Fruit and vegetable dried food product

Fruits and vegetables can be vacuum dried to produce a crispy but yet tender puffed food products having a color and appearance of the original fruit or vegetable prior to processing. Enzymatic browning and reducing sugar browning is counteracted by the treatment of the fruit or vegetable in an infusion solution that contains at least one reducing acid and a proton donor to counteract enzymatic browning and a disaccharide to counteract reducing sugar browning. In addition the infusion solution can contain chelating agents and antimicrobial agents. In addition the fruit or vegetable can undergo a freeze-thaw tenderizing process which will also enhance the puffing of the fruit or vegetable. The product is a puffed and crisp but yet has a smooth texture when being consumed.

BACKGROUND OF THE INVENTION 
This invention relates to dried fruit and vegetable products which also 
have a puffed consistency. This invention further relates to a process for 
making fruit and vegetable dried products which have a puffed consistency, 
are crispy but yet tender, and which further are not susceptible to 
browning or other discoloration during processing or thereafter. 
Various techniques have been used over the years to produce dried fruits 
and vegetables. One such technique is air drying. In such techniques the 
fruits and vegetables are washed and then laid out exposed to air and sun 
to dry. After being dried to the ambient moisture level the dried fruits 
and vegetables can be contacted with antimicrobial and preservative agents 
and then packaged. In another technique the fruit or vegetable is dried by 
being exposed to heated currents of air. In such processes the fruits and 
vegetables would be washed and then placed in a chamber whereby a heated 
air at a set relative humidity is passed through the chamber at a given 
flow rate. Depending on the temperature and the humidity of the heated air 
the fruits and vegetables can be dried to a moisture level of as low as 
about 10 percent by weight of moisture. However such processes do not 
produce a puffed dried product. Rather, what is produced in most instances 
is a product that due to shrinkage is hard and chewy. In addition such 
products have a rough rather than a smooth texture when being consumed. 
Such drying processes that are conducted at atmospheric pressure also have 
a limitation with regard to how much moisture they can remove from the 
fruits and vegetables. Generally, such processes can reduce the moisture 
level of fruits and vegetables down to about 10 percent by weight to about 
45 percent by weight moisture. This limitation is due to many factors. One 
factor is that during the dehydrating process it is desired to keep the 
temperature of the fruits and vegetables below about 70.degree. C. If the 
fruits and vegetables are maintained at above about 70.degree. C. for any 
extended periods of time the sugars in the fruits and vegetables invert 
and change thereby changing the flavor of the fruits and vegetables 
undergoing drying. 
It has been recognized in the art that in order to achieve very low 
moisture levels for dried fruits and vegetables that vacuum techniques 
would have to be used. In vacuum drying techniques the fruits and 
vegetables can first be air dried or dehydrated to a reduced level using a 
heated air stream. At this point the dried fruits and vegetables have a 
moisture level of about 10 percent by weight to about 45 percent by 
weight. The dehydrated fruit can then be vacuum fried or vacuum dried. 
Additionally while the fruits and vegetables are being exposed to the 
vacuum conditions heat can be applied to drive more moisture from the 
fruits and vegetables that are being dried. After being dried to the 
desired level the fruits and vegetables can then be packaged. 
In vacuum frying the fruit or vegetable is placed in an edible oil and a 
vacuum drawn while the oil is heated. The hot oil serves as a medium to 
heat and remove the water in the fruits or vegetables. Vacuum frying 
techniques can reduce the water content of a fruit or vegetable to less 
than about 5 percent by weight. The end product is a hard, crispy piece of 
fruit or vegetable. However, this product will contain a residual amount 
of oil that can be up to about 30 percent by weight of the fruit or 
vegetable. 
In order to further increase the drying speed of the vacuum processes the 
items to be dried can be cut into smaller pieces, or in the alternative 
macerated to a puree. This provides for increased drying speed since there 
is an increased surface area to volume. A dehydrated fruit or vegetable 
that has undergone at least part of the dehydrating treatment under vacuum 
conditions can also be produced in a puffed form. One method to induce 
puffing of the fruit or vegetable is to have a step of rapidly reducing 
the pressure on the fruit or vegetable to cause the contained water to 
rapidly vaporize and create a puffed product as it escapes from the fruit 
or vegetable. Since these fruits and vegetables are usually dried in an 
oil the pores of these puffed fruits and vegetables are impregnated with 
the oil. 
In addition, regardless of the type of vacuum drying that is used, there 
remains the problem that there is a discoloration of the fruits and 
vegetables during this processing. This discoloration is usually a 
browning of the surface of the fruits and vegetables. It is believed that 
this browning is the result of two different natural processes that are 
occurring. One is enzymatic browning. For instance, polyphenoloxidase 
causes browning in apples and peaches. The other is non-enzymatic browning 
resulting from the usually high level of fructose and other 
monosaccharides in these fruits and vegetables. Browning also affects the 
nutritional and flavor properties of the dehydrated fruits and vegetables. 
In addition, it does result in a very unattractive color for the fruits 
and vegetables and would lead one to believe that the dehydrated fruits 
and vegetables are spoiled, or in the alternative that the dehydrated 
fruits and vegetables were made from spoiled fruits and vegetables. The 
net result is that the consumer would not want to purchase and consume 
this type of a product. Therefore, it is a primary objective of this 
invention to set forth a process for producing puffed dried fruits and 
vegetables which retain their natural color. It is a further object of the 
present invention to set forth a technique whereby sliced fruits and 
vegetables can be preserved from undergoing enzymatic browning or 
non-enzymatic browning prior to or after undergoing subsequent processing 
to form the puffed products and during storage. 
The present discoveries are directed to a technique for making puffed 
fruits and vegetables that retain the color and taste of the original 
fruit or vegetable. The puffed fruit or vegetable is crispy, but yet 
tender and has a smooth texture when being consumed. In addition it does 
not contain any oil or equivalent substances since it is not produced by a 
vacuum frying technique. Rather it is produced through a vacuum drying 
step to produce the puffed consistency of the product. The vacuum drying 
can be preceded by an air drying. In addition the fruit or vegetable will 
undergo an infusion solution treatment to prevent discoloration. Further 
the product can be tenderized and the amount of puffing in the final fruit 
or vegetable product increased through a freeze-thaw step prior to the 
vacuum drying of the fruit or vegetable to tenderize. The net result is 
the ability to produce a crispy, puffed fruit or vegetable snack product 
that has the original fruit or vegetable color and which does not contain 
any oils within the pores of the fruit or vegetable. 
Various U.S. patents disclose techniques for drying fruits and vegetables 
using vacuum drying and vacuum frying techniques. In U.S. Pat. No. 
1,543,948 wafers or cakes of a fruit are introduced into a vacuum drying 
apparatus where the temperature is maintained at 70.degree. C. and the 
drying continued at a reduced pressure until the desired moisture level is 
reached. Usually the drying requires from six to eight hours. After vacuum 
drying the dried wafers or cakes are packed in a paper carton to prevent 
the loss of crispness through the adsorption of moisture from the 
atmosphere. Figs, raisins, and prunes can be dried using this technique. 
U.S. Pat. No. 2,023,536 discloses a process for the vacuum drying of fruit. 
In this process a dehydrated fruit which can be in the form of a cake is 
placed within a vacuum chamber and a vacuum drawn. In addition, heat is 
applied to the vacuum chamber in order to raise the temperature of the 
fruit up to about 72.degree. C. After being dried, it can be further 
treated or can be packaged. The dried product is substantially crisp and 
dry. 
U.S. Pat. No. 2,110,184 discloses a process for puffing a fruit as well as 
dehydrating a fruit. In the disclosed process after an initial drying 
period, and during a second drying period, the vacuum chamber is subjected 
to a momentary increase in pressure followed by a sudden reduction in 
pressure and restoration of the former drying conditions. The result is 
that the fruit being dried will be puffed as a result of the moisture that 
is vaporized during the rapid reduction of the pressure. The escaping 
vaporous moisture puffs the fruit. After the puffed fruit has reached the 
desired low moisture level the temperature is reduced and air is then 
introduced into the vacuum chamber. Both procedures are conducted in order 
not to collapse the fragile porous structure of the puffed fruit. 
U.S. Pat. No. 2,283,302 discloses the method of vacuum frying foods whereby 
a fluid is used in the vacuum chamber in order to apply heat to the foods 
that are undergoing drying. The objective in this patent is to evenly 
apply heat to the foods being dehydrated. In this process the food being 
dehydrated is immersed in an edible fat, ethyl alcohol, glycerin or other 
medium. It is possible to puff the food being dried in this process by 
raising the temperature of the liquid medium and to thereby cause an 
increase in the rate of the evaporation of moisture from the food. 
U.S. Pat. No. 2,587,939 is directed to a vacuum frying process similar to 
that of U.S. Pat. No. 2,283,302. However, in this process it is disclosed 
that in a final step the dehydrated food can be restored to atmospheric 
pressure in the presence of the liquid used as the medium to heat the food 
or in the presence of a liquid exchanged for that used during drying. The 
result is a food product wherein the puffed structure is impregnated with 
a liquid. 
U.S. Pat. No. 2,712,698 is related to the vacuum frying processes of the 
foregoing two patents and is directed to a method of removing the retained 
liquid heating medium from the pores of the dried fruit. That is, even 
when there is an attempt to remove all of the liquid in which the food has 
been vacuum dried, there will remain residues of the heated liquid in the 
dried food product. This is preferably removed by using low vapor pressure 
hydrocarbons, ethers, and halocarbons to extract the remaining liquid 
heating medium. The objective is to produce a purer product. 
The problem of fruit and vegetable discoloration has also been addressed. 
In U.S. Pat. No. 1,842,720 there is disclosed a technique of treating 
fruits and vegetables with a solution containing sulfurous acid and/or a 
salt that will yield sulfurous acid. The solution should also contain some 
hydrogen peroxide which will react with sodium acid sulfite to change it 
to sulfate. 
In U.S. Pat. No. 3,305,366 there is disclosed a process for preserving the 
color of fresh fruits by contacting the fruits with a solution containing 
pyrophosphoric acid and an alkali sulfite or bisulfite. This method for 
preserving fruits is shown to be superior to treatment with solutions 
containing ascorbic acid or citric acid. 
U.S. Pat. No. 3,754,938 discloses a technique for preserving apple slices 
using a solution consisting of ascorbic acid, calcium chloride and sodium 
bicarbonate. The sodium bicarbonate is added to maintain a pH of 7 to 9 
during treatment. When this treating solution is used a sulfiting 
treatment does not have to be used. 
U.S. Pat. No. 3,894,157 discloses a method for stabilizing the color of 
freeze-dried carrots using ascorbic acid or erythrobic acid. These acids 
are noted to be antioxidants. An aqueous solution containing one of these 
acids is sprayed onto the carrots. When ascorbic acid is the acid, the 
ascorbic acid is in a concentration of about 1 to 3 percent of the 
solution. The carrots are then freeze-dried. 
U.S. Pat. No. 3,987,208 discloses a process for extending the storage life 
of cut lettuce. This consists of treating the lettuce leaves with an 
aqueous solution of sodium meta bisulfite, citric acid, ascorbic acid, and 
potassium sorbate. Any excess solution is drained from the lettuce. The 
lettuce is then placed in bags that have a low gaseous transmission rate. 
This treatment increases the shelf life of the lettuce. 
U.S. Pat. No. 4,011,348 discloses the treatment of raw fruits and 
vegetables with an aqueous solution having a pH between about 4 and 7.5 
and containing a selected ascorbate ion concentration. The ascorbate is 
sodium ascorbate and ascorbic acid. However, it is directed that ascorbic 
acid should not be used alone. It results in an excessively low pH. 
U.S. Pat. No. 4,504,504 discloses a technique for preserving the texture of 
diced fresh foods through the use of gelled polyuronic acids. This is 
stated to be superior to the use of citric acid or calcium chloride in 
preserving dried fresh food products. 
U.S. Pat. No. 4,650,686 discloses a method for reducing excessive browning 
in a baked good containing reducing sugars. This is accomplished by adding 
to the dough baking soda and fatty acid monoglyceride esters of 
polycarboxylic acids. The agents minimize reducing sugar browning during 
the baking process. 
In addition to these patents an article titled "Controlling Storage and 
Processing Conditions Helps Produce Light Colored Chips From Sweet 
Potatoes" from Food Product Development, May 1977, discloses that color 
development in sweet potatoes being formed into sweet potato chips is also 
an ongoing problem. The recognized problem is that potatoes, such as the 
Irish sweet potato, will undergo a darkening discoloration while being 
processed into potato chips. The result would be a darkened potato chip 
after frying. The conclusions reached in this article are that an 
acceptably colored chip can be produced from potatoes stored for 48 hours 
at 23.degree. C. and then dipped in a solution containing 100 ppm sulfur 
dioxide. The dipped potato chips are then fried. If a lighter colored 
fried potato chip is desired the strength of the sulfur dioxide solution 
should be increased. Although a dip in a sulfur dioxide containing 
solution is preferred a water dip also has an influence on chip color. 
Sulfur dioxide is a known preservative for various fruits and vegetables. 
Sulfur dioxide will also prevent a product from discoloring. It is used as 
a fruit or vegetable pretreatment in many vacuum frying processes. 
However, it is an additive to which some people are allergic. As a result, 
the use of sulfur dioxide to preserve food products is decreasing. 
With regard to tenderizing fruits and vegetables U.S. Pat. No. 3,535,126 
discloses a method of increasing the permeability of cellular foodstuff 
materials. The method consists of subjecting the foodstuff to a pressure 
of greater than about 50 p.s.i.g. while freezing the foodstuff. The 
pressure is released after the foodstuff is frozen. The resulting product 
is more permeable and yet the cell walls are still intact. 
U.S. Pat. No. 3,792,184 discloses a technique for removing precipitating 
substances from plant extracts by a freezing and thawing process. Plant 
extracts such as extracts from cocoa powder or cinnamon powder contain 
undesirable precipitating substances such as proteins. These can be 
removed by freezing the extract and then raising the temperature of the 
extract to thaw the extract. Any precipitates are then easily removed by 
filtering or centrifuging the extract. Apparently this freeze-thaw 
processing coagulates these precipitating substances. 
U.S. Pat. No. 4,495,205 discloses a process for making a meat analog 
product. In the process pasteurized vegetable protein is heated in an 
aqueous medium to remove volatiles. The heating is followed by a freezing 
step wherein the structure of the texturized vegetable protein is 
disrupted and its water binding capacity decreased. The frozen texturized 
vegetable product is then thawed and combined with a binder. This is then 
formed into a loaf and frozen. Freezing aids in activating the binder. The 
frozen product is then thawed and cooked. 
In addition to these patents which discuss the freezing and/or thawing of 
substances, the book "The Freezing Preservation of Foods" by Donald K. 
Tressler and Clifford F. Evers, The Avi Publishing Co. New York 1947 
discusses on pages 256 to 259 the changes caused in foods by freezing. 
Included is a discussion of the effect on the cell walls of foods from a 
freezing and thawing cycle. 
BRIEF SUMMARY OF THE INVENTION 
Fruits and vegetables can be made into puffed food products through a 
process of vacuum drying at an elevated temperature. The fruit or 
vegetable can first be air dried and then vacuum dried. The vacuum is 
maintained on the vacuum dried fruit or vegetable until the temperatures 
has been reduced to a level where the puffed structure is stable. The 
puffed dried fruit or vegetable product is crispy and tender but yet has a 
smooth texture when consumed. 
Prior to drying the fruits or vegetables can undergo the steps of 
tenderizing and/or discoloration inhibition. Tenderizing consists of 
freezing and thawing the fruit or vegetable. It is preferred to slowly 
freeze the fruit or vegetable so as to create larger ice crystals within 
the fruit or vegetable. Fast freezing produces smaller ice crystals which 
do not tenderize and puff as effectively. The larger ice crystals rupture 
more cell walls which aid to increase the porosity of the fruit or 
vegetable. This tenderizes the fruit or vegetable. The rate of drying will 
also be increased. The step of freezing and thawing can be conducted as a 
first step after the fruits and vegetables have been prepared by washing, 
peeling and coring and/or pitting as needed; after the steps of treatment 
with an infusion solution to prevent discoloration; or after the fruit or 
vegetable has been partially dried, for example, after the step of air 
drying. 
The fruits and vegetables are inhibited from discoloring by browning during 
drying and other processing if the fruits and vegetables are contacted 
with an aqueous infusion solution formulated to counteract enzymatic 
browning and non-enzymatic browning. The fruit or vegetables may also be 
blanched either in hot water, steam or other food grade liquid in order to 
deactivate the enzymes prior to contact with the infusion solution. The 
fruits and vegetables will be contacted with the infusion solution after 
they have been cut into the desired sized pieces. Discoloration, such as 
browning, occurs after the inner flesh of the fruit or vegetable is 
exposed to the atmosphere. The infusion solution is an aqueous solution 
which will in most instances contain at least one reducing acid preferably 
selected from the group consisting of erythrobic acid, ascorbic acid and 
sulfurous acid, a proton, donor material which is preferably an acid, and 
can be a reducing acid, a disaccharide, a chelating agent, and an 
antimicrobial agent. The primary ingredients are the reducing acid, the 
proton donor material and the disaccharide. A chelating agent is present 
when the fruit or vegetable contains metal ions that must be removed or is 
in contact with metal surfaces during processing. Antimicrobial agents are 
a part of the composition to inhibit the growth of microorganisms upon 
removal from the infusion solution through the subsequent air and vacuum 
drying stages. The fruit or vegetable pieces are maintained in the 
infusion solution for a period of time of about 0.1 hours to about 10 
hours. The temperature of the infusion solution is maintained at below 
about 80.degree. C., and preferably between about 10.degree. C. to 
75.degree. C. After infusion the fruit or vegetable pieces are dried at 
atmospheric pressure to reduce the moisture content to about 10 percent to 
45 percent by weight. A temperature of about 30.degree. C. to about 
80.degree. C., and preferably about 35.degree. C. to 75.degree. C., is 
utilized in this drying. After the fruit or vegetable pieces have been 
dried to the desired level they are vacuum dried to a moisture content 
level of less than about 10 weight percent, preferably less than about 5 
weight percent, and most preferably less than about 3 weight percent. The 
end product is a puffed, crispy and very tender piece of fruit or 
vegetable. The product is hygroscopic so after removal from the vacuum 
chamber it is packaged in a moisture impermeable container. 
The process of vacuum drying is monitored by determining the temperature 
difference between the oven or tray on which the fruit or vegetable 
material has been placed and the temperature of the fruit or vegetable 
that is undergoing drying. When the fruit or vegetable is within about 
5.degree. C., and preferably within about 3.degree. C. of the temperature 
of the tray or oven a moisture content of less than about 5 weight 
percent, and usually less than about 3 weight percent has been reached. 
The fruit or vegetable product is then cooled to less than about 
40.degree. C., and preferably to less than about 30.degree. C., and the 
vacuum is released. The fruit or vegetable at atmospheric pressure is then 
packaged. 
DETAILED DESCRIPTION OF THE INVENTION 
Dried fruits and vegetables are very nutritious foods. However, besides 
being nutritious they must be appetizing in appearance. The dried fruits 
and vegetables must substantially retain their color after having 
undergone the drying process. One problem that arises is that when most 
fruits and vegetables are cut, they almost immediately start to undergo 
enzymatic browning and/or non-enzymatic browning. For example, enzymatic 
browning is caused by polyphenoloxidase in apples and peaches and exposure 
to the air. Other enzymes affect other fruits and vegetables. 
Non-enzymatic browning is the result of Maillard reactions which are 
reactions between monosaccharides such as glucose and fructose with 
proteins or carmelization caused by heating. Browning is quite evident 
when apples, peaches, pears, and similar fruits are cut into pieces. When 
an apple is sliced the newly exposed surfaces rapidly develop a brownish 
color. After a short period of time the newly exposed surfaces of the 
apple are very distinctly brown. 
The problem in producing dried fruits and vegetables, and particularly 
dried fruits and vegetables having a moisture content of less than about 
10 percent by weight, and preferably less than about 5 percent by weight, 
and most preferably less than about 3 percent by weight, is that during 
the extended drying periods the fruit or vegetable in the cut form will be 
exposed to atmospheric conditions for periods of time when browning can 
occur. If no precautions are taken the result will be fruit and vegetable 
products that will not be appealing to the consumer. It has been found 
that enzymatic browning and non-enzymatic browning can be countered 
through the use of particular aqueous infusion solutions. The fruit or 
vegetable after being cut is placed into the infusion solution for a 
period of about 0.1 to 10 hours. Prior to treatment in the infusion 
solution the fruit or vegetable can be blanched in a hot water solution or 
other food grade liquid at about 70.degree. C. to 100.degree. C. or 
through contacting with steam prior to being treated with the infusion 
solution. Blanching is completed within about 2 to 4 minutes. The 
temperature of the infusion solution is maintained at less than about 
80.degree. C. and preferably between about 10.degree. C. to 75.degree. C. 
The infusion solution is an aqueous solution that contains substances to 
counteract both enzymatic browning and non-enzymatic browning. 
All of the components of the infusion solution are necessary for most 
fruits and vegetables in order to effectively combat browning. Even if a 
fruit or vegetable does not have a high native metal ion content, it will 
pick up metal ions from the processing equipment. These metal ions should 
be removed. In addition, an antimicrobial agent should be added as a means 
to extend the processing time and shelf life of the dried fruit or 
vegetable. Consequently, in most all instances the infusion solution will 
contain all of the described components. 
Non-enzymatic browning is counteracted as a result of the infusion solution 
containing disaccharides. Most preferably the infusion solution should 
contain a nonreducing disaccharide, and in particular sucrose. The 
function of the disaccharide, is to exchange with a portion of the 
fructose and other monosaccharides of the fruit or vegetable. The 
substantial removal of fructose and other monosaccharides removes one of 
the reactants needed for a Maillard reaction to occur. In the Maillard 
reaction a reducing monosaccharide reacts with a protein. It is preferred 
that the disaccharide that is exchanged for the monosaccharide be the 
non-reducing disaccharide, sucrose. However, reducing disaccharides such a 
maltose, cellobiose and lactose can be used since the rate of hydrolysis 
is such that any significant browning will not occur. The disaccharide is 
present in the infusion solution an amount ranging from about 0.5 percent 
by weight up to 60 percent by weight, and preferably about 5 percent by 
weight to about 50 percent by weight. The exact amount used will depend on 
the reducing sugar content of the fruit or vegetable. While pineapple will 
require a disaccharide content of about 25 to 45 percent by weight, onion 
will require a level of less than about 5 percent by weight and in most 
cases less than about 1 percent by weight. 
Enzymatic browning is counteracted by incorporating into the infusion 
solution an edible reducing acid an edible proton donor material which is 
usually a non-reducing acid. The preferred reducing acids are erythrobic 
acid, ascorbic acid and sulfurous acid, or a salt or other compound that 
will yield sulfurous acid. For the purposes of this application these 
substances will be termed sulfurous acid. The preferred proton donor 
materials are citric acid, lactic acid, malic acid, acetic acid and 
phosphoric acid. When erythrobic acid is used as the reducing acid, can be 
added to function as the proton donor acid, ascorbic acid material. The 
reducing acid will be present in an amount of about 0.1 percent by weight 
to about 2.5 percent by weight, and preferably about 0.25 percent by 
weight to about 1.5 percent by weight of the infusion solution. The proton 
donor material will be present in an amount of about 0.25 percent by 
weight to about 3.0 percent by weight, and preferably about 0.5 weight 
percent to about 2.0 percent by weight of the infusion solution. The exact 
amounts to be used will depend on the fruit or vegetable that is being 
treated. While one fruit or vegetable is more susceptible to nonenzymatic 
browning, another may be more susceptible to enzymatic browning. This will 
have a direct impact on the exact composition of the infusion solution. 
The infusion solution will usually also contain a food grade chelating 
agent. The chelating agent binds up the metal ions on the fruit and 
vegetable surfaces. These metal ions may be naturally present in the fruit 
or picked up by the fruit or vegetable through contact with metal surfaces 
during processing. Any food grade chelating agents can be used. Suitable 
chelating agents are citric acid, phosphoric acid and food grade salts of 
ethylenediaminetetraacetic acid (EDTA). The chelating agent when present, 
is added in an amount of about 0.1 percent by weight to about 0.5 percent 
by weight, and preferably 0.2 percent by weight to about 0.4 percent by 
weight of the infusion solution. The exact amount to be added will depend 
on the metal ion content of the fruit or vegetable undergoing treatment. 
If there is a negligible metal ion content, and metal processing equipment 
is not to be used, the chelating agent need not be used. 
The pH value of the infusion solution will be from about 1.5 to about 4.0. 
The exact pH value will depend on the fruit or vegetable undergoing 
processing. The pH of the fruit or vegetable pieces after having undergone 
a treatment in the infusion solution will range from about 2.5 to about 
4.5. Again, the exact pH will depend on the particular fruit or vegetable 
that is undergoing processing. 
The infusion solution can also contain other additives. Such additives 
include antimicrobial agents. Antimicrobial agents will inhibit the growth 
of microorganisms in the infusion solution and during the drying sequence. 
Suitable antimicrobial agents are sodium benzoate, potassium sorbate and 
alkyl parabens. These are added to the infusion solution in a minor 
amount, usually in a content of about 0.01 percent by weight to about 0.5 
percent by weight when they are used in the infusion solution. 
Prior to or after treatment with the infusion solution to prevent 
discoloration the fruits or vegetables can undergo a tenderizing process. 
This can also be conducted after the fruit or vegetable has been partially 
dried. The tenderizing process consists of freezing and thawing the fruit 
or vegetable. The fruit or vegetable can either be fast or slow frozen, 
however, it is preferred that a technique be used that will create ice 
crystals suitable for a proper texture. For example, large ice crystals 
will rupture more of the cell walls of the fruit or vegetable thus 
creating a more tender product. Slow freezing will create large ice 
crystals as will a process of freezing, increasing the temperature but 
still keeping the fruit or vegetable frozen, and then decreasing the 
temperature of the fruit or vegetable. The cycling of the temperature has 
the effect of increasing ice crystal size. A temperature of from about 
-3.degree. C. to -20.degree. C. or lower is sufficient for freezing the 
fruit or vegetable. The fruit or vegetable should be subjected to this 
temperature for at least about 0.1 hour and for preferably at least about 
0.5 to twenty hours. The fruit or vegetable can be subjected to one or 
more freeze-thaw sequences for the purpose of tenderizing. 
The fruit or vegetable can also be fast frozen by blast freezing or 
cryogenic freezing. In blast freezing a cold air stream at below about 
-20.degree. C. is passed over and around the fruits or vegetables. This 
quick freezes the fruits or vegetables. In cryogenic freezing a cryogenic 
fluid such as liquid nitrogen is used to cool a chamber to a low 
temperature. This in turn cools the fruits or vegetables. However in the 
quick freezing techniques the ice crystals formed in the fruits and 
vegetables are smaller with fewer cell walls being ruptured. 
As noted above the freeze-thaw tenderizing process can also be conducted 
after the fruit or vegetable has been at least partially dried. 
Consequently the fruit or vegetable can be partially dried and then 
subjected to the freeze-thaw sequence to tenderize the fruit or vegetable. 
By conducting the freeze-thaw sequence after the fruit or vegetable has 
been at least partially dried the amount of the cell wall disruption and 
thus the degree of tenderizing can be controlled. 
After treatment in the infusion solution, and a freeze-thaw tenderizing 
sequence if this step is to be a part of the process, the fruit or 
vegetable is dried at atmospheric pressure to a water content of about 10 
weight percent to about 60 weight percent and preferably about 15 weight 
percent to about 45 weight percent. This drying will usually be conducted 
in an air drying chamber using a stream of heated air at about 30.degree. 
C. to about 80.degree. C., and preferably about 35.degree. C. to about 
75.degree. C. The fruit or vegetable is resting on trays. Drying in most 
instances will be completed within a period of about 1 to 10 hours, and 
usually about 2 to 6 hours. 
During air drying the temperature of the tray and the internal temperature 
of the fruit or vegetable are both monitored. This air drying can be 
conducted in the vacuum chamber with the vacuum chamber maintained at 
atmospheric pressure. After the fruit or vegetable is placed within the 
chamber for air drying the chamber is heated to a temperature of about 
35.degree. C. to about 70.degree. C. and maintained at atmospheric 
pressure. Initially there is a large temperature difference between the 
fruit or vegetable and the temperature of the tray or oven. The fruit or 
vegetable is maintained in the drying chamber at atmospheric pressure 
until the temperature difference has been reduced to less than about 
10.degree. C. and preferably to less than about 4.degree. C. The fruit or 
vegetable is then placed under a vacuum. If the vacuum chamber is being 
used as the air drying chamber then the vacuum chamber need only be 
evacuated. The temperature of the vacuum chamber is maintained at about 
50.degree. C. to about 125.degree. C. during vacuum drying. When the 
chamber is evacuated the result is that the internal temperature of the 
fruit or vegetable undergoing drying decreases rapidly. This is the result 
of heat of vaporization cooling. A vacuum of about 5 to 28 inches of 
mercury is maintained during the drying. When the temperature difference 
between the temperature of the oven or tray and the internal temperature 
of the fruit or vegetable narrows to less than about 5.degree. C., and 
preferably less than about 3.degree. C. the vacuum chamber is cooled to 
less than about 40.degree. C. and preferably less than about 30.degree. C. 
and the vacuum chamber then equilibrated to atmospheric pressure. The 
dried fruit or vegetable product is then removed from the vacuum chamber 
and packaged. The product as it comes from the vacuum chamber is in a 
puffed porous condition as well as being of a crispy consistency. However, 
although being crunchy, the product is very tender. The moisture content 
of this product is less than about 5 percent by weight and usually to less 
than about 3 percent by weight. 
Although it would not be practiced very often, it is possible for the fruit 
or vegetable to forgo the infusion treatment step and to solely use the 
tenderizing step in order to produce the crisp but yet tender puffed 
product. This would not be done very often since almost all fruits and 
vegetables undergo some form of browning. However vegetables that can be 
so processed are onions and carrots. This is particularly the case if the 
onion has been fermented for up to 6 hours in order to remove some of the 
pungent characteristics. A step of infusion solution treatment would not 
be required for onion. However at least one freeze-thaw sequence is 
necessary in order to produce a puffed tender product. 
The attractiveness of this product is that although it has a crispy texture 
it is quite tender due to the puffy porous structure of the dried fruit or 
vegetable. The fruit or vegetable product due to the infusion solution 
treatment step has substantially retained the color of the original fruit 
or vegetable and has also retained its taste. 
Flavorants can be added to the fruit or vegetable at essentially any time 
during the processing. However, flavorants if they are to be added, would 
usually be added at a point prior to the start of the drying steps or 
during the drying step. 
Essentially, any fruit or vegetable be treated in present process. These 
include, but are not limited to, apples, bananas, pineapples, peaches, 
pears, plums, grapes, apricots, nectarines, strawberries, carrots, squash, 
onions, potatoes, tomatoes, celery, and peppers. The type of processing 
that a particular fruit or vegetable will undergo can be tailored to that 
specific fruit or vegetable. For instance while carrots and onions should 
undergo freeze-thaw tenderizing processing this is not necessary for most 
fruits. As a further example it is not necessary that onions, which must 
undergo the tenderizing process, to undergo infusion solution processing. 
The reason is that onions are not susceptible to discoloration. However, 
most fruits and vegetables will undergo both tenderizing and infusion 
solution processing prior to vacuum drying. The tenderizing processing 
will result in a more tender product that has a smooth texture while being 
consumed while treatment with the infusion solution will preserve the 
color, and to a large degree the flavor of the fruit or vegetable. 
The foregoing invention will be described with particular reference to the 
following examples.

EXAMPLE 1 
This example illustrates the making of a dried puffed pineapple chips. 
Fresh pineapples are washed, trimmed peeled, cored and sliced. The sliced 
pineapple is then immersed in an infusion solution having the following 
composition: 
sucrose - 30 percent by weight 
erythrobic acid - 0.24 percent by weight 
citric acid - 0.24 percent by weight 
water - 69.52 percent by weight 
The pineapple slices are immersed in this solution at room temperature for 
about 2 hours. The ratio of soaking solution to fruit by volume is 2 to 1. 
After soaking the fruit slices are drained and placed in a single layer 
onto trays and are slowly frozen for 8 to 12 hours. The freezing 
temperature is -7.degree. C. to -12.degree. C. Subsequent to freezing 
whereby the pineapple slices are frozen throughout, the fruit slices are 
thawed and contacted with a current of air at 66.degree. C. until the 
fruit reaches a moisture content of about 15 to 20 weight percent 
moisture. This will occur in about 2 to 3 hours. After air drying the 
pineapple slices are transferred to a vacuum dryer. The pineapple slices 
are maintained at 66.degree. C. and a vacuum of 28 inches of mercury. The 
pineapple slices are dried until the moisture content is less than 2.5 
percent by weight. This requires about 3 to 4 hours. The dried pineapple 
slices are then cooled to less than 40.degree. C. and the sliced pineapple 
brought to atmospheric pressure. The resulting product is a crispy, puffed 
pineapple which has retained the original pineapple color and taste. 
EXAMPLE 2 
This example illustrates the making of a dried puffed peach chips. 
Fresh peaches are washed, pitted and sliced to a thickness of about 0.3 
centimeters. The sliced peaches are then immersed in an infusion solution 
having the following composition: 
sucrose - 38 percent by weight 
erythrobic acid - 0.4 percent by weight 
citric acid - 0.4 percent by weight 
water - 61.2 percent by weight 
The peach slices are immersed in the infusion solution for 15 minutes at 
54.degree. C. The ratio by volume of the infusion solution to sliced 
peaches is 2 to 1. 
After soaking in the immersion solution the peaches are drained and placed 
on trays in a single layer and slowly frozen at a temperature of 
-7.degree. C. to -12.degree. C. Freezing is completed in about 8 to 12 
hours. Subsequent to freezing the sliced peaches are thawed and air dried 
to a moisture content of about 10 to 20 percent by weight. Air drying is 
conducted at a temperature of 66.degree. C. After air drying the peach 
slices are placed in a vacuum drying chamber and a vacuum of 28 inches of 
mercury is drawn on the chamber. The oven is maintained at 66.degree. C. 
during vacuum drying. Vacuum drying is complete upon the peach slices 
reaching a moisture content of less than 2.5 percent by weight. The dried 
peach slices are then cooled to less than 40.degree. C. and peach slices 
brought to atmospheric pressure. The resulting product has a puffed 
structure but yet is crispy. The dried peach slices have maintained their 
color and taste. 
EXAMPLE 3 
This example illustrates the making of dried puffed carrot chips. 
The carrots are washed, trimmed, peeled and sliced to a thickness of about 
0.3 centimeters. The carrot pieces are then immersed in an infusion 
solution having the following composition: 
sucrose - 20 percent by weight 
erythrobic acid - 0.2 percent by weight 
citric acid - 0.2 percent by weight 
water - 79.6 percent by weight 
The carrot slices are immersed in this solution for 10 minutes at 
88.degree. C. The ratio of soaking solution by volume to the sliced fruit 
is 2:1. 
After soaking in the immersion solution the carrot slices are drained and 
placed in single layers on trays. The carrot slices are then slowly frozen 
at -7.degree. C. to -12.degree. C. Freezing is completed in about 6 to 8 
hours. The carrot slices are then thawed and placed in a vacuum dryer and 
dried at 74.degree. C. and 28 inches of mercury. Vacuum drying is complete 
upon the carrots reaching a moisture level of less than about 2.5 percent 
by weight. Vacuum drying is completed in about 6 to 8 hours. The dried 
carrot slices are cooled to less than 40.degree. C. and the sliced carrots 
brought to atmospheric pressure. The carrot pieces are crispy, but yet 
have a tender, puffed consistency. 
EXAMPLE 4 
This example illustrates the making of puffed onion chips. 
The onions are peeled of their outer protective skins and cut into pieces 
of approximately 2 inches by 1 inch. The onion pieces are then fermented 
for up to 6 hours at 32.degree. C. After fermentation the onion pieces are 
air dried at 49.degree. C. to a moisture level of 40 to 60 percent. This 
is accomplished in about 2 hours. The air dried onion pieces are then 
frozen at a temperature of less than -7.degree. C. until the onion pieces 
have been completely frozen. The onion pieces are then thawed at 
atmospheric pressure and placed in a vacuum chamber for vacuum drying. The 
initial temperature of the vacuum dryer is 115.degree. C. This is the tray 
temperature. The onion temperature is 82.degree. C. The onion pieces are 
held at this temperature for about 35 minutes. A vacuum of 28 inches of 
mercury is drawn on the chamber and drying is complete when the moisture 
content of the onion pieces is less than 2.5 percent by weight. The onion 
pieces now n the form of chips are then cooled under vacuum to about 
21.degree. C. and the vacuum in the chamber is released. The dried onion 
chips are packaged as is or they are flavored, such as with sour cream, 
cheese or some other flavorant. The onion chips are crisp but yet have a 
puffed, tender consistency.