Preservation of Indian pickle

 

Preservation of Indian pickle

Vijay Kumar Shah

shahvk55@gmail.com   Mobile +91 99353 60033   WhatsApp  +91 98397 84033

There are two methods of preserving food namely.

1.      By killing all microorganisms responsible by heat or by other means and then checking further entrance of fresh organisms into the preserved product.  In this case the product should be practically bacteria and oxygen free. 

2.      By making the conditions, most unfavourable to the growth of microorganisms, so that they may not multiply and thus damage the product. In this case there may be living microorganism and oxygen may be present in the product.

The first method is used for fruit and vegetable canning and second one in pickles.

 

Spoilage in Indian pickle
Spoilage of pickle is due to four main causes:

1.  Microbial –             Off flavour, softening, blackening

2.  Biochemical –        Blackening, softening

3.  Chemical –             Blackening, metallic taste, off flavour due to metal or air.

4.  Physical –               Colour fading due to sun light.

 

Microbial spoilage

The spoilage includes alteration of flavour, colour and texture of fruits such as softening, blackening, slime production, ropiness, mushy texture, unpleasant odour, bubbling etc. The colour changes from reddish yellow to brown, texture from soft slimy to lumpy and mushy, unpleasant, sour, and oily odour develop. There is surface growth too. These changes make the pickle unfit for consumption.

 

Due to acidic nature of pickle, major cause of microbial spoilage in pickle is Mould and Yeast and not Bacteria. Putrefactive bacteria prefer a near neutral pH, and they generally do not survive acidic pickle, unless the pickles are very low in acid.

 

Growth of yeast is indicated by characteristic estery odour and slimy growth on the surface (Film yeast). It forms bubble also in pickle. Being anaerobic it develops in whole pickle.

 

Mould growth formed a white matted tuft followed by dark colour fruiting heads on surface of pickle. It causes disintegration of fruits due to pectolytic activity of certain fungi followed by fermentation and putrefaction. Mould appears as surface growth as it is aerobic. So it does not grow deep down in pickle. Among moulds Aspergillus niger  was found to grow well in pickle containing salt 10 – 20% and requisite proportion of spices.

 

Darkening of pickle specialy at top: This is by a rection between tannin, iron and oxygen catalysed by Polyphenoloxidase enzyme which produces dark compounds. Tannin and enzymes are in fruit, iron may enter through salt, water, equipment, dirt etc. Oxygen is from air which is in contact with the surface of pickle. This is not common phenomena, only if there is more tannin in the fruit, the pickle have chances of getting dark. The solution is to prevent oxygen contact by oil layer or adding antioxidant like BHA or ascorbic acid, or vacuum packing.

 

Softening of pickles – Mostly in mango pickle. It is mainly due to pectolytic enzyme found in mango which is extracted in brine and causes softening. 

 

Colour fading: The red colour of chillie fades under direct exposure to sunlight, and pickle looks dull.

Principals of Preservation:  

Salt, acid, spice, oil are the important ingredients used in pickling. These substances when used in sufficient quantities, act as preservatives. However none of these alone is sufficient to give self-stable product, but a combination is used. According to Leistner (1955) there are 7 hurdles to hinder microbial growth and preserve food.

F          High temperature                                Heating
T          Low temperature                                 Chilling, freezing
a_w         Reduced water activity                       Drying, curing, conserving
pH       Increased acidity                                 Acid addition or formation
Eh        Reduced redox potential                    Removal of oxygen or addition of

                                                                        ascorbate
Pres.    Preservatives                                       Sorbate, sulfite, benzoates,
c.f.       Competitive flora                                Microbial fermentations

 

If the level of a particular hurdle is insufficient, it should be increased. If by increasing it the food quality is affected an additional hurdle should be considered. In pickle preservation a combination of many hurdles is used.

 

Salt / sugar (a_w) –        reduced water activity by binding water.

Acid (pH)        -           Increase in acidity i.e. reduced pH.  

Eh                                Oil / brine covering, cutting off contact with oxygen.

Preservative                 Addition of chemical preservative + spices as preservative.

c.f. (LAB),                  Fermentation by LAB makes it unsuitable for other bacterial growth.

F High temperature     Pasteurization is practiced in pickle in vinegar.

 

A combination of high salt and high acidity coupled with anti- microbial properties of spices prevent the spoilage of pickles by creating unfavourable growth substrate for them.

Oil helps by coating their spores and vegetative cells thus creating a barrier between microorganisms and the water nutrient media. Oil on top helps to create anaerobic conditions, and check the growth of aerobic microorganisms (aerobic bacteria, moulds and yeast) which causes spoilage. Normally pickles are shelf stable and if proper quantity of ingredients used they have long shelf life.

 

The role of different ingredient in preservation of pickle is as bellow:

 

Salt: It helps by binding water, making it unavailable for microorganisms. Different microorganism requires different quantity of water for survival. By increasing salt percentage in pickle, the types and thus number of microorganism that may grow in pickle is reduced. However salt alone cannot prevent microbial spoilage of pickle.

 

Acid: All microorganisms have minimum and maximum pH between which they may grow. By changing pH, the type of microbial flora that will grow in pickle will change. Pickles are in general acidic in nature. Bacteria prefers near neutral pH, so pickle is not their favourite media for growth. Some moulds and yeast may survive. By increasing acidity their quantity and number is reduced. Again like salt acid alone cannot make pickle sterile, but in combination with other ingredients it helps a lot. 

Acetic acid has considerably preservative effect but its efficiency is by no means total. However, it is non-toxic, adds an appealing flavour to a food, and it has no rival under these terms as a preservative. Since the bacteria that cause food poisoning do not tolerate acetic acid, pickled foods are not likely to be suspect in a poisoning incident – at least not in those cases where vinegar is used in sufficient amount.

 

Spices: Many spices produce antimicrobial compound that helps in preserving pickle. Although they alone will not preserve pickle, but they help by reducing the quantity of salt and acid required for preservation.

 

As now there is a cry for chemical free food, considerable attention has been directed to the antimicrobial properties of spices. Analysis of their volatile flavour and odour fractions, known as essential oils, has frequently identified compounds such as allicin in garlic, eugenol from cloves and cinnamon and cinnamic aldehyde from cinnamon and cassia which have significant antimicrobial activity. As a consequence, herbs and spices may contribute to the microbiological stability of foods in which they are used.

 

Spices must be used at high levels to be effective antimicrobials, but this will cause flavor issues in pickle. In the quantity used, spices do not have a major biocidal role. They are mainly used as flavouring agent. However they have supplementary effect. Turmeric powder, mustard seed or oil, ginger etc. apart from contributing flavour, help to reduce even by half the quantity of salt needed for preservation. Some of the spices affecting microorganism are:

 

Mustard: Mustard and mustard oil produces antimicrobial isothiocyanates. It helps in preventing growth of moulds. Traditionally mustard powder is added as natural preservative.

 

Cinnamon: 0.3% cinnamon is effective in preventing mould growth in pulp containing 16% salt, while 3% cinnamon was required for pulp without salt. Less salt proportionately more cinnamon is required to prevent mould growth.

 

Clove: 0.2% clove is sufficient to prevent mould growth in pulp with 16% salt while 0.6% is required in salt less pulp. Proportionately more clove is required as salt % goes down in pulp.

 

Ginger : in 5% quantity has bactericidal effect.

 

Turmeric powder : It is common to use turmeric powder at the rate 0.5 – 1 kilo / 100 kilo in brined stock of mango or lime stored for conversion to pickle.

 

Ajawain: Thymol of ajawain destroys some pathogenic yeast.

 

Oil: It reduces redox potential, by preventing contact of oxygen with pickle. Microorganisms do not grow in oil. For their nutrient supply they depend on osmosis which is they absorb nutrients from pickle in water soluble form. Oil coats their spores and vegetative cells thus creating a barrier between microorganisms and the water nutrient media.

Many of them require oxygen for growth. Oil has been used as an air-excluding ingredient since ancient times to keep foods from spoiling.

Oil on surface of pickle helps to create anaerobic conditions, and check the growth of aerobic microorganisms (aerobic bacteria, moulds and yeast) which causes spoilage.

However, as with other ingredient oil alone is not a guarantee against spoilage.

 

Preservative:  Chemical preservatives are not must in pickle. A proper pickle can have long shelf life without any preservative. But addition of preservative is common in commercial pickle. It covers up for poor hygienic condition in factory or faulty handling after opening the bottle.  It also covers up if the quantity of salt and acid is not properly balanced in recipe.

The plus side of using preservative is that with its help quantity of salt and acid can be considerably reduced without affecting self - stability of pickle.

 

The most widely used food preservatives in pickle is the Sodium Benzoate. It is only effective at pH values low enough to ensure that substantial amounts of the un-dissociated forms of the acid are present. It is well established that a major reason for this is that the un-dissociated acid readily enters into the microbial cell.

 

At the same level of concentration SO₂ is most effective preservative followed by sodium benzoate, sorbic acid and sodium propionate respectively. Adding salt helps in reducing preservative doses. Higher the salt % Lower is the requirement of preservatives.

 

Generally, in the presence of preservatives, the temperature/time values required to kill microorganisms are lower than in the absence of preservatives. In other words, microorganisms are killed more swiftly in the presence of most preservatives than at the same temperature in their absence.

 

Reduced redox potential (Eh)

That is pickle with low oxygen. It can be achieved by

Physical exclusion of air.

Residual respiration and oxygen consumption by plant cells that quickly reduce the Eh and make the environment anaerobic.

Addition of ascorbic acid or other antioxidant.

Oxygen removal by vacuum-packaging.

Cover pickle with a layer of oil or brine. All pieces covered, nothing exposed to atmosphere.

 

The advantage of exclusion of oxygen is that Pseudomonads, fungi, and other obligate aerobic microorganisms that may initially be present at high levels, have little opportunity for growth. Some of these organisms are also salt-sensitive, further reducing their ability to grow in this environment.

Improves the colour of the products.

 

Antioxidant

The contact with oxygen causes two problems:

Top blackening

Off smell of oil.

Use of antioxidant will help in preventing it.

If there is more tannin in fruit like immature mango, Anwala etc., top blackening may become a problem. In such cases Antioxidant like Ascorbic acid or Erythorbic Acid may be mixed in pickle. Or other antioxidant like BHA or TBHQ can be added to oil.

 

Chelate

Blackening – is also due to iron which may enter through salt or equipment. In some places water also is high in iron. Best is to avoid contact with iron. If water is high in iron it can be treated. If not practical then a suitable chelating agent may be added to pickle.

 

Pickles in India can be classified into following categories.

Pickle in Oil

Pickle without oil

Sweet pickle & Chutney

Pickle in vinegar

Brine stock

If proper precaution is taken, they will have long shelf life.

 

Pickle in oil

This is most popular type in India. Mango pickle, Lime pickle, Jack Fruit pickle, Mixed pickle etc. Everybody is familiar with these.

 

In India, acidic fruits like lime, mango, or gooseberry are pickled using 15 – 20% salt. In these pickle, salt and acid acts as preservative. These are not fermented by LAB or any other microorganism. 

In non-acidic fruit like jack fruit etc. and vegetables like turnip, cauliflower, green chilli etc. some souring agent like lime juice, tamarind extract, vinegar etc. or organic acids are added. 

They are made from fresh or salt cured material. Generally the raw material is not cured in brine. The fruits and vegetables are mixed with salt and spices and packed in jars. Edible oil is poured over the pickle to form a thick layer.

 

These pickles should have following specification for long shelf life -

In oil pickle salt and acid should be calculated on oil free basis i.e. Pickle mass – oil content.

 

Salt –               over 12%, best is >15%.

Under certain conditions it can be brought down to even 8%.

Acidity –         Titrable  > 2%

of which preferably minimum 0.5% should be acetic acid.

pH  -                bellow 3.5

Moisture -        bellow 50%

Oil –                sufficient to cover top completely. 

All pieces should be fully submerged into gravy. Any exposed piece will attract spoilage organism.

Analysis of a few typical Commercial Pickle in oil is as bellow::

Type                            pH                   Acidity %                     Salt %

Lime                            2.3                   3.3                               15.2

Mango                         2.98                 2.3                               14.8

Green Chillie               3.31                 2.3                               14.5

Mixed                          2.98                 2.6                               14

 

Preservative – optional but commonly used in commercial oil pickles. It should be in correct quantity and well mixed. Normaly sodium benzoate is used. A little Sodium meta bi sulphite is also useful and helps in making pickle bright.

Good pickle is of typical reddish yellow colour, pleasant flavour, and firm texture and does not show any surface growth.

 

Reduction in moisture:

In oil pickle less moisture means better shelf life. Some of the ways to reduce moisture are:

Partial dehydration by exposing ready pickle in glass jars to sun for several days.

Preserve pieces in brine and discard brine. Use only pieces for pickle making.

Add solids like Gur,

Heat - salt, spices, oil etc. to evaporate moisture in that.

Keeping pickle in sun for 2 – 3 days as done in domestic condition improves flavor.

 

Pickle without Oil

The recipe of such pickle is more or less same as that with oil, only no oil is added. Usually it is made from sour fruit like lime and mango. In these pickle quantity of salt and acid should be on higher side and preferably chemical preservative should be added. The pieces should be completely covered with brine (Gravy) – nothing exposed.

 

Sweet pickle & Chutney

FSSAI classifies sweet pickle as chutney. Both are same.

 

Sweet Mango Chutney: It is generally exported.

A value which may be called preservative index is important. The index should be not less than 3.6%, which generally helps to preserve the product. In such products, from organoleptic point of view, salt should not exceed 3 to 4%. Hence by increasing the sugar content, it is possible to reduce the acetic acid concentration. The quantity of acetic acid required may be calculated using the expression:

Acetic acid in the whole product % =

Analysis of typical Commercial Mango chutney is as bellow::

Salt                  2.3 + 0.3

Acidity            0.7 + 0.8

Brix                 58  - 60

pH                   2.5 + 0.2

 

Sweet Indian Pickle:

Sugar alone to act as preservative should be 68.5%. If salt or vinegar or both are present this quantity can be brought down. Thus if 4 – 6% salt is present and 1.5% acetic acid even 30 – 40% sugar will preserve. Analysis of a typical commercial sweet mango chunda is as bellow:

Salt                  1.8%

Acidity            1.1%

Brix                 72 - 74

Inversion         30 – 50%

As there is high brix so there is danger of sugar crystallization hence % sugar inversion is important here. Preservatives, like sodium benzoate, may be added to extend the shelf-life of the product once the jar has been opened.

 

Pickle in Vinegar

This is not common in India, but this type is very popular in western countries. Kimachi of Korea, Saurkraut of Europe, Gherkin of Amerca are some of the examples. In India radish, ginger, garlic, mixed vegetable etc. in Vinegar are made on limited scale mostly in western India. The shelf life of these pickles is dependent upon the vinegar and, where employed, on pasteurization. Vinegar contains about 4% acetic acid.

 

Acetic acid 3.5% alone will preserve and no organism will grow (3.5% of water content).  As normal moisture is 55 – 60%, so 2% acidity is sufficient. In vinegar pickle, vinegar is main preservative. To avoid dilution of the vinegar by the water liberated by the tissues of the vegetable are generally placed in strong vinegar of 10% for several days before final packing. This treatment helps to expel the intracellular gases and also prevents further dilution of vinegar in final pickle.

 

Lactic Acid bacteria (LAB)

Fermentation of foods also is a traditional and common preservation process. If lactic acid bacteria are used for fermentation, acidification (low pH) contributes to the preservation of pickles.

 

In vegetable fermentation, the desired product quality and microbial stability are achieved by a combination of factors such as salt, acidification, and so forth. Bacteria in general prefer for their growth material with little or no acid. The lactic acid bacteria (LAB), 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 to 10% salt. Advantage is taken of these two factors in pickling. The growth of undesirable organisms is inhibited by adding salt, while allowing the lactic fermentation to proceed. When lactic acid is formed in sufficient quantity, the lactic acid bacteria cease to function, and any further change in the composition of the material is prevented. Normally these are packed in Vinegar.

 

LAB fermentation is not common in Indian Pickle. However, it will improve texture and flavour of vegetables with sugar like carrot, beet root; smelly vegetables like radish, turnip; soft vegetables like cucumber etc.

 

Pieces in Brine

In India it is common to preserve fruits and vegetables in brine in season and later convert them into pickle as per the market demand. Two methods of brining are followed:

 

Dry salting – cut pieces of fruits and vegetables are mixed with 20 – 25% salt. By next morning water from fruits and vegetables oozes out and forms brine. The fruits shrink in volume due to exclusion of water and air from the tissues. The brine stock should be mixed to make it uniform. As the volume of brine stock shrinks so after a few days fill up the barrel up to top with cured material from another barrel otherwise air space will help in developing bacteria and mould to grow on top. In case pieces are not covered fully prepare brine of 20% salt and 2% acidity and cover. This is practiced where fruit and vegetable contains sufficient water like mango, Lime etc.

 

Wet brining: In this case fill up the barrel with vegetable and cover them with brine solution up to top. If lactic fermentation is desired, start with 10% brine and increase it to 20% gradually. As in case of carrot, radish, cucumber etc.

If no fermentation is desired cover with 20% brine straightway. If fruits are non -acidic like green chilli add 2% acid or lime juice in brine. Maintain overall salt per cent of 16%  and pH bellow 3.5 in the pieces.

In wet brining if fruits are floating as in green chilli, they should be pressed down so that all is under brine, otherwise they will attract bacteria and fruit flies. One may use wooden planks and stone for pressing or cover with plastic sheet and weigh down it with water.

 

In the presence of fifteen per cent salt and a certain concentration of acidity, most of the harmful bacteria are inhibited and in time destroyed if allowed to stand for a few weeks. If final concentration of salt in the material is 15 – 20%, even LAB will not grow.

 

Some people add chemical preservatives too to further safeguard from spoilage. In brine stock by adding acetic acid and SO₂ the quantity of salt could be reduced. It has been observed that:

 

Mango slices in brine: Maximum number of yeast and bacteria are noticed in 10% brine. Mango slices kept in 15% salt permitted slow multiplication of yeast but the slices were crisp and quality good.

 

Brinning condition for mango, papaya, amla, bitter gourd, onion etc – A brine containing 10% salt + 0.3 – 0.5% acetic acid + 0.5% turmeric preserved the material in sound condition.

 

When this method has been employed the vegetables can be kept in brine for more or less an indefinite period provided the right storage conditions are maintained.

 

Precautions should be taken to save it from spoilage by aerobic microorganisms. 'The presence of salt and the acid preserve the pickle by preventing the growth of putrefactive bacteria provided air is excluded. The common defects in stored brine stock:

 

Film Yeast: During brining a white scum invariably forms on the surface of the brine. Thickness of this scum varies from batch to batch and may be an imperceptible film to a thick wrinkled layer. This scum layer is formed by wild yeast, which will decrease the lactic acid formation during fermentation. So to minimize the loss of lactic acid, this scum should be removed as soon after formation as possible. If loss of lactic acid continues, there is a possibility of putrefactive bacteria developing, making vegetables soft and slimy. However addition of 1% acetic acid or even less will usually prevent the formation of wild yeast.

 

Mould growth is common on brine surface. It should also be removed as soon as formed. Addition of 100 ppm SO₂ will control it.

 

Blackening in pickle: It is characterised by the formation of black brine and occurance of black or darkened areas on the outer surface of the pieces. The black color of brine was found to be due to ferrous sulfide formed as a result of reaction between the hydrogen sulfide (produced by bacteria) and iron presnt in the salt. B. nigrificans isolated from black pieces, however did not produce Hydrogen sulfide but produced a water soluble black pigment which imparted the chareacteristic black colour to the brine.

 

Pasteurization

In pickling of fruits and vegetables, thermal treatment is sometimes employed to increase the microbial stability or safety of food products since vinegar (acetic acid) alone or even combined with salt may be insufficient to prove reliable long-term preservation. Pasteurization is quite common in fresh pack vinegar pickle. In oil pickle it is not practised.  However many people specially obese and suffering from Hypertension avoid pickle due to its high salt and oil content. Pasteurization can help to formulate pickle with less salt and oil.

 

For thermal processing, the pickle industry usually uses a procedure established in the early 1940s that recommended an internal pasteurizing temperature of 74°C for 15 min followed by prompt cooling.

 

However for products with pH < 3.7, the slowest heating spot in the container should achieve a minimum of 65°C for 16.7 min or 70°C for 2.1 min. Accordingly  for oil pickle of < 3.5 pH pasteurization at 70⁰ C retort water temperature, 30 minutes dip.  10 minutes air cooling then water cooling is sufficient.

 

Hygiene

The initial microbial load of the raw material greatly influences the stability and safety of food products. Good Sanitary condition should be followed.

 

Decontamination of raw materials is effective. However it is not must.

 

Fruit washing water-   Should have 15 – 25 ppm chlorine then plain water. Wash fruits and air dry.

 

Pickles are in general self stable product with little preservation probelum. The parameters mentioned above if followed will give pickles a long shelf life.

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