GB2173088A - Process and apparatus for roasting peanuts - Google Patents

Abstract

Roasted peanuts are produced by de-shelling green peanuts, followed by immersion with their skins at least substantially intact in an aqueous solution of a comestible coat-forming polysacharide, and subsequent roasting of the coated product to produce an oxidation resistant roasted peanut. The peanuts may be roasted in an apparatus comprising an enclosed body (1) provided with infra-red heating means disposed around drum (8), an inlet (5), an outlet (6) and a cylindrical mesh drum (8) rotatable about a horizontal axis and operatively connected to said inlet and said outlet. The central axis (9) of the drum may have ports (11) through which vapours generated during roasting are evacuated. <IMAGE>

Description

SPECIFICATION Process and apparatus for roasting peanuts and peanuts produced thereby The present invention relates to a process and apparatusfor roasting peanuts, and to peanuts produced thereby. More particularly it relates to a process and apparatus for roasting peanuts adapted to prevent sepa ration of the peanut skin during the process to allow oxidation ofthe peanuts during distribution and sale.

When peanuts with shells are distributed and sold, theyarenotonly bulky and difficultto eat, butit is also difficult to apply seasoning thereto. Therefore peanuts are conventionally sold aftertheirshells have been removed and seasoning such as salt applied thereto.

However, if peanut skins are separated from the core ofthe peanut unsaturated fatty acids contained in the peanut tends to be oxidized, and it is therefore conventional that peanuts are roasted in a roasting machine. A predetermined quantity of peanuts is then sealed into a thin plastic bag for convenience of distribution and sale.

However, it is difficultfora conventional roasting machine, in terms of the construction thereof, to roast peanuts without separation of the peanut skin from the core (edible portion) thereof. An extensively used peanut roasting machine (called a flat roasting machine) operates asfollows: Peanuts are put onto a mesh approximately one metre square upon which the peanuts are oscillated.

Heat is applied from below to roastthe peanuts on the mesh. Several cones are arranged on the mesh to prevent the oscillating peanuts from being roasted on a single side only During this process the peanuts violently impinge upon the cones so that the peanuts skins become totally or partially separated from the cores, and the peanut cores themselves are damaged.

Moreover, further damage occurs in the peanuts due to the shocks resulting from contactwith the cones during the roasting process.

Accordingly, peanuts roasted by the existing roasting machine tend to have their skins separated therefrom. The separated skin stays atthe bottom of the bag in which they are stored and sold, which not only result in a lowering of productvalue, but also allows oxidation of unsaturated fatty acids contained in the peanuts. Particularly in the summer season, peanuts so stored can emitan offensiveodourina short period,for example, one month.

These phenomena pose a significant problem in the trade of peanuts, particularly in the import of peanuts into Japan from China.

It is therefore an object of the present invention to provide an arrangement wherein peanuts with shells removed are subjected to roasting, after processing with a comestible polysacharide and/orto a treatment during roasting of the peanuts which alleviates the problem of separation of the peanuts'skinsand oxidation during transportation and storage.

Furthermore it is an object ofthe invention to provide a peanut roasting apparatus which imparts no shock as encountered in the prior art, to peanuts with their skins intact during the roasting process.

According to a firstfeature ofthe present invention there is provided a process for roasting peanuts which comprises de-shelling green peanuts, immersing said green peanuts with their skins at least substantially in-tact in an aqueous solution of a comestible coatforming polysacharide, and roasting said so formed product to produce oxidation resistant comestible roasted peanuts.

According to a second feature of the present invention there is provided a de-shelled roasted peanut comprising an oxidation resistant coating of a comestible polysacharide.

According to a furtheraspectofthe invention there is provided a de-shelled peanut roasting apparatus comprising, an enclosed body provided with heating means, an inlet and an outlet for peanuts, a cylindrical mesh drum rotatable about a generally horizontal axis and operatiely connected to said inlet and said outlet, wherein the heating means are infra red heaters disposed in the periphery of the cylindrical drum.

The invention will now be described, by way of illustration only, with reference to the following example, and the accompanying drawings wherein Figure lisa front view of a roasting apparatus in accord with the invention, Figure 2 is a side view ofthe same, and Figure 3 is a frontviewofa cylindrical drum and exhaust outlet as generally shown in Figure 1.

An oven body(1) is formed with a cover (4) provided on a machine bed (2) and having moisture removing vents (3) which may be opened and closed as desired.

An inlet (5) and an outlet (6) for peanuts are positioned on one side thereof, and a power section (7) is positioned on the other side thereof.

The oven body is internally provided in the central portion thereof with a cylinder (8) made from a stainless steel mesh which is mounted rotatably about a horizontal shaft, and which is rotated by a transmission means such as a beltfromthe power section (7).A pipe (9) which extends through the mesh is secured to the centre ofthe cylindrical drum and a centrifugal exhaust fan (10) is provided on one end of the pipe (9) which is formed with a suitable number of intake ports (11 )which gradually increase in diameter as they are positioned away from the fan (10).

As heating sources for the roasting step a plurality of long wavelength infra-red heaters are arranged at the periphery ofthe rotary drum (8). In the drawings reference number (12) designates a heater cover, and (13) designates a centrifugal fan cover.

In roasting peanuts with the skins in-tact by the aforesaid machine, peanuts are charged into the inlet (5), and the cylindrical drum (8) is slowly rotated by the power section (7) while heating it bythe infra-red heaters. At the same time, the centrifugal fan (10) is driven ata high speed bythe power section (7).

Vapour is generated from the peanuts during processing and henceaircontaining moistureistaken in through the intake ports (11) and discharged to the exterior of the oven (1 ) through the exhaust pipe (9).

When the polysacharide solution is sprayed onto the peanuts to increase adhesion ofthe peanut skin, the solution may be evenly sprayed by means of an atomizer situated at the top ofthe rotating cylindrical drum (8).

Example In use ofthe above roasting apparatus green peanuts with their coats attached are immersed for about 40 seconds in a solution containing up to 3% starch, and up to 3% of oc-starch made up, for example, of 2% Pullulan (Registered Trade Mark) and up to 1%, preferably 0.5%, of Matsunorin (Registered Trade Mark). The solution also contains up to 3% of dextrin. For example, it may contain up to 2% of Pinedex 100 (Registered Trade Mark).

The so-treated peanuts are then immersed for about 40 seconds in a solution of 0.2% phytin in saturated salt water with 30% of saint dissolved therein.

The peanuts arethen removed with a sticky coating and the sticky peanuts are put into a containersuch as a bamboo basket th rough which air readily circulates and are naturally dried in the shade for about eight hours until the peanuts assume an approximately half-dried state.

Then thethus-dried peanuts are roasted by a roasting apparatus as described above. When the humidity has reached approximately 25%, an aqueous solution containing 8% Pullulan and 2% of Shellac is sprayed thereon twice at an interval of several minutestoform another coating, thus finishing the roasting process. If the peanuts with their skins intactwhich have been subjected to toasting as hereinbefore setforth are sealed into a bag with an oxygen absorbative agent included, the keeping properties arefurtherimproved.

The roasting apparatus according to the present invention constructed to achieve the results described above has, it is believed, thefollowing beneficial effects: (1) Heat evenly penetrates the peanuts because they are roasted by infra-red radiation while rolling inside a cylindrical drum which slowly rotates.

(2) Since no obstacles such as projections, agitating blades orthe like, are present within the drum over which the peanuts move during the roasting process, the peanuts are notsubjectedtoshockand hence there is no possibility ofseparation ofthe peanut skins from the cores, or damage to the peanut cores per se.

(3) A polysacharide solution may be sprayed over the peanuts during roasting. This may be effected by opening the oven, rotating the drum, and heating it by means ofthe heater. Thus, a liquid polysacharide or othersolution may be not only applied thoroughly to the peanuts during rotation, but heating may be continuously effected and therefore the peanuts will not suffer deterioration in taste as a result of undesired cooling.

(4) Since moisture produced during the roasting stepisdischargedthrough acentralexhaustpipeand peanuts are always roasted under conditions of low humitidty, the peanuts are roasted crisp to improve theirtaste.

(5) When the polysacharide solutioin is sprayed thereon, peanuts rolling inside the drum are treated whiletheirskins are pressed againstthe core due to the weight ofthe peanuts in the drum. This makes for positive adhesion and atthe same time increases lustre by virtue ofthefriction between adjacent peanuts.

(6) Since heat produced in the outer peripheral portion ofthe drum by irradiation from longwave infra-red heaters, is drawn as hot air towards the central portion by suction applied by the axial exhaust pipe, the whole charge of peanuts may be evenly heated and thermal efficiency may be increased.

The peanuts in accordance with the present invention which have been subjected to the foregoing process have the following properties and advantages: (i) Ifthe roasted peanutsarecharged into a bag made by coating thereon a gas-impermeable material such as nylon and stored, no deterioration in quality is discernible for at least three to five months. It has thus become possible to import peanuts with their skins intact produced in foreign countries, particularly in China, while retaining their quality.

(ii) No blackening ofthe peanut coat has been found during storage.

(iii) During transportation and other handling in connection with importand/orexportforexample, separation of the peanut skins hardly occurs, and the peanuts with their intact skins can be distributed and sold without lowering the value ofthe goods.

(iv) The material used for processing principally comprises polysacharides such as starch. The human body is not adversely affected by this.

(v) Peanuts immersed in Pullulan aqueous solution and then dried provide anti-oxidation and lustrous effects on the coated surface ofthe peanuts, and in addition the peanut skins are strengthened to thereby restrain separation thereof from the core.

(vi) Starch is used as an adhesiveto prevent separation ofthe peanut skin, butoc-starch has a greater adhering force resulting in better effects.

Further, starch per se is hygroscopicand so presents a problem in view of shelf life. If dextrin and/orShellac are added the coating is strengthened and rendered less hydroscopic and provided with a lipophilic nature. This is very desirable with peanuts rich in oil.

(vii) Treating the peanuts with sodium chloride and phytin acid solution has the following results, it is believed; the sodium chloride gives a desired seasoning as well as anti-oxidation effects. Phytin acid has an intensive chelating function which renders iron ions inert. Peanuts contain an iron component in their skins which is oxidized in air with the result that the skins tend to change to a black colour during storage. This is prevented bytreatmentwith phytin acid.

(viii) While the starch solution and the phytin solution may be successively used as separate solutions it is to be noted thatthey can be used as a single mixed solution.

(ix) Peanuts formed into a sticky state by immersion in a solution discussed above, may be dried to an approximately half-dried state to facilitate roasting and to fully permeate the sodium chloride and other components thereinto.

(x) By atomizing a Pullan solution while effecting roasting, the Pullulan forms a coat on the surface of the intact skin to increase lustre and provide for moisture barrier properties.

"Pullulan" referred to herein is a neutral glucan which dissolves in watertoform a viscous, non gelling solution; particularly it is a natural polysacharide with a linearstructure comprising X1-6 linked maltose units wherein glucose is the minimum unit.

Phytin acid (phytic acid) is an ester of myo-inosilol hexaphosphoric acid.

Claims (19)

1. A process for roasting peanuts which comprises de-shelling green peanuts, immersing said green peanuts with their skins at least substantially intact in a aqueous solution of a comestible coat-forming polysacharide, and roasting said so-formed product to produce oxidation resistant comestible roasted peanuts.

2. A process according to Claim 1 wherein the polysacharide is selected from one or more of starch, oc-starch and/or dextrin.

3. A process according to Claim 1 or Claim 2 wherein the aqueous solution comprises upto 10% of the polysacharides.

4. A process according to Claim 2 or Claim 3 wherein the polysacharide is formed of up to 3% cc-starch, upto 3% starch perse,and upto 3% dextrin.

5. A process according to Claim 4 wherein the starch is "Pullulan".

6. A process according to any preceding Claim wherein during orafterthe roasting stepthetreated peanuts are sprayed with an aqueous solution of starch and a comestible resin.

7. A process according to Claim 6 wherein the starch is "Pullulan" and the resin is "Shellac".

8. A process according to any preceding Claim wherein the immersion step includes immersion of the peanuts in liquid phytin acid.

9. A process according to Claim 8 wherein the phytin acid is disposed as an aqueous starch solution.

10. A process according to any preceding Claim wherein the preliminary drying step is effected immediately priorto roasting.

11. A process substantially as herein before set forthwith referenceto,and/orasillustratedin,the accompanying drawings or example of the invention.

12. A de-shelled roasted peanut comprising an oxidation resistant coating of a comestible polysacharide.

13. Apeanut according to Claim 12whereinthe polysacharide is one or more of a starch, an a-starch, and/or dextrin, and the coating additionally comprises a comestible resin.

14. A de-shelled roasted peanut comprising an intact skin treated with phytin acid.

15. A de-shelled roasted peanut substantially as hereinbefore setforth with reference to, and/or as illustrated in,theforegoing example.

16. A de-shelled peanut roasting apparatus comprising an enclosed body provided with heating means, and inlet and an outlet for peanuts, a cylindrical mesh drum rotatable about a generally horizontal axis and operatively connected to said inlet and said outlet, wherein the heating means are infra-red heaters disposed in the periphery of the cylindrical drum.

17. An apparatus according to Claim 16 wherein the axis of the drum is formed as an exhaust outlet with a pluralityofexhaustportstherein, and wherein theapparatusfurtherincludesmeansforinducinga negative pressure in said axial exhaust outlet.

18. An apparatus according to Claim 17 wherein the axial exhaust outlets increase in size with increasing distance from the negative pressure inducing means.

19. An apparatus substantially as hereinbefore set forth with reference to, and/or as illustrated in, Figures 1 to 3 ofthe accompanying drawings.