FSC Practicals No.7

Production of Fruit Leathers

D.K.C.Mendis

AS2013151

FSC

Date – 25.08.2015

Practical number – 07

Practical – Production of fruit leathers

Introduction-

Fruit leathers are dehydrated fruit products which are eaten as snacks or desserts. They are flexible sheets that have a concentrated fruit flavor and nutritional aspects. Most fruit leathers are prepared by mixing fruit puree and other additives like sugar, pectin, acid, glucose syrup, color, and potassium metabisulphite and then dehydrating them under specific conditions. Various drying systems including combined convective and far-infrared drying, hot air drying, microwave drying, solar drying, and sun drying have been used to make fruit leathers. Most fruit leathers are dried at 30 to 80°C for up to 24 hours until the target final moisture content (12–20%) has been reached. Research about fruit leathers began in the 1970s. This work has reviewed published papers on fruit leathers in order to summarize useful information about fruit leathers on methods of preparation, effects of drying condition, and effects of packaging and storage, which will be useful to many in the food industry and consumers who are health-conscious. Fruit leather, also called a fruit bar or a fruit slab, is a dehydrated fruit-based confectionery dietary product which is often eaten as snack or dessert. It is chewy and flavorful, naturally low in fat and high in fiber and carbohydrates; it is also lightweight and easily stored and packed. Consuming fruit leather is an economic and convenient value-added substitute for natural fruits as a source of various nutritional elements. Furthermore, fruit leather has far fewer calories, less than 100 kcals per serving, than many other snacks. Fruit leathers are restructured fruit made from fresh fruit pulp or a mixture of fruit juice concentrates and other ingredients after a complex operation that involves a dehydration step Fruit pulp-based fruit leathers are nutritious and organoleptically acceptable to customers. They contain substantial quantities of dietary fibers, carbohydrates, minerals, vitamins, and antioxidants (which remain constituents of the finished product).

Most fresh fruits have a short harvest season and are sensitive to deterioration and even when stored under refrigerated conditions; therefore, making fruit leather from fresh fruits is an effective way to preserve fruits. Fruit leathers are manufactured by dehydrating a fruit puree into a leather-like sheet. Moisture is removed from the wet purees, which are usually laid on a large flat tray until the fruit puree or a prepared boiled fruit juice with additives changes into cohesive “leathery” sheets. Fruit leathers are often considered as a health food and health food marketing images such as “pure,” “sun-dried,” or “rich in vitamins” are used to describe them. There are large numbers of fruit leather products available on the market, such as mango leather, apricot fruit leather, grape leather, berry leather, kiwifruit leather, and jackfruit leather. In addition, mixed fruit leathers like guava and papaya fruit leather are also available.Basically, fruit pulps are mixed with appropriate quantities of sugar, pectin, acid, and colour and then dried into sheet-shaped products. Gujral and Brar added sugars and pectin to

mango leathers. The sugar gave the product a sweeter taste and increased the solids content; then pectin was used to thicken the pulp, modify the flexible texture, and ensure the retention of the shapes of the dried product. Furthermore, they also prepared mango leather with the addition of potassium metabisulphite to get better sensory qualities and the results were satisfactory for customers/consumers. Chan Jr. and Cavaletto [8] made papaya leathers with sucrose and sodium bisulfite (SO2). They found that SO2 reduced the change in color of the papaya leathers during processing and storage. Various additives can be used, such as glucose syrup, sodium metabisulphite, and sorbic acid, depending on the types of fruit leather.Sun drying is the simplest method of drying foods. Raisins, sultanas, and dried apricots are examples of the most popular sun-dried fruits. Sun drying permits the final product to have a translucent appearance, a normal color, and a gummy texture. However, there are disadvantages, such as a long drying process-exposure of the products to environmental contamination, dependency on weather conditions, and hand labor requirements. Therefore, alternative drying methods were developed to overcome the problems of hygiene and time, as these methods are rapid, safe, and controllable. Modern dryers, such as tunnel dryers and forced air circulation cabinet dryers, have been used for making fruit leathers with a better color and flavor. Over 85% of industrial dryers are of the convective type with hot air or direct combustion gases used as the drying medium. The product changes during drying include shrinkage, puffing, and crystallization. Sometimes there are also desirable or undesirable chemical or biochemical reactions occurring that will cause changes in color, texture, odor, and other properties in the final product. Drying occurs from vaporization of the liquid by supplying heat to the wet material. Conduction, like contact or indirect dryers, convection such as direct dryers, and radiation or volumetrically by placing the wet material in a microwave or radio frequency electromagnetic fields are various methods that are used in making fruit leathers. The methods chosen are dependent on what kind of fruit and the commercial conditions. In many processes, incorrect drying methods result in irreversible damage to the quality of the final product which makes the product nonsaleable. With modern dehydrators and well-designed drying methods, fruit leathers can be dried at any time of the year to reach the requirements of customers.

In the current growing market of fruit leathers, commercial packaging is necessary. Packaging materials for fruit leather are required to prolong the shelf-life of the product and, normally, relate to the stability of water activity, microbiological stability, sensory properties, and physicochemical characteristics.

This paper/review will consider various researches on fruit leathers including the methods of preparation, the effect of drying conditions (e.g., temperature and velocity), and packaging and storage.

The general process of making fruit leather involves the preparation of the fruit puree, with or without addition of other ingredients before mixing and then drying. These processes may vary depending on the fruit used, the nature of the additional ingredients, and the drying method and technology. It has been investigated the advantages and disadvantages of the method of preparation of the different fruit leathers. As the results show, most fruit leathers have few disadvantages which are mostly on the lack of preservatives to protect the color.

MATERIALS

MangoPineappleThermometerSpoonsTraysStainless steel saucepanCitric acid

PROCEDURE

Fruits were cleaned, washed and cut into slices. Then those fruit pieces were blended. When blending somewhat water was added to

the mango and for pineapple, water was not added. After blending puree was taken and puree was strained by using a strainer. Then TSS of the puree was measured. Next, fruit pulp was put into a stainless steel saucepan and 5% sugar and 1% citric acid

were added and mixed thoroughly. Saucepan was placed on fire until pulp reached 78oC temperature and it was stirred

continuously for 3 minutes. Then the fire was closed and 0.1% SMS was added to the pulp. At this temperature fruit pulp got thickness and pulp was transferred immediately to the

trays which were coated with a very thin layer of margarine and wrapped with high density polythene tissues.

Paste was spread evenly area of the trays at the thickness of 3mm. Trays were covered with thin material and dried in an oven at 60oC for 6 – 8 hours.

OBSERVATIONS

Mango PineappleInitial weight of the puree(g) 385.356 365.410Added sugar weight(g) 19.260 18.270Added citric acid weight 3.85(pH of the mixture was

3.70 and citric acid wasn’t added)

3.65

Added SMS weight(g) 0.385 0.365Initial pH 3.70 2.84Initial Brix(TSS) 18.8 21Final pH 3.77 2.88Final Brix(TSS) 8 8Colour Yellowish orange Brownish orangeTaste Good flavor( as good as

mango puree flavor)Acidic tamarind flavour

Texture Leathery Leathery texture at the periphery and it decreases towards the middle of the tray

DISCUSSION

A high quality product can only be made from good quality raw materials and production should not, as too often happens, be based on second grade fruit that is not suitable for the fresh market. Fruit that has been rejected for being too large, too small or because of surface blemishes is, however, usually acceptable.

Fully ripe soft fruits are very susceptible to bruising when handled and bruised areas will quickly begin to rot. It is thus better to purchase semi-ripe fruit (which is usually cheaper) and allow it to fully ripen in the processing area. This also has the advantage of allowing the daily selection of fruits of equal ripeness.

Incoming fruit should be selected and any unsuitable material removed from the processing area and properly disposed of. Selected fruits are then washed in chlorinated water (one teaspoon of bleach per gallon of water) and then peeled, de-stoned etc, depending on the type being used. Only stainless steel knives should be used as mild steel will corrode and stain the flesh. Some fruits require special attention.

Blanching, in where scalding of vegetables in boiling water or steam for a short time, is done as a pretreatment. It stops enzyme actions which can cause loss of flavor, color and texture. Blanching cleanses the surface of dirt and organisms, brightens the color and helps retard loss of vitamins. Blanching time is crucial and varies with the vegetable and size. Underblanching stimulates the activity of enzymes and is worse than no blanching.

Overbalancing causes loss of flavor, color, vitamins and minerals. Therefore it should be followed recommended blanching times( in here it is 3 minutes in steam blanching.)

Sugar was added to increase its sweetness and total soluble solids.Citric acid was added to prevent sucrose crystallization. Firing is done to thicken the pulp and to inactivate enzymes.

sodium metabisulphite is used to control enzymatic browning. When it is mixed with water, sodium metabisulfite releases sulfur dioxide (SO2). At high temperatures, it releases sulfur dioxide, leaving sodium sulfite behind. SO2 has been widely used in fruit and vegetable products to control enzymatic colour changes. It also acts as a preservative, controlling the growth of moulds and yeasts. SO2 production by dissolving sodium metabisulphite in water is more controllable. Concentrations of 400 to 1000ppm are used for dips to control colour changes and retard the growth of moulds and yeasts. In recent years, the use of SO2 has been increasingly controlled and it has been banned in many foods in the USA. Similar changes to food laws are is likely in Europe. In such situations browning can be controlled by the addition of citric acid but this is far less efficient than sulphur dioxide which was also used in preparation of fruit leather in this experiment. The most convenient production plan for very small producers is to use fruits that are in season at any given time. This does, however, have disadvantages that include: one particular flavour of fruit leather may be much more popular than others, it will only be possible to produce small quantities of product in a short season and it is, however, possible to produce all year by preserving prepared fruit (or fruit puree) in sealed drums with added SO2 at a level of 600ppm. Fruit may be stored for many months in this way. Intermediate preservation also allows fruits to be purchased at the peak of the harvest when prices are at their lowest. While most of the SO2 absorbed during intermediate preservation will be lost during drying it is recommended that purees made from preserved fruits should be briefly boiled prior to drying to reduce the level of residual SO2.

Coating with glycerin (in this experiment butter was used instead of glycerin) was done to remove fruit leather from the tray easily after completion of fruit leather preparation otherwise the prepared leather would stick to the tray firmly.

Drying is done to reduce the moisture content and prolong the shelflife. The efficiency of drying is dependent on the method of drying and the equipments used for drying. Various drying systems are used in making fruit leather depending on what fruits are being dried and how the products are designed. Combined convective and far-infrared drying provides a shorter drying time due to its higher heat and mass transfer coefficients. Hot air drying, including oven drying, forced-air cabinet drying, and thin-layer drying, is widely used and the time taken depended on the drying temperatures and sample thicknesses. Microwave drying reduces the sample mass rapidly and has a very short drying time. Solar drying included cabinet drying, solar tunnel drying, and sun drying. Solar cabinet dryers were well suited to drying small quantities of fruits; solar tunnel drying was a forced convection mixed-mode solar dryer which collected solar radiation from the atmosphere to input solar radiation into solar tunnel dryer. Sun drying is simple but lengthy and unhygienic. It is recommended that fruit leathers are not dried in direct sunlight as there will be considerable loss of colour and vitamins A and C

The effects of types of packaging materials on the physicochemical, microbiological, and sensory characteristics of fruit leather during storage vary. Water activity is one of the most

important quality factors for long-term storage. Laminated aluminum foil (LAF) gives a higher score for overall acceptability from panelists and low-density polyethylene has a lower score for packaging fruit leathers. The product packed in metalized polyester polyethylene and aluminum foil shows low losses of moisture. Other packaging materials like high-density polyethylene, polypropylene, butter paper, and biaxially-oriented polypropylene are shown to be acceptable for storage of fruit leathers at low temperatures (8–100C) for up to two months.

Thee food additives are mixed with the fruit puree to make fruit leathers with a higher quality, longer storage, or better organoleptic quality than the original fruit. These include, spices — Allspice, cinnamon, cloves, coriander, ginger, mace, mint, nutmeg or pumpkin pie spice. flavorings — Almond extract, lemon juice, lemon peel, lime juice, lime peel, orange extract, orange juice, orange peel or vanilla extract., marshmallow cream or peanut butter. delicious Additions— Shredded coconut, chopped dates, other dried chopped fruits, granola, miniature marshmallows, chopped nuts, chopped raisins, poppy seeds, sesame seeds or sunflower seeds, fillings — Melted chocolate, softened cream cheese, cheese spreads, jam, preserves, marmalade and potassium metabisulphite, sodium bisulfite, sodium metabisulphite, sucrose, soy protein and skim milk powder, corn syrup, and starch.

When the pineapple puree is considered it had acidic range pH value. This is due to the fruit itself contains organic acids. The TSS of the paste denotes the low amount of soluble solids within the paste. After adding sugar to the paste the TSS value has increased. By adding sugar and citric acid to the paste the soluble solids amount has increased. When considering about the moisture content of the raw pineapple and mango it was very high. As this is pure fruit it has this much of moisture amount. When fruit has such kind of high moisture amount, that fruit has high water activity (aw) within that fruit. Because of this high water activity within the fruit microorganisms easily can grow and damage to this fruit. But when considering about the fruit leather it has only a moisture content. When comparing this moisture amount with the raw pineapple moisture amount, this is very low value. As having this kind of low moisture amount the water activity of fruit leather also gets very low value. When getting water activity of a product very low that product is not easily susceptible to microorganisms’ degradation. Therefore the shelf life of the product can be increased and because of that the fruit leather can keep for a long time than the raw paste.

In considering about the taste of the fruit leather which has been made from pineapple, it gave the real taste of the pineapple and mango where only that of pineapple gave an acidic tamarind flavor which slightly differs from original flavor of a pineapple puree. It denotes that preparing fruit leather don’t do any harmful effect to the natural flavor quality and taste of then natural fruit. The fruit leather which has prepared has got real texture of good product. It gave shiny appearance and stretched quality. The shiny appearance of the product can be obtained because of the oil or butter layer which was applied on the tray. The stretching quality is got by the fibers which were contained in the pineapple. And also when heating of the fruit puree when making leathers the sugars which was contained in

the puree can be caramelized somewhat. As caramelizing of sugar it can build binding ability within the product. This also may affect to this stretching quality.

As well as preparing fruit leathers is a good solution for the preventing wastage of then fruit commodities. Because of for preparing fruit leather purees of the fruits’ are used. If fruits get damages such as knobbing and squashing when they are transported, those somewhat low damaged fruits can be used for making purees and these can be undergone with making fruit leathers without throwing away. This is a good solution for minimizing the wastage of the fruit commodities. And also making fruit leather is a good solution for preventing transport damages to the fruits and preventing microorganisms’ degradation of natural fruits. If the fruit leathers produce their own fruit growing areas fruit leathers can be supplied to the market. Because of this there is no any transport damages and microorganisms degradation.

CONCLUSION

By preparing fruit leathers the shelf life of the fruit commodities can be increased. Transport damages of fruits can be reduced by preparing fruit leathers.

REFERENCES

1. C. Raab and N. Oehler, Making Dried Fruit Leather, Fact Sheet 232, Oregon State University Extension Service, Tillamook, Ore, USA, 1976.

2. E. Ayotte, Fruit Leather, Publication no. P-228, University of Alaska Cooperative Extension Service, Fairbanks, Alaska, USA, 1980.

3. X. Huang and F.-H. Hsieh, “Physical properties, sensory attributes, and consumer preference of pear fruit leather,” Journal of Food Science, vol. 70, no. 3, pp. E177–E186, 2005.