Process for producing fruit extracts

A process for producing concentrated fruit extracts from raw fruit is described. The raw fruit, which may be whole or chopped into bits and at various states of ripeness, is mixed with water and the wetted fruit placed in a pressurized heating container such as an autoclave, where the fruit is heated at a predetermined temperature and pressurized at a predetermined pressure for a predetermined period of time so as to extract the fruit. The extracted fruit is then fed to a separator device which separates the extract from the fruit residue. The extract is then concentrated under vacuum to provide a concentrated fruit extract while the residue is discarded.

FIELD OF THE INVENTION 
The present invention relates to a new process for producing concentrated 
juices of fruit extracts, so-called fruit extracts such as prune extract 
obtained by extracting plums and concentrating the resulting extract. 
More particularly, it relates to a process for producing fruit extracts 
wherein a heating step for extraction is followed by a concentration step 
to obtain the extracts. 
BACKGROUND OF THE INVENTION 
Heretofore, various processes for producing so-called fruit extracts have 
been developed and employed, wherein fruits are heated for extraction in 
the presence of added water to give an extract, which is then concentrated 
into a juice. 
For example, prune extract obtained by extracting plums, particularly dry 
plums as raw material, and concentrating the resulting extract, has 
recently been widely marketed and consumed. 
Most of the prior art processes for producing prune extract and the like 
have been generally carried out by first adding water to fruits as the raw 
material, and cooking this material at atmospheric pressure, and 
subsequently concentrating the resulting extract; or as a variation of the 
above process, by continuously feeding steam into fruits dipped in water 
so as to cook such fruits to thereby obtain a concentrated extract. 
However, with such various conventional processes, the time required for 
the extracting treatment often exceeds several hours and is often of the 
order of 9 hours. Thus, they have a disadvantage of a very high energy 
cost. Further, they have the drawback of inefficiency in that with such a 
long processing time, greater attention from operating personnel is 
required. Moreover, they have the additional drawback in that treatment 
without any cover, i.e. so-called open type treatment, usually employed 
for operational efficiency, causes the hazard of the unhygienic mixing of 
extraneous matter into the resulting product. 
In the case of fruit extracts, it is desired that the extracts be made into 
a pasty juice through the modification of pectin contained in the fruits 
as raw material. Also, for increasing the yield and further shortening the 
extraction time and thereby reducing the energy cost, means for removing 
seeds, etc. in advance is inherently desired. This however inevitably 
injures the fruit. As a result, undesirably, the extraction of pectin in 
view of the injury to the fruit is too rapid and the resulting extract 
jellifies and forms an extract having a considerably inferior quality to 
that of the above-mentioned desired product. 
The reason for the above undesirable results is that in case of the 
injured, so-called diced or flaked fruits, their sarcocarp contacts 
directly with the extraction liquid and the pectin substance readily 
jellifies in the form of sugar and acid. 
Thus, not only the use of the above-mentioned diced or flaked fruits as raw 
material, but also uninjured fruits, or socalled "whole" fruit, fails to 
help the situation, and hence there is an inherent drawback in the prior 
art of a high cost with respect to all types of raw material. Moreover, 
there is a problem raised with unripe whole fruit. In case of "unripe 
whole" fruit, unlike the case of "ripe whole" fruit, pectin is yet in the 
form of protopectin, which combines with calcium and minerals to form a 
salt, which is integrated with cellulose to maintain a hardness in the 
form of cells. Thus, there is the danger that in the above-mentioned 
treatment in hot water, the pectin modification will be insufficient to 
make the viscosity higher in the form of sugars and acids whereby a jelly 
is formed. Accordingly, the use of overripe whole fruit wherein pectin has 
been modified into pectinic acid which is water-insoluble and stable, is 
desirable. However, in dealing with raw material, it is nearly impossible 
to detect the degree of ripeness of whole fruit, or to screen overripe 
whole fruit from unripe whole fruit, and even if this may be possible, 
there occurs a disadvantage in that a high-level screening apparatus is 
required, resulting in a high cost. 
In addition, although ripe fruits contain mainly pectin, they have a 
disadvantage in that they jellify as well by virtue of the water-soluble 
property of pectin. 
SUMMARY OF THE INVENTION 
A first object of the present invention is to provide a new process for 
producing fruit extracts, having overcome the above-mentioned various 
drawbacks of the prior art. 
A second object of the present invention is to apply heating under pressure 
onto raw fruit which has heretofore been tabooed in the art and contrary 
to conventional approaches, thereby providing a new process for producing 
fruit extracts wherein raw fruit material, irrespective of the extent of 
the degree of wholeness, amount of dicing and degree of ripeness thereof, 
is dipped in water to add such water thereto, and heated under pressure in 
an autoclave to extract the fruit and also carry out the pectin 
modification in an effective manner, and thereafter the resulting extract 
is separated from the resulting fruit residue and concentrated, e.g. in 
vacuo, to obtain a fruit extract. 
Further, a third object of the present invention is to provide a new 
process for producing fruit extracts wherein water is again added to the 
fruit residue separated in the above process, followed by heating under 
pressure in an autoclave and separation of the resulting extract from the 
resulting fruit residue as in the above process, and this extract is 
combined with the extract obtained in the above process and concentrated 
together to give a yield (percentage attainment) of substantially 100%.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The present invention will be mentioned below in detail referring to 
embodiments and the accompanying drawing. 
As mentioned above, pectin contained in fruits is present in various types, 
depending on their degree of ripeness and the condition of the fruit, i.e. 
whole, flaked, diced, etc. Protopectin contained in unripe fruits combines 
with calcium and minerals and further combines with cellulose to be 
integrated therewith. As a result, it is converted into pectin in hot 
water and becomes insoluble and jellifies. 
Pectin contained in ripe fruits is also water-insoluble and becomes a cause 
of jellification. Further, in case of flaked fruit too, pectin substance 
through the contact of the sarcocarp of fruits with the extraction liquid 
becomes a cause of jellification. 
However, due to the heating under pressure in the presence of added water, 
the above-mentioned pectin is rapidly hydrolized and a pectin modification 
occurs rapidly to form water-insoluble pectinic acid, which together with 
the pectinic acid of overripe whole fruit forms a stabilized pasty 
extract. 
As for the apparatus for the above-mentioned heating under pressure in the 
presence of added water, it is possible to employ a conventional autoclave 
which is generally in use. 
Next, as an embodiment based upon the above-mentioned theory, a process for 
producing prune extract having an improved yield will be described, 
wherein dry plum having a water content of about 20% is employed as raw 
material. 
Referring to FIG. 1, dry plum 1 as raw material in a given amount, e.g. 500 
g, is passed through a water-washing step 2 as a pretreatment; the 
resulting washed dry plum 1 is dipped in a hot water W at 80.degree. C. in 
an amount of 3 times the volume of the dry plum 1 (step 3), where it is 
brought into a water-containing state for promoting its hydrolysis; and 
the resulting contents are introduced into a conventional autoclave 4 in 
which they are subjected to an action of steam heating under pressure, 
i.e. under 2 atmospheric pressure, at 121.degree. C. and for 60 minutes to 
carry out pectin modification and extraction of fruits into extract. 
In the above-mentioned step of heating under pressure, pectin modification 
and extraction of fruits are carried out in the short time mentioned above 
by virtue of the elevation of the boiling point and the above-mentioned 
pectin modification, which constitutes the principal mechanism based on 
which prune extract is obtained. 
Further, the making-up of prune extract into paste as the final product is 
also promoted. 
After completion of the extraction through the heating under pressure, the 
resulting extract and plum residue are taken out of the above-mentioned 
autoclave, and the plum residue is removed by filtration by means of a 
sieve of a rough mesh, and further the liquid is passed through a sieve to 
carry out liquid-solid separation 5. The fruit plum residue is transferred 
to a container where it is discarded (step 6), while the extract 7 is 
concentrated in a conventional vacuum concentration step 8, e.g. at 
65.degree. C. under 20 mmHg, to give a prune extract 9 with a good yield 
and a high efficienty (i.e., high percentage attainment). 
An example according to the above-mentioned embodiment is shown as follows: 
EXAMPLE 
Raw material plum: Water content 18%; total weight 500 g 
Dipping water: Temperature 80.degree. C. (amount 3 times the volume of raw 
material) 
Treatment in autoclave: 2 atm., 121.degree. C., one hour (steam) 
Filtration: Rough mesh and 200 mesh 
Concentration: 20 mmHg, 65.degree. C. 
Prune Extract: Actual yield, 77.6%; efficiency (percentage attainment based 
on theoretical yield) 93.3% 
A comparison test with a prior art conventional process indicates that with 
the same raw material the extraction time was 6 hours, with an efficiency 
(percentage attainment based on theoretical yield) of 71.8%. 
Further, the cost required with the conventional process was 234.57 Yen, 
while that with the example given above was 212.66 Yen. 
Next, another embodiment will be described below, referring to FIG. 2. 
The steps down to the solid-liquid separation step 5 are carried out in the 
same manner as in the above-described embodiment shown in FIG. 1. 
Thereafter, the extraction liquid 7 is transferred to a concentration step 
8', while plum 1' separated by filtration is again dipped in hot water at 
80.degree. C. in an amount of 3 times the volume of plum 1' to the volume 
of added water 3'. After a given time, the contents are introduced into an 
autoclave in which they are subjected to an action of heating under 
pressure 4' at 121.degree. C. with steam under 2 atm. and for 30 minutes 
to again carry out pectin modification and extraction of plum 1' by the 
medium of hydrolysis and elevation of boiling point. Thereafter the 
resulting material treated is taken out of the autoclave and subjected to 
solid-liquid separation 5' where filtrations by means of rough mesh and 
200 mesh are carried out to give an extract 7'. The resulting residue is 
transferred to a discarding step 6", while the extract 7' is combined with 
the abovementioned extract 7 and the resulting combined extract is 
concentrated in a vacuum concentration step 8' under 20 mm Hg at 
65.degree. C. as in the first embodiment, to give a prune extract 9'. 
Of course, as a further embodiment it is also possible to connect the 
above-mentioned two-step extraction to a three-step extraction and effect 
a recycle. 
An example according to the last described two-step extraction embodiment 
is as follows: Since the raw material plum, water dipping, filtration and 
concentration steps are the same as those of the first described example, 
they are omitted. 
EXAMPLE 
The first stage autoclave heating under pressure treatment: 2 atm., 
121.degree. C., 60 minutes (steam) 
The second stage autoclave heating under pressure treatment: 2 atm., 
121.degree. C., 30 minutes (steam) 
Prune extract: Actual yield, 84.5%; efficiency (percentage attainment based 
on theoretical yield, 102.0%) (including a measurement error) 
As already indicated, with a conventional prior art process, the extraction 
time was 6 hours; the percentage attainment based on theoretical yield was 
71.8%; and the cost required was 234.57 Yen, whereas, according to the 
last described two-step treatment process of the present invention, the 
cost required was 183.32 Yen, and hence reduced by 22%. 
The prune extract thus obtained is not basically different from that 
obtained according to the conventional process, in that it is a pasty 
juice, but a subjective test gave rather positive results as to taste 
characteristics and the body of the extract. 
Further, in the case of prune extract obtained according to conventional 
processes, since it is difficult to screen overripe fruit and fruit having 
a high degree of wholeness according to the degree of ripeness thereof, as 
mentioned above, the percentage modification of pectin is unstable and 
hence the resulting extract has a latent element of jellifying due to 
mixing of pectin into pectinic acid. Thus it has often occurred that the 
viscosity of the extract increases with a lapse of time, and finally after 
a further time lapse, it hardens and jellifies. 
Whereas, according to the examples of the present invention, any of 
protopectin of unripe fruit, pectin of ripe fruit and pectin of flaked 
fruit are converted into pectinic acid, since a rapid pectin modification 
is carried out by the water-addition and the heating under pressure, and 
they become water-insoluble together with the pectinic acid of overripe 
fruit. Thus, almost no change with a lapse of time such as jellifying was 
observed. 
Further, as for raw plum material, not only in case of whole, but also even 
in case where chopped plum, i.e. diced plum, was employed, no change in 
the quality occurred. Thus, even when flaked plum having seeds removed for 
elevating the yield was employed, no jellification occurred to give a 
prune extract having the same quality as that of the extract obtained from 
whole fruit. 
In addition, even when various experiments were carried out with unripe 
plum, ripe plum and overripe plum, there were no substantial differences 
between the data obtained from the product tests, as expected from the 
above-mentioned theoretical analysis. 
Further, the above-mentioned embodiments are directed to a process for 
producing prune extract from plum as raw material, but the pressure, the 
time, etc. can be varied depending upon fruits to be treated. It goes 
without saying that the process is also feasible in case of apple, peach 
or other fruits. 
As mentioned above, according to the process of the present invention 
consisting of the basic steps of adding water to fruits as raw material, 
thereafter heating them under pressure in an autoclave, and then 
concentrating the resulting extract, pectin contained in the fruits is 
converted into stabilized pectinic acid by a rapid pectin modification 
through hydrolysis, in a short time, irrespective of the degree of 
ripeness of the fruit and whether the fruit is flaked or whole. Further, a 
long time extraction step as needed in the conventional cooking process of 
the prior art can be omitted. Accordingly, the energy cost which accounted 
for most of the production cost in the production of fruit extracts in the 
prior art can be reduced to a large extent, due to the short time step of 
heating under pressure in an autoclave. As a result, there is an effective 
reduction of the production cost. 
Further, according to the conventional prior processes for carrying out the 
above-mentioned long time cooking, it is necessary to often replace the 
water. Whereas, according to the process of the present invention, such 
water replacement and the labor involved therein can be omitted. In this 
respect, too, there is the advantage of reducing the production cost. 
Furthermore, since the extraction in an autoclave is carried out in a 
tightly closed container, there is no hazard that extraneous matter will 
enter the contents. Thus, there is an advantage of being very hygienic. 
Further, autoclave and the other equipment used can be greatly simplified. 
Thus, there is an advantage in that the initial equipment cost can be 
reduced. 
Still further, the simplification of steps yields a very great advantage, 
from the point of production control, quality control, operational 
efficiency, etc. 
Further, as mentioned above, pectin modification into stabilized pectinic 
acid is always effected irrespective of whether the fruit material is 
whole, flaked, unripe or overripe. Accordingly, a superior product which 
does not jellify with a lapse of time and also does not change in quality, 
even after long time storage and storage at low temperatures, can be 
obtained. Thus, neither screening of raw materials nor designation of 
specified raw materials are necessary. In this respect, too, the extract 
can be produced at a very cheap cost, and yet a product having a good 
quality can be obtained with a stabilized high yield, irrespective of the 
source. Further, there is the advantage in that controlling the operation 
can be omitted to a large extent and the yield of product is improved.