Food Standard and Quality Control

Lesson 08 : Objective Methods - Chemical Methods


The nutrients and other chemical compounds present in fresh and processed foods are estimated. The changes that occur due to food storage and spoilage such as peroxides in fats, loss of important nutrients like beta-carotene are also determined using these methods. Adulterants in food e.g., presence of starch hin milk, metanil yellow in turmeric powder and loss of nutrients during cooking can also be estimated. The nutrient composition such as carbohydrates, proteins, fats, vitamins and mineral content of the foods are assessed using various chemical methods. There are standard methods available for each of the food component popularly known as AOAC methods. PFA methods for testing adulterants in each category of foods such as cereals, fruits and vegetables, fats and oils are also available.

Standard chemical methods are generally used for quantitative control evaluation in most cases. The various parameters tested for different foods are listed below.

  1. Ghee and butter: - organoleptic quality, rancid odors, moisture determination, free fatty acid estimation, salt estimation.
  2. Milk and milk products: - fat determination, protein determination, specific gravity, adulterants, lactose estimation.
  3. Vegetable oils, natural essential oils: - Acid value, saponification value, iodine value, refractive index at 40c, specific gravity, unsaponifiable matter.
    • Halphen test for cotton seed oil.
    • Bandovin test for sesame oil.
    • Molybdate test for caster oil.
    • Ferric chloride test for argemone oil.
    • Polenske value for coconut or palm kernel oil.
    • Allyl thiocyanite test for mustard and brassica family oils.
  4. Spices and condiments: - moisture determination, crude fiber, starch determination, volatile oil determination.
  5. Cereals: - moisture, total ash, gluten, protein determination, vitamins and minerals.
  6. Meat extracts: - determination of water, ash, chloride extracts, gelatin, creatinine, zinc, arsenic and copper.
  7. Jams and preservatives: - total solids, pectin estimation, total acids.
Last modified: Thursday, 16 February 2012, 11:01 AM