TECHNICAL FIELD

This invention relates to a method of browning food products. More specifically, the method relates to the browning of food products comprising a dough having an alginate based casing, by inducing a Maillard reaction at an outer surface of the dough. The invention relates also to an apparatus for browning of such food products by inducing a Maillard reaction at an outer surface of the dough.

Any reference to a “food product” in this specification must be interpreted to mean a dough and an alginate gel casing surrounding the dough. The food product may take the form of a sausage or the like, while the dough may be plant based or animal meat based.

Any reference to an “alginate based casing” or “alginate based gel” in this specification must be interpreted to mean a casing that includes sodium alginate and other ingredients, a calcium alginate based casing or a blended bi-functional alginate and collagen based casing. BACKGROUND TO INVENTION

Maillard browning of food products in order to enhance the colour and/or flavour of food products is well known. Maillard browning occurs due to a Maillard reaction which takes place between amino acids and reducing sugars at an outer surface of a food product. In a Maillard reaction, reactive carbonyl groups of the sugars react with nucleophilic amino groups of amino acids and form a complex mixture of molecules responsible for a range of colours, aromas and flavours. The Maillard reaction is a form of non-enzymatic browning which typically occurs rapidly from about 140°C to 165°C. At higher temperatures, undesirable caramelisation and subsequently pyrolysis occurs. At lower temperatures, the Maillard reaction generally occurs too slowly for use in a commercial, high-throughput, food production process. In a commercial food production process wherein Maillard browning is a requirement, there is a need to optimise the Maillard reaction so as to increase the throughput of the food product through any food processing equipment. It is known that in order for a Maillard reaction to occur at a surface of a food product, the surface must be substantially dry.

Alginate is commonly used to form sausage casings as part of a process in which a solution of sodium alginate is extruded through a circular die around a food product and subsequently treated with calcium chloride (see e.g. WO 2016/027261). During this process, the alginate solution undergoes a gelification process in which matrices of cross-linked alginate chains form.

In food products comprising a dough encased by an alginate based casing, the alginate based casing has an inherent moisture content which impedes Maillard browning. Heat treatment to achieve Maillard browning would typically occur after treatment of the sodium alginate with calcium chloride.

It is an object of the present invention to provide a method and apparatus for optimally inducing Maillard browning at an outer surface of a dough of a food product comprising a dough and an alginate based casing surrounding the dough. It is a further object of the present invention to reduce a residence time of a food product comprising a dough encased by an alginate based casing, in a heating chamber in order to induce Maillard browning at an outer surface of the dough.

SUMMARY OF INVENTION

According to a first aspect of the invention there is provided a method for browning food products comprising a dough and an alginate based casing which surrounds the dough and wherein the alginate based gel has a moisture content, the method including: heating an outer surface of the dough of the food products to a temperature range of between 140°C and 165°C in order to induce a Maillard reaction; subjecting the food products to a forced air flow within the heating chamber for drying the alginate based casing; and extracting a portion of the air within the heating chamber so as to reduce the humidity of the air within the heating chamber in order to promote drying of the alginate based casing so as to increase the rate at which the outer surface of the dough reaches the temperature range of between 140°C and 165°C.

The method may include regulating the temperature of the air to be at a constant temperature within the temperature range.

The method may include regulating the rate of air flow within the heating chamber so as to be at a constant air flow rate.

The method may include a) sensing the dry bulb temperature and the wet bulb temperature of the air within the heating chamber; b) determining a relationship between the dry bulb temperature and the wet bulb temperature expressed in a percentage moisture content per unit volume of air; and c) generating a control signal based on the relationship for controlling the volume of air to be extracted from the heating chamber.

According to a second aspect of the invention there is provided an apparatus for browning food products comprising a dough and an alginate based casing which surrounds the dough and wherein the alginate based casing has a moisture content, the apparatus including: a heating chamber including at least one heat source for heating air within the heating chamber for heating an outer surface of the dough of the food products to a temperature between 140°C and 165°C in order to induce a Maillard reaction; a conveyor for conveying the food products through the heating chamber; one or more air flow generators for generating a circulating flow of drying air within the heating chamber for drying the alginate based casing; and an air extractor for extracting air from the heating chamber thereby to reduce humidity within the heating chamber for enhancing the drying effect of the air circulating within the heating chamber.

The apparatus may include a control system including a) sensors for sensing the dry bulb temperature of the air and the wet bulb temperature of the air within the heating chamber; and b) a controller for determining a relationship between the dry bulb temperature and the wet bulb temperature expressed as a percentage moisture content per unit volume of air and for generating a control signal based on the relationship for controlling the volume of air to be extracted from the heating chamber.

The apparatus may be configured for implementing the method as defined and described hereinabove in accordance with the first aspect of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the invention are described hereinafter by way of a non-limiting example of the invention, with reference to and as illustrated in accordance with the accompanying diagrammatic drawings. In the drawings:

Figure 1 shows a three-dimensional view of an apparatus for browning food products in accordance with the invention;

Figure 2 shows a three-dimensional view of the apparatus of Figure 1 , with a side cover thereof removed in order to show internal detail thereof;

Figure 3 shows a front view of the apparatus of Figure 1 , with the front cover removed to show internal detail thereof; and

Figure 4 shows a three-dimensional view of the apparatus of Figure 1 , with the front cover and conveyor removed to show internal detail thereof.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the drawings, an apparatus in the form of an oven for browning food products comprising a dough and an alginate based casing which surrounds the dough, is designated generally by the reference numeral 10. The oven 10 comprises, broadly, a heating chamber 12 for heating the food products; a conveyor 14 for conveying the food products through the heating chamber; an air extractor 16 for extracting air from the heating chamber in order to reduce humidity within the heating chamber; and a fan 24 for generating a forced circulating air flow within the heating chamber 12.

The oven 10 is configured for heating an outer surface of the dough of the food products in the heating chamber in order to induce a Maillard reaction for browning the food products. The alginate based casing includes a sodium alginate gel which has been treated with calcium chloride. The alginate based casing has a moisture content which impedes Maillard browning.

The oven 10 includes a gas burner 18 located at a side thereof and thermally coupled to a heater box 20 for heating the heating chamber, the gas burner 18 having an exhaust conduit 22 for conveying exhaust gases from the oven. The gas burner is operable to heat an outer surface of the dough of the food products to a temperature range of between 140°C and 165 °C which is the optimal temperature range for inducing a Maillard reaction in high throughput commercial food production processes.

The fan 24 which is driven by a motor 26, generates a forced circulating air flow within the heating chamber 12 for drying the alginate based casing. The oven 10 further includes top and bottom plenum chambers 27 and 28, respectively, which define a space between them through which the conveyor 14 for conveying the food products, is displaced. The oven includes top and bottom plenum plates 30, 32 defining bottom and upper sides of the plenum chambers 27 and 28, respectively. The plenum plates each define a plurality of holes therein through which circulating drying air is forced onto upper and lower sides of the food products as the food products are conveyed through the oven. The conveyor is of a metal wire open mesh construction allowing the forced air flow to impinge upon the food products for drying the alginate based casing.

The air extractor 16 includes an air extraction conduit 17 coupled to an extraction fan. In use, the air extractor 16 is operable to extract air from the heating chamber in order to reduce the humidity of the drying air circulating within the heating chamber thereby to enhance the drying effect of the air so as to promote drying of the alginate based casing. Circulating air flow within the heating chamber and air extracted therefrom is illustrated by arrows in the drawings.

The oven 10 includes a control system including sensors housed in a sensor housing 34, for sensing the dry bulb temperature and the wet bulb temperature of the air which is extracted from the heating chamber; and a controller for determining a relationship between the dry bulb temperature and the wet bulb temperature expressed as a percentage moisture content per unit volume of air. The controller is operable to generate a control signal based on the relationship for controlling the operation of the extraction fan for controlling the volume of air to be extracted from the heating chamber. In order to optimise the Maillard reaction at the outer surface of the dough of the food products so as to increase throughput of the food products through the oven 10, the outer surface of the dough of the food products is heated within the oven to the optimal temperature range between 140°C and 165°C while simultaneously subjecting the food products to a forced air flow for drying the alginate gel casing. In order to further optimise the Maillard reaction and promote Maillard browning, a portion of the air circulating within the heating chamber is extracted, thereby extracting moisture evaporated from the alginate based casing. The extraction of a portion of the air from the heating chamber enhances drying of the alginate based casing, thereby creating optimally dry conditions for promoting the Maillard reaction to take place at the outer surface of the dough of the food products.