AMBIENT STABLE FOOD PRODUCT

Abstract: A process of producing an ambient stable food product which includes a preservative selected from an inorganic acid, an organic acid, the salts thereof and mixtures thereof, having an equilibrium pH of from 4.7 to 6.5 and an Aw of from 0.94 to 0.999, wherein the food product is heated to a temperature of from 90 to 130 DEG C for a time sufficient to provide a microbiologically safe, ambient stable food product.

Description: AMBIENT STABLE FOOD PRODUCT Technical Field of the Invention The invention relates to ambient stable food products and a process for the preparation thereof. Background to the Invention Currently, in order to achieve microbiologically safe ambient stable food products, such as sauces or soups, the food product undergoes a preservation system of either,- (a) Neutral pH plus sterilisation. Sterilisation typically involves a minimum heat treatment equivalent to 121°C for 2.45 minutes (F 0 =2.45) . (b) Low equilibrium pH (pH ≤ 4.6) plus pasteurisation in order to prolong shelf-life and inactivate vegetative pathogens. Both products produced using methods (a) and (b) may have a high water activity (A„ of above 0.93) ; or (c) Low water activity (A products (A„ ≤ 0.93) produced by introducing a relatively high level of salt and/or sugar into the product followed by pasteurisation, in order to prolong shelf-life and inactivate vegetative pathogens. All such preservation systems are detrimental to product quality and thus for some time a novel preservation system has been sought which provides an ambient stable food product with minimum loss of quality, for example product texture, colour and/or taste. Throughout this specification the definition of F 0 is that generally used ie a heat treatment for the time given in minutes at 121°C or an equivalent heat treatment using z value of 10C°. Where z equals the number of degrees of temperature change necessary to cause the decimal reduction time to change by a factor of 10. Thus F 0 3 means 3 minutes at 121°C or an equivalent heat treatment. F 0 3 is the heat treatment required to provide a 12 log reduction of Clostridium botulinum. EP 191 573 (American Can Company) discloses a process of providing a food stuff which is commercially sterile, having an equilibrium pH of 4.6 or less comprising combining the foodstuff with an acid and its lactones, preferably an aldonic acid and a lactone thereof and thermally processing the food stuff . EP 12 255 (Societe des Produits Nestle SA) discloses a food product having a water activity of 0.86 - 0.9 and a pH of 4.5 to 5.5. EP 230 122 (Oscar Mayer Foods Corporation) discloses chilled poultry or fish foodstuffs wherein lactate salt is added to delay Clostridium botulinum growth. This disclosure provides an additional safety factor where refrigeration is an essential element of the preservation system but the product may receive some transient temperature increase during its shelf-life. This process merely delays growth and does not provide ambient stability. US 4 495 208 discloses a shelf stable pet food having a moisture content of from 50 to 80%, a water activity of at least 0.9, from 0.3 to 3.0% of an edible organic acid and sufficient inorganic acid to maintain the pH of the product within the range of from 3.5 to 5.8. Additionally the pet food composition essentially comprises from 4 to 15% fructose and an antimycotic. The microbiological stability is provided by synergistic action between the sugar, acid and antimycotic. The level of antimycotic used is higher than acceptable levels for foodstuff for human consumption. This process for manufacture of shelf-stable foodstuffs is therefore not appropriate for foodstuffs provided for human consumption. GB 2 023 996 relates to foods packed in an hermetically sealed container having a pH value below 5.5 or containing a liquid having a water activity of less than 0.94 and that have been sterilised at 115 to 150°C for a relatively short time. In this document F 0 is defined as the time for complete elimination of micro-organisms or spores in their experiments. This is a different definition to that applied for F 0 in the current specification (see above) using the definition of F 0 as applied in the current specification the invention disclosed in GB 2 023 996 relates to heat treatments that are all above an F 0 >3. There is no teaching in GB 2 023 996 that ambient stability can be achieved under the conditions defined in the current specification. We have now surprisingly discovered that it is possible to achieve an ambient stable food product having excellent product quality by use of a combination of preservation treatments. Disclosure of the Invention Accordingly the invention provides a process of producing an ambient stable food product which includes a preservative selected from an inorganic acid, an organic acid, the salts thereof and mixtures thereof, having an equilibrium pH of from 4.7 to 6.5 and an A ^ of from 0.94 to 0.999 wherein the food product is heated to a temperature of from 90 to 130°C for a time sufficient to provide a microbiologically safe, ambient stable food product; providing that; when the product temperature is >100°C and the equilibrium pH is 6.5; the A„, is ≥0.94 and the food product is heated sufficiently to achieve an F 0 <2.45; when the product temperature is >100°C and the equilibrium pH is from 6 to <6.5; the A„ is ≥O .95 and the product is heated sufficiently to achieve an F 0 of <2.45; when the product temperature is >100°C and the equilibrium pH is from 5.5 to <6.0; the A ^ . is ≥0.95 and the product is heated sufficiently to achieve an F 0 <2.0; when the product temperature is >100°C and the equilibrium pH is from 5.0 to <5.5; the Aw is ≥0.95 and the product is heated sufficiently to achieve an F 0 <1.5; and when the product temperature is >100°C and the equilibrium pH is from 4.7 to <5.0; the ^ , is ≥0.95 and the product is heated sufficiently to achieve an F 0 <1.0. When the product has an equilibrium pH of from 4.7 to 6.5, it was surprising to discover that it is possible to achieve ambient stability using lower heat treatments than conventionally used. This was possible by utilising a combination of preservation treatments under milder conditions than those previously recommended, ie preservatives, reduced pH, and heat treatment. This enabled an ambient stable product to be provided which has excellent taste and texture qualities. It should be noted that the product produced is ambient stable because the bacterial spores contained therein are injured such that they cannot grow and are therefore harmless. The spores are thus not necessarily inactivated as achieved by conventional sterilisation techniques . Preferably the food product is heated to a temperature of from 90 to 110°C, more preferably from 90 to 100°C most preferably from 95 to 100°C. The time for which the product is heated in order to achieve microbial stability at a given temperature will be readily determined by the man skilled in the art. Typically for temperatures of > . 98°C, the product will suitably be heated for a time of > . 2 minutes, whereas for temperatures of < 98°C, the product will suitably be heated for a time of > . 30 minutes. Suitable organic acids and their salts may be chosen from lactic acid, acetic acid, succinic acid, malic acid, propionic acid, benzoic acid, fumaric acid, tartaric acid, citric acid, the salts thereof, glucono delta lactone, and mixtures thereof. Preferably the organic acid is lactic acid. A suitable inorganic acid is phosphoric acid, although any foodgrade inorganic acid may be used. Preferably the organic acid, inorganic acid, the salts thereof or mixtures thereof are incorporated into the food product at 0.001% to 2% weight/weight or equivalent volume/weight of the food product depending on the nature of the acid used. Preferably the food product has an equilibrium pH of from 4.7 to 6.0, more preferably from 4.7 to 5.8 and most preferably from 4.7 to 5.1. When the pH is greater than 5.1 the organic acid, inorganic acid, the salts thereof or mixtures thereof are preferably incorporated into the food product at equal to or greater than 1% w/w, preferably at greater than 1% w/w most preferably at 2% w/w. Preferably the food product has an A„ of from 0.96 to 0.999, most preferably from 0.97 to 0.999. The food product may additionally comprise further preservatives. Suitable additional preservatives include sugars, sodium chloride, ethanol, D-alanine, glycerol and mixtures thereof. This process may be used to provide ambient stable foodstuffs. In particular this process may be used to provide ambient stable sauces, soups and dressings with or without particles. EXAMPLES Examples 1 & 2 A white sauce was prepared having the following composition: Coconut oil 12% v/w NaCl 0.5% w/w Skimmed milk powder 6% w/w Colflo 67 * starch (registered trade mark) 4% w/w Lactic acid * Water to 100% * Example 1 contained 0.5% w/w lactic acid. Example 2 contained 0.3% w/w lactic acid. The composition had an equilibrium pH of 5.1, the ^ , was greater than 0.95. The heat treatment of the product was 98°C for 23 minutes. This combination preservation system in Examples 1 & 2 resulted in products which were microbiologically safe and stable after 12 months storage at 30°C when the initial challenge was 10 8 spores of Clostridium botulinum and 10 8 spores of typically encountered Bacillus species. Comparative Example A Example l was repeated except that the product was not subjected to a heat treatment. This resulted in. a product which was not microbiologically safe & stable at ambient temperatures when the initial challenge was as described in Example 1. Examples 3-60; Comparative Examples B-H A medium was prepared for C.botulinum having the following composition: g/litre Proteose peptone 12.5 Lab Lemco ® powder (Oxoid) 2.5 Neutralised soya peptone 2.5 Yeast extract 2.5 Sucrose 2.0 Soluble starch 1.0 Resazurin 0.001 Antifoaming agent (ml) 0.25 L-cysteine HC1 0.2 Salt solution A (ml) 40.0 Salt solution B (ml) 40.0 Salt solution A : CaCl^H.O 0 . 26 MgS0 4 . 7H 2 0 0 .48 NaCl 2 . 0 Salt solution B: KH 2 P04 1.0 K 2 HP0 3 H 2 0 1.3 NaHCO, 10.0 Lactic Acid 0 to 2.0% (see Table 1) A second medium was prepared for Bacillus species having the following composition: Lactic acid . 0 to 2.0% (see Table 1) Nutrient Broth (Difco) to 100% Both compositions had an A„ of 0.99 The medium for C.botulinum was incubated at 30°C anaerobically. The medium for Bacillus species was incubated aerobically at 30°C. The lactic acid concentration and heat treatment of the product is shown in table 1. Table 1 Concentration Example Lactic Acid pH Heat Treatment (% w/w) 3 0.5 4.7 98°C; 2 minutes 4 0.5 4.7 98°C; 10 minutes 5 0.5 4.7 98°C; 23 minutes 6 0.5 4.7 98°C; 100 minutes 7 0.5 4.7 110°C; 2 minutes ε 0.5 4.7 110°C; 10 minutes 9 0.5 4.7 110°C; 23 minutes 10 1.0 4.7 98°C; 2 minutes 11 1.0 4.7 98°C; 10 minutes Concentration Example Lactic Acid pH Heat Treatment (% w/w) 12 1.0 4.7 98°C; 23 minutes 13 1.0 4.7 98°C; 100 minutes 14 1.0 4.7 110°C; 2 minutes 15 1.0 4.7 110°C; 10 minutes 16 1.0 4.7 110°C; 23 minutes 17 2.0 4.7 98°C; 2 minutes 18 2.0 4.7 98°C; 10 minutes 19 2.0 4.7 98°C; 23 minutes 20 2.0 4.7 98°C; 100 minutes 21 2.0 4.7 110°C; 2 minutes 22 2.0 4.7 110°C; 10 minutes 23 2.0 4.7 110°C; 23 minutes 24 0.5 5.1 98°C; 2 minutes 25 0.5 5.1 98°C; 10 minutes 26 0.5 5.1 98°C; 23 minutes 27 0.5 5.1 98°C; 100 minutes 28 0.5 5.1 110°C; 2 minutes 29 0.5 5.1 110°C; 10 minutes 30 0.5 5.1 110°C; 23 minutes 31 1.0 5.1 98°C; 2 minutes 32 1.0 5.1 98°C; 10 minutes 33 1.0 5.1 98°C; 23 minutes 34 1.0 5.1 98°C; 100 minutes 35 1.0 5.1 110°C; 2 minutes 36 1.0 5.1 110°C; 10 minutes 37 1.0 5.1 110°C; 23 minutes 38 2.0 5.1 98°C; 2 minutes 39 2.0 5.1 98°C; 10 minutes 40 2.0 5.1 98°C; 23 minutes 41 2.0 5.1 98°C; 100 minutes Concentration Example Lactic Acid pH Heat Treatment (% w/w) 42 2.0 5.1 110°C; 2 minutes 43 2.0 5.1 110°C; 10 minutes 44 2.0 5.1 110°C; 23 minutes 45 0.5 5.5 98°C; 100 minutes 46 0.5 5.5 110°C; 10 minutes 47 0.5 5.5 110°C; 23 minutes 48 1.0 5.5 98°C; 100 minutes 49 1.0 5.5 110°C; 10 minutes 50 1.0 5.5 110°C; 23 minutes 51 2.0 5.5 98°C; 100 minutes 52 2.0 5.5 110°C; 10 minutes 53 2.0 5.5 110°C; 23 minutes 54 0.5 6.5 110°C; 10 minutes 55 0.5 6.5 110°C; 23 minutes 56 1.0 6.5 110°C; 10 minutes 57 1.0 6.5 110°C; 23 minutes 58 2.0 6.5 98°C; 100 minutes 59 2.0 6.5 110°C; 10 minutes 60 2.0 6.5 110°C; 23 minutes B 0 5.1 98°C; 10 minutes C 0 5.5 98°C; 10 minutes D 0 6.5 98°C; 10 minutes E 2.0 4.7 0 F 2.0 5.1 0 G 2.0 5.5 0 H 2.0 6.5 0 The combination preservation systems in Examples 3 to 60 resulted in products which were microbiologically safe and stable after 6 months storage at 30°C when the initial challenge was 10 7 spores of Clostridium botulinum and 10 7 spores of typically encountered Bacillus species. The preservation systems used in Comparative Examples B-H resulted in products which were not microbiologically safe and stable at ambient temperatures when the initial challenge was as for Examples 3 to 60. Examples 61-66,- Comparative Examples I-J The protocol in. Examples 3 to 60 was repeated with the conditions shown in table 2. The heat treatment of the product was 98°C for 23 minutes. Table 2 Concentration Example lactic acid pH **w (% w/w) 61 0.5 5.5 0.95 62 0.5 6.0 0.95 63 0.5 6.5 0.94 64 2.0 5.3 0.999 65 2.0 5.4 0.999 66 2.0 5.7 0.999 I 0.5 >6.5 0.999 J 2.0 >6.5 0.999 The combination preservation systems in Examples 61 to 66 resulted in products which were microbiologically safe and stable after 6 months storage at 30°C when the initial challenge was as for Examples 3 to 60. The preservation systems used in comparative Examples I to J resulted in products which were not microbiologically safe and stable at 30°C when the initial challenge was as for Examples 3 to 60. Example 67 The protocol in Examples 3 to 60 was repeated except sodium lactate replaced lactic acid. Sodium lactate was used in an amount such that the number of moles of lactate was equivalent to 0.5% w/w lactic acid. The composition had an equilibrium pH of 5.1, and A„, of 0.999 and the heat treatment was 98°C for 23 minutes. This combination preservation system resulted in products which were microbiologically safe and stable after 6 months storage at 30°C when the initial challenge was as for Examples 3 to 60. Examples 68-72 A tomato sauce was prepared having the following composition: % by weight Tomato paste (31° BRIX) 32.18 $ Soya bean oil 1.14 Salt 0.85 Pure virgin olive oil 0.05 Lactic acid 0.2 to 0.5 (see table 3) Water to 100 $ NB tomato paste contains approximately 1% citric acid. The composition had a A w of >0.98. The heat treatment of the product was 98°C for 23 minutes. Table 3 Concentration Lactic Acid Examples (% w/w) pH 68 0.5 5.3 69 0.5 5.2 70 0.4 5.2 71 0.3 5.2 72 0.2 5.2 The combination, preservation systems in Examples 68-72 resulted in products which were microbiologically safe and stable after 6 months storage at 30°C when the initial challenge was as for Example 1. Example 73 A white sauce was prepared having the following composition: % by weight Onion powder 0.03 Unsalted butter 3.50 Chicken Flavouring 1.79 Reduced wine 8.93 Cream (35% fat) 35.89 Salt 0.35 Starch 4.74 Gelatin (100 bloom) 2.64 Savoury flavour 0.80 Lactic Acid 0.5 Water to 100 The composition had an equilibrium pH of 5.1 the A Ώ was >0.98. The heat treatment of the product was 98°C for 23 minutes This combination preservation system resulted in a product which was microbiologically stable and safe after 6 months storage at 30°C when the initial challenge was as for Example 1. Example 74 ,- Comparative Examples K & L A white sauce was prepared having the following composition: % by weight Butter 3.5 Reduced wine 8.93 Cream (35% fat) 35.89 Salt 0.35 Starch 4.74 Gelatin 2.64 Flavours 2.62 Water to 100 In Example 74 the sauce additionally contained 0.5% lactic acid, and had an equilibrium pH of 5.1. Comparative Example K is a taste control and contained no added acid, having a pH of 5.3. Comparative Example L was acidified to pH 4.3 with lactic acid. This represents the pH of a conventional white sauce when prepared such that microbiological safety is ensured. All 3 sauces were subjected to a heat treatment of 98°C for 23 minutes. The Aw was >0.98. The sauces were presented to a trained sensory panel at 70°C. Sensory testing showed that the sauce made according to this invention (Example 74) clearly demonstrated a significant reduction in perceived acidity when compared to a conventional sauce formulation (comparative Example L) . Furthermore there was no significant difference in the perceived acidity of Example 74 when compared to the taste control (Comparative Example K) .

Claims: Claims 1. A process of producing an ambient stable food product which includes a preservative selected from an inorganic acid, an organic acid, the salts thereof and mixtures thereof, having an equilibrium pH of from 4.7 to 6.5 and an „ of from 0.94 to 0.999 wherein the food product is heated to a temperature of from 90-130°C for a time sufficient to provide a microbiologically safe ambient stable food product; providing that; when the product temperature is greater than 100°C and the equilibrium pH is 6.5; the ^, is ≥0.94 and the product is heated sufficiently to achieve an F 0 <2.45; when the product temperature is >100°C and the equilibrium pH is from 6 to <6.5; the A„ is ≥0.95 and the product is heated sufficiently to achieve an F 0 <2.45; when the product temperature is >100°C and the equilibrium pH is from 5.5 to <6.0; the ^ is ≥0.95 and the product is heated sufficiently to achieve an F 0 <2.0; when the product temperature is >100°C and the equilibrium pH is from 5.0 to <5.5; the A ^ , is ≥0.95 and the product is heated sufficiently to achieve an F 0 <1.5; and when the product temperature is >100°C and the equilibrium pH is from 4.7 to <5.0; the A w is ≥0.95 and the product is heated sufficiently to achieve an F 0 <1.0. 2. A process according to claim 1 wherein the food product is heated to a temperature of from 90-110°C. 3. A process according to claim 1, wherein the food product is heated to a temperature of from 90 to 100°C. 4. A process according to any preceding claim wherein the organic acid or salt thereof is chosen from lactic acid, : acetic acid, succinic acid, malic acid, propionic acid, citric acid, the salts thereof and mixtures thereof. 5. A process according to any preceding claim wherein the organic acid is lactic acid. 6. A process according to any preceding claim wherein the inorganic acid is phosphoric acid. 7. A process according to any preceding claim wherein the inorganic acid, organic acid or mixture thereof is incorporated at 0.001% to 2% weight/weight or equivalent volume/weight of the food product depending on the nature of the acid used. 8. A process according to any preceding claim wherein the food product has an equilibrium pH of from 4.7 to 6.0. 9. A process according to any preceding claim wherein the food product has an equilibrium pH of from 4.7 to 5.8. 10. A process according to any preceding claim wherein the food product has an equilibrium pH of from 4.7 to 5.1. 11. A process according to any preceding claim wherein the food product has an A w of from 0.96 to 0.999. 12. A process according to any preceding claim wherein the food product has an A u , of from 0.97 to 0.999. 13. A process according to any preceding claim wherein the food product comprises additional preservatives . 14. A process according to claim 13 wherein the food product comprises additional preservatives chosen from sugars, salt, ethanol, D-alanine and mixtures thereof. 15. A process according to any preceding claim wherein the food product is a sauce, soup or dressing with or without particles.

Inventors: BROWN MARTYN HATTON, COLE MARTIN BARRY, GODDARD MERVYN ROY, MCCLURE PETER JOHN, BROWN, MARTYN, HATTON, COLE, MARTIN, BARRY, GODDARD, MERVYN, ROY, MCCLURE, PETER, JOHN
Applicants: UNILEVER NV, UNILEVER PLC, UNILEVER N.V.
Application year: 1995
Main classification: A23L3
IPC codes: A23B7, A23L3