Introduction
Pineapple (Ananas comosus, Bomeliaceae) is one of the most important commercial fruit crops in the world. It is known as the queen of fruits due to its excellent flavour and taste. Pineapple is the third most important tropical fruit in the world after Banana and Citrus. It is a wonderful tropical fruit having exceptional juiciness, vibrant tropical flavour and immense health benefits. Pineapple contains considerable amount of calcium, potassium, vitamin C, carbohydrates, crude fibre, water and different minerals. It is good for the digestive system and helps in maintaining ideal weight and balanced nutrition. Pineapple has minimal fat and sodium. It contains 10-25 mg of vitamin. Pineapple composition has been investigated mainly in the edible portion. It contains 81.2 to 86.2% moisture, and 13-19% total solids, of which sucrose, glucose and fructose are the main components. Carbohydrates represent up to 85% of total solids whereas fibre makes up for 2-3%. Of the organic acids, citric acid is the most abundant in it. The pulp has very low ash content, nitrogenous compounds and lipids (0.1%). Mature fruit contains 14% of sugar; a protein digesting enzyme, bromelain and good amount of citric acid, malic acid, vitamin A and B. Pineapple is also recommended as medical diet for certain diseases. When taken with meals, bromelain aids in the digestion of proteins, working to break down complex proteins into simpler amino acids.
Pineapple Processing
Pineapple is one of the popular fruits and is liked by majority of the people irrespective of their age group. As is the case with most of the fruits and vegetables, their availability is limited during off-seasons. Many techniques have been developed to make available seasonal fruits as well as vegetables even during off-season. The pineapple does not lend itself well to freezing, as it tends to develop off flavours and lose texture or crispiness. This fruit is highly perishable and seasonal. Hence processing is necessary. Processed pineapple is popular and is exported by many countries. Brazil is considered the main pineapple producing country in the world since 2005. During processing, nutritional quality of pineapple can be affected but there are recent researches carried out which use new technologies to retain the nutritional quality of the pineapple fruit. This is to meet the consumer demand for healthy, nutritious and natural products. Some of the food industries based on pineapple are described below:
In Canning Industry
Canned pineapple is consumed throughout the world. In order to increase the shelf life and to make pineapple juice and slices even during off-season, canning is the most popular method.
CFTRI (Central Food Technological Research Institute), Mysore, has developed technology for these products.
The manufacturing process of the proposed pineapple products viz. slices and juice involves many steps and different sub-processes. Ripe and matured pineapples are washed, graded and peeled. Then they are crushed in the crusher to obtain juice. In case of slices, after peeling, uniform slices are made on the slicer. Juice is then taken to vessels and boiled and certain preservatives (Potassium metabisulphate, Benzoic acid etc.) are added. It is finally taken to storage tanks and packed in bottles on vacuum filling machine. In case of slices, they are dipped in sugar syrup for about 3 to 4 hours. Then the slices are taken to lacquered cans and cans are sterilised. While canning, sugar syrup is added. Cans are cooled quickly and after sealing and labelling, they are stored. Pineapple is the third most canned fruit after apples and peaches.
Dried Products
Dried pineapple for processing is used in many areas such as an ingredient in confectioneries, breads and desserts. Dried fruits are often eaten directly out of the container, with yogurt, or by adding them to homemade baked goods such as cookies. They are generally added in processed foods such as snacks including biscuits, cookies, chocolates, bread, yogurt, fruit jelly, breakfast cereal, health foods, or sauce for Japanese-style pancakes. Bakery products and breakfast cereal mixes are the largest end-users of dried fruit. According to the Institute of Food Technologists, dried fruits and fruit chips are the hottest trends in the snacks business.
Pineapple can be dried as slices. They can be freeze dried. Fresh fruit is frozen and placed in a drying chamber under vacuum. Heat is applied and water evaporates from the fruit while still frozen. The fruit becomes very light and crispy and retains much of its original flavour. Dried fruit is widely used by the confectionery, baking, and sweets industries. Because of its nature, organic production is highly suitable for small and medium-sized farmers working in areas which may not be suitable for large-scale food production. Pineapple is one among important organic products within the segment of preserved fruit for industrial use.
Dried fruit is mainly used as a snack or in breakfast cereals, bakery products, dairy products and desserts. The types of dried fruits used and the types of processed foods applicable diversify every year. Hence greater opportunities are there for pineapple drying industries.
Preserved Products
Essentially a prime table fruit, pineapple pulp is perfectly suited for conversion to frozen juices, nectars, drinks, jams, fruit cheese, concentrates or taken as such or with cream as a superb dessert. While the raw fruits are utilised for products like chutney, pickle, sauce, beverage, etc. ripe ones are used for making pulp, juice, nectar, squash, leather, slices etc.
Major export products include dried and preserved fruits, jams, fruit jellies, canned fruits and vegetables, dehydrated vegetables, frozen fruits, vegetables and pulps and freeze dried products. Ripe pineapple may be frozen whole or peeled, sliced and packed in sugar (1 part sugar to 10 parts pineapple by weight) and quick-frozen in moisture-proof containers. The diced flesh of ripe pineapple, bathed in sweetened or unsweetened lime juice, to prevent discoloration, can be quick-frozen. Half-ripe or green pineapples are peeled and sliced as filling for pie, used for jelly, or made into sauce.
Pineapple has long been one of the most popular of the non-citrus tropical and subtropical fruits, largely because of its attractive flavour and refreshing sugar-acid balance. Pineapple juice is largely consumed around the world, mostly as a canning industry byproduct, in the form of single strength, reconstituted or concentrated and in the blend composition to obtain new flavours in beverages and other products.
Spices in foods are primarily used for their flavour and stability in storage and have natural antioxidants and antimicrobial properties apart from having carminative effect and also aid in digestion through the stimulation of appetite. RTS (ready-to-serve) beverages prepared from juices could be increased by addition of spice extracts like ginger, black pepper, mint, cardamom and cumin. These spices apart from their appetising properties, also possess medicinal and therapeutic values, which have a profound effect on human health, since they affect many functional processes. The blending of juices and their spiced beverages may also improve taste, aroma and nutrition. Juice blending is one of the best methods to improve the nutritional quality of the juice. It can improve the vitamin and mineral content depending on the kind and quality of fruits and vegetables used. Moreover, one could think of a new product development by blending of fruit juices with suitable spice extracts at correct proportion in order to get highly acceptable health drinks.
It could be possible to process spiced pineapple ready-to-serve beverage by blending different spices. The spiced pineapple ready-to-serve beverages are having high potential for commercialisation and marketability. The introduction of new types of value-added and nutrient-enriched spiced fruit juice-based beverages might improve socio-economic status of the country by enhancing the export trades.
Current Trends in Processing
Some of the processing methods using the new technologies are as follows:
i. Vacuum frying - This is a technology where food products are deep fried under vacuum or near vacuum conditions to reduce the fat content compared to normal deep-frying. It is a process that produces healthy fruit snacks (pineapple chips) which partially preserve the fruit’s original colour and nutritional compounds and have a high hydrophilic antioxidant capacity.
ii. Radiation processing - Under radiation processing, the food is subjected to radiation by exposing it to a source of ionising radiation. This ionising radiation usually is in the form of gamma rays from a source of cobalt-60 or from a non-radioactive source like electron beam generated from electricity. A dose of 2 kGy did not affect significantly the nutritional value as well as the sensory quality of minimally processed pineapple.
iii. Thermal processing – Thermal treatments are critical in controlling foodborne pathogens in ready-to-eat (RTE) food products. Food products are subjected to a combination of temperature (800C to 1500C) and time (30 minutes to few seconds) required to eliminate desired number of microorganisms. It helps in the improvement of colour, as a quality attribute of processed pineapple puree. This is made possible by the increase in knowledge of kinetics of colour change.
iv. Ultrasound drying - This is a pre-treatment for drying of pineapple. Ultrasound pre-treatment consists in immersing fruit pieces in water or in an osmotic solution and to subject the fruit and solution to ultrasonic waves (at frequencies ranging from 18 to 40 kHz) for a period of time (usually less than 60 min). Ultrasound is showed to have higher influence on fruits with high water content (pineapples, melons) and high content of fibres and phenolic cells.
v. Osmotic evaporation – It is the partial removal of water from plant tissues by immersion in a hypertonic (osmotic) sugar or brine solution. Water is removed by evaporation at atmospheric pressure and temperatures near the ambient temperature. The pineapple juice is concentrated at moderate temperatures and pressures with good nutritional and sensory qualities. This process has minor changes in the concentrated juices which makes it more preferable.
vi. High pressure technology - This method is used in food processing where food borne microorganisms and enzymes are inactivated at low temperature, without the need for chemical preservation.
It is a cold pasteurisation technique which consists of subjecting food, previously sealed in flexible and water-resistant packaging, to a high level of hydrostatic pressure (pressure transmitted by water) up to 600 MPa / 87,000 psi for a few seconds to a few minutes. This is done in fruit juice processing to preserve most of the nutritional qualities similar to a fresh product.
vii. Nutraceuticals from Pineapple- Food industries have a greater understanding than pharmaceuticals of nutrition and food formulation, plus decades of consumer research and relationships with mass-market distributors. Food companies who are doing well in nutraceuticals include those that have created separate health divisions, acquired successful brands, and launched global health improvement plans.
There are many functional foods and nutraceuticals that are becoming increasingly available in the marketplace, but there is a challenge for the functional food producers because such products should address the issue of sensory acceptability which is not necessary for the nutraceuticals or pharmaceutical products. In the tropics, pineapple is also grown and used for medicinal purposes. Pineapple contains the enzyme bromelain (protease) which has several therapeutic properties including thrombus formation and control of malignant cell growth, inflammation, diarrhoea, dermatological and skin debridement. According to various studies, available evidence indicates that bromelain is well absorbed orally with its therapeutic effects being enhanced in a dose- dependent manner and if successfully incorporated in foods, it could become more acceptable as a nutraceutical product than it now is.
Byproducts from Waste
It is anticipated that discarded pineapple fruit as well as the waste material can be utilised for further industrial processes like fermentation, bioactive component extraction, etc. In this regard, several efforts have been made in order to utilise pineapple wastes obtained from different sources. The wastes from pineapple have been used as the substrate for bromelain, organic acids, vinegar, ethanol, etc. since these are potential source of sugars, vitamins and growth factors. Several studies have been carried out since decades on trying to explore the possibility of using these wastes. In past, sugar has been obtained from pineapple effluent by ion exchange and further use it in syrup for canning pineapple slices. Bromelain is probably the most valuable and the most studied component from the pineapple waste. It is a crude extract of pineapple that contains, among other components, various closely related proteinases, demonstrating in vitro and in vivo, anti-edematous, anti-inflammatory, antithrombotic, fibrinolytic activities and has potential as an anticancer agent. It is also used in food industry as meat tenderiser and as a dietary supplement.
After extraction of its juice, the left over is used as livestock feed and also the tender leaves are used for the same purpose. The utilisation of agro industrial waste by conversion into value-added products such as animal feed or manure may be an innovative solution to the environmental waste problem. Utilisation of byproducts from pineapple culture, canning and juice extraction has been encouraged for feed production.
Leaves can be used in three forms: Fresh, dried and in silage. When the pineapple fruits are canned or consumed the crown, the outer peel and the central core are discarded as pineapple waste which accounts for about 50% of the total pineapple fruit weight corresponding to about 10 tonne of fresh pineapple or one tonne of dry pineapple waste per hectare. Pineapple wastes are recommended as good sources of organic raw materials and are potentially available for conversion into useful products such as animal feeds. Pineapple waste contains high amounts of crude fibre and suitable sugars for growth of microorganisms. The waste is also used for producing paper.
Pineapple peel is rich in cellulose, hemicellulose and other carbohydrates. Ensilaging of pineapple peels produces methane which can be used as a biogas. Anaerobic digestion takes place and the digested slurry may find further application as animal, poultry and fish feeds.
Conclusion
Pineapple is a tropical fruit which is consumed fresh or in a processed form. It contains nutrients which are good for human health. It also contains antioxidants and protease. It has therapeutic properties. As pineapple contains bromelain (protease), it can be incorporated into foods which is an advantage to human health when taken orally. The world pineapple demand has been expanding rapidly. Consumer acceptance of new foods is based largely on their convenience, nutritional value, appearance, sensory values, reproducibility and economic value. The new foods from pineapple include snacks, cookies, soft drinks, salad dressings, cakes, beverages, and dietic foods, which all are accepted by the consumers. Novel technologies have emerged to produce newer foods and there are greater movements toward new foods from pineapple in the market place. Processed pineapples are consumed worldwide and processing industries are trying out or using new technologies to retain the nutritional quality of the pineapple fruit. This is to meet the demand of consumers who want healthy, nutritious and natural products. Moreover, some of these preserved products such as canned pineapple, fruit juices, dehydrated products and frozen fruits are gaining popularity in the foreign market and are good foreign exchange earners. In spite of all these reasons, only 2.2% of the total produce is processed in India as compared to 40 to 83% in developed countries. Thus, there is considerable scope for expansion of the fruit and vegetable preservation industry in India, which in turn will help in the development of horticulture and in earning more foreign exchange.
