Microwave-assisted thawing and tempering

S.J. James , ... G. Purnell , in The Microwave Processing of Foods (Second Edition), 2017

12.1 Introduction

Thawing and tempering have received much less attention in the literature than most other food processing operations. In commercial practice there are relatively few controlled thawing systems compared with chilling and freezing systems.

Frozen meat, fish, vegetables, fruit, butter, and juice concentrate are common raw materials for many food-manufacturing operations. Frozen meat, as supplied to the industry, ranges in size and shape from complete hindquarters of beef to small breasts of lamb and poultry portions, although the majority of the material is "boned-out" and packed in boxes approximately 15   cm thick weighing between 20 and 40   kg. Fish is normally in plate frozen slabs; fruit and vegetables in boxes, bags, or tubs; and juice in large barrels. Few processes can handle the frozen material and it is usually either thawed or tempered before further processing (Anon, 2008; James & Crow, 1986).

Thawing is usually regarded as complete when the temperature of all points within the frozen food has been raised to 0°C and no free ice is present. This is the minimum temperature at which the meat can be boned or other products cut or separated by hand. Lower temperatures (e.g., −5 to −2°C) are acceptable for product that is destined for mechanical chopping, but such material is referred to as "tempered" rather than thawed (Anon, 2008). The two processes should not be confused because tempering only constitutes the initial phase of a complete thawing process.

Thawing is often considered as simply the reversal of the freezing process. However, inherent in thawing is a major problem that does not occur in the freezing operation. The majority of the bacteria that cause spoilage or food poisoning are found on the surfaces of food. During the freezing operation, surface temperatures are reduced rapidly and bacterial multiplication is severely limited, with bacteria becoming completely dormant below −10°C. In the thawing operation, these same surface areas are the first to rise in temperature and bacterial multiplication can recommence. On large objects subjected to long uncontrolled thawing cycles, surface spoilage can occur before the center regions have fully thawed (Anon, 2008; Baush, Caren, Stephen, & Tuemy, 1980).

Conventional thawing and tempering systems supply heat to the surface and then rely on conduction to transfer that heat into the center of the product. A few, including microwave, use electromagnetic radiation to generate heat within the food. In selecting a thawing or tempering system for industrial use, a balance must be struck between thawing time, appearance, and bacteriological condition of the product, processing problems such as effluent disposal, and the capital and operating costs of the respective systems. Of these factors, thawing time is the principal criterion that often governs selection of the system. Appearance, bacteriological condition, and weight loss are important if the material is to be sold in the thawed condition but are less so if it is for processing (Anon, 2008).

There are a number of reviews of meat (James & James, 2002; Merts, 1999) and fish (Archer, Edmonds, & George, 2008; Haugland, 2002; Jason, 1974a, 1974b) thawing. The main detrimental effect of freezing and thawing meat is the large increase in the amount of proteinaceous fluid (drip) released on final cutting, yet the influence of thawing rate on drip production is not clear. James and James (2002) reported that studies have shown that there was no significant effect of thawing rate on the volume of drip in beef or pork. Several authors concluded that fast thawing rates would result in increased drip, while others showed the opposite. Hergenreder et al. (2011) found that slow thawing rates resulted in higher drip loss from beef subprimals independent of initial freezing rate. However, this difference did not affect the final eating quality of cooked steaks. Similarly, in a comparison of immersion (<2   h) or air thawing (24   h) of pork by Linares, Saavedra, Serrano, Les, and Sosa (2005), immersion thawing resulted in lower drip loss, 5.2% compared with 10.3% for slow frozen and 7.8% compared with 10.8% for fast frozen. Drip being the free liquid emerging from foods, especially meat and fish, during chilling, chilled storage, and especially after thawing and during subsequent storage. It is normally expressed as a percentage of the initial weight of the food item. However, James, Nair, and Bailey (1984) reported that thawing times from −7 to 0°C of less than 1   minutes or greater than 2000   minutes led to increased drip loss). The results are therefore conflicting and provide no useful design data for optimizing a thawing system. With fish, fruit, and vegetables, ice formation during freezing and frozen storage (Ostwald ripening) breaks up cell structure and fluids are released during thawing.

Fik and Macura (2001) suggested from their results that bread that underwent microwave thawing had generally better quality in comparison with air blast thawing at 50°C. Riihonen and Linko (1990) studied the effect of thawing conditions on the quality of mechanically deboned beef (MDB) and mechanically deboned pork (MDP). All samples were analyzed chemically and microbiologically immediately after thawing. Microwave thawing resulted in a better quality product (P<0.05) than thawing at 4 or 21°C. Different methods (air, immersion, microwave, and high-pressure) of thawing 2×2×2   cm3 cubes of hami melon were investigated by Xin, Rui, and Jin-Hong (2015). Less drip loss, textural damage, and discoloration were reported when 700   W of microwave power were used. Holzwarth, Korhummel, and Carle (2012) reported that maximum ascorbic acid retention was observed when strawberries were thawed in a microwave oven.

Although overall there does not appear to be a consensus on the effect of different thawing rates on the quality of the thawed product, it appears that microwave thawing may offer some advantages with some foods.

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Recent Development in Beverage Packaging Material and its Adaptation Strategy

Gargi Ghoshal , in Trends in Beverage Packaging, 2019

Bulk Packs

Since long fruit juices for industrial importance has been packed in an extensive range of drums. In classic drums made of open-head steel juice is packed inside a number of plastic bags. This type of packages are standard container used for frozen juices and usually hold approximately 200  L. Plastic drums without plastic liners are less affordable for frozen storage as the plastic has an affinity to become brittle and may break. Plastic drums have capacity of approximately 200–250   L, and for chemically preserved juices larger containers, for example, 'Rotoplas,' Israeli manufactured container of capacity 1300   L have been successfully used. Aseptic bulk packing for concentrated or RTD juice has now become a well-established means of packing with capacity as little as a 5   L up to a 1000   L bin in a 1-m3 pallet box. Finally, the transportation of fruit juice in shipping tankers at controlled temperature up to 25,000   L is well established for intercontinental transfer.

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Specific Features of Table Wine Production Technology

V.K. Joshi , ... P.S. Panesar , in Science and Technology of Fruit Wine Production, 2017

1 Introduction

Citrus is the most economically important tree fruit crop in the world. These fruits may be divided into three botanical species: Citrus sinensis, the common orange; Citrus nobilis, the mandarin group; and Citrus documana, the grapefruit (von Loesecke et al., 1936). Of these, orange is the most commonly grown citrus fruit in the world. In 2012, 68.2 million tons of oranges were grown worldwide, primarily in Brazil, the United States, China, and India (FAO, 2014 ). The majority of citrus arrives at market in the form of processed products, such as single-strength orange juice and frozen juice concentrate. One possible use of citrus fruits is in the production of fruit wines. Several classes of citrus fruits are available for the preparation of wine and other alcoholic beverages.

Wine is defined as an alcoholic beverage, which is produced by the fermentation of fresh grapes or must, and winemaking is one of the most ancient technologies and is now one of the most commercially prosperous biotechnological processes. Grapes and apples are the crops most widely grown for the production of juice for winemaking. Although grapes and apples are by far the most often used fruits, various other fruits such as oranges, kiwi, peaches, and plums may also be used to make wine. Increasing interest in human health, nutrition, and disease prevention has enlarged the consumer demand for functional food, including fruits and their products such as wine (Rupasinghea and Clegg, 2007). Additionally, the global food industry uses a variety of preservation and processing methods to extend the shelf life of fruits and vegetables so that they can be consumed year round and transported safely to consumers all over the world, not only those living near the growing region (Barret and Lloyd, 2012). Therefore, the utilization of ripe fruit or their juices for wine production is considered an attractive means of utilizing surplus and overripe fruit (Jagtap and Bapat, 2015).

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Microbial Safety of Nonalcoholic Beverages

C.S. Ranadheera , ... S. Ajlouni , in Safety Issues in Beverage Production, 2020

6.4.1.3 Listeria monocytogenes

Listeria is a Gram-positive, nonspore-forming bacterium. It is mobile by means of flagella and classified as psychrophilic, which can grow and multiply even at low temperatures (0–15°C). Listeria monocytogenes is a pathogen and presents rod-shaped cells, being microaerophilic and capable of multiplying at refrigeration temperatures. It causes the development of flu-like symptoms such as fever, headaches, vomiting, and nausea. In chronic cases, it is related to septicemia in pregnant women, fetuses or newborns, internal or external abscesses, meningitis, etc. L. monocytogenes has not yet been implicated in juice-related outbreaks, but it has been shown to be capable of long-term survival in various frozen juice concentrates ( Juvonen et al., 2011). The reason why there are no reports on listerioses (a ubiquitous pathogen) linked to the consumption of fruit or fresh juices, in contrast to the variety of outbreaks related to enteropathogens, is unclear (Tribst et al., 2009). However, Sado et al. (1998) did a microbiological survey of 50 retail juices in 1996 and observed that two unpasteurized juices were positive for L. monocytogenes: an apple juice and an apple raspberry blend with a pH of 3.78 and 3.75, respectively.

Sheela and Shrinithivihahshini (2017) evaluated milk and dairy products (n   =   415) from Tiruchirappalli city, Tamil Nadu, India, considering the incidence of L. monocytogenes. L. monocytogenes were isolated from 219 (52.7%) samples. Among the positive samples, the raw milk and flavored milk were 100% contaminated followed by branded milk (65.9%), cheese (62.5%), ice-cream (49.2%), milk powder (26.6%), milk sweets (20%), ghee and paneer (13.3%), and yoghurt (6.6%). Conversely, curd and butter were free from L. monocytogenes. The authors concluded that the milk and dairy products were vulnerable for L. monocytogenes and it is suggested to create awareness among people, especially elderly people and children, about this pathogen.

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Pitanga (Eugenia uniflora L.)

M. Vizzotto , ... A. Santos , in Postharvest Biology and Technology of Tropical and Subtropical Fruits: Mangosteen to White Sapote, 2011

Pitanga pulp

In general, the fruits destined for pulping should be of good edible quality and full flavor and be substantially more mature than fresh market fruit. Such fruit have softer tissues (which are more amenable to pulp extraction and generate a higher yield), higher sugar content, a deeper color and a lower acid content. However, overripe fruit is inappropriate as the flavor and acidity may suffer. Figure 13.1 shows the main steps for the production of pitanga frozen juice, which can then be processed at a later stage into pasteurized and concentrated pitanga juices.

Fig. 13.1. Main steps for the production of pitanga frozen juice, pitanga pasteurized and concentrated frozen juices.

The fruit are first sorted, washed and drained. The fruit are usually washed in a mechanical washer that combines immersion bathing for the removal of the sludge with an aspersion system (Tocchini et al, 1995). The fruit entering a processing operation are sorted to remove damaged fruit, diseased or rotten fruit. When performed improperly the contamination level can actually be increased during pulp and juice processing. Thus sanitation of equipment and water sanitation with chlorination is critical and the recovery of the sanitation solutions tube recycled have been pointed out as usually necessary (Soler et al., 1991).

The fruit is pulped to separate the edible pulp from the fibrous materials, seeds, peels, etc., and also, to reduce the size of the particles of the product, making it more homogeneous. Pitanga pulp extraction was studied using two depulpers: an inclined brush depulper and a horizontal blade depulper. The brush and blade depulpers presented yields of 58.47 ± 3.93% and 46.61 ± 1.80%, respectively, on pulping pitanga fruits. According to the sensory analyses, there was no significant difference for the attributes aroma and flavor between the pitanga nectars formulated with pulps obtained from the two depulpers. Therefore a brush depulper should be used rather than a blade depulper. Frozen pitanga pulp is commonly packaged for commercialization in the internal market in plastic bags in portions of 100, 200 and 400   g. If the pulp is to be used as a raw material in other industries, drums of 200   kg can be used.

The effects of process time and temperature during heat pasteurization on color (a*, b*) and enzyme activity of pitanga pulp was studied. The process was optimized from the more important responses in the experimental design: variation in a* color coordinate and decrease in pectinmethylesterase activity. The optimized time and temperature range for heat processing, obtained from the superposition of the response level curves, was between 59 and 68 seconds at about 90   °C.

The pulp can be clarified with specific enzymatic preparations that act on fibers and pectin making it less viscous and cloudy. Albumin, gelatin, casein or bentonite can also be used to improve pulp clarity. Figure 13.2 shows the main steps to produce a clarified pitanga pulp.

Fig. 13.2. Flow sheet of clarified pitanga juice.

The stability of pitanga pulp during frozen storage at −   18   °C was evaluated after different storage periods. By the sensory analysis, it was verified that pulp appearance changed significantly after 90 days of frozen storage. Thus there was a marked fall in the sensory acceptance of nectar formulated with pitanga pulp that had been stored for 90 days at −   18   °C and customers had a less positive attitude towards its purchase. Moreover, though pitanga pulp has good stability when stored under −   18   °C, the level of carotenoids decreases. This mainly happens during the first 30 days of storage; the level remains practically constant after this period (Lopes et al., 2005). Frozen storage has little effect on the pitanga anthocyanin content (Lima et al., 2005).

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Soft drink classification

L.Jagan Mohan Rao , K. Ramalakshmi , in Recent Trends in Soft Beverages, 2011

12.2 Ready-to-drink

This category of soft drinks is divided into carbonated and non-carbonated soft drinks. Non-carbonated drinks have shown considerable growth because of aseptic packaging, whereas carbonated beverages provide an effective antimicrobial effect because of the presence of CO2. Ready-to-drink soft drinks are also classified into following categories.

12.2.1 Fizzy drinks

This is made by injecting carbon dioxide into the drink at a pressure of several atmospheres. At high pressure large volumes of gas can be dissolved. As the pressure is released, carbon dioxide comes out of the solution forming numerous bubbles as being released back into the atmosphere. After the release of carbon dioxide, the drink is said to be flat. Carbonated drinks taste fizzy due to carbonic acid including a slight burning sensation and bubbles; both the phenomena are caused by carbonic acid concentration [11].

12.2.2 Natural juice

These drinks are prepared from processed fruits. These are formulated with plant-based formulations and nutrient content of fruit and vegetable juices. [12] . It includes all concentrated juices except frozen juice. Such drinks require dilution and sometimes powders for reconstitution in bottles, cans, and ready to drink or in jars. Some examples are lemon, orange and grapefruit juices.

12.2.3 Colas

Colas (Figure 12.1) are flavoured carbonated drinks, containing cherry flavour and twist of lemon. They are made essentially from an extract of cola nut and may contain caffeine.

Figure 12.1. Cola beverage

12.2.4 Fruit flavoured

These are with a sweet taste. The fruit flavours like strawberry and grape are abounding in sugar. Citrus-flavoured juices seem to be a mixture of sweet and tart; the people who like tangy drinks prefer these drinks.

12.2.5 Fruit-flavoured carbonates

These are carbonated drinks with typical fruit flavours. The fruit flavours used in this type of drinks are orange, cherry, lime, blackcurrant, apple, pineapple, lemon, grapefruit, tropical and other fruit flavours. Lemonade also belongs to this class.

12.2.6 Energy drinks

There are three basic types of energy drinks – refreshment, sports and functional.

(i)

Refreshment – These are formulated for someone whose energy levels rundown or is recovering from illness.

(ii)

Sports – These are formulated to replace fluids rapidly during exercise and also to maintain the body's blood glucose level. The top three global markets for sports drinks are North America 50%, Asia/Australia 41%, and Europe 8% [13].

(iii)

Functional – These are formulated for anyone who wants to gain alertness. The two important varieties are as follows: (1) energy supplements containing slow, medium and fast-acting sugars to supply energy, and (2) energy enhancers containing caffeine or taurine to boost alertness.

Company-wise contribution – energy drinks

Coca-Cola Company has launched a new sport drink named Powerade (low-calorie). The drink is a source of electrolytes and B complex vitamins at comparable levels. The Powerade is available in lemon, black cherry and strawberry flavours. Another energy drink launched by Coca-Cola is Von Dutch. Bravo has also come up as a new line of breakfast beverages, blended with fruits and flavours. Moreover these are fortified with naturally found antioxidants. Pepsi has launched a specialized sports drink, named Gatorade Endurance Formula, a blend of electrolytes such as Ca, Mg, Na and K with 65 carbohydrates. This comes in two flavours – orange and fruit punch. Cadbury Schweppes has re-launched 7Up as 7Up line, expanded with new flavours like cherry flavour, fruit juices and with added calcium.

Other energy drinks

Energy 69, LLC, New York, has launched a new beverage called Energy 69, (sugar free version) with ingredients such as taurine, guarana seeds, green tea leaf, caffeine, d-ribose, schizandra, L-carntine and damiana leaves. Glaceau, Whitestone, NY, has launched a vitamin water line-up, flavoured with lemon along with Ca, Mg, Na and K. Their function is to speed up hydration process. The drink is also rich in vitamin B and C. Natural Percepts, LLC, Los Angeles have launched the 'Yes' drink. The composition of the drink is 12 vitamins, 8 antioxidants, 10 fortified minerals, 70 trace minerals, 22 amino acids and other essential nutrients. Universal Food & Beverage Company has replaced its healthy drinks with its feed water selection. Frost 20 is a drink with no calories, sugar-free, vitamin enhanced and naturally flavoured. The flavours include lemon lime, mixed berry, peach and tropical fruits. Abbott Laboratories, Ohio, has launched a line of beverages including Healthy Mon snack bars and nutrition shakes specially designed for pregnant women. The lactose-free shakes contain 2   g proteins, 3   g fat with creamy milk chocolate and homemade vanilla varieties [14].

12.2.7 Mixed soft drinks

Soft drink made by mixing many soft drinks together is variously known as graveyard, pop bomb, swamp water and garbage soda. An example for mixed fruit juice is blending of ber, pomegranate and guava juice to get desired colour and flavour, which can not be obtained in their individual formulations [15].

12.2.8 Dry powder mix

These are designed to appeal to a number of consumers and for variable uses. These formulations are similar to liquid soft drinks except for water content. The compositions that differ in dry powder mix are flavours, clouding emulsions and fruit materials, which are spray dried and/or freeze dried. The long-term stability of dry powder mix is better than that of liquid drinks. These are found to be ideal for vitamin fortification because of their slow decay rate in the absence of water and air [16].

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Life experience and demographic variables influencing food preferences: the case of the US

R. Bell , in Understanding Consumers of Food Products, 2007

12.5.3 Future food trends: based on past trends or projected demographics?

The following are food preference trends in the US over the past 50   years. Most of the data are from the following sources (Day, 1996; Putnam and Allshouse, 1997; Hollman et al., 2000 ). The consumption of chicken and fish is increasing, while the consumption of beef is decreasing. Consumption of fresh and frozen foods is increasing, while cured foods are decreasing and canned foods remain stable. Frozen dairy consumption (ice cream and frozen yogurt) and cheese consumption are increasing, while animal fats and butter consumption is decreasing. But in general, all fat and oil consumption in increasing. Consumption of legumes is increasing, while flour and cereal products consumption is decreasing, perhaps owing to the recent wave of low-carbohydrate diets. Frozen juice consumption is increasing, while canned and chilled juices remain stable. Fresh fruits are slightly increasing, while processed fruits and total fruit consumption has remained stable. Vegetable intake has seen large increases recently, but consumption of potatoes is decreasing. And non-calorie sweets are increasing, while sugared sweets have been decreasing.

Total food consumption is decreasing, probably owing to the aging population, who require less total caloric intake in their diets. Eating out is increasing, while eating in is decreasing. Consumer spending at full-service and fast food restaurants will continue to grow over the remainder of this decade and the next. However, the larger increase is predicted to occur at full-service restaurants. Simulations assuming modest growth in household income plus expected demographic developments show that per capita spending could rise by 18% at full-service restaurants and by 6% for fast food between now and 2020. The assumed increase in income alone could cause such spending to rise by almost 15% and 7% at full-service and fast food restaurants, respectively. The increasing proportion of households containing a single person or multiple adults without live-at-home children will cause per person spending to rise by another 1 to 2% in each of these segments. However, the aging of the population will decrease spending on fast food by about 2% per capita (Stewart et al., 2004).

Rapid changes in nutrition recommendations by the USDA and other public health and medical sources have been conflicting, and messages have confused the population who want to eat for health. But it is likely that the concern for health has aided the organic food market to grow, and it will likely to continue to do so, even though the primary improvement provided by organic food is for the soil and adjacent crops, not for individual biochemistry, though organic eating is more advantageous for humans to eat, due to decreased frequency of exposure to pesticides.

So for health-conscious reasons, we tend to monitor our calories and fat intake during the main meal, but we save room for the high-fat, high-sugar (or alternate sweetener) dessert. This is reflected by the success of both types of foods in the marketplace. These are not always meant to satisfy one target market or another; but rather, the 'forbidden' foods are the reward for the calorie-restricting main course. Whether these preferences are a function of physiology, advertising, marketing, the explosion of brands, or psychology is unclear; but their presence is overwhelming, and could help explain how preferences and eating patterns change in the short term in response.

In contrast to the consumer buying behavior, attitudes, and demographic trends that lead to increases in food consumed away from home, the use of processed foods, and the movement toward larger supermarkets, there are some changes in local and national agriculture that could provide enough force to alter the inertia of existing larger forces. For example, the number of local farmers' markets has increased nationally (Johnson et al., 1996). This has been accompanied by a recent increased demand for fresh fruits and vegetables in the US, primarily due to the health conscious consumer and the growing obesity problem and associated diseases. The increase in 'green consumerism' – those who are concerned about the sustainability of the environment – has influenced the number of environmentally friendly products and locally grown products (Hartman, 1996). This has changed the nature of retail stores, many of whom now provide natural food sections and organic foods in their markets. Hartman and others indicate that these agricultural and green trends will likely continue, leading to a further 'fragmentation' of the food market into diverse segments. Due to their own economic demands, farmers are selling off their farmland, either getting out of the farming industry or dividing up land and selling it for housing developments. This has also been induced by larger market demands, in which commodities are bringing lower prices than they cost to produce.

Another example of the 'changing forces of change' is that in the last twenty years, Americans have purchased more salsa each year than catsup, reflecting a growing trend toward the widespread acceptance of international foods in the US diet. And one of the most interesting changes brought on by the faster pace of life and the need for convenience in food items is the increase in liquid food items, including caloric and non-caloric liquids, and most surprisingly, meal replacement drinks. Americans spend some $821   billion on food today, from supermarket produce to restaurant meals to snack foods at vending machines. The US Department of Agriculture reports this figure will grow to $1.2   trillion over the next decade. Much of that growth will be hard earned by the food industry.

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PASSION FRUITS

D.B. Rodriguez-Amaya , in Encyclopedia of Food Sciences and Nutrition (Second Edition), 2003

Production, Utilization, and Processing

Reliable and updated production statistics on passion fruits are not available. Although it is one of the better known so-called exotic fruits, it has not reached the point of being one of the fruits for which production is monitored by FAO. The major producing countries, listed in decreasing order of area of production in 1987, are: Brazil, Peru, Sri Lanka, Ecuador, Australia, Kenya, South Africa, Venezuela, Papua-New Guinea, Fiji, New Zealand and the USA (Hawaii). These countries account for 80–90% of the world's production of passion fruit. Taiwan and Colombia have been markedly increasing production, a good part of which is destined for export. Commercialization of the fresh fruit is limited, with Kenya being the principal exporter to Europe, especially to the UK. It is estimated that 50% of the world's production of passion fruit juice is exported. Brazil, Peru, and Colombia are the principal exporters of the juice, the major importers being the UK, Germany, France, Switzerland, the USA, and Japan.

After cutting the fruit in half, the pulp and seeds can be scooped with a spoon and eaten as is, or the pulp can be sieved to make a refreshing drink. Because of its intense flavor and high acidity, the passion fruit juice is considered a natural concentrate and is often diluted, sweetened, or blended with other fruit juices. The whole or sieved pulp is also used as a flavoring for yogurt, icecream, sherbet, meringue, or cake topping.

In Australia, there is appreciable consumption of the fresh fruit, although the bulk of passion fruit production is processed into juice, consumed locally as carbonated beverages. The juice is also used as a flavoring for icecream, confectioneries, and tropical fruit salads. Australian consumers are used to eating and drinking passion fruit products with the seeds still present, the seeds being regarded as evidence of passion fruit content. Elsewhere, the seeds must be removed.

Production of passion fruit in Fiji and Papua-New Guinea is largely for export to Australia and New Zealand as frozen, unsweetened pulp or juice. A significant part of production in Fiji is also consumed in homes and restaurants as mixed drinks. Passion fruit products in Sri Lanka include jams and sweetened and unsweetened juices. In India, this fruit is processed into passion fruit squash.

Most of the passion fruit produced in Hawaii is consumed as drinks blended with other fruit juices, such as orange and/or guava, the remainder being used as frozen juice bases. Passion fruit juice is considered too acidic for icecream, but this characteristic is advantageous in the preparation of sherbet. Minor uses are as a flavoring for syrups and as a pie filling.

The principal passion fruit products in Brazilian market are the juice and the frozen pulp, these two products serving as the base for other products such as drinks, yogurt, icecream, confectioneries (cakes, meringues, and chocolate fillings), gelatin, marmalades, and fruit cocktails. Fresh fruits are also marketed. In Venezuela, popular products include passion fruit juice, passion fruit icecream, and a bottled passion fruit and rum cocktail.

Passion fruits are preserved by freezing or thermal processing. Two characteristics of this fruit favor freezing. Firstly, the flavor is extremely sensitive to heat, so it is difficult to heat-process the juice without markedly altering the flavor. Secondly, the high starch content causes the accumulation of gelatinous deposits on the heating surfaces of the heat exchanger, lowering its efficiency, as well as causing deterioration of juice flavor. Enzymatic degradation of starch and centrifugal procedures for removing starch have been recommended.

Production of passion fruit juice can be done manually, as in many small cottage industries, consisting simply of hand-slicing the fruit, scooping out the pulp, and separating out the seeds either through sieving or expression through a cloth.

In Hawaii, the processing of passion fruit is highly mechanized, a centrifugal separator being the favored method for extraction of the pulp. A typical extractor has a capacity of 1725   kg   h−1 of passion fruit with an extraction efficiency of 94%. Its main disadvantages are: (1) some seeds are cut in the slicing operation, which necessitates the use of a fine screen in the finishing operation; and (2) there may be some extraction of skin flavors.

In Australia, the converging cone extractor is the most commonly employed extractor. In another method, a modified apricot-pitting machine and plunger are used. Since Australians are accustomed to consuming passion fruit products with the seeds, further processing to remove the seeds from the pulp is not necessary. Elsewhere, consumers' preference for seedless passion fruit products necessitates further processing.

The extraction unit most commonly utilized in Brazil is a three-stage system, consisting of a cutter, a perforated cylinder with a series of beaters that separates the rind from the pulp and seeds, and a pulper that separates the juice from the seeds and does the finishing of the juice.

Much of the earlier canned passion fruit juice was considerably overcooked. More recent processes make use of slightly higher temperature and shorter heating times. The most successful method for thermal processing of the juice employs a spin cooker. This cooker is an inexpensive, easily constructed unit, utilizing rapid can rotation to transfer heat quickly. Pasteurization to an 88   °C center temperature is achieved in about 1 3 4 min, after which the cans are rapidly cooled with a cold water spray while still rotating. The color and flavor retention in this method is much better than in any alternative method of heat preservation.

To concentrate passion fruit juice, centrifugal evaporators have been successfully used in Brazil and Australia. The main advantage is the short residence time (0.2–1.0   s), which minimizes heat damage. Passion fruit concentrate can be stored at −18   °C for 6 months, 4   °C for 3 months, and 20   °C for 1 month with good color and flavor retention and no microbial spoilage.

Passion fruit juice may be quick-frozen directly from the finisher. Preferably, a slush-type or scraped-surface freezer should be used to hasten the freezing process, aside from increasing the freezing capacity of the processing plant. The juice may also be frozen directly in containers in an air-blast freezer. This product is sold to manufacturers of juice blends and of foods with passion fruit as an ingredient or as a major flavor component.

According to folk medicine, passion fruit has sedative and muscle-relaxant properties. Medicinal utilization of the leaves has also been cited.

In the extraction of juice from the passion fruit, about two-thirds of the bulk is refuse, of which 90% is rind and about 10% is seeds. Passion fruit rind has been found to be satisfactory as a supplementing feedstuff for dairy cows, and so it is commercially utilized as feed for dairy animals in Hawaii. In Brazil, the passion fruit rind is used as a component of rations for cattle and hogs. Other possible uses of subproducts, such as pectin from the rind and oil from the seeds, have not reached the industrial scale.

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Effect of withering process on the evolution of phenolic acids in winegrapes: A systematic review

Giulia Scalzini , ... Luca Rolle , in Trends in Food Science & Technology, 2021

3.4 The case of icewines: a discussed topic

The evolution of phenolic acid content during the production of icewines is a peculiar and often discussed topic. The first study on this issue was conducted by Kilmartin et al. (2007) on the polyphenol composition of Canadian icewines to identify the quality markers of authentic icewines. For example, "Faux" Riesling and Vidal icewines (harvested above −8 °C) had up to 11- and 21-times higher concentrations of total HCAs than those of "Real" icewines (harvested at temperatures of −8 °C or below). These findings agree with those reported by Tian, Li, et al. (2009) who introduced a further kind of "Faux" icewine for cultivar Vidal: a refrigerator-frozen juice, artificially refrigerated at −8 °C, and a concentrated juice made using rotary evaporation at 66 °C. The artificially concentrated juice presented a concentration of phenolic acids 2.1-times higher than that of the refrigerator-frozen juice, and notably, approximately 3.6-times higher than that of naturally frozen juice. These differences were quite preserved in the icewine types produced from them, with little influence from the yeast strain used. Furthermore, the influence of the harvest date on the phenolic acid content of icewines was discussed by the same authors. Kilmartin et al. (2007) pointed out that the earliest harvest dates produced icewines with higher concentrations of HCAs in Riesling and Vidal winegrapes harvested in Canada in 1999, 2000, and 2002, while Tian, Pan, et al. (2009) argued that the contents of HBAs and HCAs increased as grape harvest time was delayed to produce icewines from the Vidal variety harvested in China in 2005 and 2006. With regard to the considerations previously made on the influence of withering conditions, it should be recalled that the traditional icewine production technique is an on-vine withering process and is thus subjected to changes due to weather conditions (e.g., freeze-thaw cycles) that could markedly affect the balance of phenolic acids in the berries.

Avizcuri-Inac et al. (2018) focused their efforts on the chemical and sensorial characterization of sweet wines to understand the influence of the dehydration process on the features of several wines made from on-vine withered grapes. The authors analyzed sweet wines obtained by using different varieties and techniques and classified them into three clusters based on the phenolic compound characteristics. The first cluster, characterized by the highest contents of HBAs, HCAs, and other phenolic compounds, such as flavonols, included a late harvest wine and a natural icewine (both involving Tempranillo red grapes). The second cluster, with intermediate amounts of phenolic compounds, included two natural icewines (one from white and one from red grapes), one artificial icewine (from Tempranillo red grapes), and a supurao wine (from Tempranillo and Grenache off-vine dehydrated red grapes). The third cluster, which was described by the lowest values of phenolic compounds, particularly for HBAs, included four icewines obtained by grape freezing in the chamber, three produced from white grapes and one from red grapes. Although these findings could have been influenced by variety, environmental and technological factors (such as grape pressing), they show that the extraction and concentration of these compounds produced by freezing winegrapes were lower than those in wines belonging to the other two clusters, produced with more traditional techniques. The concentration of phenolic acids has been associated with the quality and authenticity of icewines (Kilmartin et al., 2007; Tang et al., 2013; Tian, Li, et al., 2009, Tian, Pan, et al., 2009). However, new studies are needed to better understand the link between weather conditions and phenolic acid features in the production of these special wines. This alternative approach can be challenging and technically difficult, but will have very useful practical applications, such as a more focused choice of the harvest period.

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https://www.sciencedirect.com/science/article/pii/S0924224421004908