Module 10.  Pickles and sauerkrauts

Lesson 34

PICKLES: PRINCIPLES AND CLASSIFICATION

34.1 Introduction

Pickling is one of the oldest and most successful methods of food preservation known to humans. It is difficult to suggest a date for production of the first pickled foods, but it is known that both vinegar and spices were being used during biblical times. Pickles of various kinds are known throughout India and many parts of the world. They are good appetizers and add to the palatability of a meal. Fermentation of plant and animal foods was known to the early Egyptians, and fish were preserved by brining in prehistoric times. By the third century BC, Chinese labourers were recorded to be consuming acid-fermented vegetables while working on the Great Wall. The Koreans created kimchi from acid-fermented Chinese cabbage, radish, and other ingredients centuries ago. Corn, cassava and sorghum were fermented and became staples of the African diet. In the west, acid fermentation of cabbage and cucumbers produced sauerkraut and pickles, which are still popular today. Early explorers carried kegs of sauerkraut and pickles that prevented scurvy on their voyages. Pickles from India or achaar are unique because these are mixed with spices that only India produces. Some common Indian spices include cumin, mustard seeds, fenugreek, turmeric, coriander, etc. Some of the typical Indian pickles made from mango (aam ka achaar), lime (nimbu ka achaar), turnip, cabbage, cauliflower, etc. have become popular in several countries.

34.2 Principle of Pickling

There are mainly two methods of preserving fruits and vegetables namely (i) by killing all the microorganisms responsible for spoilage, by heat or other means and then checking the entry of fresh microorganisms into the preserved product, and (ii) by making the conditions most unfavourable for the growth and multiplication of microorganisms. The first method is generally employed in the preservation of fruits and vegetables for making fruit juices, fruit powders, etc. and the second method in the preparation of pickles. The process of preservation of food in common salt or vinegar is called as pickling. Spices and edible oils also may be added to the product. Salt, vinegar, lactic acid and oil are the important ingredients used in pickle production. These substances when used in sufficient quantities, act as preservatives either singly or in combination. The preservative action of these substances are given below:

34.2.1 Salt

Vegetables do not ferment when they are covered with strong brine or packed with a fairly large quantity of salt. Spoilage is prevented by adding sufficient common salt, bringing its final concentration in the material from 15 to 20 percent. At this high salt concentration, mould and even lactic acid-forming bacteria do not grow. This method of preservation is only applicable to vegetables which contain very little sugar because sufficient lactic acid cannot be formed by fermentation to act as preservative.

34.2.2 Vinegar

In vinegar pickles, vinegar acts as a preservative. In order to ensure satisfactory results, the final concentration of acid as acetic acid, in the finished product should not be less than 2 percent. To avoid dilution of the vinegar by the water liberated from the tissues, the vegetables are generally placed in strong vinegar of about 10 percent acidity for several days before final packing. This treatment also helps to expel the gases present in the intercellular spaces of the vegetable tissue.

34.2.3 Lactic acid

Bacteria prefer for their growth media with little or no acid. The lactic acid bacteria, however, can grow in acid media and can also produce acid through their action on the substrate. They can grow in the presence of 8 – 10 percent salt. The growth of undesirable organisms is inhibited by adding salt while allowing the lactic fermentation to proceed. In fermented pickles, microorganisms ferment sugars to lactic acid. When vegetables are placed in brine, the soluble material present in them diffuses into the salt water owing to osmosis and the liquid penetrates into the tissues. The soluble material, besides containing mineral matter, contains fermentable sugars. These sugars serve as food for lactic acid bacteria, which convert them into lactic and other volatile acids.

34.2.4 Oil

In oil-based pickles, fruits or vegetables are completely immersed in the edible oil. It acts as a barrier for air and creates an anaerobic condition which is utilized by the native bacteria for the production of lactic acid. Oil prevents growth of spoilage yeasts and moulds. Generally mustard oil is used.

34.3 Classification of Pickles

Depending on the method of preparation, pickles can be classified into three types such as pickles in vinegar, pickles in citrus juice or brine and pickles in oil. Fruit pickles are generally preserved in sweetened and spiced vinegar, while vegetable pickles are preserved in salt.

34.3.1 Pickles in vinegar

These are most important pickles in the world.

34.3.2 Pickles in citrus juice or brine

Steeping of the vegetable in a salt solution of pre-determined concentration for a certain length of time is called brining. Vegetables which do not contain sufficient water are better fermented by covering them with a weak brine solution. Alternately, dry salt is also used for vegetables which contain sufficient water content. It involves packing vegetables with a small quantity of dry salt (about 2-3 kg for every 100 kg) without adding water. Salt extracts the water from the vegetables owing to osmosis and forms the brine. The sugars present in the vegetables are extracted into the water and are fermented by the lactic-acid forming bacteria which are naturally present in great numbers on the surface of the fresh material. After certain time, enough lactic acid is formed to kill the bacteria and prevent any further change in the material, provided certain precautions are taken to prevent the growth of moulds. The lactic acid permeates to the fermented vegetables and gives characteristic flavour. It is the same acid which is present in sour milk and it is digested and utilized by the body as a source of energy. Leuconostoc mesenteroides was identified as one of the most important microorganisms for initiation of vegetable fermentation.

34.3.3 Pickles in oil

These are pickles containing some edible oil and are highly popular in India. Usually oil pickles are highly spiced. Cauliflower, lime, mango, turnip pickles, etc are prepared in this manner. The method of preparation of some of the oil pickles vary in different parts of the country. In north India, rapeseed or mustard oil is commonly used, but in south, gingelly (sesame) or groundnut oil is preferred. For example, the method of preparation of mango pickle is different in different parts of the country. However, “Avakai” pickle in Andhra Pradesh is well-known mango pickle in oil.

34.4 Desired Quality of Ingredients Used in Pickling

Raw materials used in pickling should possess certain definite characteristics for achieving a wholesome pickle. The desired qualities of ingredients used in pickling are given as follows:

34.4.1 Salt

In general, pure common salt is generally preferred for pickling. It should not contain more than 1.0% percent of impurities, should not contain chemicals like tricalcium phosphate or magnesium phosphate which are generally added to salt as anticaking agents. Salt should be free from lime (calcium oxide), as it reduces the acidity of the vinegar in which brine vegetables are pickled and also causes lime deposits of the bottom of the container. Salt should be free from iron, which in contact with the tannin of the fruit, vegetable and spice produces blackening of the pickle. It should not contain magnesium salts which impart a bitter taste to the pickle.

34.4.2 Vinegar

Vinegar of good quality should contain at least 4 percent acetic acid. Usually malt or cider vinegar is used. Vinegars of low acid content or imitation or synthetic vinegars are not suitable for pickling. Vinegar should not come in contact with iron as it leads to blackening of the pickle.

34.4.3 Oil

Good quality oil free from rancidity or oxidation is preferred.

34.4.4 Sugar

Sugar used in the preparation of sweet pickles should be of high quality.

34.4.5 Spices

Spices are added practically to all pickles, the quantity added depending upon the kind of fruit or vegetable taken and the kind of flavour desired. The spices generally used are bay leaves, cardamom, chillies, cinnamon, clove, coriander, ginger, mustard, black pepper, cumin, turmeric, garlic, mint, fennel, etc. These should be of good quality and should be stored in tin cans in a cool and dry place.

34.4.6 Water

Only potable water should be used for the preparation of brine. Hard water contains salts of calcium, sodium, magnesium, etc. which interfere with the normal salt-curing of the vegetable. If hard water is to be used, a small quantity of vinegar should be added to brine to neutralize its alkalinity. Iron should not be present in the water in any appreciable quantity as it causes the blackening of the pickle.

34.7 Legal Definition and Specifications

In India, the Food Safety and Standards (FSS) Rules (2006) defines pickles as “preparation made from fruits and vegetables or other edible plant material including mushrooms free from insect damaged or fungal infection, singly or in combination preserved in salt, acid, sugar or any combination of the three. The pickle may contain onion, garlic, ginger, sugar, jaggery, edible vegetable oil, green or red chillies, spices, spice extracts/oil, lime juice, vinegar/acetic acid, citric acid, dry fruits and nuts. It shall be free from copper, mineral acid, alum, synthetic colours and shall show no sign of fermentation”. Pickles may be of following combinations confirming to the requirements as given below:

34.7.1 Pickles in citrus juice or brine

a) Drained weight: Not less than 60 percent

b) Sodium Chloride content           

when packed in brine: Not less than 12 percent

c) Acidity as Citric acid when

packed in Citrus Juice: Not less than 1.2 percent

34.7.2 Pickles in oil

a) Drained weight: Not less than 60 percent

b) Fruit and vegetable pieces shall practically remain submerged in oil

34.7.3 Pickles in vinegar

a) Drained weight: Not less than 60 percent

b) Acidity of vinegar

as acetic acid: Not less than 2.0 percent