WO2007122260A1

WO2007122260A1 - Heat-expanded food products

Info

Publication number: WO2007122260A1
Application number: PCT/EP2007/054081
Authority: WO
Inventors: Dolores O'riordan; Michael O'sullivan; James Lyng
Original assignee: University College Dublin, National University Of Ireland, Dublin
Priority date: 2006-04-25
Filing date: 2007-04-25
Publication date: 2007-11-01

Abstract

This invention relates to heat-expanded food products. In particular, this invention relates to heat-expanded synthetic cheese products, a heat-expandable precursor for forming same and the preparation of the precursor and the cheese products. The invention provides a heat-expanded synthetic cheese product, comprising :- from about 20% to about 59% by weight of a milk protein or a source thereof; from about 12% to about 68% by weight of a starch; from about 3% to about 15% by weight of water; wherein the heat-expanded synthetic cheese product comprises no more than 22% by weight of fat, the percentages being percentages by weight of the total product.

Description

Heat-Expanded Food Products

This invention relates to heat-expanded food products. In particular, this invention relates to heat-expanded synthetic cheese products, a heat-expandable precursor for forming same and the preparation of the precursor and the cheese products.

Microwave expandable snack foods have received increased attention in recent years because of their convenience, and their diverse shapes and texture that can be obtained at home using a pre-made food formulation. Heat-expanded crispy puffed snack food products based on synthetic or imitation cheese product precursors are known. However, such heat-expanded crispy puffed food products require a complicated method of manufacture. Additionally, the volume expansion % of the precursors tends to be very low. Although there is much variation in the composition of synthetic cheeses, a typical cheese precursor composition includes water, protein and approximately 25% fat, and a typical heat-expanded cheese composition includes about 40% fat. When starch is present in such heat-expanded synthetic cheese products, it is typically present in an amount of about 10% by weight of the heat-expanded product. Because of their high saturated fat content, such food products are quite unhealthy.

It is therefore an object of the present invention to mitigate the disadvantages associated with prior art synthetic cheese precursors and heat-expanded food products made from same.

It is also an object of the invention to provide a heat-expanded food product which is a crispy, puffed synthetic cheese product and which has good organoleptic properties, is satisfying, high in protein and fibre but also low in fat, or even contains no fat, and therefore provides a healthier alternative to heat-expanded synthetic cheese products currently available.

It is a further object of the invention to provide a heat-expandable precursor for forming the synthetic cheese product of the invention, which precursor has a high protein and fibre content but is also low in fat, or even contains no fat, and is capable of achieving a good volume expansion % on heating to form the heat- expanded synthetic cheese product of the invention.

It has now surprisingly been found that the replacement of fat with starch provides heat-expanded synthetic cheese products which are high in fibre and low in fat.

According to a first aspect of the present invention, there is provided a heat- expanded synthetic cheese product, comprising :- from about 20% to about 59% by weight of a milk protein or a source thereof; from about 12% to about 68% by weight of a starch; from about 3% to about 15% by weight of water; wherein the heat-expanded synthetic cheese product comprises no more than 22% by weight of fat, the percentages being percentages by weight of the total product.

Suitable milk proteins and sources thereof include casein, total milk proteins, milk protein concentrates or isolates, and other casein whey combinations. Casein may be present in a soluble and/or insoluble form, such as acid casein, rennet casein, and soluble caseinate derivatives such as sodium caseinate, calcium caseinate and potassium caseinate. A preferred milk protein is rennet casein. The milk protein or source thereof is preferably present in an amount of from about 25% to about 55%, preferably from about 30% to about 50%, more preferably from about 35% to about 45%, more preferably from about 37% to about 43%, still more preferably from about 38% to about 42%, most preferably from about 40% to about 42% by weight of the heat-expanded synthetic cheese product.

The starch may be derived from any suitable source such as cereals especially corn and maize, or rice, or a combination thereof. Starch derived from tubers such as potato or root crops may also be used. Suitable starches include starches which are either granular or non-granular native starches, modified or unmodified. Modified starches include gelatinised, cross-linked and substituted starches. The starch is preferably in a native granular form, wherein the granule size will vary with the origin/type of the starch. A high amylose starch is preferred. The starch is conveniently a resistant starch. As used herein, the term "resistant starch" is intended to mean starch that escapes or substantially escapes digestion by enzymatic hydrolysis in the small intestine, but can be fermented in the large intestine by microflora. In this way, resistant starch is considered to be a form of dietary fibre. Resistant starches may have prebiotic properties.

The starch used preferably has a gelatinisation temperature of greater than 70⁰C, more preferably greater than 80⁰C.

Corn starch is particularly preferred, especially corn starch sold under the trade name Hi Maize, obtainable from National Starch and Chemicals, Manchester, England such as Hi Maize 260.

The starch is preferably present in an amount of from about 15% to about 60%, more preferably from about 20% to about 45% by weight, even more preferably from about 30% to about 45% by weight of the synthetic cheese product.

The heat-expanded synthetic cheese product of the invention preferably comprises water in an amount of from about 5% to about 13%, more preferably from about 6% to about 12%, most preferably from about 6% to about 8% by weight of the cheese product.

The fat used in the present invention may be selected from one or more of the following: edible marine oils and fats, edible animal oils and fats, and edible vegetable oils and fats, optionally modified by fractionation and/or hydrogenation and/or inter-esterification. Suitable oils and fats include palm oil, rapeseed oil, soy bean oil, palm kernel oil, sunflower oil, coconut oil, cotton seed oil, canola oil and safflower oil, tallow, lard, fish and mixtures thereof. Rapeseed oil is particularly preferred. In the heat-expanded synthetic cheese product of the invention, the fat is preferably present in an amount of from about 1% to about 20%, more preferably from about 5% to about 15%, more preferably no more than 10%, even more preferably no more than 9% or 8% or 7% or 6% or 5% or 4% or 3% or 2% or 1% by weight of the product. In a particularly preferred embodiment, the heat- expanded synthetic cheese product comprises no added fat or substantially no added fat.

The heat-expanded synthetic cheese product of the invention may also include one or more conventional additives. Suitable additives include emulsifying agents, acidity regulators, preservatives, flavouring agents, colouring agents, and the like.

According to a second aspect of the present invention, there is provided a heat- expandable precursor for forming the heat-expanded synthetic cheese product according to the invention, the heat-expandable precursor comprising:- from about 12% to about 26% by weight of a milk protein or a source thereof; from about 7% to about 30% by weight of a starch; from about 46% to about 60% by weight of water; wherein the precursor comprises no more than 10% by weight of fat, the percentages being percentages by weight of the precursor.

The milk protein as defined above for the heat-expanded synthetic cheese product is preferably present in the precursor in an amount of from about 15% to about 25%, more preferably from about 17% to about 25%, most preferably from about 19% to about 25%, especially approximately 24% by weight of the precursor.

The starch as defined above for the heat-expanded synthetic cheese product is preferably present in the precursor in an amount of from about 10% to about 25%, more preferably from about 15% to about 25%, even more preferably from about 17% to about 25%, most preferably from about 19% to about 25%, especially approximately 21% by weight of the precursor. The heat-expandable precursor of the invention preferably comprises water in an amount of from about 48% to about 55%, especially approximately 50% by weight of the precursor.

In the heat-expandable precursor of the invention, the fat is as defined above for the heat-expanded synthetic cheese product and is preferably present in an amount of no more than 9% or 8% or 7% or 6% or 5% or 4% or 3% or 2% or 1% or 0.5% or 0.4% or 0.3% or 0.2% or 0.1% by weight of the precursor. In a particularly preferred embodiment, the precursor comprises no added fat or substantially no added fat.

The precursor may also include one or more conventional additives. Suitable additives include emulsifying agents, acidity regulators, preservatives, flavouring agents, colouring agents, and the like.

When an emulsifying agent is present, it is preferably in the form of a salt or a combination of salts. As used herein, the term "emulsifying agent" is intended to mean a substance capable of converting protein into a dispersed form, thereby bringing about homogeneous distribution of components within the heat- expandable precursor. Thus, an emulsifying agent is necessary when an insoluble protein such as rennet casein or acid casein is used in the heat-expandable precursor of the invention.

The emulsifying agent is preferably a calcium chelating salt, preferably a sodium or a potassium salt. Suitable calcium chelating salts include salts of phosphoric acids (which may be ortho or polyphosphates) and citric acid; including but not limited to, monosodium phosphate, monopotassium phosphate, monosodium citrate, monopotassium citrate, disodium phosphate, dipotassium phosphate, disodium citrate, dipotassium citrate, trisodium phosphate, tripotassium phosphate, trisodium citrate, tripotassium citrate, tetrasodium phosphate, tetrapotassium phosphate, tetrasodium citrate; sodium polyphosphates, potassium polyphosphates, sodium calcium polyphosphate, calcium polyphosphates; and sodium aluminium phosphate; and combinations thereof. A combination of a sodium citrate and a sodium phosphate is preferred, in particular, a combination of trisodium citrate and disodium phosphate.

The amount of the emulsifying agent present in the heat-expandable precursor of the invention will vary with the amount of insoluble casein present in the precursor. A preferred ratio of emulsifying agent to insoluble casein is in the range of from about 0.05 to about 0.08, more preferably approximately 0.063, based on the weight % of each component.

In a particularly preferred embodiment, the heat-expandable precursor cheese product includes from about 0.5% to about 2%, more preferably from about 1.0% to about 1.5%, still more preferably, approximately 1.3% by weight of emulsifying agent based on the precursor. Most preferably, the heat-expandable precursor comprises a combination of approximately 0.9% trisodium citrate and approximately 0.4% disodium phosphate by weight of the heat-expandable precursor. A ratio of approximately 2: 1 trisodium citrate to disodium phosphate is particularly preferred.

When an acidity regulator is present, it is preferably present in an amount of from about 0.1% to about 1% by weight of the precursor. Suitable acidity regulators include lactic acid, adipic acid and citric acid. A preferred acidity regulator is citric acid. Citric acid present in an amount of approximately 0.5% by weight of the precursor is particularly preferred.

When a preservative is present, it is preferably present in an amount of from about 0.01% to about 0.5% of the precursor. A preferred preservative is sorbic acid. Sorbic acid present in an amount of approximately 0.1% by weight of the precursor is particularly preferred.

When a flavouring agent is present, it is preferably present in an amount of from 0.5% to about 2.5% by weight of the precursor. The flavouring agent may comprise one or more flavouring agents. A preferred flavouring agent is sodium chloride. Sodium chloride present in an amount of approximately 1.4% by weight of the precursor is particularly preferred. It will be appreciated that any other flavouring agents desired to impart a particular flavour to the heat-expandable precursor, may be used.

The heat-expandable precursor according to the invention may be prepared by a method comprising the steps of:

(a) combining the milk protein, water and fat at a temperature of from about 3O⁰C to about 9O⁰C; and

(b) adding the starch to the resulting mixture.

Preferably, step (a) comprises combining the ingredients at a temperature of from about 3O⁰C to about 7O⁰C, followed by heating the combined ingredients to a temperature of from about 7O⁰C to about 9O⁰C.

The heat-expanded synthetic cheese product according to the invention may be prepared by a method comprising the above steps (a) and (b) and a further step of:

(c) subjecting the heat-expandable precursor according to the invention to heat until the heat-expandable precursor has expanded.

Preferably, before heating in step (c), the precursor is allowed to rest for a period of from about 12 hours to about 14 days, preferably from about 24 hours to about 10 days, preferably at a temperature of from about 1°C to about 6°C, more preferably at about 4°C.

Preferably, the heat in step (c) is microwave heat.

Preferably, the precursor is heated by microwave heat until the precursor achieves a volume expansion % of from about 100% to about 1000%, more preferably from about 150% to about 800%, especially about 600%. A volume expansion % of 1000% can be achieved by allowing the precursor to rest prior to heating for about 10 days at 4°C. After 10 days, the cheeses can conveniently be stored at -20⁰C and microwaved from a frozen state.

Preferably, the precursor is subjected to the microwave treatment for a period of from about 10 to 100 seconds in a microwave set at 500- 1500W, more preferably for a period of about 60 seconds in a microwave set at 100OW.

As used herein, the term "volume expansion %" is generally intended to mean the degree of volume expansion calculated as follows:

Volume expansion % = final volume - initial volume x 100% initial volume

where the initial and the final volumes correspond to the respective volumes of (a) the heat-expandable precursor measured before heating; and (b) the heat-expanded synthetic cheese product after heating. Volume is measured by a displacement method using millet seeds. The volume of five samples is determined for each heating period and the mean taken. The volume expansion % measurements are in accordance with the American Association of Cereal Chemists, 2000, Approved Methods of the AACC, 10^th edition.

Thus, a volume expansion % of 100% implies that the final volume is twice that of the initial volume. A volume expansion % of 600% would mean that the final volume was seven times the initial volume, i.e. there had been a sixfold increase in addition to the original volume.

In a particularly preferred embodiment of the invention, the precursor of the invention has no fat and has a volume expansion % of about 600%. This volume expansion % is preferably achieved by heating the heat-expandable precursor in a microwave oven set at IOOOW for about 60 seconds.

Advantages of the products of the invention include the following: The heat-expanded synthetic cheese products of the invention provide tasty food products which also have nutritional benefits. For example, the heat-expanded products have a fat content of less than 22%, with some preferred embodiments having no fat. This is in contrast to conventional heat-expanded synthetic cheese products which have a higher fat content of about 40% fat.

Additionally, the starch in the products of the invention provides the products with the advantage of having high fibre content. This is in contrast to conventional heat-expanded synthetic cheese products which have a very low fibre content. Starch is typically only added to conventional synthetic cheese products as a replacement for the protein, in order to reduce the cost of preparation.

A further advantage of the heat-expanded synthetic cheese products of the invention is that they may be sold in a heat-expandable precursor form ready for heating by the consumer, with the result that the consumer may choose when to heat the product in order to produce a ready-to-eat crispy puffed food product. This heat-expandable precursor may be sold in a chilled or frozen form. The heat- expandable precursor may be eaten before being heated, if desired, to provide a tasty and satisfying food product. The products may also be sold in a heat- expanded form that is conveniently packaged ready to eat. The ready-to-eat heat- expanded puffed crispy synthetic cheese products are low in fat, high in fibre, and provide most or all of the nutritional benefits and taste of cheese.

An advantage of the precursors of the invention is that they have a volume expansion % superior to known synthetic cheeses upon heating. It has now surprisingly been found that the precursors of the invention are capable of achieving a volume expansion % of up to 1000% on heating, which is desirable for crispy puffed food products.

The following examples serve to illustrate the invention but it will be appreciated that the invention is not limited to these examples. EXAMPLES 1 - 5

Heat-expandable precursors according to the invention were prepared from the ingredients listed in Table 1 :

Table 1

¹KeITy Ingredients, Listowel, Ireland; ²National Starch and Chemicals, Manchester, England; ³ElHs and Everard, Dublin, Ireland; ⁴Jungbunzlauer, Pernhofen, Austria; ⁵Hoechst Ireland Limited, Dublin, Ireland; ⁶SaIt Union, Cheshire, England.

A heat-expandable precursor according to example 1 was prepared as follows:

(A) All of the ingredients listed in Table 1 except citric acid and Hi-Maize 260 (Trade Mark) were added to and mixed in a twin-screw cooker (model CC-010, Blentech Corporation, CA, USA). A temperature of 5O⁰C was maintained during the mixing by injecting steam into the steam jacket of the cooker. The mixture was then heated to 8O⁰C by direct injection of steam into the contents; this temperature was reached after approximately 3 minutes. The Hi-Maize 260 (Trade Mark) was added and the temperature was maintained at 8O⁰C (using the steam jacket) for approximately 1 minute, or until a uniform mass was obtained. Citric acid was then added and mixed for a further 1 minute.

(B) The heat-expandable precursor was then removed from the cooker. A sample of the heat-expandable precursor was obtained for analysis as described in example 6 below.

(C) The remainder of the heat-expandable precursor was cut using a cork borer into cylindrical sample pieces of approximately 2g weight, approximately 15mm diameter and approximately 5mm height. The sample pieces were wrapped in aluminium foil to minimize moisture loss and stored at a temperature of approximately 5°C in a refrigerator for 12 hours.

Heat-expandable precursors according to examples 2, 3, 4 and 5 were prepared according to the above procedure but including 2% by weight of rapeseed oil

(example 2), 4% by weight of rapeseed oil (example 3), 6% by weight of rapeseed oil (example 4) and 10% by weight of rapeseed oil (example 5) respectively. In these examples, the oil was added in direct replacement (on a weight % basis) of Hi-Maize 260 (Trade Mark) used to produce the heat-expandable precursor of example 1. Three batches of each heat-expandable precursor of examples 1 - 5 were manufactured. In accordance with step (B) above, one sample from each batch was obtained for analysis. EXAMPLE 6

The samples produced according to examples 1 - 5 were analysed.

The samples were grated and allowed to equilibrate at room temperature, following which they were analysed for moisture content, fat content, protein content and water activity as set out in (i)-(iv) below:

(i) analysis for moisture by oven drying (IDF 1958) method; (ii) analysis for fat by the Gerber method (National Standards Authority of Ireland, 1955);

(iii) analysis for protein using the semi-micro Kjeldahl method (IDF, 1993); and (iv) analysis for water activity was determined at 25⁰C using Novasina

LabMaster a_w meter (Novatron, Horsham, England). The mean of the three samples for each heat-expandable precursor according to examples 1 - 5 was calculated. The results are shown in Table 2.

Table 2

It was noted that the samples contained approximately 60% moisture, compared with approximately 51% added water in the ingredients. This increase in water is due to the method of injecting steam into the contents as explained in the procedure above. The amount of the protein had decreased slightly from an amount of approximately 24% in the ingredients to an amount of approximately 18%.

The results of the mean moisture content, protein, and water activity of the cheese samples of examples 1 -3 was 60.04+0.04%, 18.07+0.17% and 0.99+0.006% respectively. It was found that the addition of fat content in examples 2 and 3 had no effect on moisture content, protein content and the water activity of the heat- expandable precursor.

EXAMPLE 7

Heat-expanded products according to the invention were prepared as follows:

Immediately prior to microwave heating of heat-expandable precursor, the microwave was preheated by heating one litre of water for 30 minutes. The purpose of preheating the microwave was to allow the products to be evenly heated so they could be analysed afterwards. It will be appreciated that it would not be necessary for a consumer to preheat the microwave prior to microwaving the precursor. The sample pieces of heat-expandable precursor from examples 1 - 5 were removed from the refrigerator and the aluminium foil surrounding the sample pieces was removed. The sample pieces were placed individually on a piece of shrink film, to avoid the sample sticking to the plate. Each sample in turn was placed on a support about 0.5cm above a microwavable glass plate, and was then heated for different periods of times (10-10Os) in a constant power microwave oven set at 100OW, at a frequency of 2450 + 50MHz (Commercial Armana RS591SS, Armana refrigeration, Inc, Armana Iowa, USA). The output of IOOOW was verified using the International Microwave Power Institute (IMPI) two-litre test. It will be appreciated that a commercial microwave having a frequency of e.g. 915 + 25 MHz or 896+ 25 MHz may alternatively be used. The microwave heating of the sample pieces produced the heat-expanded synthetic cheese products of the invention. The cavity dimensions of the microwave were 39cm x 34cm x 27cm (depth x width x height). The heat-expanded microwave- treated sample pieces were taken out of the microwave oven and those samples originating from examples 1 - 3 were photographed immediately using a digital camera (Kodak C310). The photos were processed using Microsoft Office 2003 picture manager, the results of which are discussed below in example 8.

Heat-expanded synthetic cheese products which were heated for 60 seconds in a microwave set at IOOOW were allowed to cool at room temperature, following which they were analysed for moisture content, fat content, protein content and carbohydrate content. The results are given in Table 3 below:

Table 3

The heat-expanded products of the invention produced crispy, puffed synthetic cheese products with good organoleptic properties.

EXAMPLE 8

The heat-expanded synthetic cheese products originating from examples 1 - 5 were analysed for expansion, and the products originating from examples 1 - 3 were analysed for weight loss and structure as set out in (A)-(C) below. The results of the effect of the fat content on the heat-expanded products are given in example 9 below.

(A) Expansion:

The degree of expansion (volume expansion %) of the synthetic cheese products was determined for each of the products using the formula given above.

(B) Weight loss:

Weight loss of the heat-expanded synthetic cheese products compared with the heat-expandable precursor products was expressed as % weight loss, using the following equation:

_m ■ _{Λ Λ} initial weight - final weight . .. % weight loss - ≡ ≡— x lOO initial weight

where the initial weight (g) corresponds to the weight of the heat-expandable precursor samples and final weight (g) corresponds to the weight of the heat- expanded samples immediately after microwave heating.

(C) Structure:

A cross-section of each heat-expanded synthetic cheese product was cut using a hand saw and scanned with flat bed scanner (Epson perfection 1680). The images were processed using Adobe Photoshop^® 6.

Results for (A) Expansion and (B) Weight loss:

The volume expansion % of each of the precursors of examples 1 - 5 was measured, and the results are given in Table 4 below: Table 4

All of the precursors achieved a good degree of expansion. However, the precursor with no fat content provided the greatest volume expansion % of nearly 600%.

As described in example 7, the heat-expandable precursor samples were heated in a microwave from 10 -100s. Two major processes were observed during microwave heating: expansion and weight loss (moisture loss) (Figure 1). The time course of these processes may be divided into three distinct regions melting (heating up), moisture loss and moisture loss and burning. During the initial heating the samples became soft and started to expand from the centre. A sharp increase in volume expansion was observed up to 20s after which a maximum volume expansion was recorded. On further heating (20-10Os) the expansion remained constant. For short heating times of less than or equal to 20s samples were soft, indicating high moisture content, as heating time increased, more moisture was lost, hence the matrix was able to set and maintain a rigid structure.

A small loss in weight (approximately 5%) was recorded during the first 10s of sample heating (Figure 1), however, as the heating time increased particularly between 20 and 40s, the loss in weight increased sharply. After 50s little further weight loss occurred. The heat-expanded synthetic cheese products began to burn after heating for approximately 70s. The burning was observed to start from the centre, in the same manner as the expansion. The weight loss for the first 60s of heating period may be predominantly due to moisture loss, while after this heating period, weight loss may be due to both moisture loss and burning, resulting in chemical decomposition of the sample.

Results for (C) Structure of the heat-expanded synthetic cheese products:

The final structure of the heat-expanded synthetic cheese products depended on the composition of the cheese product and the heating time.

The heat-expanded synthetic cheese products with no added fat had a structure consisting of either a large matrix with a hollow core or a matrix with a small number of large thin- walled cells (Figure 2). The heat-expanded products with 2 and 4% added fat had a dense crumb made up of large number of small cells with thick walls (Figure 2). The cells developed during heating. It is thought that as the moisture inside the sample was heated, it created many local pressures ('bubbles'). With short heating times (less than 30s) these 'bubbles' expanded only slightly and after heating, the sample still had high moisture content and hence collapsed. As heating time increased (greater than 30s) the 'bubbles' expanded further, during which time the sample continued to lose moisture. At a critical low moisture content, the structure of each of the "bubbles" was largely retained on after heating the sample, forming cell walls, which led to a rigid structure in the expanded cheese samples.

The following is a possible mechanism for the observed changes which occur during microwave heating of the cheese product of the present invention. Initially, as the imitation cheese heats up, the starch (Hi-Maize 260) begins to undergo gelatinization and starts to swell. On continued heating, water temperature reaches boiling point, gas bubbles start to form and bubble nucleation is initiated. The bubble growth phase takes place in the starch gel as bubbles expand. Water vapour acts as both as a plasticizer of the starch during gelatinization and causes expansion of the gel during bubble growth. The starch gel bubble matrix appears to set and becomes stable as more moisture is driven off by evaporation. If insufficient evaporation occurs and too much moisture (plasticizer) remains in the sample, the bubbles can collapse. If fat is present most likely it decreases the degree of starch gelatinization and thus decreases the starch swelling. The decreased starch swelling results in eventual decrease in expansion of imitation cheese with added fat during microwave heating.

EXAMPLE 9

The heat-expanded synthetic cheese products originating from examples 1 - 3 were analysed to determine the effect of fat content on the expansion, weight loss and drying rate of the cheese product. As the fat content was decreased, the level of resistant starch was increased proportionally. The results are set out in (A)-(C) below:

(A) Effect of fat content on expansion:

As shown in example 8, the amount of fat present in the precursor of the invention affected the volume expansion % of the resultant heat-expanded synthetic cheese products of the invention.

The best results were achieved using the 0% fat precursor composition (resulting in a heat-expanded synthetic cheese product having 0% added fat). This 0% fat precursor composition had a volume expansion % of 600% following heating for 60 seconds at IOOOW in a microwave.

The precursors of the invention having a fat content of from 2% to 10% (resulting in heat-expanded synthetic cheese products having about 4.4%, 8.8%, 13% and 21.5% fat content respectively), all achieved a volume expansion % of about 150% following heating for 60 seconds at IOOOW in a microwave. (B) Effect of fat content on weight loss:

The loss in weight of the heat-expanded synthetic cheese products during microwave heating is shown in Figure 4. The weight loss profile for the three synthetic cheese products was similar. However, the rate at which moisture was lost (Figure 5) was highest for the cheeses with no added fat for the first 70s of heating. Therefore, the added liquid fat appeared to have a negative effect on the rate of moisture loss.

(C) Effect of fat content on drying rate: From the drying curve of the heat-expanded synthetic cheese products shown in Figure 5, the drying rate of the three products followed a similar pattern. The water activity in all the cheeses was reduced from 0.99 to 0.6 after heating the samples for 40s, after which, no more decrease in water activity was observed. The product with no added fat showed the highest drying rate. A sharp increase in the rate of drying was observed up to 20s, followed by a plateau region at 20-40s, then a decrease to 100s. This shows that most probably the critical moisture content is reached after heating for 40s indicating that the samples started lose the strongly bound water. This observation would be important in evaluating the stability of the expanded product.

EXAMPLE 10

A comparative heat-expanded synthetic cheese product was produced by using a typical prior art synthetic cheese product as a heat-expandable precursor. The precursor was prepared using the ingredients listed in Table 5: Table 5

One sample of the comparative heat-expandable precursor was subjected to a microwave treatment of 60 seconds at 100OW.

The comparative heat-expanded product was allowed to cool at room temperature, following which it was analysed for moisture content, fat content and protein content. The volume expansion % of the product was also measured. The results are given in Table 6 below:

Table 6

The heat-expanded comparative product had a high fat content of 41%. Unlike the heat-expandable precursor of the present invention, the conventional synthetic cheese had very limited expansion. After 60 seconds of heating in a microwave set at 100OW, the volume expansion % was only about 95%. The resultant product also tended to be flat and elongated with very little vertical expansion, which is undesirable.

In summary, the heat-expanded synthetic cheese products of the invention of the present invention are crispy, puffed food products which have good organoleptic properties, are satisfying, high in protein but also high in fibre and low in fat, or even contain no fat, and therefore provide a healthier alternative to ready-to-eat synthetic cheese products currently on the market. The heat-expanded food products of the invention containing no fat produce the best volume expansion %.

The present invention is not limited to the examples described herein, which may be modified or adapted without departing from the scope of the present invention.

Claims

CLAIMS:

1. A heat-expanded synthetic cheese product, comprising:- from about 20% to about 59% by weight of a milk protein or a source thereof; from about 12% to about 68% by weight of a starch; from about 3% to about 15% by weight of water; wherein the heat-expanded synthetic cheese product comprises no more than 22% by weight of fat, the percentages being percentages by weight of the total product.

2. A heat-expanded synthetic cheese product as claimed in claim 1, wherein the milk protein or source thereof is selected from casein, total milk proteins, milk protein concentrates or isolates, and other casein whey combinations.

3. A heat-expanded synthetic cheese product as claimed in claim 2, wherein the milk protein is casein, which is present in a soluble and/or insoluble form.

4. A heat-expanded synthetic cheese product as claimed in claim 3, wherein the casein comprises a soluble caseinate derivative selected from sodium caseinate, calcium caseinate and potassium caseinate.

5. A heat-expanded synthetic cheese product as claimed in claim 3 or 4, wherein the casein comprises insoluble casein selected from acid casein and rennet casein.

6. A heat-expanded synthetic cheese product as claimed in any one of claims 1 to 5, wherein the milk protein or source thereof is present in an amount of from about 25% to about 55%, preferably from about 30% to about 50%, more preferably from about 35% to about 45%, even more preferably from about 37% to about 43%, still more preferably from about 38% to about 42%, most preferably from about 40% to about 42% by weight of the heat-expanded synthetic cheese product.

7. A heat-expanded synthetic cheese product as claimed in any preceding claim, wherein the starch is derived from a cereal selected from corn and maize, or rice, or is derived from tubers such as potato, or root crops, or a combination thereof.

8. A heat-expanded synthetic cheese product as claimed in any preceding claim, wherein the starch is in a native granular form.

9. A heat-expanded synthetic cheese product as claimed in any preceding claim, wherein the starch is a high amylose starch.

10. A heat-expanded synthetic cheese product as claimed in any preceding claim, wherein the starch is a resistant starch.

11. A heat-expanded synthetic cheese product as claimed in any preceding claim, wherein the starch has a gelatinisation temperature of greater than 70⁰C, more preferably greater than 80⁰C.

12. A heat-expanded synthetic cheese product as claimed in any preceding claim, wherein the starch is corn starch, especially corn starch sold under the trade name Hi Maize.

13. A heat-expanded synthetic cheese product as claimed in any preceding claim, wherein the starch is present in an amount of from about 15% to about 60%, more preferably from about 20% to about 45% by weight, even more preferably from about 30% to about 45% by weight of the synthetic cheese product.

14. A heat-expanded synthetic cheese product as claimed in any preceding claim, wherein the water is present in an amount of from about 5% to about 13%, more preferably from about 6% to about 12%, most preferably from about 6% to about 8% by weight of the synthetic cheese product.

15. A heat-expanded synthetic cheese product as claimed in any preceding claim, when the fat is selected from one or more of the following: edible marine oils and fats, edible animal oils and fats, and edible vegetable oils and fats, optionally modified by fractionation and/or hydrogenation and/or inter- esterification.

16. A heat-expanded synthetic cheese product as claimed in any preceding claim, wherein the fat is selected from the following: palm oil, rapeseed oil, soy bean oil, palm kernel oil, sunflower oil, coconut oil, cotton seed oil, canola oil and safflower oil, tallow, lard, fish and mixtures thereof.

17. A heat-expanded synthetic cheese product as claimed in any preceding claim, wherein the fat is rapeseed oil.

18. A heat-expanded synthetic cheese product as claimed in any preceding claim, wherein the fat is present in an amount of from about 1% to about 20%, more preferably from about 5% to about 15%, more preferably no more than 10%, even more preferably no more than 9% or 8% or 7% or 6% or 5% or 4% or 3% or 2% or 1% by weight of the product.

19. A heat-expanded synthetic cheese product as claimed in any preceding claim, wherein the synthetic cheese product comprises no added fat or substantially no added fat.

20. A heat-expanded synthetic cheese product as claimed in any preceding claim, wherein the heat-expanded synthetic cheese product includes one or more conventional additives selected from the following: emulsifying agents, acidity regulators, preservatives, flavouring agents, colouring agents, and the like.

21. A heat-expandable precursor for forming the heat-expanded synthetic cheese product according to any preceding claim, the heat-expandable precursor comprising :- from about 12% to about 26% by weight of a milk protein or a source thereof; from about 7% to about 30% by weight of a starch; from about 46% to about 60% by weight of water; wherein the precursor comprises no more than 10% by weight of fat, the percentages being percentages by weight of the precursor.

22. A heat-expandable precursor as claimed in claim 21, wherein the milk protein or source thereof and/or the starch and/or the fat are as defined in any of claims 2 - 5, 7 - 12 and 15 -17.

23. A heat-expandable precursor as claimed in claim 22, wherein the milk protein is present in an amount of from about 15% to about 25% by weight, more preferably from about 17% to about 25%, most preferably from about 19% to about 25%, especially approximately 24% by weight of the precursor.

24. A heat-expandable precursor as claimed in any one of claims 21 to 23, wherein the starch is present in an amount of from about 10% to about 25%, more preferably from about 15% to about 25%, even more preferably from about 17% to about 25%, most preferably from about 19% to about 25%, especially approximately 21% by weight of the precursor.

25. A heat-expandable precursor as claimed in any one of claims 21 to 24, wherein the water is present in an amount of from about from about 48% to about 55%, especially approximately 50% by weight of the precursor.

26. A heat-expandable precursor as claimed in any one of claims 21 to 25, wherein the fat is present in an amount of no more than 9% or 8% or 7% or 6% or 5% or 4% or 3% or 2% or 1% or 0.5% or 0.4% or 0.3% or 0.2% or 0.1% by weight of the precursor.

27. A heat-expandable precursor as claimed in any one of claims 21 to 26, wherein the precursor comprises no added fat or substantially no added fat.

28. A heat-expandable precursor as claimed in any one of claims 21 to 27, wherein the precursor includes one or more conventional additives selected from the following: emulsifying agents, acidity regulators, preservatives, flavouring agents, colouring agents, and the like.

29. A method for preparing the heat-expandable precursor as claimed in any one of claims 21 to 28, comprising the steps of:

(b) adding the starch to the resulting mixture.

30. A method as claimed in claim 48, wherein step (a) comprises combining the ingredients at a temperature of from about 3O⁰C to about 7O⁰C, followed by heating the combined ingredients to a temperature of from about 7O⁰C to about 9O⁰C.

31. A method for preparing a heat-expanded synthetic cheese product as claimed in any one of claims 1 to 20, comprising the method as claimed in claim 29 or 30 and further comprising the step of:

32. A method as claimed in claim 31, wherein prior to step (c) the precursor is allowed to rest for a period of from about 12 hours to about 14 days, preferably from about 24 hours to about 10 days.

33. A method as claimed in claim 31 or 32, wherein the precursor is allowed to rest at a temperature of from about 1°C to about 6°C, preferably about 4°C.

34. A method as claimed in any one of claims 31 to 33, wherein the heat is microwave heat.

35. A method as claimed in any one of claims 31 to 34, wherein the precursor is heated until the precursor achieves a volume expansion % of from about 100% to about 1000%, more preferably from about 150% to about 800%, especially about 600%.

36. A method as claimed in any one of claims 31 to 35, wherein the precursor is subjected to microwave heat for a period of from about 10 to 100 seconds in a microwave set at 500- 1500W, more preferably for a period of about 60 seconds in a microwave set at 100OW.