Fruits and vegetables products

 

Processing of fruits and vegetables

Fruits and vegetable products 

a. Beverages; juices, nectar and drinks

b. Fruit preserves; jams , jelly marmalade,

c. Pulps

d. Tomato products; tomato juice, ketchup, chili sauce, concentrate, puree

e. Pickled products; sauerkraut (fermented cabbage)

 

FRUIT BEVERAGES

Fruit juice is the natural liquid expressed by pressure or other mechanical means from the edible portion of the fruit. Fruit juices are generally extracted from fruits in a number of ways, depending on their structure and composition.

Types of fruit juice and beverages

a) Unfermented beverages

Fruit juices which do not undergo alcoholic fermentation are termed as unfermented beverages or natural juice pressed out of the fruit and remains practically unaltered in its composition during processing and preservation. They include natural fruit juices, sweetened, ready to serve drinks, nectar, cordial, squash, crush, syrup, fruit juice concentrate and fruit juice powder.  Ready to serve (RTS) drinks, nectar, squash, cordial, appetizer are all fruit juice beverages.

Synthetic drinks: Synthetic drinks are prepared by using sugar, water, flavourants, acidulents, colour etc. These drinks do not contain any fruit juice or pulp.

Ready to serve (RTS) drink: This is a type of fruit beverage which contains atleast 10% fruit juice (for lime drink 5% juice) and not less than 10% total soluble solids. The acidity in these drinks shall not exceed 3.5% as citric acid. RTS beverages are preserved by using class II preservatives not exceeding 70 ppm SO2 or 120 ppm benzoic acid. It is not diluted before serving hence it is known as ready to serve drink for example mango drink, guava drink, pineapple drink etc.

Fruit nectar: This type of fruit beverage contains atleast 20% fruit juice or pulp and 15% total soluble solids and is preserved by heat processing. The acidity in fruit nectars shall not exceed 1.5% as citric acid. No class II preservative like SO2 or benzoic acid is permitted in fruit nectar as per Indian Food Laws. It is not diluted before serving.

Squash: Fruit squash consists of fruit juice or pulp to which cane sugar is added for sweetening. According to Indian Food Laws, the fruit squash shall contain atleast 25% fruit juice or pulp and not less than 40% TSS. It shall not contain class II preservative in excess of 350 ppm SO2 or 600 ppm benzoic acid. Acid content in squashes generally remain between 1-1.5% but shall not exceed 3.5% as citric acid. Squash is generally diluted with water in 1:3 ratio before serving. Lime, lemon, mango, orange, guava and pineapple squashes are commercially manufactured.

Fruit juice cordial: It is a sparkling, clear, sweetened fruit juice from which pulp and other suspended substances have been completely removed. It contains atleast 25% juice, 30% total soluble solids and not exceeding 350 ppm SO2 or 600 ppm benzoic acid as preservative. It is also used for mixing with alcoholic drinks for example lime juice cordial.

Fruit Appetizer: Fruit appetizer is similar to fruit squash but also contains spices, condiments and herb extract. Spices like black pepper, cumin, large cardamom, ginger along with mentha extract and salt are used for manufacture of appetizer. They are also called as spiced fruit squash. Plum and apricot appetizers are quite common.

Fruit crush: Fruit crush contains minimum of 25% fruit juice or pulp, 55% total soluble solids (TSS) and not exceeding 350 ppm of SO2 or 600 ppm of benzoic acid. It is diluted before serving.

Fruit syrup: It is prepared by using minimum of 25% fruit juice or pulp and sweetened by using cane sugar. It shall contain not less than 65% total soluble solids and not exceeding 350 ppm SO2 or 600 ppm benzoic acid as class II preservative.

Synthetic syrup: Heavy sugar syrup of 70-75 percent strength is used as the base of all synthetic syrups, which are flavoured and coloured with artificial flavour and colours. They may or may not contain fruit pulp or juice. Rose, sandal, almond, khuskhus, kewra sherbets/syrups are quite common.

Carbonated fruit beverages: It is a ready to serve fruit juice beverage which contains variable amount of fruit juice, sugar, acid etc and impregnated with carbon dioxide gas. Apple juice, lime, lemon and grape juice can be used for the preparation of carbonated fruit juice beverages. They are prepared either by pre mix or post mix method.

Fruit juice concentrate: It is a fruit juice, which has been concentrated by removal of water either by evaporation, freezing or reverse osmosis. Several products can be made from fruit juice concentrate. Apple juice concentrate, orange juice concentrate etc are commercially prepared in the industry.

Fruit juice powder: This is a fruit juice which has been converted into a free flowing powder. They can be prepared either by freeze drying, foam mat drying or spray drying processes. They are readily reconstituted to yield full strength fruit juice drinks.

 

 

Specifications for different fruit beverages

Product	Minimum % of total soluble solids in final product (w/w)	Minimum % of fruit juice in final product (w/w)	Maximum acidity expressed as citric acid (%)
Unsweetened juice	Natural	100	3.5
Fruit syrup	65	25	3.5
Crush	55	25	3.5
Squash	40	25	1.5
Fruit nectar (excluding orange and pineapple)	15	20	1.5
Orange and pineapple nectars	15	40	1.5
Cordial	30	25	3.5
Sweetened juice	10	85	-
Lime/lemon Ready to serve beverage	10	5	-
Ready-to-serve beverage/drink	10	10	-
Fruit juice concentrate	32	100	-
Synthetic syrup/sherbet	65	-	-

 

b) Fermented beverages

 

Fermented fruit beverage is a fruit juice which has undergone alcoholic fermentation by yeast like Saccharomyces cerevisae. The product contains varying amount of ethyl alcohol. Apple cider, plum wine, grape wine, vermouth etc are common fermented beverages.

 

Fruit juice beverages processing

Selection of fruits: check on the variety and maturity of the fruit and locality of cultivation as it influences the flavor and keeping quality of its juice. Only fully ripe fruits are selected. Over ripe and unripe fruits adversely affects the quality of the juice.

Sorting and washing: Diseased, damaged or decayed fruits are rejected or trimmed off. Dirt and spray residues of arsenic, lead etc are removed by washing with water or by using dilute hydrochloric (HCl) acid solution (0.5%) followed by washing in water.

Juice extraction: Generally juice is extracted by crushing or grating the fruit and pressing the crushed mass in a basket or hydraulic press. Juice can also be extracted by using a screw type juice extractor.

Common equipment used for juice extraction are fruit grater or mill, basket or hydraulic press, screw type juice extractor, rosing or burring machine, fruit pulper etc. There are two types of extraction methods i.e., single and double operation system.

Single operation: In single operation, screw type, plunger type or roller type press is generally used to crush and press the prepared fruit to extract the juice.

Double operation: In this system, the fruits are crushed and then pressed separately.

De-aeration: Freshly extracted juice contains appreciable quantity of oxygen which may affect the quality of juice if not removed before packing. Air in juice is due to the presence of intra-cellular spaces present in the fruits. Most of the air as well as other gases are removed by subjecting the fresh juice to a high vacuum. This process is called as de-aeration and the equipment used for the purpose is known as the deaerator. Heating of juice during heat processing also helps in removal of the air.

Clarification of Juice: Un-clarified fruit juices contain varying amounts of suspended matter consisting of broken fruit tissue, seed, skin, pectic substances and protein in colloidal suspension. Clarification is achieved through the following ways:

a. Straining or screening: The fruit juices are strained or screened by muslin cloth or stainless steel mesh sieves manually to remove coarse particles in a small-scale industry. But in large industries power operated screening system or filter press is used.

b. Finishing: Citrus juices need finishing for separating cloudy but otherwise clean juice from pulp, rag and seeds. The finisher separates the pulpy matter from the juice by the action of a rotating auger inside a cylinder screen. Screen hole size range from approximately 0.020 to 0.030 inch in diameter, depending on the condition and softness of the fruit. Finishing is judged by the pulp content in the orange fruit juice.

c. Decantation: Decantation is the simplest method of clarification, in which the juice containing solids is allowed to settle down and then clear juice is decanted or siphoned out. Keep juice at low temperature for long periods also helps in setting of solid to allow clarification.

d. Centrifugation: The clouding particles can be separated by centrifugal action. The juice containing solids is fed into a basket or disc type centrifuge, where the centrifugal force separates the light and dense components in each layer. The clear juice is collected and unwanted solids are separated.

e. Enzymes: The plant carbohydrates, pectin, starch and proteins make the colloidal suspension in the freshly extracted fruit juice. The pectinase enzyme is widely used for better juice recovery as well as clarification of fruit juices as it breaks pectin into soluble form thereby freeing the suspended particles which settle down and leaves the juice clear. Similarly, proteolytic and starch liquefying enzymes i.e. amylases are used to remove protein and starch from fruit juices. Pectinase is more effective in the case of acidic juices. Fruit juices can be clarified in about 1-2 hours at 40-500C but requires 20 hrs at 200C.

f. Physical finings: Certain fining agents, which have physical or mechanical action are kaolin, diatomaceous earth, Spanish clay, bentonite or china clay and are known as filter aids. Generally 0.5 to 0.1 percent earth is mixed with fruit juice and then passed through the filter press. Ultra filtration is a process that separates particles based on molecular weight and has better retention of the nutrients in the juice. It is necessary to degrade the pectin enzymatically before ultra-filtration, to reduce viscosity and allow a satisfactory juice.

g. Chemical finings: Gelatin and casein are used to clarify the fruit juices and act partly to neutralize the electrical charged particles and partly by forming insoluble precipitate with the constituents of the juice. The gelatin combines with tannins and casein with acid of the juice. The gelatin may cause juice cloudy if used in excess.

Depending on the tannin content of the fruit juice, gelatin solution is mixed and allowed to stand for 18 to 24 hrs to ensure that the precipitated matter clots together and settles down. The clarified juice is then siphoned off. Albumin (egg white) can also be used in clarification of juices.

 

h. Clarification by freezing: Grape juice contains cream of tartar or potassium hydrogen tartarate along with pulp and skin which is removed by freezing and thawing the juice or by refrigeration for a long storage. Apple juice can also be clarified using this method after freezing is precipitated on thawing.

 

i. Clarification by heating: During heating, the colloidal material in fruit juices coagulates and settles down on cooling which can be separated by using a filter press. For clarification of apple and pomegranate juice, the juice is heated to 80-850C for few minutes and cooled immediately followed by filtration by passing the juice through a filter press.

 

j. Addition of sugars: All juices are sweetened by adding sugar, except those of grapes and apple. Sugar can be added directly to the juice or as syrup made by dissolving it in water. Fruit squash, cordial, syrups are made by adding appropriate quantity of sugar into the pulp or juice using cane sugar. Similarly ready to serve drinks and fruit nectar are sweetened by using cane sugar.

 

Juice preservation: this achieved through pasteurization (LTLT or HTST), aseptic filling, filtration to remove microorganisms and use of chemical preservatives e.g. Squashes, crushes, syrups and cordials are preserved by adding chemical preservative like potassium meta-bisulphite, sulphur IV oxide or sodium benzoate. Also, there is carbonation of fruit juices, addition of sugar, drying to produce fruit powders.

 

 

                                                                JAMS, JELLIES AND MARMALADES

Jams, jellies and marmalades constitute an important class of preserved fruit products. Apple jam, pineapple jam, strawberry jam and mixed fruit jam prepared by using pulp of two or more fruits are quite common.

JAM:

Jam is prepared by boiling the fruit pulp with a sufficient quantity of sugar to a thick consistency, firm enough to hold fruit tissues in position. The method for preparation of jam and jelly is the same except that pulp and pieces of fruit are used in jam while, for jelly making clear fruit extract is used.

Fruit preparation

Washing is done thoroughly to remove any adhering dust and dirt.

Preparation of fruits vary as seen below:

Ø  Strawberries are crushed between rollers; raspberries are steamed, crushed and passed through sieves to remove the hard cores.

Ø  Plums, peach and apricots are heated with a small quantity of water until they become soft and are then passed through a wide mesh sieve to separate the stones. Fruit after softening by boiling with small quantity of water can be passed through the pulper to extract the pulp.

Ø  Pears are peeled, cored and cut into small pieces.

Ø  Mangoes are peeled, stones separated and then the slices are passed through a pulper.

Ø  Pineapples are peeled, sliced and the cores punched. The slices are then cut into smaller pieces and passed through a screw type crusher to get a fairly coarse pulp suitable for making the jam.

When two or more fruits or fruit pulps are mixed in appropriate proportion for preparation of jam, the jam is called as mixed fruit jam.

Addition of sugar

Generally 55 parts of cane sugar (sucrose) is used for every 45 parts of fruit for preparation of jam. The prepared jam should contain 30 to 50 percent invert sugar to avoid crystallization of sugar in the jam during storage. If the percentage of invert sugar (reducing sugar) is less than 30, then jam develops crystallization and if it is more than 50%, the jam will develop into a honey like mass due to the formation of small crystals of glucose. Sugar should not be added in excess as jam with higher total soluble solids becomes gummy and sticky.

 

Addition of acid, color and flavor

Citric, tartaric or malic acid are used to supplement the acidity of the fruit for jam making. Addition of acids to fruits which are deficient in acid is required to get appropriate combination of pectin, sugar and acid for proper setting of jam. The pH of the mixture of fruit juice and pectin should be 3.1 before sugar is added. Only permitted edible food colors should be used and these should be added towards the end of the boiling process. Flavors are added at the end of cooking process and just before packing.

 

Boiling

The fruit is placed in the boiling pan along with a small quantity of water to facilitate pulping. It is then cooked sufficiently to liberate the pectin. After addition of sugar, the mixture is boiled to concentrate the soluble solids to about 68.5 percent and also to allow the necessary degree of inversion of the sugar. Boiling can be performed in steam jacketed kettle or stainless steel or aluminum boiling pan. Boiling in a vacuum pan using reduced pressure is used to prepare jam at lower temperature (65-750C) to minimize undesirable changes and for retention of vitamin.

 

End Point

The end point can be determined by carrying out a jelmeter test. Generally, fruits which are fairly rich in pectin, the weight of the finished jam is one and a half times (11/2 times) the weight of sugar used. Jam containing 68.5 percent of soluble solids boils at 1050C at sea level. It should yield a definite quantity of the finished jam.

 

Storage

The jam is packed in sterilized glass jars. It should be noticed that unless the jars are stored in a fairly cool place, moisture will evaporate from the jam resulting in shrinkage of the jam. If jam is prepared from fresh, unsulphited fruit pulp then it is advisable to add about 40ppm of sulphur dioxide in the form of potassium meta-bi-sulphite to the jam, which is permitted by law. A layer of molten paraffin wax can be put on the top surface of the cooled jam in the glass jar, which on cooling sets. This acts as a safeguard against any possible moulding on the surface of the jam.

 

JELLY

Jelly is prepared by boiling the fruit with or without addition of water, straining the extract and mixing the clear extract with sugar and boiling the mixture to a stage at which it will set to a clear gel.

The jelly should be transparent, well set, but not too stiff and having original flavor of the fruit. It should be of attractive color and should keep its shape with a clean cut surface. In the preparation of jellies, pectin is the most essential constituent. Pectin is present in the cell wall of fruits. In order to get a good quality jelly fruits rich in pectin, but deficient in acid should be preferred.

Selection of fruits: The fruits should be sufficiently ripe, but not over ripe and they should have good flavor. Slightly under-ripe fruit yields more pectin than over-ripe fruit; as during ripening the pectin present is decomposed into pectic acid, which does not form a jelly with acid and sugar. The amount of pectin extracted from a fruit depends on the degree of disintegration of protection during the heating process.

Pectin requirement: Usually 0.5 to 1 percent of pectin in the extract is sufficient to produce a good jelly. If the pectin content is in excess, a firm and tough jelly is formed and if it is less, the jelly may fail to set.

Pectin, sugar, acid and water are the four essential constituents of a jelly and must be present approximately in the following proportions:

Pectin 1 percent

Sugar 60 to 65 percent

Fruit acid 1 percent

Water 33 to 38 percent

However, the exact proportion of the sugar depends on the pectin grade.

 

Pectin grades: Grades of pectin means the weight of sugar required to set one gram of pectin under suitable conditions to form a satisfactory jelly. e.g. 100 grade pectin means 100g of sugar is required for setting of 1 g pectin.

 

Determination of end-point: The end-point in jelly can be judged by using following methods:

 

1) Cold plate test: A drop of the boiling liquid from the pan is taken and placed on a plate and allowed to cool quickly. If the jelly is about to set, the mixture on the plate will crinkle when pushed with a finger. The main drawback in this method is that while the drop on the plate is cooling, the jelly mixture continues to boil in the pan and there is a risk of over-cooking the product or of missing the correct setting point.

 

2) Sheet or flake test: This test is more reliable than the plate test. A small portion of jelly is taken with a large spoon or wooden ladle, cooled slightly and then allowed to drop off. If the jelly drops like syrup, it requires further concentration. Falling of the drop in the form of flakes or sheet indicates the end point.

 

Problems in Jellies

 

a)      Failure of jellies is due to the following reasons:

 

i)                    Lack of acid or pectin

ii)                   Addition of too much sugar: corrected by adding fresh clarified juice rich in pectin.

iii)                 Cooking below the end point: If the cooking is stopped before the concentration of sugar reaches 65 percent, the jelly may fail to set and may remain syrupy and highly soft.

iv)                 Cooking beyond the end point: If heating is continued beyond the end point, the jelly becomes tough due to over-concentration. This occurs when the juice is rich in both acid and pectin and enough sugar has not been added. If the acid is in excess, the pectin breaks down and forms syrup like jelly.

 

b)      Synersis or weeping of jelly: The phenomenon of spontaneous exudation of fluid from a gel is called synersis or weeping of jelly. It is caused by following factors:

 

Ø  Excess of acid due to decomposition of pectin

Ø  Too low concentration of sugar or soluble solids

Ø  Insufficient pectin

Ø  Premature gelation: Gelation is caused due to breakdown of pectin during pouring of jelly into the containers. The jelly becomes weak and remains broken.

Ø  Fermented jellies: Fermentation usually takes place in those jellies in which synersis has taken place.

 

c)      Cloudy or foggy jelly: It might be due to use of non-clarified extract, use of immature fruits (immature fruits contain starch which is insoluble in juice), Over cooking and cooling, non-removal of skum, faulty pouring (when jelly poured from a great height, air get trapped in bubbles form and jelly become opaque) and premature gelation is also a reason for cloudy or foggy jelly.

d)      Formation of crystals: Crystals in the jelly may be formed due to addition of excess sugar.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MARMALADE

 

It is similar to fruit jelly but the slices of the fruit or of the peel are suspended. Marmalades are generally made from citrus fruits like oranges and lemons in which peel shreds are added as a suspended material. The quantity of fruit and soluble solids in the final product shall not be less than 45 and 65 per cent (w/w) respectively for jelly and marmalade.

 

Procedure for marmalade preparation

 

Preparation of fruits:

**The outer yellow flavedo portion of the peel of citrus fruits contains coloring matter and volatile oils, whereas the inner white albedo portion contains pectin.

**The yellow portion of the peel is peeled off thinly from the fruit with a stainless steel knife. The thin yellow peel is cut into fine shreds with a knife or by using a shredding machine. The shreds are boiled and drained to remove the bitterness.

 

The sliced or crushed fruit is boiled gently by simmering with 2 or 3 times water to extract the pectin. The boiling process usually takes 45 to 60 minutes. After boiling the extract is filtered through a muslin cloth. The pectin extract can be clarified by using a filter aid by passing through a filter press.

 

Preparation of peel shreds: The peel is cut into shreds (1.9-2.5 cm long and 0.8-0.12 cm thick). The shreds are softened by boiling before they are added to the marmalade. If they are added directly without preliminary softening to the sugar solution and boiled, they become tough. Generally, three methods are employed for softening the shreds.

 

i) The shredded peel is boiled for 10-15 minutes in several changes of water. The bitter principles present in the peel are also removed in this process.

 

ii) The shreds are boiled in 0.25 percent solution of sodium carbonate or 0.1 percent ammonia solution.

 

iii) The shreds are then autoclaved at 1160C to 1210C (70-105 k Pa). The time required to soften shreds depends upon their size and shape.

 

Cooking: The extract is boiled along with required quantity of sugar in a steam-jacketed kettle or stainless steel vessel. Boiling is continued till the jellying point is reached which is determined by using either sheet test, drop test or weight test.

 

Cooling: The marmalade is cooled in a shallow pan or in a water-cooled pan by slow stirring to allow the uniform distribution of shreds in the marmalade. During cooling, when the temperature reaches 82 to 88 C, a thin film begins to form on the surface of the marmalade which becomes sufficiently thick to prevent floating of the shreds onto the surface.

 

Addition of flavor: Due to volatilization of natural flavor during cooking process, addition of artificial flavor is desirable to compensate the loss. It is desirable to add a small amount of flavor to the product, because most of the natural flavor volatilizes during the boiling and cooking processes. Generally, a small quantity of orange oil is added to the marmalade at the time of filling into jars or cans as a flavoring agent.

 

Packing: After cooling the marmalade is filled into jelly glasses or glass jars, which can be closed air-tight or is packed in cans which are hermetically sealed. In jelly glasses, the marmalade is allowed to set overnight and on cooling a thin layer of molten paraffin wax is poured on the top.

 

 

                                                                                    DRIED FRUITS AND VEGETABLES

 

 

Dehydration of vegetables: Dehydration of vegetables consists of the following steps.

Ø  Cleaning

Ø  Peeling and slicing or trimming

Ø  Blanching in steam

Ø  Sulphiting

Ø  Drying.

 

 

 

 

 

TOMATO PRODUCTS

 

Method for preparation of tomato juice

Washing: Tomatoes should be washed in plenty of running water to remove dust, dirt etc present in cracks, wrinkles, folds and stem cavities not easily dislodged by gentle washing.

Crushing: Tomatoes, after trimming are cut into four to six pieces for extraction of pulp. Alternatively, they may be crushed by means of fluted roller crushers or by passing through the fruit grater.

Pulping: Tomato pulp can be extracted either by passing through the pulper after crushing without heating (cold pulping) or after boiling the crushed or whole tomatoes till softening followed by extraction of pulp in a pulper (hot pulping). During pulping, the fine juice and pulp passing through the sieves of pulper are collected while skin and seeds are separated through another end.

a) Cold pulping: It is commonly referred to as cold break process in which the tomatoes after washing are sliced or crushed in a fruit grater and immediately passed through a pulper to extract the pulp. The characteristics of cold break process are as under:

Ø  The yield of juice is less as extraction in cold process is comparatively difficult.

Ø  The extracted juice is lighter in colour as natural red colour in tomatoes is released only after heating the skin.

Ø  Cold break process results in destruction/oxidation of natural vitamin C in juice due to incorporation of air during cold extraction.

Ø  The extracted juice is thin in consistency probably due to action of inherent pectinase enzyme on the natural pectin.

Ø  The flavour of cold break juice is much sharper and more acidic than that of hot pulped juice.

Ø  The cold pulped juice need to be processed immediately to avoid the chances of microbial spoilage.

 

b) Hot pulping: It is also known as hot break process. The tomatoes after slicing or crushing in a fruit grater are boiled in pressure cooker/ steam jacketed stainless steel kettle or aluminum pans till softening to facilitate pulp extraction in pulper. The merits of hot pulping are as under:

Ø  Hot pulping destroys the inherent enzymes (pectinase) which otherwise hydrolyze the pectin, to make the extracted juice thin in consistency.

Ø  Heating results in release of natural lycopene (red colour) present in the skin into the juice.

Ø  It also causes partial sterilization of juice to check the growth of micro-organism.

Ø  It helps in inactivation of oxidative enzymes which otherwise cause destruction of ascorbic acid in the juice.

Ø  The yield of juice in hot pulping is higher than cold pulping.

4. Equipment for juice/pulp extraction: Tomato juice/pulp is extracted either by passing the crushed tomatoes through a continuous spiral press or pulper.

 

a) Continuous spiral press: It consists of a long spiral screw which presses the tomatoes against a tapered screen of fine mesh. The juice passes through the screen while seeds and peel are removed from the lower end of the sieve.

 

b) Pulper: The pulper consists of a horizontal cylinder made of fine stainless steel. The heavy paddles inside the cylinder rotates rapidly, forcing the fine pulp to pass through the screen/sieves which is collected separately while the pieces of skin, seeds, fibre etc pass out through another end of the machine. However, at home scale, the crushed tomatoes after heating can be strained manually through stainless steel sieves.

 

5. Finishing and homogenization: After extraction, edible common salt (0.4-0.6 %) and sugar (1%) are added to the extracted pulp/juice to improve the taste and flavour of the finished product. For commercial production, the juice is homogenized for separation of liquid from the pulp and to impart a thick consistency and uniform appearance. For homogenization, the juice is heated to 66oC and forced under high pressure (70 kg/cm 2) to shear the particles and bring them to almost same size.

 

6. Filling: The finished juice is heated to 82-880C and filled hot in pre-sterilized glass bottles. The bottles are then hermetically sealed using crown corks and sterilized in boiling water (1000C) for about 25-30 minutes. Hot tomato juice (82-880C) can also be packed into plain or lacquered tin cans of appropriate size.

 

7. Labeling and storage: After sterilization, the cans are cooled and stored in a cool dry place. Glass bottles are allowed to air cool. Both bottles and cans are labeled before sending them to market/sale.

 

 

Tomato puree

Tomato puree is prepared from tomato pulp after evaporation/concentration of the juice or pulp to desired total soluble solids with or without addition of salt.

According to FPO specification, tomato puree shall contain minimum of 9 % total soluble solids excluding salt. The percentage of total soluble solids is required to be declared on the level of the product.

 

Method for preparation of tomato puree:

For preparation of puree the tomato pulp is prepared from ripe tomatoes either by hot pulping or by using cold pulping method. The pulp/juice is then concentrated either by using open cooking method in steam jacketed kettle or cooking by using vacuum pan.

 

However, cooking under vacuum is desirable as the juice/pulp boils at much lower temperature (71 C) which results in retention of original red color and flavor with natural vitamin C.

The pulp is concentrated to desired solids (9 to 12% solids), packaged in pre-sterilized bottles, crown corked and processed in boiling water for 25-30 minutes. Tomato puree can also be preserved by adding sodium benzoate (250 ppm benzoic acid). For packing in tin cans, the tomato puree is filled hot at 82-88oC and then the cans are closed and processed for 20 minutes at 100oC.

 

Tomato paste

A concentrated tomato juice or pulp without skin and seeds and containing not less than 25% of tomato solids is known as tomato paste. Depending on the degree of concentration, tomato paste can be further grouped into three groups:

 

a. Light tomato paste containing 25-29% of salt free tomatoes.

b. Medium tomato paste containing 29-33% of salt free tomatoes.

c. Heavy tomato paste containing not less than 33% of salt free tomatoes.

 

Method for preparation of tomato paste: Tomato pulp or juice is concentrated to 14-15% soluble solids in open pans followed by concentration in vacuum pans and packing in pre-sterilized bottles while still hot. In large scale processing units, the tomato paste is manufactured by using vacuum evaporators and packed either in tin can or in bulk aseptic packages. The tomato paste is utilized for manufacture of different tomato products like ketchup, soup and sauce etc.

 

** The minimum percentage of soluble solids (w/w) free of salt in tomato paste and tomato puree should be 25% and 9% respectively.

 

Tomato ketchup

Tomato ketchup is the commercial product made either from fresh tomato by converting them into juice/pulp or by using tomato puree or tomato paste. It is made by concentrating tomato juice or pulp without seeds and skin. Spices, salt, sugar, vinegar, onion, garlic etc. are added to the extent that the ketchup contains not less than 12% tomato solids and minimum of 25 % total soluble solids (w/w). The juice or puree prepared earlier can be used for preparation of tomato ketchup.

 

Method for preparation of tomato ketchup:

The tomato juice is concentrated with spices, salt, sugar etc. About 1/3 of the sugar is added initially at the time of commencing the boiling and the balance is added a little before the ketchup is ready.

The sugar added initially helps to intensify and fix the red tomato color. However if whole sugar is added initially with the pulp, it will require the boiling of pulp for longer duration, which will adversely affect the color of the ketchup.

Salt is added towards the end of boiling, as otherwise, it bleaches the tomato color. Spices are placed in the muslin cloth and cloth is placed in boiling mixture. At the end cloth bag is pressed to squeeze the spices and cloth is taken out. Vinegar should be added when the ketchup has thickened sufficiently, so that the acid does not volatize away. Tomato ketchup generally contains 1.25-1.50% acid. The tomato ketchup is generally concentrated to 25-30% solids, out of which 12% solids are tomato solids. The ketchup is filled hot (88 C) into pre-sterilized glass bottles, crown corked and processed for 30 minutes and cooled at room temperature. Tomato ketchup may also contain benzoic acid as preservative.

 

 

 

 

FRUIT PRESERVE

A fruit preserve is made from properly matured fruit, by cooking it whole or in the form of large pieces in heavy sugar syrup, till it becomes tender and transparent.

 

Procedure for preserve preparation: In preparation of preserve, at least 45 kg of the fruits are used for every 55 kg of sugar and cooking is continued till a concentration of at least 68 percent of soluble solid is reached.

 

Selection of fruit: Fruit should be fully developed, firm and slightly under-ripe. Unripe or over-ripe fruit with loose pulp should be rejected.

 

Preparation of fruit: Fruit are washed thoroughly and damaged portions are removed. Thin skinned fruits like berries are not peeled. Thick skinned fruits like mango, apple, bael, petha are peeled. The cores, seeds or stones are removed. Fruits are preserved either whole or in pieces.

 

Pricking/puncturing: The whole fruits or slices are uniformly punctured/pricked with stainless steel/wooden pickers to enable proper permeation of sugar syrup. Excessive pricking should be avoided to prevent softening of fruit/slices. Aonla and petha (ash gourd) can be pricked by using mechanical prickers.

 

Soaking: The fruits or their slices are soaked in water, brine or alum solution for few hours to few days before blanching and to enable proper permeation of syrup. Soaking make hard fruits porous, check browning, remove astringency, minimize shrinkage and prevents stiffening of fruits.

 

Blanching: The soaked fruits or slices after thorough washing are placed in muslin cloth and blanched in boiling water for few minutes (5-10) according to their texture to soften the hard texture. Excessive blanching should however be avoided.

 

Preparation of syrup: The quantity of sugar varies for various fruits, ranging from equal to double of the prepared fruits or slices. Syrup is prepared by boiling the sugar with 2-3 times of water and adding 0.3-0.4% citric or tartaric acid. Addition of acid also helps in removing the dirt from the sugar.

 

Cooking in syrup: The prepared fruits or slices are cooked in syrup in three different ways i.e.

 

a) Open kettle one-period process

b) Open kettle slow process; and

c) Vacuum cooking process

 

Open kettle one period process: The fruits are cooked in syrup containing low sugar contents. Boiling is continued with gentle heating until the syrup become sufficiently thick.

 

Open kettle slow process: In this process, the sugar equal to half the weight of fruit is added to the prepared fruit or slices in alternate layers in a vessel and allowed to stand for 24 hours. During this period, excess water from the fruit is leached out and sugar turn into a solution of 37-38oBrix. The concentration of syrup is raised to 60oBrix by adding more sugar.

 

Vacuum cooking: Vacuum cooking results in better retention of flavor and color of the product. In this process, the fruit is initially softened by boiling and then placed in the syrup of 30-35oBrix concentration. The fruit syrup blend is then transferred to vacuum pan and concentrated under reduced pressure to 70oB. To facilitate sugar penetration, slow boiling is practiced for hard fruits.

 

Precaution during cooking: In both methods, deep pans should be used otherwise the syrup becomes concentrated within a short period in shallow pans and fails to permeate the fruit. While adding fruit slice in boiling syrup, the consistency should not be too thick. The thick coating of the juice prevents the sugar syrup to enter and the product becomes tough or shriveled. Fruits should always be covered in the syrup to prevent drying of top pieces and improve the quality.

 

Cooling and packing: For storage in bulk, the preserve is cooled quickly after final boiling to avoid discoloration. For packing in A2½ size cans, the preserved fruits are drained and filled in to the cans. Freshly prepared boiling syrup (68 B) is then poured into the containers (A2½ size can), exhausted for 8-10 minutes at 100oC in steam, hermetically sealed, sterilized for 20-25 minutes at 100 C and cooled immediately.

 

 

 

 

 

 

 

 

 

 

CANDIED FRUITS

The method for making candy is practically the same as that followed for preserves, with a minor variation that the fruit is impregnated with a higher concentration of sugar or glucose. The total sugar content of the impregnated fruit is kept at about 75 percent to prevent fermentation. The most suitable fruits for candying are those which possess pronounced flavour like peels of orange, lemon, grape fruit and ginger.

 

Procedure for preparing candied fruits

Preparation of fruit: Stored fruit or peel is taken out from barrels and washed thoroughly in running cold water to leach out as much of the brine as possible. The fruit or peel is then placed in a cooking pan and boiled for about 15 minutes to remove traces of salt and to soften its texture.

 

Cooking in syrup: The prepared fruit or peel is boiled in cane sugar syrup (30oB) containing 0.1% citric or tartaric acid for 10-15 minutes and then left in syrup for about 24 hours. Next day, the syrup concentration is raised to 40oB by adding more sugar. The whole mass is boiled for about 5 minutes and left for another 24 hours. The process is repeated until the syrup reaches 60oB. Beyond this concentration, the syrup strength is progressively raised to 75oB at the rate of 5oB and boiling the mass on every alternate day.

 

Draining and drying: After syrup treatment, the fruits or the slices are removed from syrup and drained for about half an hour and sorted out to separate any defective and unwanted pieces. After this, the fruit/slices are dipped for a moment in boiling water to remove the adhering syrup followed by slow drying in the shade or in a drier at 66oC for 8 to 10 hrs.

 

Glacing: For glacing process, the sugar syrup is prepared by boiling sugar and water in 2:1 ratio in a steam pan at 113-114oC followed by cooling to 93oC. Sugar granulation is achieved by rubbing the syrup with a wooden ladle on the side of pan. Dried candied fruits are passed through this granulated portion of the syrup and then placed on the trays for drying in drier at 49oC for 2-3 hours. When the pieces become crisp, they are packed in air tight-containers.

 

Packaging: For retail trade, tin containers (15-20 kg capacity) and glass jars are used for storing preserves. Candied and crystallized fruits and peels are packed singly or in combination in layer in water proof paper or in polythene. Attractive china and porcelain jars are sometimes used for packing these products intended for exclusive export market. In addition to metal and glass containers, the newer flexible films can also be used, which are cheaper and highly effective.

 

Defects and spoilage: Spoilage due to fermentation occurs in the initial stages of preparation of preserves and candies when the concentration of sugar in the syrup is low. This can be checked by proper boiling of product at proper intervals. Storing of candied/glaced fruit in wet containers or under humid conditions brings about spoilage due to mould growth. Thus, storage of such product in air tight dry containers is recommended. Common defects and spoilage in preserves, candies, glazed and crystallized fruits is given in Table below.

 

S. No.	Defect	Causes	Prevention
1.	Shrunken preserve	Use of heavy syrup	Use correct amount of sugar and water
2.	Dull brownish colour or cloudy appearance	Inferior fruit quality Over cooking after addition of sugar Failure to remove scum.	Use good quality fruit Use correct cooking time
3.	Tough fruit skin or peel	Fruit or peel not cooked until tender before sugar addition	Cook the fruit or peel until tender and then add sugar.
4.	Moulds on surface	Use of inferior quality fruits Under cooking Warm or damp storage	Use good quality fruit
5.	Fermented preserve after storage	Not enough sugar used Insufficient cooking Storage in warm place	Store in a cool and dry place.
6.	Sticky candy (after drying)	Final syrup not sufficiently concentrated	Always prepare syrup of correct concentration.
7.	Sticky during storage	Poor packing Damping storage	Always prepare syrup of correct concentration.

 

 

 

 

 

 

 

MAKING OF PICKLES

Pickling ingredients

Salt

Salt is mostly used as preservative in pickles in combination with acid. Minimum concentration of salt to act as preservative is about 12%. It inhibits enzymatic browning/discoloration by acting as an anti-oxidant. It exerts its preservative action by:

·         Causing high osmotic pressure and thus suppress the microbial cells.

·         Dehydrating food by tying up the moisture thus making it unavailable for the growth of microorganisms.

·         Salt in the food affects the solubility of oxygen and thus growth of aerobic microorganisms is inhibited

·         Chlorine in sodium chloride being good oxidizing agent is toxic to microorganisms

·         Salt increases the permeability of the cell wall and thus cause changes in the permeability. Only the haloduric microorganisms can tolerate these effects while others are unable to survive.

·         Similarly addition of acid to the food lowers the pH of the food which inhibits the growth of spoilage causing microorganisms.

Salt: The concentration of 15-20% salt is used for pickling. Mold and lactic acid forming bacteria do not grow at this concentration.

Vinegar

Vinegar acts as preservative in vinegar pickles by lowering down the pH of final product. The final concentration of acid as acetic acid in the finished pickle shall not be less than 2%.

Lactic Acid

Though bacteria do not grow in acidic media, yet lactic acid bacteria are capable of growing in acidic media and can also produce acid through their action on the substrate. They can also grow in high salt concentration of 8-10%.

This principle is used in pickling as growth of undesirable organism is inhibited by adding salt and allowing the lactic fermentation to proceed.

 

 

Addition of spices and edible oil in these products besides improving flavor and taste also help in preservation.

Pickling process:

Pickling is the process of fermentation by lactic acid forming bacteria, present on the surface of commodities.

Lactic acid bacteria (active at 30 C) convert fermentable sugar in the food to lactic acid and volatile acids.

The acid and brine acts upon vegetable tissues to produce characteristic taste and aroma of pickle.

The salt and lactic acid formed preserve the pickle by preventing the growth of putrefactive bacteria provided oxygen is excluded.

 

Pickling process

Pickle is prepared by using either of following processes followed by finishing and packing:

·         Curing or fermentation with dry salting

·         Fermentation in brine

·         Salting without fermentation

A). Dry salting

The dry salt added to the prepared vegetables, extracts the juice from the vegetables and forms the brine. The brine is then fermented by lactic acid forming bacteria which serves the purpose of pickling. The method is known as dry salting.

Procedure for dry salting

Vegetables are washed, sliced and placed in barrel in layers to which salt is sprinkled followed by placing another vegetable layer and sprinkled with salt. Generally, 3 kg dry salt is used for each 100 kg of prepared vegetable. The salt is added in layers till the barrel is ¾ full. The vegetables are covered with a cloth and wooden board along with a weight to press the vegetable. Brine is formed in 24 hours.

The barrel is placed in warm and dry place to allow the fermentation to proceed within short period. Once brine is formed, fermentation and bubbles of CO2 begin to rise from the liquid. The fermentation temperature is 27-320 C and completes in 8-10 days.

When the gas bubbles cease to form, the fermentation is considered as complete. This may be confirmed by taping the barrel gently. The pickle is then pressured and packed by excluding the air.

If air is not removed from the pickle, pickle scum (a type of mold yeast) appears on the surface, which destroys the lactic acid formed by fermentation and spoils the pickle.

 

B). Fermentation in Brine (Brining)

Immersing vegetable or unripe fruits like mangoes in salt-solution of known concentration for a certain length of time is called brining. Brining is generally used for pickling of cucumber, olives, raw mangoes and similar other vegetables, which do not contain sufficient juice to form brine with dry salt.

 

Brine preparation: Brine is prepared by dissolving common salt in water and filtered through a muslin cloth. The amount of brine required to cover the vegetable is approximately equal to about half the volume of the material to be fermented (for each barrel of 100 litres, about 50 litres of brine is required). Brine with 8 -10 % strength is considered optimum for the growth of salt tolerant lactic acid bacteria.

Thus vegetables are placed in 10 % brine to allow lactic acid fermentation to take place and then the proportion of salt is increased gradually, so that when pickle is ready, salt concentration would have reached 15 % level. The brine strength can also be maintained by adding dry salt. Brining takes about 4-5 weeks.

 

C). Salting without fermentation

In this method, vegetables raw mango slices are packed with a large quantity of salt to inhibit fermentation. Generally, 25 kg salt is mixed with 100 kg of prepared vegetable. The cured vegetables are drained and excess salt is removed by soaking in cold or warm water. After removal of salt, the vegetables are stored in plain vinegar 10% (100 grain) strength. This treatment reduces the tendency of the vegetable to shrivel when packed in sweetened and spiced vinegar and also helps in absorption of vinegar by the vegetable tissues.

 

Packing: After curing, the vegetables become semi translucent in appearance with their color changing from green to dark olive green or yellowish green. During this process the raw flavor of the vegetables is lost and the texture becomes firm and crisp. For good keeping quality they are packed by using salt, vinegar and lactic acid in sufficient quantities which act as preservative either singly or in combination.

 

Example of pickled products: pickled cucumbers

Fermented pickles: Cucumber pickle, dill pickle and olive pickle.

Fermented cucumber pickle: For preparation of fermented cucumber pickle, the immature cucumber are washed, placed in barrels or tanks and filled with brine (salt solution). The cucumbers are kept submerged in brine and it lakes about 6-9 weeks for completion fermentation.

During fermentation, most of the lactic acid is produced by the action of Lactobacillus planetarium. The total titratable acid on completion of fermentation range between 0.6-0.8 percent.

Common defects noticed in different pickles during storage.

S.No.	Common Defects	Cause
1.	Blackening	It is mainly due to the presence of iron which enters through the brine or from the equipments. Blackening may also be caused by the action of microorganisms.
2.	Dull and faded pickle	It is due to either insufficient curing or use of water of inferior quality.
3.	Shriveling	It occurs when vegetables like cucumber are placed directly in a very strong solution of salt or vinegar. To avoid this, use weak solution at the start and increase gradually.
4.	Softness and slipperiness	It is the most common type of spoilage caused by the action of bacteria. Use of weak brine or improper covering with brine results in these defects. Thus this defect can be checked by using brine of proper strength and keeping the pickle well below the surface of the brine.
5.	Bitter Taste	It is due to the use of very strong vinegar or cooking the spices for a long time or by using spices in excess.
6.	Scum formation	It is due to growth of film yeast on the brine kept for curing of vegetables. The scum may be thin or thick varying from imperceptible film to a thick wrinkled layer. It retards the formation of a lactic acid and helps in the growth of putrefactive bacteria which makes the vegetable soft or slippery. The scum may be removed as soon as it is formed. Use of 1% acetic acid to the brine prevents the growth of wild yeast on the brine, without hindering the formation of lactic acid.
7.	Cloudiness	In many fermented solid vegetables like onion, cucumber, olives etc the vinegar becomes cloudy and turbid, thus spoiling the appearance of the product. It is due to non-penetration of acetic acid from vinegar deep in to the tissues to check the activity of bacteria or other micro organisms. This results in fermentation which make the vinegar cloudy. Use of brine and vinegar of proper strength prevents cloudiness.
8.	Blemishes in pickles	In onion pickle in brine, white blotch is seen under the first layer of the skin which is termed as blemish. Blemishes are generally caused by improper fermentation or non removal of all brine prior to the final pickling of cured onion in vinegar.