|| Type of commodities
|| Signs of detection
|| Starch, including modified
|| Iodine-starch reaction
|| Appearance of blue staining
|| Soda drinkable
|| Hydrocarbonate sodium
|| Titration with acid
|| Release of CO2 by reaction with acid
|| Food pectin
|| Formation of white precipitate of calcium pectate
|| Food acids
|| Titration with alkali in the presence of phenolphthalein
|| Disappearance of red color
|| Synthetic dyes of red color
|| Synthetic dyes
|| Addition of alkali or soda
|| Stain stability
|| Natural dyes
|| Anthocyanins, betanine
|| Change in color to blue or violet
|| Boiling in water
|| On the brown-green
| Carotene and carotenoids
|| Boiling in a weak alkali solution
Starch is a stabilizer and improver for the consistency of many products. However, different types of it have different ability to stabilize and improve consistency. The most valuable technological properties are potato starch, the least valuable - corn. Therefore, often enough potato, more expensive starch is replaced with cheap corn.
Falsification of starch can be assorted, qualimetric, quantitative and informational. Storing starch in rooms with high humidity in order that it absorbs moisture and becomes heavier, leads to quantitative falsification.
Assortment falsification is carried out only at the species level, when potato or rice starch is partially or completely replaced by less valuable corn. In addition, a partial or complete replacement of starch as a more expensive product with wheat flour is possible. You can detect falsification by the shape and size of the starch grains, and the addition of wheat flour - when washing by the presence of gluten.
Qualitative falsification manifests itself in the form of re-sorting, while the Extra variety and Extra variety (in potato starch) are partially or completely replaced by the lower ones - 1st or 2nd grade. To identify this type of falsification, reliable identification features are known (ash content, number of craters per 1dm2, color, chandelier (shine) - in higher grades).
Information falsification often serves as reinforcement of the first two types of falsification and is almost not used as an independent species.
Table salt is one of the cheapest products, so it rarely undergoes falsification. Exceptions are only two types of salt: iodized and fluorinated, in which valuable trace elements of iodine and fluorine are absent due to falsification of formulations and are not included in their composition. In addition, iodized salt after the expiration of the storage period (6 months) loses iodine due to its oxidation and destruction.
The salt is a crystalline free-flowing product in which foreign mechanical impurities are not allowed, not related to the origin and nature of the salt. The color of the salt is white with possible shades of grayish, yellowish or pinkish color, depending on the place of salt production and its grade, determined by the degree of purification. The smell of table salt is absent. According to the method of production, the salt is divided into stone, self-planting, batch and evaporation. The quality is classified by salt: extra, higher, first and second grade.
Iodized salt is a common salt with a small amount of iodide or potassium iodate. With prolonged or improper storage, loss of iodine ions or, accordingly, of useful functional properties occurs, and therefore a constant control over the iodine content is necessary.
In table salt as salts of various acids or acid residues, lead, copper, potassium, arsenic, mercury, zinc and other elements can be contained. However, their allowable content should not exceed the level established by the SanPiN. To determine the degree of safety of goods, including food, in recent years test methods are widely used based on determining the presence of a component in the product according to the sensitivity limit of the chemical or biochemical reaction. Test methods are close to measuring values, and from simplicity to sensory methods, so now these methods are increasingly used in identification and replace more expensive measuring methods.
Objective: To carry out identification examination of starch and food iodized salt using measurement and test methods. Means of education:
1. GOST 7699-78. Potato starch. Technical conditions.
2. GOST R 51985-02. Corn starch. General specifications.
3. GOST R 51574-2000. "Food salt of salt".
4. Samples in packages of iodized table salt, potato and corn starch.
Equipment and materials: drying cabinet, microscope, stopwatch (hours), thermometer, laboratory scales, conical flasks and glasses with a capacity of 50, 100 ml, test tubes, pipettes for 5 and 10 ml, spatula.
Reagents: 1% solution of sodium sulphide, zinc metal, nitric silver (crist.), Diphenylamine, concentrated sulfuric acid, tannin, starch solution, ethyl alcohol (50 ml).
Situational challenge. Conduct species identification of starch samples by microscopic method (samples without marking are given by the teacher).