IL41776A - Method for preserving perishable materials - Google Patents

Abstract

1379707 Preserving perishable material SNAM PROGETTI SpA 1 March 1973 [1 March 1972] 10099/73 Heading A2D A method for preserving perishable material comprises passing through said material a stream of nitrogen having a relative humidity in the range from 45 to 70%; monitoring the humidity of the stream of nitrogen after its passage through the perishable material; and controlling, in response to the monitored humidity, the relative humidity of the stream of nitrogen before its passage through the perishable material. The nitrogen stream may comprise pure nitrogen or may contain small amounts of oxygen e.g. less than 2% of oxygen. Other gases inert to the perishable material may be present in the nitrogen stream in small amounts. The method may be carried out in the apparatus shown in Fig. 1 wherein nitrogen is passed from supply pipe 1 via pipe 6 to the upper region of container 7. A monitoring device 9 in the nitrogen exit pipe determines the relative humidity of exit nitrogen and, depending upon the value of the relative humidity, two-way valve 2 may be activated to divert incoming nitrogen into humidifier 3. The relative humidity of the incoming nitrogen is thus controlled. The method is particularly applicable to the preservation of cereals and seeds. [GB1379707A]

Description

VpVpnnV Method preserving perishable materials Enrico Shejbal no Method for preserving perishable materials Enrico Shejbal The present invention relates to a method reserving perishable material and to apparatus suitable carrying out this More particularly the present invention consists in a method for preserving cereals and valuable seeds by storage in suitable containers under a continuous of The preservation of wheat and cereals after the has always been a serious problem which has been dealt with and solved in many is well known that after the harvesting and the the storage of cereals can generally not exceed a period of days unless they are previously and suitably At present the tendency is to store the cereals in vertical silos for economical reasons to the ease of loading and and to the saving of Such a method involves however several drawbacks among which the following ones ma be mentioned the storage in silos requires a very low humidity of the cereals which should not exceed because beyond this limit an abundant fungous or bacterial flora capable of considerably altering the organoleptic properties of the stored material appear in a short the even when retain slight breathing power causes a considerable increase in temperature in the deep layers of the Because of this water evaporates from the waraer deep layers and condenses in the surface The grains in the top layers of the silo may thus reach a high humidity which creates optimum conditions for development of This particular and harmful phenomenon called owing to the fact that the silos cannot be made absolutely tight a development and growth of insects which are to control For limiting the damages caused by the insects a large variety of insecticides are used for disinfestation before or after the or during the storage It is known that these substances are very toxic and may cause serious damage during the treatment or by accumulation in the the storage in large silos causes a considerable decrease of the germination power which represents a serious drawback for valuable From the above enumerated drawbacks it results that the of cereals in silos is and requires suitable apparatus for controlling and regulating the for aerating the compartments of the silo and for transporting and mixing the cereals inside the Further methods known for storing perishable materials make use of artificial like the for preserving fresh fruit and However these methods allow suitable utilization of the means required for since the preserving involves sealing of the containers so that no sampling is possible and maintaining at the same time the remaining part of the silo under the action of the inert enviro or use is made of which cause serious damage to the germination capacity Le 85 811 In accordance with the present a new and inexpensive method for storing perishable materials has been found in which nitrogen allowed to flow continuously in suitable This permits sampling without depriving the remaining part of silo from the benefit of the inert The method of the present invention prevents the growth and reproduction of parasitic insects and of their larvae without using toxic insect allows a simpler storage of an easy control of the humidity and further the need of expensive for preventing the growth of In fact many Aspergilli may produce substances known for their carcinogenic activity and which are particularly toxic for domestic animals and By the method according to the invention perishable materials are stored in suitable containers through which nitrogen is allowed to flo The nitrogen used may be pure or contain certain amounts of oxygen o other inert The amount of oxygen should however not exceed and the possible presence of other inert like CO and should be kept within the range of 5 of the total amount of amoun of oxygen higher than that indicated above might cause serious by permitting the survival insects which keep active in presence of a relativel low oxygen The nitrogen further be humidified so as to keep unaltered the germination capacity of the stored said properties being very important if these products are intended for and also in order to prevent a reduction of the yield of the stored This fact is very important if valuable seeds or species are The humidity must range limits from to Outside this range serious drawbacks can such as considerable loss of weight if the is very or a quick growing of moulds in the stored materials if the nitrogen is too if the stored products are not binder the original anaerobic The method of the present invention is of general it may be advantageously applied for storing perishable material of every in particular cereals and valuable According to this method the perishable materials are stored in suitable which are then The outlet point is located in the lower part of the The gas inlet is located in the upper part and the gas outlet is situated in the lower part of the silo beneath the layer of the stored The humidity of the inlet gas is suitably regulated so as to keep the stored products within the above mentioned With reference to the diagram of 1 is the line for supplying which may be fed in the gaseous state or in regasified state from liquid supplied from gas exhaust nitrogen resulting from preceding Utilizations of the same from refrigeration or from any other Through valve 2 the nitrogen is introduced at 3 into the humidi and then through conduits 5 and 6 into the container 7 The valve 2 is actuated by a relay 9 which controls the outlet humidity and this determines whether the nitrogen has to pass through the and what should be the humidity percentage of the nitrogen entering at If the degree of humidity established by the relay 9 is too the nitrogen enters the container 7 directly through valve 2 conduits 5 and 6 without passing through the There are suitable gas flow regulators provided in the nitrogen The method of the present invention is illustrated by way of example i the description of a particular namely the storage of From this description those skilled in the art may deduct the various required for adopting it to a more general use without departing from the scope and the ambi of the present The results obtained storing wheat for eight months in a small silo a continuous flow of suitably moistened technical nitrogen showed that by means of this treatment no variation of germinating capacity of protein content of the wheat while all the advantages of ventilation and anaerobic condition were during the whole storage there was no development of mould or of insects inside the Furthermore laboratory tests have shown that the simulated infection of wheat with parasitic insects was easily and totally eliminated in a short due to the fact that the technique of passing a continuous nitrogen stream through the silo produces an uninterrupted anaerobic medium and thus makes g of any parasitic insects The results have further shown that by ventilating the wheat with suitably moistened gases it is possible to easily regulate the humidity of the wheat and therefore its without danger of mould EXAMPLE For testing the wheat storage in controlled enviroment two small cylindrical silos having an inside diameter of 50 cm and an inside height of 250 cm were The cylinders were made of and had a wall thickness of The upper and lower closures consisted of metal flanges with rubber gaskets and adhesive on the basis of At three 70 130 cm and 190 cms from the there were provided wheat sampling points consisting of valves gas having a stainless steel ball and a chromium plated bronze bod with the same heights there were provided thermometers for measuring the temperature at the center of the wheat In the lower part of the silos there was provided an outlet having the shape of a metal chute with a tight closure having The column of wheat was supported by a stainless steel net 20 from the bottom of the The gas inlet ft was located at the part of the silos 15 cm from the while the gas outlet was in the lower part of the silo beneath wheat column 10 the lower The silo and the iron were covered wit a synthetic oil and painted with synthetic humidity of the entering gas was adjusted by means of system for mixing gas of high obtained by bubbling the gas through a water with dry The humidity of inlet and outlet gas was continuously measured with a recording thermohygrometer and manually regulated by means of suitable The of the inlet and outlet gas was measured low rate flowmeters 10 The wheat for the storage test in a was soft wheat Cultivated by Conte in Monterotondo and sacked soon after threshing without being subjected to any The moisture content of the wheat at time of harvesting was The used for purging of the two silos were the following technical nitrogen supplied by the in Rome in the form of liquefied having an oxygen concentration of less than regasified and heated to room temperature having a low relative humidity The silos were loaded with wheat from the upper part 450 and soon afterwards A nitrogen and air stream of from 4 to 8 1 h and relative humidity 45 was was the mean value values of 30 and were admitted only for periods of time not exceeding 24 In addition to the continuous recording of the temperature and humidity either of the gas inside the silo o of the inlet and outlet the inlet and outlet gas and the temperature inside the silos at the levels of the wheat sampling valves recorded periodically times per At predetermined periods two times per a least once every three the wheat from the inside of the wheat mass was sampled at three heights of the measurement of the humidity of the wheat was carried out by drying samples in an oven at and then desiccator at room temperature up to a constant and by establishing the germinating capacity in days tests at room for each grains of wheat for each analysis of whea protein content as well as tests on the survival of parasitic insects in the inert were also carried The methods used are described hereinafter together with the results As may be seen from no significant difference of germinating capacity between the wheat stored in silos with an air flow and the one stored in silos with a technical nitrogen flow containing less than of oxygen for an 8 month period was After starting values of less the germinating capacity reached in both cases a mean value of about corresponding to the germinating capacity of the same wheat stored in ventilated The figure shows the germination values of the lots stored with an air and nitrogen The germinating capacity has been indicated on the and the time in weeks on the content of the wheat increased during the storage from the initial value of to a value abou 3 where the ordinates represent the humidity and the abscissae the time in weeks Curve 1 refers to air and curve 2 to a nitrogen During the storage period the silos neither mould growth nor macroscopic modifications of the er The moulding of the wheat during the germinability test did exceed indicating a very low contaminatio of the stored Tests with small amounts of wheat in containers with a nitrogen having a high humidity showed that it is possible to humidify the wheat up to without causing mould growth provided the wheat is kept for a limited period of time in an inert Because of thermal inertia the temperature inside the silos during the whole storage of the wheat rarely exceeded that of the medium flowing through the silo indicating thereby a sufficient ventilation of the wheat and the absence of In the temperature is by the ordinates and the time in weeks by the Curve 1 refers to air and curve 2 to After four months from the beginning of the storage an analysis of the protei content of the wheat stored in an atmosphere of air or of nitrogen was made by the eiectrophoretic tive method on acrylamide gel specified by Silano et Wo difference in content of gliadins and globulins i the wheat stored in the two silos was During the whole storage period of the wheat no spontaneous contamination due to wheat parasitic insects has been In order to produce such an and to study the effect of the gases which flowed through survival tests on two species o insects generally present in Italian Sitophilus granarius and Tribolium were The insects per with some wheat grains in order to their were put in tiolit glass containers and kept under a continuous flow of the following gases air leaving the silos conbined with humidified nitrogen leaving the silos combined with humidified technical humidified highly pure nitrogen 5 ppm of The results were the following the survival of the insects of both species in the silos outlet air was for the whole period the test The behaviour of the insects was In the initial period of the treatment with nitrogen leaving the silos an acceleration of movement of the insects of both species was noticed for about 2 At the end of this period the reached the comatose whereas the granarius kept on moving slowly and reached the comatose state only after about 24 As shown in table the survival of insects of both species was very The LD 100 at room temperature of of the confusum was reached after 24 hours of being held in a nitrogen whereas for the granarius 120 hours was The behaviour of the insects when reaching the stage of complete asphyxia in high purity nitrogen at a temperature of was similar to the one in technical but the induction times of the comatose state and for reaching the LD 100 were shorter A test of wheat preservation completely anaerobic humidity and temperature was also carried A small amount of wheat was preserved for 3 months under a flow rate of highly pure nitrogen 5 ppm humidified at at two temperatures temperature and ft TABLE Characteristics of wheat preserved under completely anaerobic conditions for three pure humidity at two Germinating capacity Humidity Untreated control 97 Room 97 As it may be seen Table no decrease of germinating capacity of the wheat was whereas humidity reached was and without of the wheat at both insufficientOCRQuality

Claims (6)

1. Method for preserving perishable materials, preferably cereals and valuable seeds, consisting in storing the perishable material in suitable containers through which nitrogen having a humidity of from 45f° to 05S is allowed to flow continuously,

2. Method according to Claim 1 , wherein the nitrogen is a highly pure nitrogen.

3. Method according to Claim 1 , wherein the nitrogen contains oxygen in an amount of less than 2$ of the total amount of nitrogen.

4. Method according to Claim 1, wherein the nitrogen contains oxygen in an amount of less than 2$ and inert gases, such as CO and CQ^ in an amount of less than 5 - 6$ of the total amount of nitrogen.

5. Method for preserving perishable materials according to one or more of the preceding claims consisting in storing the materials in silos, tightly closing the silos, passing nitrogen via the upper part thereof, through the column of the stored material and controlling the humidity of the stored materials.

6. Method for preserving perishable materials according to one or more of the preceding claims characterised in that the stored material is grain.