Cooking fats, requirements for the quality of cooking fats. Cooking fats, quality requirements for cooking fats Transportation and storage

This standard applies to vegetable oils and animal fats, as well as to their processed products (hydrogenated, interesterified, fractionated fats and oils, spreads, baked mixtures, margarines, etc.), and establishes the following methods for determining the mass fraction of trans isomers of fatty acids:
- infrared spectrometry method (IR spectrometry);
- gas chromatography method with a capillary column;
- method of infrared spectrometry attenuated total internal reflection (ATR IR spectrometry)

Title of the document: GOST 31754-2012
Document type: standard
Document status: active
Russian name: Vegetable oils, animal fats and products of their processing. Methods for determining the mass fraction of trans isomers of fatty acids
English name: Vegetable oils, animal fats and products of their processing. Methods for determination of the content of trans fatty acid isomers
Date of text update: 01.08.2013
Date of introduction: 01.07.2013
Description update date: 01.08.2013
Number of pages in the main text of the document: 37 pcs.
Publication date: 02.07.2013
Reissue:
Last modified date: 16.07.2013
Is located in:
OKS All-Russian classifier of standards
67 FOOD PRODUCTION
67.200 Edible oils and fats. Oilseeds
67.200.10 Animal and vegetable oils and fats (Oil see: 67.100.20)
























Many products contain cooking oil. What is it? Essentially, it is an anhydrous mixture of various fats of animal and vegetable origin, as well as lard. Such a substance is capable of melting at temperatures above 60 °C. What kind of cooking oil is there? Margarine does not fall into this category. Although it is often confused with cooking fat. It is not right. After all, margarine is an aqueous mixture of fats.

How the product came about

Cooking fat was first produced back in Soviet times. Food industry specialists were faced with the task of creating a cheaper product. As a result of the work carried out, many combinations of various fats were created that could replace rendered fats of animal origin.

Initially, new products were not in great demand among USSR citizens. After all, their taste and aroma were not so attractive. Therefore, new compounds were gradually introduced into the food industry. The product was used in canteens and also in places of mass production. In conditions of crisis, the new cooking oil was nevertheless recognized by the citizens of the USSR and took its place of honor among its more expensive analogues.

cooking oil

How does cooking fat differ from other varieties of this product? First of all, organoleptic properties:

  1. The taste corresponds to the type of product, without impurities, pure.
  2. Nice smell.
  3. The color of the product can be white or yellow.
  4. The consistency is ointment-like, dense and without impurities.
  5. When melted, cooking fat becomes transparent.

This product is sold exclusively in briquettes, wrapped in or packaged in special bags.

Types of cooking fat

Cooking fat can consist of many components. At the moment there are several varieties of it:

  1. Deep frying product. It is made only from lard of plant origin. The main purpose is deep-frying food. Whale oil is often added to this fat.
  2. Vegetable lard. This product is made from vegetable oils.
  3. "Belorussian". Made from
  4. "Ukrainian". In its production, pork fat is taken as the basis.
  5. "Oriental". The main component of the product is lamb fat.
  6. Margaguselin. The basis is taken to have the taste of fried onions. It is worth noting that marnanuseline is the only product that contains fragrance.

Cooking fat: composition

What is included in such mixtures? According to GOST, the product may contain components such as:

  • sunflower oil;
  • soy;
  • cotton;
  • rapeseed;
  • Palm;
  • peanut;
  • salomas;
  • palmitine;
  • stearin;
  • animal fats;
  • vitamin A;
  • antioxidant;
  • dried onions.

It is worth noting that all fats are deodorized and refined before mixing. In other words, the components become depersonalized and become odorless. The product is usually stored at temperatures from -25 °C to +16 °C. The room should be well ventilated, dark and dry.

Is the product useful?

Does it bring culinary? The effect of a given product on the human body depends on its chemical composition, which is determined by the recipe. All cooking fats are healthy to some extent and should be present in every person's diet. It should be noted that such products are absorbed by 96%. It is for this reason that they are considered irreplaceable sources of energy.

Cooking fats are rich in vitamins D, K, A, E. In addition, this product contains components that actively participate in the construction of body cells. Thanks to them, the skin becomes firmer and more elastic, the condition of the hair and blood clotting are significantly improved, and the effects of toxins are neutralized.

As numerous studies show, for the normal functioning of the adult body, approximately 20 grams of fat per day are required. Thanks to these components, beta-carotene and cooking oil are better absorbed. Also, cooking oil has a positive effect on the health and beauty of the female body.

Harm from cooking fats

Despite the benefits of such compounds, they should not be abused. After all, excessive consumption of fat leads to the development of various diseases of the cardiovascular system, as well as obesity. Good digestibility of the product has not only a positive, but also a negative side. When you abuse cooking fats, the body receives a large number of unnecessary calories. In addition, a product that was not prepared in accordance with GOST can lead to the development of cancer. Therefore, you need to choose cooking oil correctly.

Cooking fats- an anhydrous mixture of various types of processed and natural fats. For the production of culinary fats, refined liquid vegetable oils (sunflower, cottonseed, soybean, etc.), lard, rendered animal fats (beef, lamb, pork), and interesterified fats are used. Vitamins, dyes, antioxidants, and flavors are used as additives.

Chemical composition of cooking fats . The fat content in cooking fats is not less than 99.7%, water - no more than 0.3%. The energy value of 100 g of fat is 897 kcal. The melting point of fats is 28-36° C, digestibility is 96.5%. Of the polyunsaturated fatty acids in cooking fats, linoleic acid predominates, and of monounsaturated fatty acids, oleic acid predominates. Vitamins mainly contain vitamin E.

Fats are classified according to two criteria: By purpose - culinary, confectionery, bakery; By composition of the recipe- herbal and combined.

Range of fats:

Cooking fats- deep-frying, vegetable lard, Ukrainian, Belarusian fats, etc.

Vegetable fats- vegetable lard (a mixture of vegetable oil and lard), confectionery fat for waffle and refreshing fillings (a mixture of vegetable lard with coconut or palm kernel oil), fat for the production of chocolate products, candies and food concentrates (vegetable lard based on cottonseed and peanut oils).

Combined fats along with natural vegetable oils and lards, they contain rendered animal fats and interesterified fats obtained from vegetable oils and animal fats. This is confectionery fat for the production of cookies (vegetable lard with the addition of animal fats), liquid baking fat, and cooking fats.

Requirements for the quality of cooking fats. Cooking fats are not divided into commercial grades.

Organoleptic indicators: consistency at a temperature of 20°C - dense or paste-like, pure taste and smell, without foreign or unpleasant tastes and odors, uniform color - from white to yellow. When melted, fats should be transparent.

physical and chemical indicators: each fat has a certain melting point, for most fats it is from 26 to 36 ° C, the mass fraction of fat is at least 99.7%.TO unacceptable defects include unpleasant tastes - greasy, rancid, fishy, ​​soapy, unclean, the presence of mold.

Packaging and storage . Fats are packaged in plywood boxes with a capacity of up to 30 kg and wooden barrels with a capacity of no more than 100 liters. Packaged fats are produced in bags of fat-insoluble polymer films of 200 and 500 g, as well as in metal cans of 500 and 1000 g. Fats are stored at a temperature of 1° C and relative humidity 80% for 4 months, fats with antioxidants - up to 6 months.


Merchandising of food products: Textbook.
T.P.Lapina, Kovalevich T.I.


Appendix 3

Appendix 3

Appendix 3

Appendix 3

Appendix 3

TU 10.10739-88*

________________
* Specifications mentioned here and further in the text are the author’s development. For more information please follow the link. - Database manufacturer's note.

5. The validity period was lifted according to Protocol N 5-94 of the Interstate Council for Standardization, Metrology and Certification (IUS 11-12-94)

6. REPUBLICATION. December 2009


This standard applies to fats for the culinary, confectionery and baking industries, which are various mixtures of fats.

1. CLASSIFICATION

1. CLASSIFICATION

1.1. Depending on their purpose, fats are divided into types: culinary, confectionery, and baking. Depending on the type, the names of fat indicated in Table 1 are established.

Table 1

Type of fat

Name

Culinary

"Fryer"

"Vegetable lard"

"Ukrainian"

"Belorussian"

"Prima"

"New"

"Oriental"

"Margaguselin"

Confectionery

For waffle and cooling fillings

For chocolate products, candies and food concentrates

Solid

Bakery

Liquid

2. TECHNICAL REQUIREMENTS

2.1. Characteristics

2.1.1. Fats must be manufactured in accordance with the requirements of this standard according to technological regulations and recipes approved in the prescribed manner.

2.1.2. In terms of organoleptic indicators, fats must meet the requirements specified in Table 2.

table 2

Characteristics of fats

culinary

confectionery

bread-
bakery

Name-
new indicator

"Fryer", "Vegetable lard", "Prima", "New"

"Ukrainian", "Belarusian", "Eastern", "Margaguselin"

for chocolate products, candies and food concentrates

For
waffles
nykh
and cooling fillings

Taste and smell

Pure taste with a characteristic taste of added animal fat, without extraneous taste; "Margaguselina" is characterized by the taste of fried onions

Pure taste characteristic of depersonalized fat, without foreign taste or odor

When introducing flavoring -
torov - pronounced aroma, causing
flavored with injected
torus

White to light yellow

From white to light yellow. A grayish or creamy tint is allowed when using cottonseed oil.

From white to light yellow. Grayish or creamy shades are allowed when using lard made from cottonseed and soybean oils

White to cream

From light
yellow to yellow

Uniform throughout the mass

Consistency at 18 °C

Homogeneous, hard, plastic or pasty

Homogeneous, hard. Plastic allowed

Homogeneous, hard, prickly

Homogeneous, mobile

Transparency

Transparent when molten

Notes:

1. For uncongealed confectionery and baking fats, the “Color” and “Consistency” indicators must be:

"Color" - from light yellow to light brown;

"Consistency" - homogeneous, mobile.

2. The consistency of liquid baking fat is determined at a temperature of 16 °C.

2.1.3. In terms of physical and chemical parameters, fats must meet the requirements specified in Table 3.

Table 3

Indicator name

Norm for fats

culinary

confectionery

bakery

"Fryer"

"Lard vegetable-
new"

"Novin-
ka", "Prima"

“Ukrainian”, “Belarusian”, “Eastern”, “Margaguselin”

for chocolate products, candies and food concentrates

for waffle and cooling fillings

solid

Mass fraction of fat, %, not less

Mass fraction of moisture and volatile substances, %,
no more

Acid number, mg KOH/g, no more

Melting point, °C

Based on salomas -
no higher than 17;
based on transester-
defined fats - 17-27

Pour point, °C

Not lower than 29

At least 21

Not lower than 30

Not higher than 15

Hardness according to Kaminsky, g/cm

At 15 °C: not less than 550

At 15 °C: 150-250

At 20 °C: not less than 850

Mass fraction of nickel, million (mg/kg)

Notes:

1. The hardness of confectionery fat intended for food concentrates is allowed to be at least 450 g/cm.

2. It is allowed to increase the melting point of cooking fats “Ukrainian”, “Belarusian” and “Vostochny” to 38 °C when they are manufactured with the addition of animal fats in an amount of 20% or more, as well as with the introduction of palm stearin and lard using palm oil.

3. By agreement with the consumer, the melting temperature for confectionery fat for chocolate products is allowed to be 35-37 °C.

2.1.4. Energy and nutritional values ​​are given in Appendix 2.

2.1.5. Residues of pesticides in fats should not exceed the maximum permissible levels approved by the Ministry of Health (see Appendix 1).

2.1.6. The temperature of unfrozen confectionery fats and liquid baking fat when poured into tank trucks should not exceed 55 °C.

2.2. Requirements to raw materials

2.2.1. The following raw materials are used for the production of cooking fats:



sunflower oil according to GOST 1129*;
________________
GOST R 52465-2005 (hereinafter).


GOST 1128;

GOST 7825 * and unrefined soybean oil according to the current NTD;
______________
GOST R 53510-2009

corn oil according to GOST 8808;

rapeseed oil according to GOST 8988 *, hydrated rapeseed oil;
______________
* The document is not valid on the territory of the Russian Federation. GOST R 53457-2009 is valid, hereinafter in the text. - Database manufacturer's note.

peanut oil according to GOST 7981;

palm oil and other edible vegetable oils suitable after processing for the production of fats;

palm stearin;

cotton palmitine;

interesterified fat grades 1 and 2;

unrefined lard for the margarine industry, grades 1 and 2;

refined lard for the margarine industry, grades 1 and 2;

rendered edible animal fats of the highest grade (beef, pork, lamb) according to GOST 25292;

dried onions (for “Margaguselina”) according to GOST 7587*.
________________
* GOST R 52622-2006 is in force on the territory of the Russian Federation.


Allowed input:

antioxidants approved by the USSR Ministry of Health;

vitamin A - highly concentrated preparations (concentrations not lower than 300,000 IU per 1 g of preparation) according to the State Pharmacopoeia and other vitamins in quantities approved by the USSR Ministry of Health.

2.2.2. For the production of confectionery fats, the following raw materials are used:

2.2.2.1. For confectionery fat for chocolate products, candies and food concentrates:

unrefined lard for the margarine industry, grade 3;

refined deodorized lard for the margarine industry, grade 3;

2.2.2.2. The following raw materials are used for confectionery fat for waffle and cooling fillings:

unrefined lard for the margarine industry, grade 1;

refined deodorized lard for the margarine industry, grade 1;

coconut oil according to GOST 10766 or palm kernel oil;

It is allowed to introduce antioxidants approved by the USSR Ministry of Health.

2.2.2.3. The following raw materials are used for solid confectionery fat:

interesterified fat;

It is allowed to introduce antioxidants approved by the USSR Ministry of Health.

2.2.3. The following raw materials are used for the production of liquid baking fat:

Vegetable oils suitable for processing into food products:

sunflower oil according to GOST 1129;

Refined soybean oil according to GOST 7825;

Refined cottonseed oil according to GOST 1128;

corn oil according to GOST 8808;

rapeseed oil according to GOST 8988, hydrated rapeseed oil;

peanut oil according to GOST 7981;

unrefined lard for the margarine industry, grades 1 and 3;

refined deodorized lard for the margarine industry, grades 1 and 3;

interesterified fat grade 1;

food phosphatide concentrate;

emulsifier MHD.

It is allowed to introduce flavorings approved by the USSR Ministry of Health.

2.2.4. All vegetable oils, cotton palmitine, palm stearin, interesterified fat and lard must first be subjected to complete refining, including deodorization, and have the taste of impersonal fat without foreign odors and tastes and meet the requirements of the USSR Ministry of Health for permissible levels of pesticide contamination provided for deodorized food oils (see Appendix 1).

2.3. Package

2.3.1. Cooking fats are produced packaged and unpackaged.

2.3.2. Confectionery and baking fats are produced in bulk form.

2.3.3. Cooking fats are packaged in the form of bars with a net weight of 200 to 500 g, wrapped in parchment according to GOST 1341, parchment weighing 1 m (50 ± 3) g and laminated foil.

It is allowed, by agreement with the consumer, to pack fats in metal cans for canning in accordance with GOST 5981 with subsequent sealing, with a net weight of 500 to 7500 g. It is allowed to use cans made of tinplate with electrolytic tinning EZhK - in accordance with GOST 13345.

2.3.4. Packaged cooking fats are packaged in:

non-dismountable plank boxes according to GOST 10131 N 2;

wooden boxes in accordance with GOST 13358 (fats packaged in metal cans) N 8, 13, 17;

plywood boxes according to GOST 10131 N 7;

GOST 13511;

boxes made of corrugated cardboard according to GOST 13516 (fats packaged in metal cans) N 1, 8, 9, 30, 31, 32, 39, 41, 49;

boxes made of container cardboard according to GOST 13515;

Imported cardboard boxes.

The net weight of fats must be the same in all boxes of a given batch and range from 10 to 22 kg.

For local sales, it is allowed to pack fats in polymer reusable boxes for the meat and dairy industries and in packaging equipment in accordance with GOST 24831.

2.3.5. Unpackaged fats are packaged in:

the boxes indicated above, with the exception of boxes made of corrugated cardboard in accordance with GOST 13516;

wooden barrels according to GOST 8777;

plywood stamped barrels according to TU 10.10739;

plywood drums according to GOST 9338;

cardboard wound drums according to GOST 17065.

The net weight of fats must be the same in all packaging units of a given batch and be:

when packed in board, plywood and cardboard boxes from 10 to 22 kg;

when packed in drums and barrels no more than 50 kg.

By agreement with the consumer, it is allowed to pack fats for industrial processing into barrels with a net weight of up to 100 kg.

2.3.6. The permissible deviations in the net mass of a packaging unit of fat are, in percentage, no more than:

±1.5 - from 200 to 250 g inclusive;

±1.0 - St. 250 to 10000 g inclusive;

±0.5 - St. 10000 to 100000 g incl.

2.3.7. Before packing bulk fats, boxes, drums and barrels must be lined with parchment in accordance with GOST 1341, parchment and sub-parchment weighing 1 m (50±3) g or polymer films (polyvinyl chloride "Poviden" grade U-1; polyethylene-cellophane grades PC-2 and PC-4, polyethylene for packaging food products in accordance with GOST 10354 and other polymer films approved by the Ministry of Health for contact with fats) or an insert bag made of polymer materials approved by the Ministry of Health for contact with fats must be placed in the specified container.

Boxes made of corrugated cardboard for packaging bulk fats can be supplemented with liners in accordance with GOST 9142, the type of connection of valves and pasting of cardboard boxes is carried out in accordance with GOST 9142.

2.3.8. Unfrozen confectionery fats and liquid fats are packaged in steel barrels in accordance with GOST 13950, in flasks in accordance with GOST 5037, as well as in wooden barrels in accordance with GOST 8777 with a net weight of no more than 50 kg, with a net weight of up to 100 kg - as agreed with the consumer.

Wooden barrels must have an insert bag made of polymer materials approved by the USSR Ministry of Health for contact with fats.

2.3.9. The use of returnable wooden containers is allowed.

2.3.10. When transported by water or mixed modes of transport, fats must be packed in planks, plywood boxes, barrels and drums.

2.3.11. Fats intended for the Far North and equivalent areas must be packaged and transported in accordance with GOST 15846.

2.4. Marking

2.4.1. Consumer containers of cooking fats must be marked with:

trademark, name of the manufacturer and its subordination;

Name of product;

net weight;



temperature and shelf life;

energy value of 100 g of product - 897 kcal;



The markings on the parchment or foil of each bar and on the label of each jar are applied with a special quick-drying paint, previously tested to ensure that there is no imprint on the inner surface of the parchment and on the surface of the fat.

It is allowed to mark the date of fat production with a clear composter or any other method that ensures its clear indication.

The label must be artistically designed.

2.4.2. Each packaging unit containing fat is additionally marked with a label characterizing the product:

trademark, name of the manufacturer, its address and subordination;

Name of product;

content of antioxidant and vitamin A (in case of input);

net weight of a packaging unit;

net weight and number of packing units for packaged fat;

net weight for bulk fat;

production date (day, month, year);

batch number and (or) serial number of the packaging unit;

temperature and shelf life;

designation of this standard.

The marking is applied typographically on a paper label or using a clear stamp directly on the end of the cardboard box.

It is permissible to affix the production date, batch number, and packaging unit number on a paper label with a clear stamp or a clear stamp.

2.4.3. Marking of transport containers is carried out in accordance with GOST 14192 with the application of the handling sign “Keep away from sunlight”.

3. ACCEPTANCE

3.1. Acceptance rules - according to GOST 976 *.
________________
* GOST R 52179-2003 is in force on the territory of the Russian Federation (hereinafter).

3.2. The indicators “Residual amount of pesticides” and “Mass fraction of nickel” are determined by the manufacturer periodically, at least once a month.

If unsatisfactory results of periodic tests are obtained, they are transferred to acceptance tests until positive results are obtained in three batches in a row.

4. TEST METHODS

4.1. Sampling of fats and methods for determining organoleptic indicators, mass fraction of fat, moisture and volatile substances, melting point, pour point, hardness - according to GOST 976.

4.2. Determination of acid number - according to GOST 5476*.
________________
* GOST R 52110-2003 is in force on the territory of the Russian Federation.

4.3. Determination of the mass fraction of nickel - according to Appendix 3.

4.4. Determination of residual amounts of pesticides - according to methods approved by the Ministry of Health.

5. TRANSPORTATION AND STORAGE

5.1. Fats are transported by all modes of transport in covered vehicles in accordance with the rules for the transportation of perishable goods in force for the relevant mode of transport.

Unfrozen and liquid fats are transported in assigned specialized railway tanks and tank trucks in accordance with GOST 9218.

It is allowed to transport fats in open vehicles by motor transport with the obligatory covering of them with a clean tarpaulin or other materials.

Transportation of fats in packages must be carried out in accordance with the requirements of GOST 21650, GOST 22477 and GOST 23285.

5.2. Fats should be stored in warehouses or refrigerators at temperatures from minus 20 to plus 15 ° C (solid confectionery fat - from minus 20 to plus 20 ° C), constant circulation and air flow and relative air humidity not exceeding 80%. It is not allowed to store fats in general warehouses along with products that have a strong specific odor.

5.3. Boxes, drums and barrels with fats during storage must be stacked using mechanized palletizing; for non-mechanized installations - on slats or gratings (under-stacks) in stacks with gaps between the stacks for free air circulation at a distance of 0.5 m from the walls.

When storing fats in corrugated cardboard boxes on pallets, no more than 5 boxes should be stacked in height, the height of the stack should be no more than 10 boxes (two pallets); with non-mechanized laying in no more than 6 tiers.

6. MANUFACTURER WARRANTY

6.1. The manufacturer guarantees that fats comply with the requirements of this standard subject to the conditions of transportation and storage.

6.2. The guaranteed shelf life of culinary and confectionery fats shipped in frozen form from the date of manufacture is indicated in Table 4.

Table 4

Guaranteed shelf life, months

Storage temperature, °C

Cooking fats, as well as confectionery fat for waffle and cooling fillings

Confectionery fat for chocolate products, sweets and food concentrates

Solid confectionery fat

From minus 20 to 0

St. 1 to 4 inclusive.

Note. When adding antioxidants, the shelf life increases by 1.5 times.


The guaranteed shelf life from the date of manufacture of unfrozen confectionery fats for chocolate products, sweets and food concentrates, as well as for wafer and refreshing fillings at temperatures up to 40 °C is 5 days, liquid baking fat at a temperature of 15-20 °C is 10 days.


APPENDIX 1 (for reference). Maximum permissible levels of pesticides in fats for direct food consumption and for use in the confectionery and baking industries

ANNEX 1
Information

Table 5

Pesticide name

Maximum permissible levels,
million (mg/kg)

Hexachlorocyclohexane - HCH (sum of isomers)

Heptachlor - GPC (heptachlor epoxide)

DDT (sum of isomers and metabolites)

APPENDIX 2 (for reference)

APPENDIX 2
Information

The energy value of all types of culinary, confectionery and baking fats (with a mass fraction of fat of at least 99.7%) is 897 kcal per 100 g of product.

Nutritional value of 100 g of fat - 99.7 g.

APPENDIX 3 (mandatory). Determination of the mass fraction of nickel using the colorimetric method

APPENDIX 3
Mandatory

The method is intended for the determination of nickel in culinary, confectionery and baking fats in factory laboratories and during scientific research.

The range of measured values ​​of the mass fraction of nickel is 0.5-20 million (mg/kg).

The method is based on the formation of a soluble, reddish-brown complex when nickel reacts with dimethylglyoxime in the presence of oxidizing agents in an alkaline medium.

1. Sampling - according to GOST 976 *.
________________
* GOST R 52179-2003 is in force on the territory of the Russian Federation.

2. Equipment, reagents

Equal-arm laboratory scales in accordance with GOST 24104 *, 2nd accuracy class and the highest weighing limit of 200 g and 3rd accuracy class scales with the highest weighing limit of 500 g or other scales with similar metrological characteristics.
________________Photocolorimeter FEK, KFK-2 or similar, having a light filter with an effective wavelength of (540±10) nm. Sulfuric acid according to GOST 4328, aqueous solution with a mass fraction of 5%.

Ammonium persulfate according to GOST 20478, aqueous solution with a mass fraction of 3%.

Dimethylglyoxime according to GOST 5828, solution with a mass fraction of 1% in an aqueous solution of sodium hydroxide with a mass fraction of 5%.

3. Preparation for the test

3.1. Construction of a calibration graph

3.1.1. Preparation of the basic standard solution

Dissolve 4.7860 g of nickel sulfate in double-distilled water in a 1000 ml volumetric flask, mix, add 1 ml of concentrated sulfuric acid and adjust the volume of the solution with water to the mark. The solution contains 1 mg/cm of nickel and can be stored in an airtight container for up to 1 year.

3.1.2. Preparation of intermediate standard solution

An intermediate standard solution with a nickel concentration of 10 μg/cm is prepared by diluting the main standard solution with bidistilled water in a ratio of 1:100. The solution is prepared before use.

3.1.3. Preparation of standard solutions for constructing a calibration curve

Standard solutions for constructing a calibration curve are prepared as follows.

0, 1, 2, 4, 6, 8 and 10 cm of the intermediate standard solution are taken using a burette into 50 cm volumetric flasks. To each flask add 2 cm of Rochelle salt solution, 5 cm of sodium hydroxide solution, 2 cm of ammonium persulfate solution and 2 cm of a solution of dimethylglyoxime in a 5% solution of sodium hydroxide, the volume of the solution in a volumetric flask is adjusted to the mark with double-distilled water.

The concentrations of the prepared standard nickel solutions will be, respectively: 0.0; 0.2; 0.4; 0.8; 1.2; 1.6 and 2.0 μg/cm. The optical densities of standard solutions should be measured 10 minutes after the appearance of color on a photocolorimeter at = (540 ± 10) nm in relation to a control sample, for the preparation of which all the specified reagents are used, with the exception of nickel salts. The optical density of standard solutions is measured at solution layer thicknesses of 1.2 and 5 cm.

Based on the obtained optical density values, calibration graphs are constructed for each cuvette thickness, plotting the optical density values ​​on the ordinate axis, and the concentration of the nickel solution in μg/cm along the abscissa axis.

A calibration curve is constructed for each type of device and checked when using a new batch of reagents and after repairing the device by determining the optical density of three or four standard solutions of a certain concentration.

3.2. Sample mineralization

A sample of fat of 1-5 g, weighed with the result recorded to the fourth decimal place, is placed in a quartz or porcelain cup or crucible and burned on an electric stove until the emission of smoke stops. Then it is placed in a muffle furnace at a temperature of about 400 ° C with the muffle door open until the smoke stops. Then close the muffle door and increase the temperature to 450-500 °C. Mineralization is continued under these conditions for 5-6 hours until gray ash is obtained. The cup or crucible with ash is removed from the electric furnace, cooled to room temperature and the gray ash is moistened with 0.5-1.0 cm of nitric acid. Then the acid is evaporated to dryness on an electric stove with low heat and the cup with the sample is again placed in a muffle furnace at a temperature of 450-500 ° C and kept for 1 hour. Mineralization is considered complete when the ash becomes white or slightly colored, without charred particles. If there are charred particles, repeat the treatment of the ash with a solution of nitric acid.

4. Conducting the test

1 cm of hydrochloric acid solution and 6 cm of bidistilled water are added to the dry sediment, completely dissolving the ash.

The solution is transferred quantitatively into a 25 cm volumetric flask, washing off the remaining solution in the crucible with bidistilled water into the volumetric flask. Then, 2 cm of Rochelle salt, 5 cm of sodium hydroxide, 2 cm of ammonium persulfate and 2 cm of dimethylglyoxime are successively added to the resulting solution. The volume of the solution is adjusted to 25 cm with bidistilled water.

Measurement of the optical density of samples is carried out under the same conditions as standard solutions.

5. Processing of results

The mass fraction of nickel () in million (mg/kg) is calculated using the formula

where is the concentration of nickel solution in the test solution, found from the calibration curve, μg/cm;

- volume of the analyzed solution, cm;

- mass of fat taken for testing, g.

Calculations are carried out to the second decimal place, followed by rounding the result to the first decimal place.

The permissible relative discrepancy between the results of two parallel determinations in the range of 0.5-2.0 mg/kg is no more than 30%, in the range of 2.0-20.0 mg/kg - no more than 15% (relative).

Electronic document text
prepared by Kodeks JSC and verified against:
official publication
Margarines, fats for cooking, confectionery
and baking industry: Sat. GOST. -
M.: Standartinform, 2010