AU643607B2 - Non-freeze fruit products - Google Patents

Description

Our Ref: 426086 643607 P/00/011 Regulation 3:2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT

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55 S. See.

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g e Applicant(s): Address for Service: Invention Title: Byron Agricultural Company Pty Ltd 19A Boundary Street RUSHCUTTERS BAY NSW 2011

AUSTRALIA

DAVIES COLLISON CAVE Patent Trade Mark Attorneys Level 10, 10 Barrack Street SYDNEY NSW 2000 Non-freeze fruit products

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The following statement is a full description of this invention, including the best method of performing it known to me:- 5020 0371c:DB 1 NON-FREEZE FRUIT PRODUCTS Fruits are regarded as a highly desirable food, both from a nutritional and an organoleptic viewpoint. Most fruits are seasonal, many with quite short periods of availability. Distribution of various types of fruits depends to a large extent on lattitude. Tropical fruits are not readily available in temperate and cold climates, and temperate and cold-climate fruits are not readily available in tropical areas.

The preservation of fruits represents a large industry. Common methods of preservation include canning, freezing, sun drying, freeze-drying and hot air drying.

The canned fruit industry is an extensive one and most fruits lend themselves to canning. The main disadvantages of canned fruits is their high cost of production, bulky nature, and associated high freight costs. Canned fruits are not very convenient for industrial use since can size is severely limited and cans are becoming increasingly more expensive.

Dried fruits, such as apple, pear, apricot, peach, cherry etc. are shelf-stable products, which, for storage at S ambient temperatures, must be dried to moisture contents of 17% (or lower) to 23%. The drying of fruits to these low moisture levels requires long dehydration periods, often in the order of 16 to 24 hours. During this long period of dehydration, the sugars in the fruits become partially caramelized, the natural aroma of the fruit is lost and the colour darkens. The retention of colour during 'dehydration and storage can be maintained to some extent by the addition of sulphur dioxide or sulphites to the fruits, but this in itself adds a "sulphur" flavour, the use of sulphur dioxide is becoming unacceptable and the demand for additive-free fruit products is increasingly important.

Dried fruits, darken appreciably on storage, tend to be tough and leathery to eat and have flavours that differ substantially from that of fresh fruits.

Frozen fruits are common articles of commerce, but have 0371c:DB 2 not developed into a major consumer group of products mainly because frozen fruits are slow to thaw and, because of production of ice crystals in the fruit on freezing, there is substantial "drip" from the fruit on thawing. The tissues, as a result of the ice crystal damage, become mushy, and unattractive to eat unless consumed in a semi-frozen state.

A substantial market for fruits is in products such as yoghurts and ice creams. Up to the present time, fruit of, satisfactory quality for use in this type of product is not readily available. Canned fruits tend to be too soft and "mushy" for use in yoghurts, they are bulky to store and inconvenient to use since the cans have to be opened and the contents drained. They cannot be satisfactorily used in frozen desserts such as ice cream because the fruit pieces freeze hard and are therefore objectionable.

*Frozen fruits are likewise unsuitable for ice creams because they are too hard. In yoghurt they lack flavour intensity, have to be thawed for use with subsequent drip, are not sweet enough and are generally less than satisfactory.

Conventional dried frui.ts can be used in yoghurt, but are unattractive in colour and lack distinctive flavours.

The presence of sulphur dioxide in the fruit can have a disadvantage for the reason that sulphur dioxide can be a deliterious effect on the yoghurt organisms. If used in ice do's cream, the fruit pieces become excessively hard and lack *:of natural flavour.

Some fruit products are known which are regarded as satisfactory for use in ice creams and similar products.

The patents of Kahn et al Patents, 4,332,824, 4,356,195, 4,418,082, 4,350,711, 4,390,550 and 4,551,384) describe the production of fruits and fruit products which are impregnated with sugar solution (where 50% of it sugars are in the form of dextrose or fructose). The fruits are produced by a form of osmotic dehydration, and are steeped in increasingly concentrated sugar solutions. These 0371c:DB 3 products will not freeze at normal freezer temperatures of 0°C to 25 0 C, however steeping causes loss of fruit flavour and acid and the products are excessively sweet. Moreover the products tend to be expensive since considerable wastage of sugar solutions occurs.

Other fruit products have been described whereby partial dehydration of fruits is followed by hard freezing as disclosed in U.S. Patent of Jakobsson et al 4,647,469, but in these cases, no attempt is made to produce a product wA 1 ±ch is resistant to becoming hard when frozen.

Lewis and Lewis (Australian Patent No. 575,198) have described a process for the production of shelf-stable high moisture fruits. This process requires the use of low levels of sulphur dioxide in many fruits to avoid discolouration on storage and the p:oducts need to be held in an oxygen free atmosphere. There is now a universal consumer resistance to the use of even low levels of sulphur dioxide in all foods.

The present invention has for its object the provision of a natural edible fruit product without added sugars, which will not freeze at -20 0 C. Such a product can be added to yoghurts, ice creams, frozen desserts etc. without itself freezing so that it is soft to eat. This is surprising in the light of the teaching in the mentioned prior art which requires the addition of substantial amounts of sugars to achieve a non-freeze product. The products of the present invention have a high intensity of natural fruit flavour, a quality which is important particularly in the ice cream industry where intensely flavoured products are necessary to produce an acceptable flavour impact required by industry.

.The invention is applicable to all types of edible fruits.

dehydration in appropriate ways.

The invention in its broadest form comprises a A S 0371c:DB ready-to-eat preserved edible fruit product comprising natural fruit or fruit pieces which have been dehydrated to a soluble solids level of 40% 60%, a moisture level of 55% and a water activity level of 0.75 0.90, said product having no water activity controlling solutes added thereto and remaining unfrozen at temperatures with the range of -0°C to -25 0

C.

The invention also relates to a process for preparing a preserved ready-to-eat edible fruit product of the type referred to.

A water activity (a w) us defined as a ratio aw P/po where p is the partial pressure of water vapour in the test material and po is the saturation vapour pressure of pure water under the same conditions. Water activity is numrrically equal to equilibrum relative humidity (ERH) expressed as a decimal.

Larger fruits such as apples, pears, mangoes, cantaloupes peaches and pineapples are peeled and cut into pieces of the required size. Fruit such as some apple varieties that discolour due to the presence of polyphenol oxidases may be blanched after preparation for a short period before dehydration. However it has been found that even with fruits such as apples, a very short steam blanch just sufficient to inactivate enzymes at the surface of the fruit is sufficient to prevent browning during dehydration.

Inactivation of enzymes within the body of apple pieces then occurs during the heating which occurs during the dehydration process. This minimal blanch has negligible effect on leaching of solutes from the fruit piece and on the texture of the processed fruit. Other diced or cut fruits are fed directly onto the belt or tray of a dehydrator. Fruits such as seedless grapes, prunes, blueberries, raspberries and cherries, may be fed directly to the dehydrator. In some instances, treatment of the skins with steam, hot water or alkali may be desirable to aid in removing the waxy coating on the skin.

p U 0 .4 0371c:DB -4a- The fruits are dehydrated to a soluble solids content of to 60%, depending on the nature of the fruits. Dehydration may be carried out in any form of dryer such as a through-bed or cross-flow hot air dryer, vacuumr drying, a reverse-cycle (electric dehumidifier heat pump) dryer or any combination of these. In the initial stages of drying, temperature up to 100°C may be used, though the preferred *e It i *r U 00 0*I

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*p 0 0371c:DB 5 temperature in a hot air dryer is 60'C 70*C. In a reverse-cycle or vacuum dryer, temperatures will be considerably lower, preferably 409 50°C. As the fruit dries, the temperature may be decreased to avoid scorching.

If a hot air dryer is used, when most of the water intended to be removed has been removed and the drying rate becomes slower, the latter stages may be carried out in a vacuum or reverse cycle dryer at temperatures of about 45°C, but this is not essential. In general, a 45 55% soluble solids content is preferable. The end-point of the process can readily be determined by taking refractometer, moisture, or water activity readings. After drying to the required soluble solids content, the fruit is cooled, packaged and placed in the freezer either immediately or after an equilibration period of, for example, 24 hours.

After dehydration, the water activity of the fruit will have been reduced to a level 0.75 0.9 at which it will not readily spoil. If, therefore, the temperature of the I0.. product rises above O0C for short periods during storage or transport, the product is not materially affected, and it is a not subject to damage due to freezing and thawing as is 0 usual with frozen foods. However if the product is held for extended periods at temperatures above freezing, slow spoilage by microorganisms and colour deterioration may occur. Accordingly, such products are quite different from the well known-dried fruits of conmmerce.

In the dehydration of fruits, the initial loss of moisture is relatively rapid. The drying of fruits to 0.0 moisture content takes approximately 25% of the time it takes to dry the same product to 20% moisture. Furthermore, as the solutes in the fruit become more concentrated with .0 dehydration the more rapidly do chemical and physical changes occur. In the dehydration of fruits to the traditional levels of about 20% or lower, most of the undesirable flavour and colour changes occur when the moisture level decreases below about In ice creams and frozen desserts, it is usual for the 0371c:DB 6 pieces of fruit used to be of a size no larger than 10mm x We have found to dehydrate pre-diced or otherwise prepared pieces of fruit of this approximate volume or size to the solute content such that they do not freeze, may require as little as approximately 60 minutes at 70°C in a dehydrator with good air flow. This makes the process very economical in terms of energy usage and plant capacity.

Since no ice is produced when the dehydrated fruits are placed in the freezer at normal freezer temperatures, the energy used to reduce the fruit to the temperature of the freezer is very low. Because the volume has been decreased substantially to about 25% to 12% of the original fruit volume, freezer storage costs and transport costs are greatly reduced. This is particularly important where long distance or international shipment is necessary.

The processed product can be consumed directly out of the freezer; it is quite soft to bite and has a good mouth feel. Since dehydration time is very short, the natural fruit flavour is retained in quality, and its concentration is increased two to five fold as is the sugar content. This Se ee S* makes such products ideal for their intended use and superior to any alternative processed fruit. Essentially no solutes are lost from the fruit during the process and no solute is added. It has not been found necessary to add sulphur dioxide or sulphites, and the shelf-life in the freezer at -20*C has been found to be over two years.

While these products have been developed for use in oe 5 frozen confections and for eating out of hand, they can as 0'"0 stated be used in any other way that natural or preserved fruits are used. They are excellent when used in fruit yoghurts, in pies, in cakes, Danish pastries, fruit jellies S etc. Because they are partially dehydrated, they retain their shape and texture. If placed in water, light syrups, or yoghurt they rehydrate rapidly and take on the appearance, flavour, and texture of fresh fruit pieces. For addition to some products such as ice cream and yoghurts, some manufacturers require a pasteurized fruit piece. This 0371c:DB 7 may be readily achieved with the fruit prepared by this process, for example, by heating to the required temperature in a minimal quantity of light syrup. During this pasteurization process, the syrup used as the heating medium can be almost totally absorbed by the fruit pieces.

The term "freeze" as used herein is meant to convey as state where ice and/or solute crystals are formed in a product making it hard and/or brittle.

Example 1.

Apples of the Golden Delicious variety were peeled, diced into pieces approximately 20mm x 10mm and steam blanched for 1 1/2 minutes. The blanched dice had soluble solids as measured by refractometer of 13%. The dice were dried in a through-bed hot air dryer with rapid air .flow for minutes at 100C. The temperature was reduced to and the dice dried to a soluble solids content of 50%. This O involved a weight loss of approximately 74%. The drying was complete in about 65 minutes. The final moisture content of the apple pieces was 43% and the water activity was 0.86.

OSeO The apple pieces were allowed to stand for 2 hours and were then placed in a freezer at -20°C. After storage for twelve months at -20'C, the apples had not deteriorated in colour and were not frozen. They could be readily eaten directly out of the freezer.

Some apple dice were taken out of the freezer and added to full cream yoghurt. After standing in the yoghurt for 24 hours at 40C, the apple pieces had absorbed moisture from the yoghurt and had a fresh taste and crisp texture much superior to commercial apple yoghurt prepared from canned apple dice.

Example 2 Pineapples of the rough-leaf variety were peeled, cored and cut into segments approximately 10mm thick and wide. The pineapple pieces had a soluble solids content of 17%. The pieces were dried in a hot air dryer at 70*C for minutes, and were then transferred to a reverse-cycle (dehermidifier heat-pump type) dryer at 45*C for a further 0371c:DB 8 minutes, by which time the soluble solids content was The moisture content was 48% and the water activity 0.90. The fruit pieces were a bright yellow colour, had a fresh aroma and typical pineapple flavour. They were placed in a freezer at -20 0 C. After storage for 9 months, the fruit pieces were not frozen and were sufficiently tender to be eaten directly out of the freezer. No apparent deterioration in flavour or colour had occurred.

Pieces of pineapple were mixed with soft frozen ice cream and the mixture placed in the freezer at -20'C and stored for 7 days. On consumption, the pineapple pieces were soft to eat and had an intense pineapple flavour.

Example 3 Sour cherries of the North Star variety were pitted and placed in a hot air dryer. The soluble solids content of the cherries was 17%. They were dried to a soluble solids content of 55%. Drying time was 2 1/2 hours. After drying the cherries had a moisture content of 43% and a water activity of 0.87. They had a typical cherry-red colour and intense cherry flavour. They were placed in the freezer at -20"C and stored for 12 months. The cherries did not freeze and no apparent deterioration had occurred.

The stored cherries were used to prepare yogiurt and ice cream as in examples 1 and 2, and also used to prepare a fruit jelly. For the fruit jelly the cherries were simmered in apple juice for 5 minutes, and some pre-moistened gelatine was added and dissolved. The jelly was put aside Oki* r to cool and then chilled to set. The set jelly contained plump cherries with excellent colour and flavour.

Example 4 Pears of the "Williams" variety were peeled, cored and cut into halves. The pear halves were blanched in steam for two minutes. The soluble solids content of the blanched halves was 14%. The halves were dried in hot air on trays at 70*C until the soluble solids was 55%. Dehydration time was 4 1/2 hours. The water activity of the resultant pears was 0.77 and the moisture content 39.7%. The pears had a 037 lc:DB -9bright yellowish colour and an intense typical pear flavour. The pear halves were placed in the freezer at After 7 months storage, no apparent deterioration had occurred.

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Claims (8)

1. A ready-to-eat preserved edible fruit product comprising natural fruit or fruit pieces which have been dehydrated to a soluble solids level of 40% 60%, a moisture level of 35% 55% and a water activity level of 0.75 0.90, said product having no water activity controlling solutes added thereto and remaining unfrozen at temperatures with the range of O'C to

2. N ready-to-eat preserved edible fruit product as claimed in claim 1 wherein the natural fruit or fruit pieces have been blanched prior to dehydration.

3. A ready-to-eat preserved edible fruit product as claimed in claim 1, said product having been cooled and packaged prior to being stored in a freezer.

4. A ready-to-eat preserved edible fruit product as claimed in claim 3 wherein said product has been held for an equilibriation period of 24 hours prior to being placed in said freezer.

5. A process of preparing a preserved ready-to-eat edible fruit product which comprises dehydrating natural fruit or fruit pieces to a soluble solids level of 40% 60%, a moisture level of 35% 55% and a water activity level of 0.75 0.90, said product having no water activity controlling solutes added thereto and remaining unfrozen at temperatures within the range of 0°C to

6. A process as claimed in claim 5 wherein the fruit or fruit pieces are blanched prior to dehydration.

7. A process as claimed in claim 5 wherein said product is cooled and packaged prior to being stored in a freezer.

8. A process as claimed in claim 7 wherein said product is held for an equilibration period of 24 hours prior to being placed in said freezer. DATED this 1st day of April, 1992. BYRON AGRICULTURAL COMPANY PTY LTD By Its Patent Attorneys DAVIES COLLISON CAVE 0371c:DB ABSTRACT The invention relates to a ready-to-eat preserved edible fruit product formed of natural fruit or fruit pieces and having no water activity controlling solutes added thereto. The fruit or fruit pieces being deydrated to a soluble solids level of 40% to 60% and a water activity level of 0.75 0.90 and remaining pliable and unfrozen at temperatures within the range of O'C to 4 4 up S, Se 0• 9 4 0 0 M* 0 9