How to Test the Moisture Content of Ghee

Moisture test is required for ghee to ensure its quality and shelf life. 

Materials required:

* Moisture dish (aluminum, nickel, or stainless steel)

* Desiccator

* Hot air oven

* Analytical balance

Procedure:

1. Weigh accurately about 10 grams of ghee into the moisture dish.

2. Place the dish in the hot air oven at 105 ± 1°C for 1 hour.

3. Remove the dish from the oven, cool in a desiccator, and weigh.

4. Repeat steps 2 and 3 until two successive weighings do not differ by more than 1 mg.

Calculation:

Moisture and volatile matter % = (M1 - M2) / (M1 - M) * 100

Where,

* M1 = Mass in g of dish with ghee before drying

* M2 = Mass in g of dish with ghee after drying

* M = Mass in g of empty dish

Interpretation:

The moisture content of ghee should not be more than 0.3% as per AGMARK and 0.5% as per FSSR regulations. If the moisture content is higher than the permissible limit, it indicates that the ghee may not be of good quality and may have a shorter shelf life.

Precautions:

1. The moisture dish should be clean and dry before use.

2. The ghee sample should be representative of the entire batch.

3. The oven temperature should be maintained at 105 ± 1°C.

4. The desiccator should contain an efficient desiccant, such as anhydrous calcium chloride.

5. The dish should be cooled to room temperature before weighing.

If you are unsure about how to perform the moisture test, it is best to have it done by a qualified laboratory.

Source: https://www.academia.edu/25614403/Determination_of_Moisture_in_Ghee

Why Ghee required moisture test?

Moisture test is required for ghee to ensure its quality and shelf life. High moisture content in ghee can lead to the following problems:

Microbial growth: Moisture provides a favorable environment for the growth of microorganisms, such as bacteria and yeast. This can cause ghee to spoil and become unsafe for consumption.

Rancidity: Moisture accelerates the hydrolysis of fats, which leads to the formation of free fatty acids. Free fatty acids are responsible for the rancid flavor and odor in ghee.

Reduced shelf life: High moisture content reduces the shelf life of ghee by making it more susceptible to spoilage and rancidity.

In addition to the above, moisture test is also required for ghee to detect adulteration. Adulterants, such as vegetable oils and animal fats, often contain higher moisture content than ghee. Therefore, a high moisture content in ghee can be an indication of adulteration.

Here are some of the benefits of performing a moisture test on ghee:

1. Ensure the safety and quality of ghee for consumption.

2. Detect adulteration in ghee.

3. Determine the shelf life of ghee.

4. Comply with food safety regulations.

Overall, a moisture test is an important quality control measure for ghee. It is recommended to perform a moisture test on ghee regularly to ensure its quality and safety.

FFA Test for Ghee: Procedure and Interpretation

The FFA test is a quick and easy way to determine the quality of ghee. It is a standard test that is used by food manufacturers and quality control laboratories to ensure the safety of ghee products.

Ghee with a high FFA content is not safe to consume. FFAs can irritate the digestive system and cause nausea, vomiting, and diarrhea. In addition, FFAs can promote the growth of harmful bacteria.

Materials:

1. 0.1 N sodium hydroxide (NaOH) solution

2. 95% ethanol

3. Phenolphthalein indicator solution

4. Analytical balance

5. Burette

6. Conical flask

7. Pipette

Procedure:

1. Weigh 5 grams of ghee into a 250 ml conical flask.

2. Add 50 ml of 95% ethanol to the conical flask.

3. Boil the mixture for 5 minutes in a water bath.

4. Add 1 ml of phenolphthalein indicator solution to the mixture.

5. Titrate the mixture with 0.1 N NaOH solution until a permanent pink color is obtained.

6. Record the volume of NaOH solution used in the titration.

Calculation:

FFA (%) = (Volume of NaOH solution used in the titration x Normality of NaOH solution x 282.2) / (Weight of ghee sample in grams x 1000)

The FFA value of ghee is typically expressed as a percentage of oleic acid. Ghee with a high FFA value will have a rancid taste and odor.

Interpretation of results:

• FFA < 0.5%: Good quality ghee

• FFA 0.5-1.0%: Acceptable quality ghee

• FFA > 1.0%: Poor quality ghee

If the FFA value of your ghee sample is greater than 1.0%, it is not recommended to consume it.

Palmarosa (Cymbopogon martinii)

 

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What is phase reversal theory?

The phase reversal theory theory was proposed by Fischer and Hooker in 1927, the theory is therefore also referred as Fischer and Hooker’s theory. According to this theory churning is a process of phase reversal i.e. changing of oil in water emulsion (O/W) to water in oil emulsion (W/O). The stability of emulsion is related to the relative volumes of the two constituents present. When oil and water are mixed together, the resulting suspension may be a suspension of (o/w) or suspension of w/o. The type of emulsion obtained depends on the proportion of the two main constituents present, the order in which they are added and the type of emulsifier used. 

In churning cream, initially the ratio of surface area to volume (S/V) of the fat globules is large. When the churning proceeds, surface area decreases and with progressive churning, surface area keeps on decreasing. The reduced surface area can no longer hold all the butter milk so it breaks i.e. separates out. 

Agitation of cream during the churning process causes coalescence and clumping of fat globules until eventually the ratio of surface area to volume of the fat units becomes so small that the reduced surface area can no longer contain the butter milk in stable form. The O/W emulsion then suddenly breaks; giving butter grains consisting of an emulsion of W/O and free butter milk. The supportive evidence of this theory is established by the fact that in normal butter, water is not in continuous phase. It has been demonstrated that plastic cream, containing 80-82% fat, conducts electricity and it responds to the pH determination showing water is in continuous phase but butter is a very poor conductor of electricity and pH determination cannot be done on butter but only on serum separated from it.

Microscopic structural studies conducted by Rahn (1928) revealed that butter is not a true W/O emulsion. A proportion of globular fat are still intact in worked butter. He explained that since butter fat is cooled and largely crystallized before the start of churning, true W/O type emulsion is rarely possible.

What is Rahns Foam churning theory?

This theory was put forward by Rahn (1928). According to Rahn, cream (and also milk) contains a foam producing substance which gets solidified gradually when cream (or milk) is agitated. 

During churning first foam is produced. The fat globules then, due to surface tension, tend to concentrate on the foam bubble and thus are bought into such close contact that clumping of fat globules take place. Subsequently the foam producing substance assumes a solid character and the foam collapse. The fat globules then coalesce and butter is formed. 

According to Rahn’s theory, fat in cream at churning time is completely crystallized and the pass in to butter with their membrane intact and thus butter is a compact mass of fat globules in which butter milk, water and air are distributed as small globules. Rahn’s theory was based on his findings that air was necessary for normal churning of butter. Application of normal amount of mechanical agitation, in the absence of air did not result in churning of cream. The effect of overloading of churn resulting in increased churning time supported this theory (in case of overloading the churn, there was no sufficient space in the churn for the formation of required amount of foam hence more time). 

This theory was, however, subsequently criticized because of the fact that foam formation i.e. presence of air, is not required in some of the continuous butter making processes developed subsequently.

Definition of Ripening and the objective of ripening.

Ripening refers to the process of fermentation of cream with the help of suitable starter culture. This step can be eliminated if sweet-cream butter is desired. The main object of cream ripening is to produce butter with higher diacetyl content. Ripening improves the keeping quality of salted butter but it reduces the keeping quality of a salted butter. Starter culture consisting of a mixture of both acid producing (Streptococcus lactis, S.cremories) and flavour producing (S.diacetylactis, Leuconostoc citrovorum and/or Leuc. dextranicum) organisms is added. Amount of starter added depends on several factors and usually ranges between 0.5-2.0 percent of the weight of the cream.

Objective of ripening:

The fundamental objects of cream ripening are to produce butter with a pleasing, pronounced flavor and aroma, and to produce this flavor and aroma uniformly from day to day. Ripening also influences somewhat the exhaustiveness of churning and it affects the keeping quality of the butter variously, according to quality of original cream, churning acidity, and whether made into salted or unsalted butter.

Define Cream and its classification.

According to Food Safety and Standards Regulations (FSSR) 2011, Cream including sterilized cream means the product of cow or buffalo milk or a combination thereof. It shall be free from starch and other ingredients foreign to milk. It may be of following three categories, namely:- 

• Low fat cream-containing milk fat not less than 25.0 percent by weight. 
• Medium fat cream-containing milk fat not less than 40.0 percent by weight. 
• High fat cream-containing milk fat not less than 60.0 percent by weight. 

Note:- Cream sold without any indication about milk fat content shall be treated as high fat cream.

Classification:

The fat in cream varies from 18-85%. As the fat percentage in cream increase the components of milk in cream gradually decreases. The SNF content constitutes lower proportions than present in milk. Broadly, cream may be classified into two groups:

• Market Cream: The cream used for direct consumption.
• Manufacturing or Industrial Cream: It is used in production of various milk products. 

Different types of cream following under these groups are:

Why MBRT is done?

 The MBRT test is therefore used for 

• Judging the hygienic quality of milk and grading raw milk supplies, 
• For assessing the quality of the probes of milk,
• For detecting post pasteurization contamination in milk.

What are the varieties of Khoa?

 There are three distinct varieties of khoa. They differ in their composition, body and textural characteristics and end use.

Pindi

This variety is identified as a circular ball of hemispherical pat with compact mass, homogenous and smooth texture. It shall not show any sign of fat leakage or presence of free water. It possesses pleasant cooked flavour and devoid of objectionable tastes like burnt, acidic, etc. This variety of khoa is used in the manufacture of burfi, peda and other varieties of sweets.

Dhap

It is a raw (katcha) khoa characterized by loose but smooth texture and soft grains and sticky body. Dhap variety carries highest percentage of moisture over other varieties of khoa. This high moisture is necessary to provide adequate free water for soaking of maida (refined wheat flour) and semolina (suji) and for homogenous distribution of other ingredients in the preparation of smooth gulabjamun balls. This variety of khoa is used in the manufacture of gulabjamun, kalajamun, pantooa, carrot halwa, etc.

Danedar

This is characterized by the granular texture with hard grains of different sizes and shapes embedded in viscous serum. Slightly sour milk is preferred in the manufacture of this variety as it yields granular texture. This variety of khoa is used in the manufacture of kalakand, milk cake, etc.

What are the types of Rancidity?

There are three types of Rancidity. They can be classified as follows:

1. Hydrolytic Rancidity:-

In some fats, there exist the predominance of short-chain fatty acids. The LIPASE enzyme can breakdown the linkage between glycerol and fatty acid. A few fatty acids (when not bound to the glycerol) contain flavour that in high concentration is undesirable (same as in Butter). Long time storage at unrefrigerated temperatures, butter contamination with microbes producing lipases, and more can accelerate hydrolytic Rancidity.

2. Oxidative Rancidity:-

The large unsaturated fatty acids are more susceptible to oxidation. The oxidation products are given as aldehydes, ketones, and related ones that can give off-flavour at high temperature (exposure to air, cooking, and some chemical contaminants can accelerate oxidation).To reduce the oxidation, antioxidants are added to the oils.

3. Microbial Rancidity:-

This type of Rancidity takes place when the microorganisms such as bacteria use their enzymes to break down chemical structures of fat.

What are the Packaging Materials for milk and dairy products?

 The packaging materials include paper and paper based products (coated or lined), glass, tin plate, aluminium foil, timber (wood), plastics and laminates ( Tetra packs) 

1. Paper and paper based products 

• The paper and paper based products form an excellent packaging material for milk and milk products. They may be kraft paper, grease proof paper, vegetable parchment paper, glassine paper, wax coated paper, plastic coated paper, paper boards, solid fibre boards, liner boards, box boards etc. 

• The papers are used in the form of boxes, bags, wrappers, cartons, cups etc. The advantage of using paper is that it is weightless, capability for printing on the surface, low cost and easy disposability. The disadvantages include low wet and tear strength. 

2. Glass

• The glass may be transparent or opaque. Glass is used in the form of bottles, tumblers, jars, jugs etc. 

• The advantages cited for glass as a packaging material include its strength, rigidity, ability to have a barrier for water and gas and inertness to chemical substances. The disadvantage is its heavy weight, and fragility. 

3. Tin plate 

• It may be made up of a thin sheet (0.025 mm thick) of mild steel coated on both sides with a layer of pure tin. It is desirable to have an internally lacquered can, which provides better resistance to corrosion. 

• The advantages cited for tin containers as a packaging material are their good strength and excellent barrier properties. The disadvantages are their high cost, heavy weight, difficulty in closing the lid of the container, and disposal. The containers are mostly used in the form of can.

4. Aluminium foil 

• The common thickness of the foil used is 0.012 – 0.015 mm. To increase corrosion resistance, it may be lacquered (coated with lacquer) or a thin film of plastic can be applied for packing dairy products. 

• The advantages of these containers are good barrier properties, grease proof, non-absorption, shrink proof, odourless, tasteless, hygienic, non toxic, opaque to light, bright in appearance etc. The demerits are its low tear strength, susceptibility to strong acids and alkalis. It is mostly used in the form of wrapper, carton and box. 

5. Timber

• The required qualities for the timber to act as a packaging material are it should be free from odour, have an attractive appearance, and required mechanical strength. It may be treated with casein formalin, or sprayed with paraffin wax or plastics or to make it more water resistant and to avoid the passage of timber taint to butter. It is generally used in the form of a box, tub, cask or barrel. 

6. Plastics

• The use of plastics in packaging has made tremendous progress in recent years all over the world. A wide variety of plastics can be used as thermoformed, injection moulded or blow moulded containers, such as bottles, cartons, cups, boxes etc. The merits of rigid plastic containers are its low cost and ease of fabrication. 

• The demerits cited are lack of product compatibility, low barrier properties, plastic deterioration, lack of resistance to high heat and fragility at lower temperatures. Flexible plastic packaging films are used as wrappers or sachets or bags or pouches for packaging milk and dairy products. The flexible plastics can be classified in to two types. 

Low polymers - They include cellophane (coated with plain or nitrocellulose / saran / polyethylene), treated with cellulose etc. 

High polymers - Polyethylene, polypropylene, polystyrene, poly vinyl chloride, poly vinyledene chloride (cryovac), rubber hydrochloride (pliofilm), polyester, polyamide (nylon), saran (a mixed polymer), etc. form good packaging materials. 

The merits cited for flexible packaging films are they can be easily applied and the packaging process can be readily mechanized; loss of moisture from the dairy product is practically nil; it confers protection to dairy products against attack by microorganisms, insects etc. The demerits are: not all technical problems in film packaging have been solved; failure to obtain a perfect seal and removal of all air before packaging may lead to spoilage; the most careful attention to detail is necessary, else faulty production will result; etc. Care has to be exercised in selecting food grade plastics for packaging of milk and dairy products; otherwise toxicity, if any, from the package will be transferred to the products. 

7. Laminates

• They are formed by combining the complete surfaces of 2 or more webs of different films with the primary object of overcoming the defects of single films.

• Usually laminations are made to strengthen the film material, to improve barrier properties, to improve grease resistance, to provide a surface that will heat seal, etc. Some of the typical laminates available for packaging are paper-polythene, cellophane-polythene, aluminium foil-polythene, paper aluminium foil-polythene, polyester-polythene, etc. 

8. Tera pack has Internal polyethylene layer seals in the liquid,

9. Polyethylene layer needed for lamination process

10. Aluminium foil provides a barrier to oxygen, flavours and light

11. Polyethylene adhesion layer needed for lamination process

12. Paperboard gives stability and strength

13. Polyethylene layer protects food from external moisture

Dye reduction tests

(A) MBRT test:

This test is based on the principle that methyl blue (an oxidation-reduction dye or indicator) which is blue in its oxidized state, is reduced to colorless compound (leuco form) as a result of the metabolic activities of bacteria in milk. When a solution of dye is added, the organisms present in milk consume the dissolved oxygen and lower O-R potential to a level where methyl blue or similar indicators are reduced or decolorized.

MBRT Procedure:

• Prepare a standard methylene blue solution by dissolving one tablet of methylene blue thiocyanate in 200 ml of sterile water.
• Add this to 10 ml of milk, shake well and keep in water bath.
• Note the time taken for the blue color to change to white.
• The total time gives MBRT time.

MBRT Test result:

5 hrs and above - Very Good

3 – 4 hrs - Good

1 – 2 - hrs - Fair

Half an hour - Poor

(B) Resazurin Test:

The resazurin test is conducted similar to the methylene blue reduction test with the judgement of quality based either on the color produced after a stated period of incubation or on the time required to reduce the dye to a given end-point. Numerous modifications have been proposed. The two most commonly used are the "one-hour test" and the "triple-reading test" taken after one, two, and three hours of incubation. Other modifications have value in specific applications.

Procedure:

• Prepare resazurin solution by dissolving one resazurin tablet (dye content/ tablet, approximately 11 mg, certified by Biological Stain Commission) in 200 ml of hot distilled water as was done in the methylene blue test.
• Place one ml of dye solution in a sterile test tube, then add 10 ml of sample. Stopper the tube, place in the incubator and, when the temperature reaches 36o C, invert to mix the milk and dye. Incubate at 36C.
• Tubes are examined and classified at the end of an hour in the "one-hour test" or at the end of three successive hourly intervals in the "triplereading test."

Color and Quality of Milk:

Blue (no color change) - Excellent

Blue to deep mauve - Good

Deep mauve to deep pink - Fair

Deep pink to whitish pink - Poor

White - Bad