Two-stage apparatus for heating skins of fruit

Details Two-stage apparatus for heating skins of fruit Two-stage apparatus for heating skins of fruit

2000-02-11

2001-11-06

Hendricks, Keith (Department: 1761)

Foods and beverages: apparatus

Subjecting food to an enclosed modified atmosphere

With removal of solid foreign matter

C099S478000, C099S483000, C099S540000, C099S584000

Reexamination Certificate

active

06311611

ABSTRACT:

TECHNICAL FIELD
The present invention relates to steam peeler apparatus for separating tomato skins from the bodies of tomatoes and, more particularly, to a two-stage process for heat treating tomatoes in a manner that minimizes loss of tomato tissue.
BACKGROUND ART
It is desirable to minimize loss of tomato tissue, that is tissue from the body of a tomato, when separating the skins from the tomatoes. A common device for heat treating tomatoes to separate their skins is a steam peeler, which is a pressurized chamber of hot, saturated steam through which tomatoes are conveyed for a relatively short period of time to heat their skins, which causes the skin material to break away from the tomato body. After the steam peeler, the tomatoes move through scrubbers, which physically remove the skins. The assignee of the application herein, FMC Corporation of Madera, Calif., USA, manufactures a steam peeler apparatus, Model SP-20, which is a complete tomato peeler system in which the present invention is designed for use. FMC's brochure “SP-20 STEAM PEELER SYSTEM” describes the peeling process in more detail and is incorporated herein by reference.
It is known that subjecting tomatoes to a two-stage heating process reduces loss of tomato tissue during peeling due to a reduction in breakdown of skin cell structure. Two-stage heating has a minimum effect on inner mesocarp cells of tomatoes, and results in localized breakdown of the first couple layers of skin cells. An article “Microstructure of Steam Peeling”, Journal of Food Science, Vol. 53, No. 3, 1988, discusses in more detail the science and advantages of two-stage heating. This article is also incorporated herein by reference.
U.S. Pat. No. 5,862,812 of Dahl et al., entitled “Fruit Steam Peeler,” discloses a fruit peeler system that includes a conveyor belt elevator that delivers tomatoes to a pressure steam auger wherein high pressure steam separates the skins from the tomatoes. Tomatoes then pass into a flexible cable peeler and then to a pinch roller assembly, to remove the skins from the tomatoes. The '812 patent is also incorporated herein by reference.
The capacity of a continuous, auger-type pressure steam peeler is limited by the number of tomatoes that can be exposed to steam. This is due to the decreasing percentage of surface area effectively exposed as the depth of fruit increases with increased throughput. For a given geometry and residency time, the depth of product is a function of the RPM and volume of fruit fed into the auger. Increasing throughput while keeping the fill level at its optimum level requires that the residency time be shortened. This reduces the amount of time available to heat the product and as a result, processing rates for industry standard auger-type steam peelers has been limited to throughput of approximately 20 tons/hr.
An object of the present invention is to increase capacity of auger-type steam peelers beyond present capabilities while still maintaining minimum tomato tissue loss.
DISCLOSURE OF INVENTION
Briefly described, the two-stage steam peeler of the present invention includes an infeed conveyor for delivering fruit to a pressurized steam chamber and an enclosure for enclosing part of the infeed conveyor immediately adjacent the steam peeler. A steam introduction device introduces steam into the enclosure for the purpose of preheating the skins as part of a first stage of the two stage heating process. The pressurized steam chamber comprises the second stage of a two stage heating process. The outer skin layers of the fruit are heated in the first stage and the inner skin layers are heated to the extent necessary to remove the skins after the second stage.
According to an aspect of the invention, the infeed conveyor includes a vertical section followed by a horizontal section and the enclosure encloses the horizontal section and at least a part of the vertical section. The steam introduction device includes a series of steam nozzles positioned to direct steam into the vertical section of the enclosure. The steam introduction device also includes a series of steam nozzles positioned to direct steam into the horizontal section of the enclosure. The steam nozzles for the horizontal section are spaced laterally to direct steam into the enclosure from the sides of the conveyor.
According to another aspect of the invention, a feed valve transfers fruit from the enclosure to the pressurized steam chamber, and the feed valve includes an inlet opening for receiving fruit from the conveyor. The enclosure surrounds the inlet opening so that the fruit moves immediately from the first stage of heating into the feed valve.
According to another aspect of the invention, the enclosure and steam introduction device extend down along the vertical section a distance corresponding to the through-put of fruit by the steam peeler apparatus. A greater through-put generally requires a longer first stage heating enclosure.
According to another embodiment of the two-stage steam peeler, the first stage heater includes a hot water flume. Preferably, the hot water flume includes a steam coil or heat exchanger for heating the water.
The present invention also comprises a method of heating skins of fruit and includes the steps of conveying the fruit on a conveyor to a pressurized steam chamber, while the fruit is being conveyed to the pressurized steam chamber, pre-heating the fruit with steam heat within an enclosure of the conveyor that raises the temperature of the fruit skins to a first predetermined temperature, and in the pressurized steam chamber, heating the skins of the fruit with steam heat to a second predetermined temperature sufficient to separate the skins of the fruit upon flashing of steam.
According to as aspect of the method, the step of conveying the fruit to a pressurized steam chamber includes conveying the fruit first up a vertical conveyor section and then horizontally to the steam chamber. Preferably, the step of pre-heating the fruit with steam heat includes directing steam through a series of nozzles positioned along the vertical and horizontal conveyor sections.
These and other features, objects, and advantages of the present invention will become apparent from the following description of the best mode for carrying out the invention, when read in conjunction with the accompanying drawings, and the claims, which are all incorporated herein as part of the disclosure of the invention.


REFERENCES:
patent: 2556385 (1951-06-01), Allan
patent: 5342640 (1994-08-01), Roussel et al.
patent: 5682812 (1997-11-01), Dahl et al.
patent: 6082252 (2000-07-01), Creed et al.
patent: 59210877A (1984-11-01), None

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