CHAPTER 11

PRACTICAL ASPECTS OF CITRUS JUICE PROCESSING

11.1 What is citrus and where is it grown?

Citrus is the largest fruit crop in the world with about 60 000 000 MT (1 MT = 1 000kg) grown, slightly exceeding grape production (FAO, 1999). Citrus is grown in two belts on both sides of the equator from about 20 to 40 degrees of latitude (Figure 11.2). All citrus is thought to originate in the Himalayan region of southwestern China and northern India. Columbus brought citrus seeds to the western hemisphere in 1493 and planted them first on the island of Hispaniola, now called Haiti (Figure 11.1). Citrus became commercialized in the Americas in the late 1800s. In the early to mid 1900s the principal producing states were Florida, Texas and California in the United States (Figure 11.3). Following a devastating freeze in Florida in 1962, a group of Florida businessmen began to establish citrus groves and later a processing industry around Sao Paulo, Brazil. This industry grew rapidly and after being sold to the Brazilians, it soon surpassed Florida in production by the mid-1980s. Brazil has become the dominant market leader in citrus concentrate. Orange production far outstrips the production of all other citrus (see Table 11.1). Brazil leads the world's orange production with 19 million MT in 1996 to 97. Argentina produces about one-fourth of the world's lemons at 800 000 MT.

Figure 11.1: Colonial Florida orange planting.

Figure 11.2: Global citrus growing regions.

Figure 11.3: Citrus grove, Central Florida.

Table 11.1: Citrus fruit production in specific countries (1 000 metric tonnes).

FAO Production Yearbook, 1999, ** USDA, 2000D

Citrus is botanically a large family whose dominant members are the sweet orange (Citrus sinensis), mandarin or tangerine orange (Citrus reticulata), grapefruit (Citrus paradisi), lemon (Citrus limon) and lime (Citrus aurantifolia). Because most citrus are propagated vegetatively by bud wood cuttings, all the millions of trees around the world that are called "Valencia orange" are in fact clones, essentially the same plant genetically. The benefits of this vegetative propagation are that all of the trees of a single cultivar in a grove are genetically identical and will react in the same way to their environment. Their fruit will become ripe and can be harvested at the same time, the oil and speciality products will be of similar composition and juice processors can schedule the timing of the harvest to keep their plants operating at full capacity. Citrus fruit typically store well on the tree. On the other hand, these genetically identical trees are very susceptible to the same diseases and physiological disorders. Nevertheless, all commercial groves that are being established are vegetatively propagated to produce uniform high quality fruit.

In commercial citrus nurseries the bud wood, called the scion, is the top portion of the new tree that controls the type of fruit (Figure 11.4). The scion is grafted on a different rootstock than the bud wood used for the scion. Valencia bud wood could be grafted on to different rootstocks where the rootstocks were known to impart disease resistance or drought resistance. For example, seedling trees or citrus trees grown from seeds typically have extensive root systems and are utilized by budding or top working with good commercial scion wood.

Figure 11. 4: Vitrus scion and rootstock.

Ripe citrus fruit are utilized either as fresh fruit or processed into juice and speciality products. Citrus grown for fresh market requires more extensive inputs in production and harvesting than citrus grown for processing. Typically prices paid for fresh market fruit are higher than fruit grown for processing. As is true for most agricultural commodities, the lowest price paid for fresh fruit is when all of the fruit in a region of a country is ripe simultaneously. Processing gives the citrus grower the business opportunity to shift the sale of a portion of his oranges several months to a time of higher prices due to a scarcity of fruit. Processing citrus provides an economical way to store and transport citrus from regions of production to distant markets. Processing allows small and medium sized businesses to create jobs in growing, processing, marketing and to contribute to the economic growth of a region.

Florida is the principle citrus growing state in the United States of America. In recent years about 90 percent of Florida's oranges have been processed into one of three basic types of orange juice: (1) frozen concentrated orange juice (FCOJ) (2) chilled orange juice (COJ) or (3) canned single strength orange juice called hot pack juice. Both the Brazilian and Florida processing industries have been built around producing and shipping FCOJ. In recent years there has been a trend in consumer preference to not-from-concentrate, chilled orange juice (COJ) that is preferred as a ready-to-serve product. However, the cost is prohibitive to ship all of the water in single strength juice for very long distances. There is also a small amount of "fresh squeezed Florida orange juice", (FSFOJ) that is not pasteurized by heat to reduce the enzyme activity and viable microorganisms. However, there are increasing food safety concerns with food borne illness like Salmonella outbreaks from citrus juices that are not pasteurized.

Citrus juice may be hot packed in regions of countries without refrigeration or freezing facilities. Hot packing involves heating the citrus juice to at least 90°C and putting it in clean glass bottles and capping the bottle while the juice is still hot. Entrepreneurs can blend citrus with other juices, or add spices or sugar to this juice prior to heating to make a beverage to meet local preferences in taste. More details on the hot pack process will be presented later in this publication.

11.2 Nutritional benefits from consuming citrus

Citrus fruits and juices are excellent sources of vitamin C containing more than the minimum daily requirement of 60 mg of vitamin C in 240 ml of juice. Citrus fruit are also a good source of folic acid, vitamin B1 thiamine and potassium (Nagy, et al., 1993; Brown, 2000; USDA, 2000a).

New opportunities to produce "healthful beverages" are now available on a small scale. Some of the current beverage categories are:

• Sport or isotonnesic
• Energy
• Nutraceutical
• Herbal
• Smart
• Fun.

Each of these beverage types needs to be adapted to consumers' taste preferences, bottled attractively and priced competitively with beer or Coca-Cola on the local market. Several of these beverages taste very good and compete effectively with carbonated beverages on the local markets. In the recipe or formulation of these beverages it is critical to try the addition of several food grade ingredients and let potential customers tell you what they like or don't like about a particular beverage. It is absolutely necessary that any ingredients that are used in this beverage are food grade and be approved for use in foods in your country.

It is relatively easy to start developing new beverages by making small batches, pasteurizing and hot packing the beverage. Hot packing the beverage provides a margin of safety against food borne diseases or food poisoning. Details on small-scale beverage manufacturing are covered in the next section of this text. Most of the beverages have a juice base that will provide acidity, a pH less than 4.0, cloudy appearance, typically recognized flavours and juice gives a general basis of consumer acceptance. Typically the more juice that is used in a beverage the more difficult it is to control settling of the particulates to the bottom of the bottle and the more difficult to produce a consistently high quality beverage.

11.2.1 Sport or isotonnesic beverages

These products are designed to replace fluids and electrolytes and provide extra energy during periods of intense exercise. Typically they have a low content juice base of 5 to 10 percent juice, added levels of sucrose, glucose (less sweet) or maltodextrin and elevated levels of electrolytes potassium and sodium in the forms of monopotassium phosphate, potassium chloride, sodium chloride (table salt) and sodium citrate. Workouts lasting less than one hour typically do not benefit from elevated carbohydrates (Brown, 2000). However, many consumers of Sport Beverages enjoy the taste and associate them with the good feelings that come about from strenuous exercise.

11.2.2 Energy beverages

These are designed to increase the consumers' perception they have more energy either by increasing the levels of sugars in the beverage or providing a stimulant like caffeine.
Caffeine is a bitter tasting white powder that can have its taste masked in an orange beverage. These can be marketed to office workers in cities who want an afternoon "pick-me-up" or to labourers who need additional energy during a long day.

11.2.3 Nutraceutical beverages

This category is designed to provide healthful benefits beyond the calories they contain and are aimed at reducing the risk of chronic diseases like cancer. These beverages can contain vitamin C from citrus, vitamin A from fruits or vegetable juices rich in carotene and a mixture of plant extracts that are believed by local consumers to promote good health.

11.2.4 Herbal beverages

Can be similar to Nutraceutical drinks, but are made by adding herbs to a beverage. Examples of herbs that can be added are ginseng (believed to boost energy), ginkgo (believed to sharpen the mind), Echinacea (believed to increase the immune system), kava (believed to help relieve stress) and St. John's Wort (believed to be an antidepressant) (Brown, 2000). Caution, while many of these herbs are safe at low levels of consumption they can become toxic at higher levels. Check local regulations before formulating these beverages. Two minerals, selenium and chromium, that may be present are toxic at higher levels.

11.2.5 Smart beverages

This popular group is believed to increase mental capacities on a short-term basis. Some of these drinks contain carbohydrates, such as glucose or galactose, that are readily absorbed and converted into glycogen in the liver then transported by the blood stream for fuel for the brain. Other Smart beverages may contain herbs like ginkgo or stimulants like caffeine discussed above. There is little research evidence that compounds such as amino acids: choline, L-cysteine, taurine or phenylalanine boost mental powers. Still, some of the beneficial effects may be only in the perception of the consumer, termed the placebo or sugar pill effect, that can never the less have a positive effect and be demanded by consumers.

11.2.6 Fun beverages

This category of products are designed to have a maximum eye appeal and must taste very good. Some of these have suspended coloured particles or have weird names that appeal to kids. Typically Fun beverages contain a minimal amount of juice, but a maximum amount of advertising and label hype.

11.3 Economically feasible by-products from citrus and an idea of volumes

By-products, sometimes called speciality products, are those saleable products made from fruit besides juice. One of the opportunities of starting a new citrus processing operation is the unique opportunity to tailor the citrus processing plant's production of speciality products to the customer's needs. This needs to be done early in the design phase so the plant can be specially designed for the production of multiple products. We will give the reader an overview of speciality products currently produced by large citrus operations to give an idea of what additional products can be produced.

Over 400 speciality products can be made from citrus in addition to juice. (Figure 11.5) Many of these products are only research realities that have lacked either the backing or timing to be made profitably.

Figure 11.5: Some of the many citrus by-products.

Many similar by-products can be made from the residue of juice operations from other fruits. It is vital before engaging in a fruit juice operation to make plans on how to economically dispose of the peel and other solid wastes from the operations. Often small quantities of peel that is still wet can be fed to cattle. Larger quantities of peel will ferment before they are eaten, attract flies and become nuisances. The proper disposal of wastewater from a citrus processing operation must be planned for in accordance with local regulations. However, there are probably 6 to 12 citrus speciality products that have established markets. These are:

• Pectin
• Pectin pomace and dietary fibre
• Dried citrus peel
• Pulp wash
• Juice sacks and whole juice vesicles
• Beverage bases and clouding agents
• Healthful, nutraceutical citrus beverages
• Fractionated citrus oils and D-limonene
• Citrus molasses and beverage alcohol base
• Flavonids and limonin.

11.3.1 Pectin

Pectin has been manufactured from citrus peel for more than 50 years. All citrus contains pectin and the richest sources are limes, lemons, oranges and grapefruit in decreasing importance. The soft, white spongy layer called the albedo, just under the coloured portion of the peel is the principle source of pectin. Figure 11.6 shows a cross section of an orange that describes these portions. Pectin manufacture involves leaching to remove sugars and acid from the fresh peel, an acid extraction, precipitation, purification and standardization. Liquid pectin is less expensive to manufacture for use in a local market area. Citrus peel is extensively leached with water and this leach water has the potential for large pollution problems. Pectin plants are capital and energy intensive operations that require sophisticated operation and control. Tropical developing countries may have a locally owned pectin manufacturing operation, but it is typically hard pressed to compete with imported pectin unless the native operation is given governmental protection. Typically pectin operations are co-located with large-scale juice operations that run at least 30 000 MT per year of fruit. A handful of manufacturers make the majority of pectin. Curiously, all of the pectin used in the United States of America is imported, principally from Europe, Central and South America.

11.3.2 Pectin pomace and dietary fibre

Leached, dried citrus peel mainly lime and lemon, is termed pectin pomace. Because of its high pectin content, pectin pomace is shipped from production facilities in Central and South America to Europe for pectin extraction. Pectin manufacturers must run their operations 7 days a week, 24 hours per day so having a stable source of raw materials like pectin pomace is essential to an economical operation.

In addition, leached citrus peel can be treated to make either a moist or dry peel fibre. This dietary fibre contains both soluble and insoluble fibre sources. Dietary fibre is becoming more popular as a healthful way to lower total cholesterol. Several sources of citrus dietary fibre have been shown to be useful food ingredients in meat emulsions, possessing excellent water and fat binding properties.

Figure 11.6: Citrus cross-section.

11.3.3 Dried citrus peel

Orange peel, from the extractors in large-scale citrus processing operations, contains about 80 percent water. These large volumes of peel are treated with hydrated lime Ca(OH)2 to release the water and some of the sugars. The treated peel is then pressed and dried in direct-fired rotary dryers. The partially dried peel is pelletized before being stored and transported in bulk. Dried, pelletized, citrus peel at about 10 percent moisture is shipped to Europe as a source of carbohydrate used principally in dairy cattle rations. Citrus peel from small and medium scale processing operations can be treated by: drying in the sun (weather permitting) or soaking the peel with a 1 percent Ca (OH)2 solution prior to pressing. This will reduce the water content of the peel that must be transported. Figure 11.7a. and b. gives a material balance for the weights of speciality products and juice that can be manufactured from 1 MT of Valencia oranges (Kesterson, et al., 1978).

Figure 11.7a: Material balance on citrus processing.

Figure 11.7b: Material balance on citrus processing.

1.3.4 Pulp wash

About 5 percent of the weight of an orange are made up of juice sacs or juice vesicles. Juice vesicles contain orange juice that is about 12ºBrix. After the juice is extracted, the juice vesicles still contain a considerable amount of 12ºBrix juice that can be recovered. The juice vesicles can be taken into a multiple-stage finisher and counter current water washing operation that recovers about 90 percent of these juice solids (Figure 6.7). These solids may have pectic enzymes added to reduce their viscosity and then combined with the juice from the extractors to increase the primary juice yields or sold separately as beverage bases. Pulp wash provides an opaque appearance called cloud to a beverage and is a source of less expensive fruit solids than regular juice for label declarations.

11.3.5 Juice sacs and whole juice vesicles

Juice sacs from the extractors can be pasteurized, dried and then sold. Washed juice sacs from the pulp washing operation described above contain less than 2 percent juice and can be dried. However, drying juice sacs that have not been washed with water produces a dark brown, unappealing product. These juice sacks full of juice can be frozen for storage. Juice sacs can be added back to frozen concentrated orange juice or sold to beverage manufacturers to give eye appeal for beverages containing low levels of juice solids and improve the mouth feel.

Whole, turgid citrus juice vesicles are very popular in Japan where they are added to beverages and yoghurt. These turgid juice vesicles are removed from intact fruit by the judicious use of heat or enzymes. In a very sweet beverage these vesicles, full of juice, provide a turgid squirt of citric acid when crushed between the teeth. This is like getting to drink and eat an orange simultaneously.

11.3.6 Beverage bases and clouding agents

Citrus peel, core and juice vesicles all contain vitamin C sugar solids and natural clouding agents. Processes have been developed to water leach citrus peel so that the leached peel can later be used for pectin manufacturing and concentrate the leach water for an inexpensive beverage base as discussed earlier (Crandall, et al., 1983).

Natural beverage clouding agents are used as a healthful replacement for typical clouding agents made of brominated vegetable oils or glycerol esters of wood rosins. A number of new products can be developed using all natural citrus-based clouding agents especially for overseas markets.

11.3.7 Healthful, nutraceutical citrus beverages

Citrus has long been regarded as one of the most healthful sources of vitamin C. Only recently have other health benefits from consuming citrus come to light. There is an increase in the introduction of new juice products fortified with vitamins and minerals due to an increase in health awareness and lower costs. Drink manufacturers can blend beverages with sugar solids, flavours and essences, pectin and vitamins. Besides vitamin C, both folic acid and carotenoids are found in appreciable quantities. This provides an additional source of income and new products for a citrus processing plant.

11.3.8 Fractionated citrus oils and D-limonene

Within a citrus fruit there are two principle locations of flavouring oils, the peel and within the juice (Figure 11.6). The extraction of peel oil by hand or with small-scale extractors will be discussed later in this text. This oil may be further fractionated to yield aldehydes, alcohols and esters used to flavour citrus beverages. During juice concentration the oils in the juice are evaporated off and can be condensed using refrigerated condensers on the evaporator. During the concentration or `folding' of these oils unwanted flavours can be removed and additional speciality products called orange essences manufactured for sale. These essences contain the characteristic flowery or fruity aromas of the orange and are used to provide flavour to the juice. For a medium sized citrus processing operation it may be well worth the efforts to plan to capture these oils. For citrus fruits like lemons and limes the oils are sometimes worth 20 times the value of the juice. Citrus terpenes, principally d-limonene, are removed from the peel oil during folding under vacuum. D-limonene can be sold for hand cleaners, thinner or as an industrial feed stock.

11.3.9 Citrus molasses and beverage alcohol base

After citrus peel has been limed and pressed many of the sugar solids are removed from the liquid called press liquor. It is routinely evaporated to about 50°Brix molasses. This molasses is either added back on the peel before drying to increase the solids sold, or sold separately. Molasses can be used as an industrial fermentation feedstock for manufacturing beverage alcohol because it meets the definition of alcohol fermented from fruit juices. The alcohol can be used in a range of beverages or subsequently fermented to vinegar (acetic acid). Amino acids can also be manufactured from the fermentation of citrus molasses.

11.3.10 Flavonoids and limonin

The flavonoids, narigin and hesperidin, are found mainly in the peel. Hot water or treatment with base can remove these. These flavonoids are reported to have therapeutic benefits in treating capillary diseases and as anti-carcinogens.

11.3.11 Conclusions

This is a quick overview of the economically viable speciality products that can be made from oranges. The specifics on the yield of product like pectin need to be assayed on the particular orange cultivar that will be used in any project.

11.4 Overview of large scale citrus processing operation

Before going into the appropriate size equipment for small and medium sized fruit juice operations it is important for the reader to understand some of the current concepts being utilized in present day fruit juicing operations. We have chosen to use citrus processing operations in Florida as an example, but most of the concepts discussed can be adapted to other fruit. It is important that the reader realize that a modern citrus processing plant has a tremendous amount of infrastructure and specialization to keep the plant operating at near full capacity 6 or 7 days a week for as long as 200 days a year. A single modern citrus juice extractor will extract about 10 MT of oranges per hour. This is equivalent to almost 5 000 oranges per hour! A modern citrus plant is comprised of three rows of 8 to 10 extractors in each row and each row is fed carefully sized oranges (Figure 11.8) . This gives the plant the capacity of 300 to 400 MT / hour with the largest plants in Brazil able to run more than 1 000 MT/hour.

Figure 11.8: Sizing conveyor feeding citrus extractors.

Fruit processing can only preserve the raw product quality, not greatly improve it. To produce consistently high quality juices and beverages it is important to start with the very highest quality fruit. First, look at options then decide on how to best motivate growers to produce the highest quality fruit. One of the best, long-term options is to enter into
mutually beneficial relationships with your growers. In years of excess supply, the processors help the growers by paying a fair price for the excess fruit. When there are years of tight supply growers agree to take a little less than the market demand so that fruit processors can fulfil their obligations and contracts. This becomes a mutually beneficial relationship whereby both growers and processors are able to benefit from a long-term, loyal relationship.

11.4.1 Harvesting and transporting oranges into the processing plant

Manual (hand harvesting) is used to harvest 99.9 percent of Florida's orange crop (Figure 11.9). Picked fruit, called grove run, moves directly from the grove to the processing plants without ever being graded in a packinghouse. Hand harvested fruit is hand picked into harvesting sacks that are manually dumped into 400 kg bins in the grove. These bins are lifted by small trucks and taken to the edge of the grove where the bin is dumped into a semi-trailer. Each semi-trailer hauls about 22 MT of fruit to the processing plant that can be many kilometres away. The time from harvest to processing is only one or two days because harvesting of the fruit is paced to keep the processing plant running at near capacity seven days a week. Figure 11.10 illustrates typical processing operations.

Figure 11.9: Citrus hand harvesting.

In Japan and many other citrus growing regions all of the fruit is picked and taken into fresh fruit packinghouses where it is washed and graded and only the fruit eliminations are sent on to the processing plant. Typically fresh fruit packinghouses pay more for fresh citrus, but the fruit going to the processor is several days old and can be of lower quality than grove run fruit. A new processing operation may want to plan to operate on both sources of fruit in order to get sufficient volume to efficiently operate the plant.

In Florida, a single over-the-road-trailer load of grove run fruit usually represents one grower's fruit and is driven onto a scale where the gross weight is recorded. Elevating the entire truck hydraulically after opening the end gate unloads the fruit. It only takes about 15 minutes to unload about 22 MT, the capacity of the trailer (Figure 11.11). Next, the empty truck and trailer are re-weighed to determine the net fruit weight. In Brazil fruit is received from the grove in bulk containers and in Australia the fruit is unloaded from the side of the trailer. After the fruit is unloaded, leaves, stems and other debris are removed and unwholesome fruit is removed either mechanically or by hand grading.

In Florida, a statistically representative sample of citrus, about 20 kg is removed from each trailer load and graded and tested to insure the fruit meets standards for quality. A government inspector, an impartial third party, uses a special extractor to remove some juice, which is weighed and the sugar solids are measured. The amount of sugar as soluble solids are calculated for the entire trailer load based on the sample of fruit and this is the basis of the processor's payment to the grower. This method of payment encourages the grower to produce fruit with a high juice and high solids yield. Additional payments can be made to the grower on the basis of profits from the by-products like peel oil or dried peel sold as cattle feed. These agreements are typically called "participation plans" and are used by grower's cooperatives that own the citrus processing plant. In all other countries growers are paid strictly on MT of fruit. Paying growers strictly on the weight of fruit is counterproductive and encourages growers to grow as much fruit as possible regardless of the sugar solids content; and quality can suffer.

Fruit is pulled out of the bin and the individual grower's load of fruit is blended with other loads of fruit to achieve the desired Brix and sugar/acid ratio of the final extracted juice. The oranges are washed with detergents, brushed and rinsed with clean water before being carefully sized for each row of extractors.

1. Fruit production	6. Yield and quality sampling
2. Load weighing and recording	7. Segregated storage
3. Fruit unloading	8. Fruit washing
4. Rough grading, debris removal	9. Final grading and sizing
5. Grading and cull removal	10. Extractor surge bin

Figure 11.10: Citrus processing operations flowchart.

11.4.2 Citrus juice extraction systems

Several extraction systems are used worldwide, FMC, Brown, Indelicato Speciale/Bertuzzi and Pelatriche/Sfmatrice/Torchi. The FMC or Brown systems are used primarily in Brazil, the United States, Australia, Japan and Israel. Due to space limitations we will only discuss the FMC system (FMC, 2000). FMC extractors are rented rather than owned by the juice processor. The rental fee for most extractors is based on the volume of juice extracted. This arrangement gives the maintenance and updating responsibilities to FMC.

After the fruit is graded to eliminate unsound fruit, it is washed; it is sized for each extractor to obtain a maximum yield of good quality juice. There are three basic models of FMC extractors: the Model 291 for small oranges, lemons or limes, the Model 391 for large oranges and small grapefruit and Model 491 for large grapefruit. The Model 291 with 5 cups extracts about 5.3 MT per hour and the Model 391 with 5 cups for larger fruit extracts about

Figure 11.11: Citrus delivered for processing.

4.7 MT per hour. Figure 11.12 gives an overview of the FMC extraction process. A plug is cut in the centre of the fruit and a strainer pushed up inside the orange. A mechanical hand presses the juice and pulp against this strainer keeping the juice away from the exterior of the fruit and strongly flavoured peel oils. The juice exits out the bottom of the FMC Extractor after being separated from the pulp and the peel is pushed up and out the front. At the precise moment the peel is being put under pressure a fine mist of water is sprayed on the peel making an emulsion of the peel oil that is being forced from the peel. Thus in one stroke five oranges are separated into juice, pulp, peel, peel oil, seeds and rag.

Figure 11.12: Citrus extractor diagram.
(Courtesy FMC, FMC, 2000)

The juice and any remaining pulp are sent to specially designed finishers to remove any small seeds, bits of peel and excessive pulp from the juice prior to evaporation. FMC personnel work closely with plant personnel to insure the highest yield of good quality juice is being maintained.

11.4.3 Manufacture of peel oil

Oil glands are located in the flavedo, the coloured portion of an orange peel (Figure 11.6). When an FMC extractor puts pressure on the peel, the oil in the oil glands is forced out and is mixed with water to form an emulsion. This emulsion goes to a special finisher then to a self-cleaning, de-sludging centrifuge and the final separation is made in a high-speed centrifuge called a polishing centrifuge. Polished oil is stored in the cold to precipitate waxes. Cold-pressed oil gets its name from the original process where peel was mixed with water then pressed in a screw-press with only a small increase in temperature. Even though oil still retains the cold pressed name; the cold press process is no longer used. Table 11.2 gives a yield of cold pressed oil from various citrus cultivars (Kesterson, et al., 1978). Citrus oils are used as flavour and fragrance enhances in beverages, foods and household cleaning supplies.

Table 11.2: Yield of oil from citrus fruit (Kg oil/tonnes fruit).

11.4.4 Evaporation, concentration of the juice, storage and transportation

After the juice is removed from the fruit and has gone through the finisher it is sent to an evaporator feed tank. Almost all orange juice is concentrated on Thermally Accelerated Short Time Evaporators, TASTE (Figures 8.9 and 8.10). These multi-stage, forward feed evaporators take juice that is 10 to 12 percent solids or ºBrix and remove the water to concentrate the juice to 62o to 65°Brix. This concentrate is mixed with a small amount of oil and stored in enormous 500 000 to 18 000 000 L bulk storage tanks. Bulk storage tanks represent significant savings, about 20 percent, over storing concentrate in barrels.

Citrus processors in Brazil pioneered the use of large bulk, refrigerated ships carrying more than 11 000 MT from the Port of Santos in Brazil to Florida, New Jersey or Rotterdam (Figure 8.23). Substantial quantities of orange concentrate are shipped from Mexico in semi-trailer tankers holding about 16 000 litres or in square 1 100 litre bag-in-box containers. Citrus oils, d-limonene and citrus essences may also be transported in bulk.

11.4.5 Saving money by manufacturing 72ºBrix concentrate

Citrus concentrate is shipped around the world at about 62ºBrix, which means that 38 percent of all the storage capacity and transportation costs are due to transporting water. Tank farm and transportation storage capacity could be increased by 14 percent by increasing the concentration from 62ºBrix to 72ºBrix. This more highly concentrated orange juice is less susceptible to attack by microorganisms and may be kept at refrigerated rather than frozen conditions for periods of time, which further increases the energy savings. The 72ºBrix concentrate is more viscous and can require a new operation to be designed to handle this higher concentration. Initially there were concerns that concentrating the reactants could increase chemical degradation reactions such as the Maillard reactions. However, research later showed that this was not the case and the 72ºBrix concentrate was stable for extended periods of storage. There are several methods of manufacturing 72ºBrix, depending on the customer's specifications (Crandall, et al., 1981; Crandall, et al., 1987, Fox, 1994). The 72ºBrix concentrate may be a very viable alternative for a new citrus processing operation needing to transport citrus concentrate long distances.

11.5 Principal pieces of citrus extraction equipment for use at an appropriate scale

We will discuss appropriate equipment for use in small and medium size fruit juicing operations. We will start with citrus extraction and pasteurization equipment that is appropriate in size for a village group of about three dozen persons extracting up to 1/2 MT of citrus per hour. Then we will move to the next scale of purchasing extractors and finishers for plants wanting to process 3 to 10 MT per hour. The modern citrus processing equipment just discussed is for operations wanting to process multiples of 10 MT of fruit / hour.

11.5.1 Small village-scale harvesting

The villagers and their neighbours typically grow fruit for small-scale operations. As with most fruit, all of the fruit in a region becomes ripe at the same time and must be processed, sold at the lowest prices of the year or left to rot. Villagers can collect the fruit they want to harvest and collect the glass containers for the finished juice. They must decide whether to process 100 percent full strength juice or blend the citrus juice with other locally available juices or flavourings for a juice based beverage.

11.5.2 Washing and storing fruit

Citrus stores very well on the tree so the rate of harvesting must be controlled so only a one or two-day supply of fruit is on hand at the processing operation. Freshly harvested fruit should be stored dry in the shade. The first Critical Control Point is to juice fruit only after the rotten and diseased fruit has been removed and fruit has been washed to remove soil and dirt from the grove. These operations should be performed just prior to processing. Once citrus is washed it is more likely to decay if held at ambient temperatures. Before processing, stems and leaves need to be removed from the fruit and the fruit needs to be washed and rinsed in clean water. Washing will help minimize the amount of microorganisms getting into the juice. Glass bottles and bottle caps such as used soda or beer bottles need to be collected and washed out with hot water with soap and rinsed in clean water and turned upside down to dry. The hot juice filled into the bottles will kill many microorganisms but this hot pack treatment is not sufficient to kill very large concentrations of microorganisms found in dirty bottles. Bottle caps that can be reused need to be free from rust and reshaped to be flat across the top and have the flanges bent slightly outward. Reshaping the metal caps can be done with a wooden dowel placed inside the cap and striking the dowel with a hammer. The caps then can be clean by rinsing in very hot water.

It is envisioned that the next two pieces of portable processing equipment would be brought to the village by a circulating processing expert after the villagers have their fruit and bottles ready. The person knowledgeable in the fruit processing operation could be an entrepreneur or governmental employee. They could be paid in bottles of juice at an amount agreed to before beginning the processing. The equipment is portable and designed to fit on the back of a man or on a single bicycle. This bicycle can also be used to provide power for the fruit extractor. However, in less remote situations small electric or diesel motors can replace the labour of several persons and can be paid for by the sale of the bottled juice. Details on the construction of the bicycle powered citrus reamer and portable fruit juice pasteurizer are contained in Annex A.

11.5.3 Small-scale citrus

The bicycle or small engine powered reamer uses two standard juice reamers. Alternative fruit grinders for different types of fruit could be powered by a similar system. This extractor uses 5 or 6 people and will extract about 70 kg of citrus per hour. This will give a juice yield of about 30 L/ hour which is only 1/3 as fast as the flow rate of the tubular pasteurizer at 90 L/hour. Three sets of bicycle reamers will keep one tubular pasteurizer operating on 100 percent juice or the extraction can start and get 40 to 50 L of juice ready before pasteurizing starts. Alternatively other juice and flavourings can be used to increase the volume of juice going to the pasteurizer. The whole rear bicycle axle, tire, rim and chain drive sprockets are first removed. An 18-cm threaded shaft with a toothed rear wheel-driving sprocket, two reamers and a bearing are used to replace the rear bicycle axle. The bicycle chain is placed around the threaded shaft, fitted to the driving sprocket and tightened in the rear wheel axle mounting brackets in the bicycle frame. Metal or plastic troughs are constructed to protect the bearing from the acid fruit juice and to direct the extracted juice into a collection bucket. A stand made from old bicycle handlebars is used to elevate and stabilize the reamers. Figure 11.13 illustrates a bicycle-powered reamer in operation and a close up of the reamer.

11.5.4 Small-scale citrus extraction

After the citrus has been thoroughly cleaned, one person cuts the fruit in half between the stem and blossom ends. A second person rides the bicycle or operates a small engine powering a drive chain providing power to vertical mounted reamers. A third and fourth person press the cut cup halves against the reamer and collect the juice in a bucket. A fifth person presses the juice through a metal colander, a perforated metal cone with a wooded dasher; to remove the excess pulp and seeds that would plug the pasteurizer coils (Figure 11.14). This juice is now ready to be pasteurized or can be blended with other juices and flavourings to make a citrus beverage. Citrus juice contains enzymes and microorganisms that can destroy the quality so the juice needs to be run through the colander and to be heated within 30 minutes of the time it is extracted.

Figure 11.13: Bicycle powered citrus extraction.

11.5.5 Small-scale citrus juice pasteurization

The second Critical Control Point is to check the pH of the fruit juice or beverage to be pasteurized. The pH is a measure of the amount of acid in the juice and the pH absolutely must be below 4.5, but it is much better to have the pH below 4.0 to have a safety margin. The spores of Clostridium botulinium are prevalent in most soils and contaminate many types of fruit. These spores require a pH above 4.5 and almost no oxygen conditions to grow and produce their toxins. Washing the fruit will minimize the number of spores in the juice and adding an acid juice like lemon or lime juice to reduce the pH of some beverages is required. Pasteurization of fresh citrus juice requires that it be heated to at least 90°C to inactivate the heat stable pectinesterase enzyme that causes the juice to clarify. This can be accomplished by pouring the juice through a stainless steel coil suspended in a boiling water bath.

Figure 11.14: Juice strainer and pasteurization coil.

Figure 11.15 shows the construction of a heating oven, the placement of any type of metal container to hold the boiling water, the coil placed in the boiling water, the placement of the funnel to control the rate of juice flow and measuring the outlet juice temperature. The third Critical Control Point is to make sure the temperature of the juice exiting the pasteurization coil is at least 90°C going into the cleaned glass bottles. Initially the funnel where the fresh juice was poured in is placed 1 metre above the outlet of the juice tubing (Figure 11.16). If the temperature is less than 90°C the juice is running through the coil too fast and the height of the funnel, the hydrostatic head must be reduced. If the juice gets close to 100°C exiting the pasteurizer it may boil inside the tube creating steam that can cause the juice to flash out and can cause serious burns. That is why one person who understands what is needed must keep the temperature of the juice leaving the coil just slightly above 90°C.

Figure 11.15: Pasteurizer coil heater.

Figure 11.16: Pasteurizer feeding and bottle filling.

The pasteurization coil is made from a 5.3-metre length of stainless steel tubing, 9.5 mm outside diameter and 7.7 mm inside diameter. The stainless steel grade is 316. Copper, brass or lead metal tubing must not be used to make this pasteurization tube because these metals are soluble in the acid juice and can make the juice toxic.

The 90ºC juice is hot filled into cleaned glass bottles almost to the top of the bottle. The cap is crimped on the bottle with a bottle-capping machine (Figure 11.17) and the bottles laid on their sides for at least 3 minutes to allow the hot juice to sterilize the cap. Then the bottles are cooled in running water to preserve the flavour. Whenever the juice supply is running low the coil can be filled with clean water and pulled out of the boiling water bath until there is sufficient juice ahead to resume pasteurizing. Be sure to flush the water from the coil and insure the exiting juice temperature is at least 90ºC before resuming filling the glass bottles. Immediately after finishing running all of the juice for the day, remove the coil from the boiling water; flush the coil with large amounts of water to remove any traces of juice. Then flush the coil with 1 percent NaOH, a strong base, to remove any scale that may have formed inside the coil. Then this base needs to be washed from inside the coil with a large amount of water. The remaining water is poured from the coil and the coil allowed to dry. This extraction, pasteurization and bottling system can now be transported to the next village. Additional details are contained in Annex B.

11.6 Overview of small scale fruit processing equipment with references on how to make equipment

This equipment is designed for fruit juicing operations wanting to process 3 to 10 MT per hour and to operate in regions where there is electricity or diesel fuel to power generators (Annex C). The fruit supply needs to be available for a long enough period of time within reasonable transportation distances to the plant. It is vital to the success of any new fruit juice processing operation that the supply and cost of fruit be secured before beginning each season.

11.7 Sanitation and good manufacturing practices

Fruit entering a processing operation is sorted to remove damaged fruit, diseased or rotten fruit. Fruit is stored for as short as time as is possible to keep the processing operation running efficiently. Fruits are washed to remove any soil, disease or mould. It is important not to include the white, albedo and portion of citrus by over extracting the juice. While the peel contains vitamin C and bioflavonoids it also contains a number of very bitter compounds and the highest concentrations of pesticides that have been sprayed on the fruit during production and should not be included in the juice.

Most food safety recommendations call for fruit juice to be pasteurized. Pasteurization is a heat treatment that kills the bacteria Escherichia coli O157:H7 that is a public health hazard. Most juice manufacturers are no longer willing to accept the liability risk of producing fruit juice that has not been pasteurized. Acid juices like citrus containing pH levels less than 4.0 can be pasteurized by heating the juice to 90°C for a few seconds (Somogyi, 1996; Ashurst, 1995; 1998).

11.7.1 International

There are several approaches that may be taken to comply with Good Manufacturing Practices, food laws and regulations. The suggested approach is to first determine where you want to sell the processed fruit juice or beverages. If you ever expect to export your fruit juice products to another country it will be important to evaluate the FAO Codex regulations for the products you want to manufacture. There is a worldwide effort to make these regulations the same or harmonize the regulations for a region producing similar products. Many national and local regulations use international regulations like Codex as the basis for their regulations. A complete list of FAO Codex regulations pertaining to fruit and vegetable juice and beverage regulations can be found in FAO, 1992 and at FAO 2000a. and c.

11.7.2 National and local regulations

It is not possible to go into detail about food safety regulation for each of the 180+ countries where FAO has contacts. However, we have accumulated some advice and references where more information on each of these subjects may be found.

Growing fruits or vegetables for distribution only within a country or exporting to another country may have different requirements. However, the export requirements to grow under Good Agricultural Practices (GAPs) means that the fresh produce coming into a processing plant will be of the highest quality. Information on GAPs can be found in Sections 4.1 to 4.3.

11.8 Processing citrus other than oranges

There is a great variety of the citrus species: tangerines, grapefruit, lemons, limes and exotic citrus. Most of the processing operations describe above will apply to extracting juice and making by-products from these other species.

11.8.1 Tangerine

Tangerines or Mandarin or Zipper-skin easy to peel oranges are the exceptions. There are many types of tangerines grown around the world because they are delicious when eaten out-of-hand and they have different disease susceptibility than sweet oranges. However, most tangerines and navel orange juice contains a bitter lactonnese structured compound in the juice that reacts closes the ring and forms a very bitter compound when the juice is stored or heated. This makes most tangerine juice a poor choice for beverages that contain more than 10 to 15 percent juice because the juice will become too bitter. However, using small concentrations of tangerine juice together with sweet orange juice can impart a richer, more orange colour to some pale coloured sweet orange juices. Certain types of tangerines may be difficult to juice on a reamer and may need to be peeled then the juice pressed out. Tangerine oil can command a high price but should not be used to flavour orange beverages because it can develop off flavours during storage.

11.8.2 Grapefruit

This fruit was so named because of the tendency to grow in clusters like large grapes. Duncan, a seedy variety, came to Florida in the early 1800s. Marsh, a seedless variety and several pink fleshed varieties are thought to be spontaneous mutations. As with all fruit it is important to process high quality, fully mature fruit. This is especially true of grapefruit. Immature grapefruit juice contains excessive amounts of naringin and limonin that impart an extremely bitter flavour to the juice. Grapefruit juice is considered as an excellent candidate for small-scale juice processing operations because it is the easiest to process and maintains its flavour better during pasteurization and storage. Grapefruit juice extraction requires larger diameter reamers. Before starting on a grapefruit processing operation it is vital that a determination be made that there are sufficient numbers of customers who prefer grapefruit to other types of juice.

11.8.3 Lemon and lime

These are separate species of citrus. Limes are typically grown in humid tropical climates and lemons in the subtropical regions. Both came into cultivation in Europe from Southeast Asia during the crusades. Lemon juice was probably the first commercially processed fruit juice in the early 16th century when it was bottled as a medicinal to prevent scurvy on British navy ships. Lemon juice is used for its acid content, typically above 4.5 percent by weight. Limes have thinner skin and are processed in a manner similar to the one just described.
Entrepreneurs planning on processing either lemons or limes need to make provision to extract the oil from the peel. Lemon and lime oil is valued at many times the value of thejuice. There are special hand oil extracting techniques if there is a market for this very fine oil. The peel from both of these fruit are leached with water and dried for pectin pomace.

11.8.4 Exotic fruits

In some regions there is grown an orange with a blood red coloured juice. The pulp from this blood orange contains red pigments, anthocyanins, which develop an undesirable muddy colour upon processing so this fruit should be used only as fresh fruit and for fresh juice products. (In contrast, pink grapefruit contain the carotenoid pigment, lycopene).

Kumquats (Fortunella margarita) and sour orange contain naringin that can impart an undesirable bitter taste to the juice. Often these small fruit are ground whole and used as a base for manufacture of marmalades.

11.8.5 Conclusion

Citrus is by far the most technologically developed juice industry. Yet we see that operations can range in size and technology from the immense and global to small and village. Mid-size citrus processors can borrow ideas from both extremes and processors of other fruits should adapt (and improve upon) the best (location- and circumstance-appropriate) citrus practices (Crandall and Hendrix, 2001). In addition, citrus equipment manufacturers and suppliers have experience and insights into other fruits well worth exploiting. Citrus is, therefore, a good (but not exclusive) model on which to plan and develop a juice processing operation.