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Problems in Jellies
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Problems in Jellies |
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Problems in Jellies
A). Failure of jellies to set: Sometimes the jellies do not set due to the following reasons: i) Lack of acid or pectin: A jelly may fail to set due to lack of acid or pectin in the fruit from which it is made. It may also fail to set due to insufficient cooking of the fruit resulting in inadequate extraction of pectin and acid. ii) Addition of too much sugar: If sugar is added in excess of the required quantity, a syrupy or highly soft jelly results. It can be 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: i) Excess of acid: Addition of excess of acid results in the breakdown of jelly structure due to the hydrolysis or decomposition of pectin. ii) Too low concentration of sugar or soluble solids: This causes the network of pectin to hold more liquid than it possibly can do under normal conditions. iii) Insufficient pectin: This results in the formation of a pectin network which is not sufficiently dense and rigid enough to hold the sugar syrup. iv) Premature gelation: Gelation is caused due to breakdown of pectin during pouring of jelly into the containers. The jelly becomes weak and remains broken. v) 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. 3. 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. As per FPO specifications, 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 colouring 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. While it is being boiled, a teaspoonful of the clear extract is taken from the pan and tested with alcohol for its pectin content. 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 and the impurities rising to the surface are removed. When the temperature of the boiling mixture reaches 1030C at sea level, the prepared shreds are added to it at the rate of 62 g for each kg of the original extract. 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 880C, 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 flavour: Due to volatilization of natural flavour during cooking process, addition of artificial flavour is desirable to compensate the loss. It is desirable to add a small amount of flavour to the product, because most of the natural flavour 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 flavourant. 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. When packed in A21/2 size cans, the cans are inverted upside down to sterilize the lids and stored in a cool dry place. 4. 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 a) 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. The final concentration of sugar should not be less than 68oBrix corresponding to a boiling point of 106oC. Rapid boiling should be avoided, as it makes the fruit tough. b) 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. Citric or tartaric acid is added @ 0.06-0.12% to invert the portion of sugar. The whole mass is boiled for 3-4 minutes and kept for overnight. On the third day, concentration of syrup is raised to 68oBrix by adding more sugar and the whole mass is boiled again for 3-4 minutes and the fruit is then left in the syrup for another 3-4 days. Finally the strength of syrup is raised to 70oBrix and the preserve is packed in containers. However the stages may vary with the type of fruit. c) Vacuum cooking: Vacuum cooking results in better retention of flavour and colour 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 (68oB) 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 100oC and cooled immediately. 5. 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 9.1.
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Last modified: Wednesday, 7 March 2012, 5:17 AM