of moisture content in the cabinets СЭШ should be used the weighing bottles only of one size (45×20 mm) and dried the hinges quantities at a temperature of 130ºC during 45 min from the moment of load, in this case the duration of drop and rise in temperature after the load of cabinet must be not more than 20 min. For the flatter drying of hinges quantities in the process of drying it is allowed two, triple turning of disk with the weighing bottles.

4-5 g of the analyzed product weigh with an accuracy to 0,01 g on the counterbalances. The prepared hinges quantities in the open weighing bottles, set to the covers taken from them, are placed into the preheated to 130ºC electrical cabinet drier. It is necessary that the deviations from the temperature during the drying indicated would not exceed ± 20. After 40 min, counting from the moment of establishing the temperature 130ºC, cups take out from cabinet by crucible tongs, they cap they transfer into the exsiccate for the cooling, moreover to leave by those not weighted in the exsiccate the cooled hinges quantities not more than 2 h is not allowed.

Humidity, % is determined from the formula:

m1 − m2

B = ------------- 100

M

m1- the mass of weighing bottle with the product before the desiccation, g;

m2 - mass of weighing bottle with the product after desiccation, g;

m - mass of product, g.

For the humidity assumes arithmetic mean of two parallel determinations.

Between the parallel determinations the divergence is allowed not more than 0,2%, and with the control rooms and arbitration - not more than 0,5%.

The acid test

10 g of the ground test is introduced into the dry Erlenmeyer flask. Then from preliminarily measured 100 ml of water (at a temperature of 18-25ºC into the flask pour about 30 ml and they intermix before obtaining of uniform mass. Remaining water is added after this; again they shake up, following then so that it would not remain on the walls of the sticking particles of the analyzed test. Mixtures give to be defended by 15 min, pour the liquid through the close-meshed screen or gauze into the dry vessel, 25 ml of filtrate select from it, they add 5 drops 1% - GO of the solution of phenolphthalein and titrate 0, 1 n. by the solution of alkali before obtaining of the pink dyeing, which does not disappear during the minute. Titration continues, if during the minute painting disappears and does not appear from the addition of 2-3 drops of indicator.

For the expression of acidity in the degrees a quantity of milliliters, gone for the neutralization alkali, measured with accuracy to by 0, 1 ml, they multiply by 4. Eventual result expresses as the mean arithmetic of two titrations, the divergence between which there must not exceed 0, 1 ml.

Divergence as results of acid test in the different laboratories in one and the same test must be not more than 0, 5 deg.

The obtained results compare with the indices, regulated in the All-Union State Stan.s to the appropriate articles.

Control questions:

1. The determination of a quantity of scrap and crackers of the reduced size

2. The determination of swelling

3. The determination of moisture content