Abstract:
A process for producing a fried food, which comprises placing a starting material suitably applied with a necessary pretreatment into a fryer filled to an intermediate level with heated oil, moving the material vertically to repeat the operation of dipping the material into the oil and withdrawing the material above the oil surface for several minutes, then allowing the material to rest in the oil for a while and finally draining off the oil by vibrating the material with small amplitudes above the oil. 
     This process can be carried out by using a device comprising a fryer vessel equipped with a sealing lid at the upper portion on one side, a pipe for feeding heated oil which feeds the heated oil from an oil heater into said fryer vessel, a return pipe which returns used oil from said fryer vessel through an oil filter to the oil heater, a level gauge for monitoring the oil level of the heated oil filled to an intermediate level in the fryer vessel, an air cylinder which drives a waggle frame housed within the fryer vessel vertically to dip the frame into the oil or withdraw the frame above the oil surface and a starting material case housed within the waggle frame so as to be freely dischargeable by opening the above sealing lid.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a device for producing fried food from fruits such as apples, pineapples, etc., vegetables such as pumpkins, sweet potatoes, etc., and fish such as octopus, cuttlefish, short-necked clam, etc. 
     2. Description of the Related Art 
     In the prior art, this kind of fried food has been produced according to a frying process in which a basket containing a starting material is moved vertically in heated oil in a fryer vessel maintained under a reduced pressure while preventing mutual adhesion of the starting material in the shape of chips, as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 52-3848 and No. 59-210853. 
     However, since the frying process of the prior art as mentioned above merely moves the starting material vertically in the heating oil, the starting material is insufficiently dried, resulting in bending or destruction of the starting material. This gives rise to problems such that not only is the product value lowered, but also the product has an inferior taste and the oil content is markedly reduced. 
     SUMMARY OF THE INVENTION 
     Accordingly, the object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method and a device for producing fried food which is not only capable of producing homogeneous products by frying the starting material evenly and uniformly but can also provide fried food having a good taste by draining the oil quickly therefrom. 
     In accordance with the present invention, there is provided a process for producing the fried food of the present invention, comprising placing a starting material suitably applied with a necessary pretreatment into a fryer filled to an intermediate level with heated oil, moving the material vertically to thereby repeat the operation of dipping the material into the oil and withdrawing it above the oil surface for several minutes, then leaving the material to rest in the oil for a while, and finally draining off the oil by vibrating the material with small amplitude vibrations above the oil. 
     In accordance with the present invention, there is also provided a device comprising a fryer vessel equipped with a sealing lid at the upper portion on one side, a pipe for feeding heated oil which feeds the heated oil from an oil heater into the fryer vessel, a return pipe which returns used oil from the fryer vessel through an oil filter to the oil heater, a level gauge for monitoring the oil level of the heated oil filled to an intermediate level in the fryer vessel, an air cylinder which drives a waggle frame housed within the dryer vessel vertically by dipping it into the oil or with drawing it above the oil surface, and a starting frying case which is housed within the waggle frame so as to be freely dischargeable by opening the above sealing lid. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The present invention will be better understood from the description set forth below with reference to the accompanying drawings illustrating, but is not intended to be limited to, the preferred embodiments of the present invention, in which: 
     FIG. 1 is a schematic illustration showing an example of the vacuum fryer device for practicing the process of the present invention; 
     FIG. 2 is a graph showing the vertical movement operation in the first preparation example of the process of the present invention; 
     FIG. 3 is a graph showing the drying condition of the starting material; 
     FIG. 4 is a graph of the vertical movement operation in the second Preparation Example; and 
     FIG. 5 is a graph of the vertical movement operation in the third Preparation Example. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawing, an example of the present invention is described. 
     In FIG. 1, 1 is a lateral type fryer vessel, and three vessels are provided in this example. On one end of the fryer vessel 1, a sealing lid 1a is mounted. 1b is a level gauge. 
     At the bottom of the fryer vessel 1, a heater 2 is arranged so as to heat an oil to a desired temperature. A steam pipe 3, through which steam is supplied, is connected to the heater 2. 
     Also, at the bottom of the fryer vessel 1, an inlet for introducing a pipe 4 for feeding heated oil is opened so that oil may be fed from an oil heater 5. 4a is a return pipe. 
     Steam is supplied from the steam pipe 3 to the oil heater 5 so as to heat the oil for frying. The oil heater 5 is connected to a supplementing tank 6 so that oil may be supplemented if desired. 
     A waggle frame 7 is housed within the above fryer vessel 1, which is movable vertically by an air cylinder 8. Air pipes 9, which are connected through a change-over valve 10 to an air compressor 11, are connected to the air cylinder 8. 
     A limit switch 12 detects the respective positions of the ascending end and the descending end of the above waggle frame 7 and performs a change-over operation of the above change-over valve 10. The starting material, frying case 13 can be housed within the above waggle frame 7, so as to be freely dischargeable. 
     An evacuation pipe 14 is connected to the upper portion of the above fryer vessel 1, which introduces the vapor within the fryer vessel 1 into a mist separator 15. The mist separator 15 is further connected to a first condenser 16. Cooling water is introduced into the first condenser 16 from a cooling water pipe 17, and a second condenser 18 is also connected thereto. 
     In the FIG., 19 is a drain tank, 20 is an auxiliary vacuum pump, 21 a main vacuum pump, 22 an oil reservoir, 24 an oil filter, 23 an oil circulating pump, 25 a vacuum valve, and 26 a valve. Next, the mode of operation of the above exemplary device is described. 
     First, the oil in the oil reservoir 22 is introduced into the oil heater 5 by the oil circulating pump 24, to be heated, and then sent through the pipe 4 to feed oil into the fryer vessel 1, and then circulated by passing through the oil filter 24. Further, the flow of the oil is adjusted by the heater 2. 
     Next, by opening the sealing lid 1a of the fryer vessel 1, the starting material frying 13 filled with a starting material is mounted within the waggle frame 7. 
     After the above sealing lid 1a is resealed, the main vacuum pump 21 and the auxiliary vacuum pump 20 are run, and when the auxiliary vacuum pump 20 reaches 50 to 100 Torr, the evacuation system is changed to that of the main vacuum pump 21 by the vacuum valve 25. When the vacuum degree reaches 10 Torr or higher, the solenoid of the change-over valve 10 is turned ON to actuate the air cylinder 8. 
     The air cylinder 8 causes the waggle frame 7 to descend and dip the frying case 13 into the oil, thereby beginning to fry the starting material in the frying case 13. 
     When the waggle frame 7 reaches the descent limit, the limit switch 12 activates the change-over valve 10 to cause the waggle frame 7 to ascend. When the waggle frame 7 ascends above the oil surface, the limit switch 12 activates the change-over valve 10 to cause the waggle frame 7 to again descend into the oil. 
     As described above, the operation of dipping the waggle frame 7 into and withdrawing it above the oil is repeated for several minutes, to cook the starting material in the frying case 13, and after an elapse of a predetermined time, the cooked material is left to rest in the oil, by actuation of a timer, for finishing cooking, and finally, the waggle frame 7 is withdrawn from the oil by the air cylinder 8 and draining of the oil is effected by waggling the frame above the oil surface. 
     Then, when the vacuum valve 25 is closed, the valve 26 is opened to return the pressure in the fryer vessel 1 to atmospheric, and the frying case 13 within the waggle frame, out from within the fryer 1 by opening the sealing lid 1a, and the product is then taken out. 
     In carrying out the frying process by repeating the above operation, the oil is supplemented to a desired oil level by observing the level gauge 1b. The frying process was conducted by repeating the above operations for the three fryer vessels according to the following pattern. 
     
         ______________________________________Upper stage     Middle stage                       Lower stagefryer           fryer       fryer______________________________________1      Running      Preparing   Taking out2      Taking out   Running     Preparing3      Preparing    Taking out  Running______________________________________ 
    
     Running: the step of frying the starting material. 
     Preparing: the preparatory steps of charging the starting material, maintaining a predetermined vacuum degree with the auxiliary vacuum pump, controlling oil temperature, etc. 
     Taking out: the step of taking out the material from within the fryer after completion of the frying process. 
     After the completion of the frying process, the used oil in each fryer vessel is collected into the oil reservoir 22 and placed under a reduced pressure (vacuum), whereby oxidation of the used oil is prevented, and thus no problems arise concerning reutilization. In the following, some preparation examples of the above frying process are described. 
     PREPARATION EXAMPLE 1 
     Apples were sliced into chips and soaked in a low sugar thick malt syrup adjusted to a sugar degree of 35 to 45 Bricks at a temperature of 20° C. for 4 to 6 hours. After draining off the syrup, the chips were placed in a rectangular wire cage with a height of 200 mm, introduced into the case of a vacuum fryer, and the case was moved vertically. The number of vertical movements of the vacuum fryer may be variable from about 1 to 20 times/minute. 
     In the vacuum fryer, frying was performed under the conditions of a vacuum degree of 5 to 20 Torr and an oil temperature of 110° C. 
     As shown in the graph in FIG. 2, of the total frying time of 12 minutes, vertical movement was performed five times/minute at intervals of 30 seconds for 5 minutes after the initiation of frying, then at intervals of one minute for the next 4 minutes, further standing in oil performed for the next 3 minutes, followed by vertical movements with very small amplitudes (30-50 m/m) on recording the final oil temperature (finishing oil temperature) of 90°-95° C. for 30 seconds, to complete the frying process. 
     For the drying condition of the starting material during the above operations, the result as shown in FIG. 3 was obtained. 
     Therefore, in the first zone, most of the constant rate drying is effected within 10-15 seconds from the start-up, followed by the reduced rate drying zone, and the movement in the first zone is necessary for uniformalization of the temperature distribution and the prevention of mutual adhesion between the chips. 
     In the second zone, where drying has proceeded to a considerable extent, the article is handled so as not to be broken, and the third zone is the zone for controlling the final water content. The final step is the oil draining of the case and the fry box, and the product is moved vertically with an amplitude of 10 to 50 mm as shown in FIG. 2. When the final oil draining step was conducted, a reduction of the oil content by about 3 to 5% was observed as compared with the case when no such operation was conducted. 
     Consequently, highly satisfactory results could be obtained with the fried product of apple chips, in that there was no adhesion between the chips or color fading, and there was a good taste and good oil draining. 
     The results of comparison with the vacuum fryer which was not vertically moved are shown in Table 1. 
     
                       TABLE 1______________________________________                               DryingTaste       Color   Flavor  Oil content                               degree______________________________________Preparation   +++     +++     +++   15-20%  +++example 1When fried   ++      +       ++    20-25%  +without                               Much layeredvertical                              and driedmovement                              product______________________________________ Note: (+++) very good, (++) common, (+) slightly inferior 
    
     PREPARATION EXAMPLE 2 
     Pineapple cut in round slices was applied with the same treatment as Preparation Example 1 by using a fine white sugar syrup and under the operational conditions shown below by means of the same device as in Preparation Example 1. 
     (1) Operational conditions 
     Oil temperature 120° C., 
     Frying times 15 minutes, 
     Operational vacuum degree 10 Torr or lower, 
     Final temperature 94° C. 
     (2) Vertical movement condition 
     As shown in FIG. 4, vertical movement was performed 5-6 times/minute at intervals of 30 seconds for 5 minutes after the initiation of frying, 4-6 times/minutes at intervals of 1 minute for the next 5 minutes, and 3-6 times/minute after 2 minutes for the next 3 minutes. After the elapse of 15 minutes, vertical movement with an amplitude of 30-50 m/m was performed for 5 to 10 times, followed further by standing in vacuum for 3 minutes, the product was then taken out by breaking the vacuum, and cooled. 
     (3) Results: 
     The results of comparison between the product obtained by frying while performing vertical movement as described above and the product obtained by drying without vertical movement are shown in Table 2. 
     
                       TABLE 2______________________________________                               DryingTaste       Color   Flavor  Oil content                               degree______________________________________Preparation   +++     +++     +++   15-20%  +++example 1When fried   ++      +       ++    18-25%  Much layeredwithout                               and driedvertical                              productmovement______________________________________ Note: (+++) very good, (++) common 
    
     Consequently, the product according to the method of Preparation Example 2 was found to be very good and satisfactory results were obtained 
     In contrast, the product obtained by frying for 15 minutes without performing vertical movement was dried non-uniformly and had a bad taste and color. 
     PREPARATION EXAMPLE 3 
     Pumpkin sliced into chips was pretreated in the same manner as in Preparation Example 1 and fried under the following operational conditions by means of the same device as in Preparation Example 1. 
     (1) Operation conditions 
     Oil temperature 110° C., 
     Frying time 9-10 minutes, 
     Operational vacuum degree 10 Torr or lower, 
     Final temperature 95° C. 
     (2) Vertical movement condition 
     For 5 minutes after the initiation of frying, vertical movement was performed 5-6 times/minute at intervals of 30 seconds, and for the next 3 minutes 4-6 times/minute at intervals of 1 minute, 9-10 minutes later, vertical movement was conducted 5-10 times with amplitudes of 30-50 mm, followed by standing in vacuum for 1 to 2 minutes, the product was taken out by breaking the vacuum, and cooled. 
     (3) Results 
     The results of comparison between the product fried with vertical movement and the product fried without vertical movement are shown in Table 3. 
     
                       TABLE 3______________________________________                               DryingTaste       Color   Flavor  Oil content                               degree______________________________________Preparation   +++     +++     +++   15-18%  +++example 1When fried   +       ++      ++    18-22%  Much layeredwithout                               and driedvertical                              productmovement______________________________________ Note: (+++) very good, (++) common, (+) slightly inferior 
    
     Consequently, very satisfactory results could be obtained for the product according to the method of Preparation Example 3, while the product fried for 9-10 minutes without vertical movement was found to be irregularly dried with a bad taste and color. 
     PREPARATION EXAMPLE 4 
     Sweet potato, kiwi, papaya and mango were treated in the same manner as in Preparation Example 1 and the above starting materials were fried under the following conditions by means of the same device as in Preparation Example 1. 
     (1) Operational conditions 
     
                       TABLE 4______________________________________  Initiation           Final      Frying  Operational  temperature           temperature                      time    vacuum______________________________________Sweet potato       120° C.                  115° C.                          15 min.                                10 Torr or                                lowerKiwi     115         90         9    10 Torr or                                lowerPapaya   130        100        11    10 Torr or                                lowerMango    120        100        15    10 Torr or                                lower______________________________________ 
    
     (2) Vertical movement condition 
     For half of the total frying time after the initiation of frying, vertical movement was performed 5-6 times/minute at intervals of 30 seconds-1 minute, and 4-7 times/minute at intervals of 1 minute to 3 minutes for the next half of the time. On completion of the frying time, vertical movement with amplitude of 20 to 50 m/m was performed 5 to 10 times, followed by standing in vacuum for 1 to 5 minutes, the product was taken out by breaking the vacuum, and cooled. 
     (3) Results 
     The results of comparison between the product fried with vertical movement and the product fried without vertical movement are shown in Table 5 and Table 6. 
     
                       TABLE 5______________________________________Fried with Vertical MovementSweet potato    Kiwi      Papaya   Mango______________________________________Taste   +++         +++       +++    +++Color   +++         +++       +++    +++Oil content   15-20%      15-22%    15-22% 15-22%Flavor  +++         +++       +++    +++Drying  No layers and               Same as   Same as                                Same asdegree  properly dried               on left   on left                                on left   product______________________________________ 
    
     
                       TABLE 6______________________________________Fried without Vertical MovementSweet potato    Kiwi       Papaya   Mango______________________________________Taste   ++          ++         ++     ++Color   +++         +++        +++    +++Oil content   18-22%      17-25%     17-25% 18-25%Flavor  ++          ++         ++     ++Drying  No layers and               Many layers                          Same as                                 Same asdegree  properly dried               and not    on left                                 on left   product     properly               dried product______________________________________ Note: (+++) very good, (++) common, (+) slightly inferior 
    
     From the above results, the marked effects of vertical movement can be seen That is, 
     (1) there is the effect of peeling of the fried product being caused by the shock against the oil surface from the vertical movement, and 
     (2) there is the stirring effect of the vertical movement. 
     Therefore, there is no adhesion between the products due to the effect of (1), and there is no frying irregularity by uniformalization of the oil temperature due to the effect of (2). 
     PREPARATION EXAMPLE 5 
     Raw or boiled octopus, cuttlefish, scallop adductor, scallop strand, short-necked clam were fried under the following conditions by means of the same device as in Preparation Example 1. 
     (1) Operational conditions 
     
                       TABLE 7______________________________________  Initial  Final      Frying  Operational  temperature           temperature                      time    vacuum______________________________________Octopus     130° C.                  105° C.                          15 min.                                10 Torr or                                lowerCuttlefish    130        105        13    10 Torr or                                lowerScallop  110         95        10    10 Torr oradductor                             lowerScallop  110         95         7    10 Torr orstrand                               lowerShort-necked    110         95        10    10 Torr orclam                                 lower______________________________________ 
    
     (2) Vertical movement condition 
     For 1/3-1/2 of the total frying time after frying initiation, vertical movement was performed 5-6 times/minute at intervals of 30 seconds to 1 minute (at initiation of frying, the number of vertical movements is increased), and 4-7 times/minute at intervals of 1 minute to 3 minutes for the remainder of the time. On completion of the frying time, vertical movements with an amplitude of 10 to 50 m/m were further performed, followed by standing in vacuum for 1 to 5 minutes, the product was taken out by breaking the vacuum, and cooled. 
     (3) Results 
     The results of comparison between the product fried with vertical movement and the product fried without vertical movement are shown in Table 8 and Table 9. 
     
                       TABLE 8______________________________________Fried with Vertical Movement               Scallop  Scallop                               Short-neckedOctopus    Cuttlefish               adductor strand clam______________________________________Taste +++      +++      +++    +++    +++Color +++      +++      +++    +++    +++Flavor +++      +++      +++    +++    +++Oil   10-15%   10-15%   11-18% 10-15% 10-15%contentDrying +++      +++      +++    +++    +++degree______________________________________ 
    
     
                       TABLE 9______________________________________Fried without Vertical Movement               Scallop  Scallop                               Short-neckedOctopus    Cuttlefish               adductor strand clam______________________________________Taste ++       ++       +++    ++     ++Color +++      +++      ++     ++     ++Flavor ++       ++       ++     ++     ++Oil   15-20%   15-20%   15-20% 15-20% 15-20%contentDrying With     Same as  Same as                          Same as                                 Same asdegree drying   on left  on left                          on left                                 on left irregular- ity______________________________________ Note: (+++) very good, (++) common 
    
     As can be seen from the above results, the effect of the vertical movement is markedly exhibited. 
     [Effect of the Invention] 
     (1) By placing the starting material in a fryer filled with heated oil to an intermediate level and repeating the operation of dipping into oil and withdrawing above the oil surface by vertical movement of the fryer for several minutes, not only can mutual adhesion between the starting material be prevented, but also an even and uniform frying can be preformed to produce homogeneous products. 
     (2) Since the starting material is left to stand for a while in the oil after the above vertical movement operation, the fried product has an improved taste, color and flavor. 
     (3) By performing final oil draining by vibration with small amplitudes above the oil, not only is the flavor increased with a reduced oil content without drying irregularities, but the reduction of the oil content becomes less.