Module 15. Ghee

 

Lesson 36

QUALITY AND GRADING OF GHEE 

 

36.1 Introduction

Competition in the organized ghee production sector leads to create brand value to the product. This brand value comes with quality and special features associated with the product. Today, consumers are much aware of the brand quality through media. Manufacturers or producers are   looking forward continuously for innovations that helps to create market for their product, may be through mode of packing, through product aesthetic quality.

36.2 Ghee Composition and Changes During Manufacture

Ghee majorly consists of milk lipids and richest source of milk fat of all Indian Dairy products. The constituents of ghee tend to vary with the method of its manufacture. Chemically ghee is a complete lipid of glycerides, 97-98% triglycerides. Small amount of di-and mono-glycerides are also present in traces. Also cow milk ghee is different from buffalo milk ghee in terms of its composition. Chemical composition of cow milk ghee and buffalo milk ghee are given in table 36.2.

Fatty acid composition of buffalo milk ghee also varies from cow milk ghee. The amount of butyric acid is significantly higher in buffalo than in cow ghee. The levels of short chain fatty acids caproic to myristic are significantly higher in cow than buffalo ghee where as levels of palmitic and steoric are higher in buffalo than in cow ghee.  Major fatty acid in buffalo and cow milk fat is given in table 36.3.

Ghee made from buffalo milk is white (lack of carotenoids) with greenish tinge and that made from cow milk is golden yellow. The characteristic colour of buffalo fat has been attributed to “tetrapyrozole” pigments- “biliverdin and bilivubin” this pigment is conjugated to a protein in milk, but is released during the manufacturing process of ghee making. Thus, imparting yellowish-green colour to buffalo ghee.

During manufacturing, water gets evaporated and fat present in the cream or butter getting concentrated (curd particles (MSNF present in cream or butter) starts settling at the bottom during clarification process. Flavour formation in ghee happens during fermentation of cream and during clarification process. Colour development and granulation also happens during clarification for the subsequent packaging of ghee.

36.3 Flavour Formation in Ghee

Free fatty acids, carbonyls and lactones are the major groups of compounds contributing to ghee flavour. The flavour profile is affected by method of preparation temperature of clarification and storage period.

36.3.1 Carbonyls

The quantity of carbonyls is directly proportional to the temperature of clarification. ‘Head space’ and ‘volatile’ carbonyl content of fresh desi cow ghee is higher that of buffalo ghee, where as total carbonyl content of fresh desi buffalo; whereas total carbonyl content of fresh desi buffalo ghee is higher than that of cow ghee. Carbonyl content found to increase during storage.

36.3.2 Lactones

The lactone level in buffalo ghee has found to be higher than that in cow ghee. It was the highest in direct cream (DC) ghee, followed by creamery butter (CB) and lowest in desi ghee. The lactose level in butter (12 ppm) increased 1.9, 2.4, 2.8 and 3.0 fold on clarifying at 110°C, 120°C, 140°C and 180°C respectively. Clarification butter at 100-120°C doubles the lactones level from butter. The lactone level in ghee showed a significant rise on storage.

36.4 Flavour Components of Ghee

Table 36.1 Major flavor components in ghee

Components

Cow ghee

Buffalo ghee

Total carbonyls (m/g)

Alkan-2-ones = 90%

Alkanals = 6%

Alk-2-enals = 2%

Alka-2, 4 dienals = 2%

7.2

8.64

 

 

 

 

Volatile Carbonyls (m/g)

0.33

 

Head-Space Carbonyls (gas stripped)m/g)

0.035

0.027

 

Formation of flavour components are due to

(i)     Heat interaction between the native  carbohydrates and protein system of cream;

(ii)   Due to heat effect on the unfermented residue as well on fermented metabolic products formed by ripening process.

Cream constituents like lactose, citrate and glucose were responsible for the increase in ghee flavour components. Flavour in ghee is the resultant of four different mechanisms, they are

(i)     Hydrolysis – Free fatty acid formation

(ii)   Oxidation – Saturated and unsaturated aldehyde, ketones, alcohols and hydrocarbons.

(iii)  Decarboxylation – Alkan-2-Ones

(iv)  Dehydration and Lactonization – Lactones

36.4.1 Texture of ghee

When ghee is stored at room temperature, it crystallizes into three distinct fractions or layers, (i) Oily (ii) granular semi-solid at the bottom and (iii) hard flakes portion floating on the surface and sticking to the sides of the container.

According to Singhal et al. Layer formation in ghee could be prevented by storing it at 20°C or below immediately after preparation. Ghee thus solidified could subsequently be stored at higher temperature without formation of layer. The liquid portion of ghee varies with storage temperature, shape and size of container, repeated heating and agitation, ripening of cream/butter, storage and handling, external seeding etc.

36.4.2 Market quality of ghee

Consumer judge the quality of ghee base on its inherence flavour, colour and appearance. Ghee should have characteristic pleasant, nulty, slightly cooked rich aroma. Ghee flavour is best described as lack of blandness, sweetly rather than acid. Golden yellow to light yellow colour of ghee is appreciated largely. Granular appearance of the product rather more score as it is important quality as well as purity preventer of ghee.

Apart from above sensory characteristics, its chemical and other physical preventers are evaluated to judge the quality of ghee and also to prevent adulteration of ghee.

(i)        Refractive Index: It is the ratio of the velocity of light in vacuum to the velocity of light in the sample medium. More generally, it is expressed as the ratio between the sine of the angle of incidence to the sine of the angle of refraction when a ray of light of a definite wave length wave length (usually 589.3 m the mean of the D-lines of sodium) passes from air into the fat. In case of milk fat reading is normally made at 40°C using Abbe refractometer and its values range from 1.4157 to 1.4566. This value is low in comparison to the other fats and oils. The RI if ghee is influenced by both the molecular weight and the degree of saturation of the component fatty acids. RI could be used as indicator of adultration.

(ii)      Iodine Number: It is defined as number of grams of iodine absorbed by 100 g of fat under specified conditions. Thus constant is a measure of the unsaturated linkages present in a fat. The iodine number for milk fat falls within the range of 26 to 35 which is low in comparison to other fat and oils. This is estimated using Wig’s method. One molecule of halogen compound is absorbed by each unsaturated linkage and the absorption is expressed as the equivalent number of grams of iodine absorbed by 100 g of fat.

(iii)    Reichert-Meissl Number (RM Number): This is defined as number of ml of n/10 Sodium hydroxide required to neutralize the steam volatile water soluble fatty acids distilled from 5 g of ghee under precise conditions specified in the method. It is primarily measure of butyric acid and caproic acid. The value for milk fat ranges between 17 to 35 and it is above that of all other fats and oils. Therefore, milk fat contains more of these acids than any of the fats.

(iv)    Polenske Number: It is defined as number of ml of N/10 Sodium hydroxide required to neutralize the steam volatile water insoluble fatty acids distilled from 5 g of fat under precise conditions specified in the method. Caprylic acid, capric acids which are somewhat steam volatile but longely insoluble in water are indicated mainly in Polenske number and it ranges from 12 to 24 for milk fat.

(v)      Saponification Number: It is defined as the number of milligrams of potassium required to saponify one gram of fat. The value ranges from 210 to 233 and more often falls in the range of 225 to 230. This constant is an indication of the average molecular weight of the fatty acid present. Saponification value is more useful in detecting the presence of minerals oils such as liquid paraf fims in ghee as they are not acted upon by alkali and such a sample doesn’t form a homogeneous solution on saponification.

(vi)    Melting Point: Melting point for milk fat ranges from 30°C to 41°C as reported in literature.

36.5 Factors Affecting The Market Quality of Ghee

(i)        Raw-materials (Milk, Dahi, Cream, Butter) used for ghee making

 Milk used should be clean, fresh and strained. Use of ripened cream, butter improves the flavour score of ghee.

(ii)      Method of preparation and temperature of clarification

Flavour compounds of ghee vary according to its method of preparation. For example desi methods have more volatile Carbonyl compounds than cream method. Temperature of clarification also has influence on the quantity of Carbonyl compounds and lactones formation during ghee production.

(iii)    Type of feed

It is the main factor affecting variation in fatty acid composition of milk fat. Roughages in the feed mainly consist of cellulose contribute to the formation of fatty acid of 4 to 16 carbon chain length and lipid content of the feed contributes to the formation if long chain fatty acid if C16 and above. Animals fed with cotton seed meal will have high amount of C1010 and C1210 fatty acids.

(iv)    Season

In winter and monsoon, the granulation is more due to changes in the fatty acid profile. Winter ghee showed higher acidity, melting point and grain size where as in summer the saponification value was found to be higher.

36.6 Grading of Ghee

The quality of ghee can be judged by physical and chemical analysis. Customer can only perceive appearance, taste and aroma of ghee. Therefore grading i.e. classification according to its quality and purity is necessary to assure the customer. The Agricultural Produce (Grading & Marking) Act, 1936 empowers the Central Government to fix quality standards, known as ‘AGMARK’ standards and to prescribe terms and conditions for using the seal of ‘AGMARK’. The word 'AGMARK' is a derivative of "Agricultural Marketing".

36.6.1 Objectives of AGMARK

i).     To assure the consumer a producer of pre-tested quality and purity

ii).   To enable manufacturers of high grade product to obtain better returns

iii).  To develop an orderly marketing of the commodities by eliminating malpractices when transferring from producer to consumer.

AGMARK is a certification mark of Government of India to ensure the purity and quality of Agricultural and allied products in India. The Act empowers the Directorate of Marketing and Inspection to

·         Authorize a person or a body of persons to use the grade designation marks under prescribed condition.

36.6.2 AGMARK Ghee Specifications

Grade designation marks for ghee- The grade designation mark shall consist of a label specifying the name of the commodity, grade designation and bearing a design consisting of an outline map of India with the word “AGMARK” and the figure of rising sun with the words produce of India and resembling the design as set out as follows.

Table 36.2 AGMARK grades of ghee

Grade

Letter and Circular border colour

Special

Red

General

Green

Standard

Chocolate

 

36.6.3 Design of label

 

  1. Special Grade                        2. General Grade                  3.Standard Grade

 

 

The word ‘Regional’ shall be printed on each label used on a package of the ghee not conforming to the normal physical and chemical constants specified as follows.

Table 36.3 AGMARK standards of ghee

Parameters

Special Grade

General Grade

Standard Grade

Baudouin Test

Negative

Negative

Negative

Butyro-refractomer reading at 40°C

40.0– 43.0

40.0– 43.0

40.0– 43.0

Reichert Meissl value

Not less than 28.0

Not less than 28.0

Not less than 28.0

Polenske value

1.0 – 2.0

1.0 – 2.0

1.0 – 2.0

Moisture content

Not more than 0.3%

Not more than 0.3%

Not more than 0.3%

Percentage of Free Fatty Acid (as oleic acid)

Not more than 1.4

Not more than 2.5

Not more than 3.0

 

For cotton tracts areas such as part of Saurshtra and Madya Pradesh following standards are applicable.

Table 36.4 AGMARK standards for ghee produced in cotton tract areas

Parameters

Special Grade

Winter

Summer

Baudouin Test

Negative

Negative

Butyro-refractomer reading at 40°C

41.5 – 43.0

42.5 – 45.0

Reichert Meissl value

Not less than 23.0

Not less than 21.0#

Polenske value

0.5– 1.2

0.5 – 1.0

Moisture content

Not more than 0.3%

Not more than 0.3%

Percentage of Free Fatty Acid (as oleic acid)

Not more than 1.4

Not more than 2.5

 

General and Standard grade have Percentage of Free Fatty Acids (as Oleic acid) shall not exceed 2.5 and 3.0 respectively.

According to the law it is not compulsory for every trader and manufacturer, to get his produce certified under AGMARK symbol. Presently it is only a voluntary scheme of the Government.

36.7  Requirements of High Grade Ghee

Consumer judges the quality and accepts it on the basis of three main attributes, taste and aroma(flavour), granularity and colour.

  1. Flavour: High grade ghee should have natural sweet and pleasant odour, an agreeable taste and it should be free from rancidity and any other objectionable falvour. A pleasant, nutty, slightly cooked aroma is appreciable in the product.
  2. Texture: Large uniform grains with very little liquid fat is desirable, greasy texture is objectionable. Upon melting ghee should be clear, transparent, free from sediment and foreign colouring matter.
  3. Colour: The colour should be uniform throughout, it should be bright yellow for cow milk ghee and white with or without a yellow or greenish tint for buffalo milk ghee.

36.8  Score Card of Ghee

Ghee can be evaluated using the following score card

Table 36.5 Score card of ghee

Parameters

Score

Flavour

45

Texture

10

Acidity (Olieic)

25

Colour

10

Freedom from suspended matter

5

Package

5

 

36.9 Defects in Ghee and Their Prevention

Possible defects in ghee are listed in below table with their causes and prevention. Defects are categorized according to the sensory characteristics such as flavor related, texture related and appearance related.

  1. Flavor Defects

Defects

Causes

Prevention

Smoky

Smoky fire used for boiling of milk/cream/butter

Use non-smoky fire for boiling milk/cream/butter

Overcooked

Or bunt

Excessively high temperature of clarification

Optimum temperature of clarification of ghee

Undercooked

Excessively low temperature of clarification

Optimum temperature of clarification of ghee

Rancid

Fat hydrolysis due to lipase action in milk/cream/curd/butter/ghee

Inactivation of lipase by proper heat treatment

Clarify at optimum temperature which ensures minimum moisture content in ghee

Oxidized/oily/

metallic

Fat oxidation due to direct contact of milk/curd/cream/butter/ghee with copper or iron, exposure of these product to sunlight

Storage of the milk/curd/cream/butter/ghee in properly tinned or aluminum alloy/ss vessels

Filling ghee upto the brim to minimize the headspace & use opaque containers

Avoid ghee storage at high temperature (>21°C) & avoid long storage

 

  1. Texture Defects

Defect

Causes

Prevention

Greasy

Rapid cooling of hot ghee after clarification

Slow cooling of hot ghee after clarification

Subjecting ghee to further heating and cooling treatment after preparation

Avoid further heating and cooling of ghee after preparation
  1. Appearance Defects

Defects

Causes

Prevention

Burnt colour

Excessively high temp. of clarification

Optimum temp. of clarification of ghee

Higher Sediment

Incorrect straining of ghee

Correct straining of ghee

36.10 Adulterants in Ghee

Adulteration of ghee in India is more prevalent especially in unorganized sector. Being the most expensive fat people started to adulterate the product to make profits. Major adulterants of ghee are as follows:

i).     Vanaspati (Hydrogenated vegetable oil). Because of close resemblance in its texture most commonly used this as adultrant to ghee.

ii).   Refined (de-odourized) vegetable oil.

iii).  Animal body fat.

Government has made it compulsory that all Vanaspati must contain a maximum of 5% of Sesame oil which can be identified in ghee by a simple colour test (known as Baudouin test). By means of this Adultration of ghee with Vanaspati ti an extent of 3% can be detected.