A container, method of manufacture and use thereof The present invention relates to a container comprising multiple servings of a heat-treated liquid dairy product, more particularly, a heat-treated (e.g. sterilised or retorted) liquid dairy product having a solids level of at least 55 wt%, and a pH of greater than 5.5. The present invention also relates to a method for the manufacture of the filled container. The container of the present invention can be used to safely, from a health perspective, dispense multiple servings of the liquid dairy product over a time period of at least 24 hours whilst the container and the liquid dairy product therein are kept unrefrigerated.
"Dairy Processing Handbook", published by Tetra Pak Processing Systems AB, 1995, provides an extensive overview of dairy products and their industrial processing, from the production and chemistry of milk to the processing and production of dairy products, including pasteurised and long-life (i.e. ultra-pasteurised -e.g. ultra-high temperature (UHT) or retort) milk products.
Pasteurisation and ultra-pasteurisation are well-known techniques in the art and are considered to be "heat-treatments" as described herein, i.e. a thermal process intended to reduce microbial content of a product. UHT processing preserves liquid dairy products by heating the product to a specific temperature for a predefined length of time to kill the bacteria and micro-organisms present in the product. For dairy products, this is typically a temperature of from 120 °C to 150 °C, such as from °C to 145 °C for less than 1 minute, such as from 1 to 45 seconds (though appropriate temperature-time combinations can be readily determined for a given product by those skilled in the art).
An ultra-pasteurised liquid dairy product can remain under aseptic conditions and be packaged in a sterilised container. In retort processing, the product is packaged in a thermally resistant container and heated at a high temperature, typically more than 1 minute (i.e. longer than UHT processing). Such processes can involve aseptic processing and/or packaging in which the containers produced are tight enough to prevent recontamination of the sterile contents (i.e. hermetically sealed).
Sterilised dairy products have increased shelf-life when compared to equivalent pasteurised dairy products. As such, liquid dairy products such as UHT milk can remain shelf-stable for an extended period of time at ambient conditions, often from 1 to 12 months. However, as is well-known, once such products are opened by the end user and the seal is broken, they must be kept refrigerated in order to prevent rapid spoiling, much like fresh products. That is, the shelf-life of the sterilised product once opened is equivalent to the fresh product and must be stored as such. Refrigeration typically requires temperatures of less than 8 °C, preferably less than 6 °C (e.g. about 3 °C to about 5 °C).
Many other technologies are described in the art which provide various solutions to the problem of providing shelf-stable liquid dairy products. This includes the addition of additives such as preservatives/antioxidants and concentration of the product through evaporation and/or filtration techniques to provide so-called "extended shelf-life" (ESL) products (e.g. evaporated milk, condensed milk).
WO 02/089591 relates to the ultra-high temperature (UHT) pasteurisation of condensed milk. More particularly, to packaging concentrated milk for dispensing reconstituted milk from juice dispensing equipment and for transporting large amounts of ultrapasteurised (UP) liquid milk concentrate worldwide.
WO 2008/002492 relates to a process for the treatment of fresh cream, fresh milk, skim milk, flavored milk, lactose reduced milk and other liquid milk products to prolong the shelf-life of such products.
WO 2010/008865 relates to processes for making a shelf stable milk based beverage concentrate.
WO 2012/033927 relates to high-solids concentrated dairy products, and more specifically, to non-gelling, non-browning, organoleptically pleasing, high-solids concentrated dairy products, such as concentrated milks having at least about 38 percent total solids, and methods for producing the same. The products disclosed therein relate to high solids concentrated dairy liquids that remain retort and shelf stable for an extended shelf life at ambient conditions with substantially no negative flavor notes.
WO 2013/116687 relates to liquid dairy products and, more specifically, to liquid dairy products fortified with dairy minerals, such as concentrated milk, and method for producing the same. It is disclosed that a stabiliser may be added, such as calcium-binding stabiliser which include citrate and phosphate buffers.
EP 2179658 relates to beverage concentrates and, in particular, shelf stable blended coffee and dairy fluid concentrates in which the blended fluid concentrate may include a blend of at least a fluid dairy component, a coffee component, a stabilising or buffering component, and optional mouthfeel enhancers. In one aspect, the fluid dairy component is preferably obtained from an ultrafiltered and, most preferably, an ultrafiltered and diafiltered, liquid dairy source to concentrate the dairy solids and remove lactose and other minerals.
WO 2017/076940 relates to a method of producing a concentrated ingredient for providing milky beverages or the milky portion of a beverage, such as a lane. In particular, the disclosure relates to a method for forming the ingredient from cream, without the risk of butter formation.
Despite these developments in the prior art, there is a focus on "closed" shelf-life, i.e. the shelf-life of the product after packaging and before opening by the end user. Once opened, there is an expectation in the art that dairy products are to be kept refrigerated in order to extend the "open" shelf-life.
Accordingly, it is desirable to provide an improved heat-treated liquid dairy product suitable for dispensing from a container without requiring refrigeration once opened and/or to tackle at least some of the problems associated with the prior art, or to at least provide a commercially useful alternative thereto.
Thus a first aspect of the present invention provides a container comprising multiple servings of a heat-treated liquid dairy product, wherein the liquid dairy product has a solids level of at least 55 wt%, a pH of greater than 5.5, and comprises a first antioxidant which is TBHQ and a second antioxidant which is propyl gallate, wherein the first and second antioxidants are present in a combined total amount of from 100 to 400 ug/mL.
The inventors have surprisingly found that the specific combination of antioxidants with the pH and high solids content, together permit a heat-treated liquid dairy product to remain useable after opening for a protracted period of time without becoming unsafe. This opens the door for a commercial product that can be used in circumstances where refrigeration may not be available, such as a trolley service on a train or plane.
The present disclosure will now be described further. In the following passages, different aspects/embodiments of the disclosure are defined in more detail. Each aspect/embodiment so defined may be combined with any other aspect/embodiment or aspects/embodiments unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.
A further aspect of the present invention provides a method for the manufacture of the container described herein, the method comprising: heating a liquid dairy ingredient; adding water and adjunct ingredients which include TBHQ and propyl gallate to the heated liquid dairy ingredient to form a liquid dairy product; and heat-treating and filling a package with the liquid dairy product.
In yet a further aspect, the present invention provides a use of an unrefrigerated container as described herein to provide multiple servings of a beverage product over a period of at least 24 hours.
Therefore, as will be appreciated, the present invention relates to a container comprising multiple servings of a heat-treated liquid dairy product and features described in respect of such a product may apply equally to the method of manufacture or use thereof, and vice versa. As such, the container is preferably obtainable by the method described herein.
The first aspect provides a container comprising multiple servings of a heat-treated liquid dairy product. The container (which may also be referred to as a package or packaging) is a packaged product containing the liquid dairy product. The container is ideally a sterilised product hermetically sealed with the liquid dairy product content (i.e. the container is sealed to prevent passage of bacteria, micro-organisms and gases/vapour into or out of the container, particularly oxygen gas).
The packaging may be any package well-known in the art of dairy processing, preferably aseptic packaging. Suitable packaging includes cartons (generally being formed of layers of paperboard, plastic (typically polyethylene) and optionally aluminium foil), such as those available from Tetra Pak®, or simply plastic pouches, such as those sold under the name Air Aspetic from Ecoleane. As will be appreciated, other suitable packages, such as glass or plastic bottles, will be known to those skilled in the art.
The container package may be provided with or without a lid (i.e. means for resealing the container).
As will be appreciated, such means do not allow the consumer to re-establish a hermetic seal such that once the container is opened to dispense the first serving, the shelf-life of the product is affected due to the exposure to atmospheric contamination (i.e. bacteria, micro-organisms and oxygen). Dispensing of the liquid from the container provides the main risk for contamination. A resealable container generally serves to prevent spillage of the liquid product and may help to reduce the rate of spoilage by restricting passage into and out of the container. A lid may be designed to break the hermitic seal upon first opening, or the opening for the lid may be provided with a thermoweldable, plastic and/or foil, seal which is removed by the user, for example. Nevertheless, a package without a lid or other means may be used (i.e. a non-resealable container) and the package may be opened by the user, for example by ripping the container (for example, along a pre-scored and weakened tear line), or cutting the container open (for example, with a pair of scissors).
The container comprises multiple servings of the liquid dairy product. As such, the container of the present invention is distinguished from single-serve containers, such as stick-packs or pots. These typically contain about 10 or about 12 mL of liquid. Generally, a consumer finds that a single serving is in the range of from 10 to 25 mL. Accordingly, the container of the present invention comprising multiple servings will generally contain a volume of at least 50 mL of the heat-treated liquid dairy product, preferably at least 100 mL. In some embodiments, the container will contain at least 250 mL, at least 500 mL. Cartons of heat-treated liquid dairy products are often sold with a volume of about 500 mL or about 1 L, and generally up to about 3.5 L, preferably up to about 2 L (with such volumes being approximately equal to 1, 2, 6 and 4 imperial pints, respectively).
The container comprises a heat-treated liquid dairy product. Heat-treatment processes may vary from country to country, generally in accordance with local regulation, but generally refers to a heat treatment for a sufficient time in order to ensure that bacteria and micro-organisms are destroyed, as is well-known to those skilled in the art. Thus a heat-treated liquid can be identified as one having a particularly low bacteria and micro-organism content. Preferably the heat-treatment is at a temperature in excess of 100°C and preferably for a duration of at least 10 seconds. In preferred embodiments, the liquid dairy product is heat-treated by heating to a temperature greater than 120 °C, e.g. from 120 °C to 150 °C, preferably from 135 °C to 145 °C, and/or for a time of less than 1 minute.
The heat-treatment of the liquid dairy product may be assessed by considering the Fo value. This would be measured as a property of the liquid dairy product at the moment of first opening the container. Measurement of Fo values is described in the Dairy Processing handbook (Tetra) and the discussion of Fo values and their measurement is incorporated herein by reference. Fo allows quantification of a heat-treatment as an equivalent to the minutes of sterilisation at 121 °C, e.g. a heat-treatment with an Fo of 5 is equivalent to 5 minutes of sterilisation at 121 °C. Preferably the heat-treated liquid dairy product has an FO value of at least 5, preferably at least 6, preferably at least 7, and more preferably at least 8.
A "liquid" dairy product or ingredient is one comprising sufficient water to be pumpable. The liquid dairy product will have a solids content of at least 55 wt%, since the inventors have found that ambient temperature shelf-life is dependent on the high solids content of the product. More particularly, high solids products were found to exhibit reduced or eliminated growth of a number of gram positive and negative microbes such as non-proteolytic Clostridium botulinum, Clostridium perfringens, Escherichia coli and Salmonella, even when maintained at 37 °C for 24 hours.
Preferably, the liquid dairy product has a solids level of at most 70 wt%, more preferably at most 65 wt%. Accordingly, the liquid dairy product is generally consumed by the end-user after dilution, for example with water to form a milk-beverage, or as a creamer for whitening of a beverage such as tea or coffee.
It will be appreciated that the dairy liquid ingredient will be essentially a suspension of milk-derived fats and proteins. A dairy ingredient is a food product produced from the milk of mammals, typically cows, however, other mammalian milk suitable for human consumption can be used if desired, such as buffalos, goats and sheep. Liquid dairy ingredients typically take a number of forms, most notably milk and cream. Milk products directly obtained tend to separate (or can be separated) into fractions depending on the relative fat content. In this way a cream layer may form on top of a milk and the fat contents will generally be at least 18 wt% for the cream and less than 5.5 wt% for the milk. Different fat levels can be achieved by concentrating and/or mixing milk and cream fractions.
Due to the high solids content of the liquid dairy product, this may also be referred to as a liquid dairy concentrate, or as described above, a liquid dairy creamer. However, as described herein, it is preferred that the liquid dairy product is obtained without concentrating (e.g. evaporation to increase solids content and/or filtration to remove dairy minerals and lactose, as well as reducing bacteria and micro-organisms). That is, it is preferred that the liquid dairy ingredient used in the method to manufacture the liquid dairy product of the container is a fresh or raw product which is also distinguished over acidified or cultured/fermented products. Optionally, the ingredient used in the process may be homogenised or subjected to any other treatment (e.g. heating) so as to maintain the original nutritional profile and solids content of the ingredient. It is particularly preferred that the liquid dairy ingredient comprises, or consists of, cream. Preferably, the liquid dairy ingredient has a fat content of 25 to 50 wt%, more preferably 30 to 45 wt%.
The liquid dairy product has a pH of greater than 5.5. In some instances in the prior art, liquid products may be stabilised by the addition of acidic additives. It is however generally preferred to maintain an about neutral to slightly acidic pH which corresponds to pHs typically found for fresh and raw dairy ingredients. It is therefore preferred that the liquid dairy product has a pH of less than 7.5, preferably less than 7.0. More particularly, such a pH range is believed to be suitable for the antioxidants described herein which may be unstable to decomposition during the high temperature treatment where the pH is too acidic or too alkaline (particularly when too acidic).
The liquid dairy ingredient comprises a first antioxidant which is TBHQ and a second antioxidant which is propyl gallate. Individually, TBHQ and propyl gallate are well-known antioxidants. TBHQ refers to tert-butylhydroquinone (or 2-tert-butylbenzene-1,4-diol) and is used as a preservative for oils and fats in many foods such as cheese and yogurt. As a food additive, its E-number is E319. Propyl gallate refers to 3,4,5-trihydroxybenzoic acid propyl ester (or propyl 3,4,5-trihydroxybenzoate) and is used as a preservative for oils and fats in many foods, commonly snack foods, baked goods and vegetable oils. As a food additive, its E-number is E310.
The first and second antioxidants are present in the liquid dairy product in a combined total amount of from 100 to 400 pg/mL. The European Food Safety Authority (EFSA) and the United States Food and Drug Administration (FDA) have evaluated TBHQ and propyl gallate and determined that these are safe to consume at the concentration allowed in foods. In some jurisdictions, the amount of each additive may be limited to 200 pg/mL or less, and as such, the amount of each antioxidant is preferably limited accordingly, otherwise, there is no particular upper limit in order to provide the benefits described herein.
Generally, at least 100 pg/mL total antioxidants may be provided by including at least 50 pg/mL of each of the first and second antioxidants. Accordingly, in some embodiments, a ratio of about 1:1 (by weight) of each of the first and second antioxidants may be used and is most preferred (such as 100 mg/mL each), though it is more generally also preferred that these are present in a ratio of from 2:1 to 1:2 (by weight).
More preferably, the first and second antioxidants are present in a combined total amount of from 150 to 300 pg/mL, preferably about 200 pg/mL. In some preferred embodiments, the first and second antioxidants are the only antioxidant additives present in the liquid dairy product. Where other antioxidants are present, the combined total amount of antioxidants may also preferably be from 100 to 400 pg/mL (or narrower), provided that the minimum amount of first and second antioxidants of the ranges described are included (i.e. at least 100 pg/mL, preferably at least 150 pg/mL or about 200 pg/mL of the total amount of first and second antioxidants).
The inventors were surprised to find that the combination of TBHQ and propyl gallate provided a synergistic stabilisation of liquid dairy products so as to inhibit growth of a broad spectrum of microbes, particularly when measured after an extended period of time (typically above 24 hours after opening and even up to 168 hours, or more for certain microbes) at ambient temperature (which may be controlled to be about 25 °C).
More specifically, as described above, whilst a similar synergistic effect may be observed for low solids content products in respect of a number of microbes, the inventors still observed growth of other microbes such as Bacillus cereus, E. coli and Salmonella. The combination of antioxidants advantageously inhibits growth at ambient temperature of microbes such as, most notably, Listeria monocytogenes and Staphylococcus aureus, together with E. coli and Salmonella, which was unexpected based on the microbe growth in equivalent liquid dairy products comprising only one of TBHQ or propyl gallate.
As a result, the liquid dairy product described herein may advantageously be used without refrigeration to provide multiple servings after opening. Furthermore, the liquid dairy product maintains a fresh taste desirable to the consumer (at least comparable with known heat-treated liquid dairy products).
Consequently, a further aspect of the present invention provides a use of an unrefrigerated container to provide multiple servings of a beverage product over a time period of at least 24 hours, wherein the container comprises multiple servings of a heat-treated liquid dairy product, wherein the liquid dairy product has a solids level of at least 55 wt%, a pH of greater than 5.5, and comprises a first antioxidant which is TBHQ and a second antioxidant which is propyl gallate, wherein the first and second antioxidants are present in a combined total amount of from 100 to 400 pg/mL.
In other words, the present invention provides a use of a container as described herein to dispense multiple servings of an unrefrigerated heat-treated liquid dairy product over a time period of at least 24 hours. That is, the present invention provides a method of providing multiple servings of an unrefrigerated heat-treated liquid dairy product, the method comprising dispensing multiple servings of the liquid dairy product from the container described herein over a time period of at least 24 hours, wherein the container is unrefrigerated throughout the time period. The container may be stored under refrigeration at a temperature of about 8 °C or less though this is not required. Once opened, the container does not need to be kept refrigerated (even if it had been previously chilled in storage) whilst the container is used to provide multiple servings of the liquid dairy product. This is particularly advantageous for consumers who require a liquid dairy product be available where refrigeration is not (e.g. remote locations) or occasions or events where the container is made available for communal use.
As will be appreciated, the use is intended to equally include dispensing the entire liquid dairy product contents from the original supplied container into another container, for example a jug or a container of a beverage preparation machine, from which the multiple individual servings are subsequently dispensed, for example by the consumer with the jug or by a computer-controller of the beverage preparation machine. Particular examples includes coffee machines, such as so-called "bean-to-cup" coffee machines, which can dispense an array of different beverages to numerous consumers. The Cafitesse range of coffee machines available from Jacobs Douwe Egberts are examples of particularly suitable machines. Advantageously, a room temperature stable product allows for a reduction in the energy consumption of such machines by avoiding the need for refrigeration. This further reduces the complexity of the machine and the associated maintenance which is desirable for customers of such machines.
What is essential is that the liquid dairy product contained within the container is suitable to be dispensed (and ultimately consumed) 24 hours or more after the container is first opened to the atmosphere (in which the first serving is generally dispensed thereby initiating the spoiling process). A serving of the liquid dairy product of the container described herein may be dispensed up to 168 hours (i.e. 7 days) after first opening the hermetically sealed container, though this is generally the upper limit since at this time period, the inventors have found some growth of undesirable microbes, in particular Salmonella, may begin. Typically, it is preferred that the second serving is dispensed up to 72 hours (3 days) hours of first opening. As such, the container is particularly suitable for providing multiple servings over a time period of 24 hours to 72 hours, such as about 48 hours (2 days).
It is also particularly preferred that the liquid dairy product has a water activity (A4 of 0.950 or less, preferably 0.940 or less. These values for water activity are preferred on the same basis of the preferred high solids content. Lower solids content products typically have a higher water activity. For example, the water activity of concentrated whole milk with a solids content of about 28% to 35% is about 0.983. Preferably, the liquid dairy product has a water activity of 0.875 or more, preferably 0.900 or more.
Preferably, the liquid dairy product further comprises one or more saccharides. Saccharides are well-known and generally refer to carbohydrates that includes sugars, starches and cellulose. These are generally divided into four groups of monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Preferably, saccharides are present in a total amount of from 20 to 50 wt% by weight of the liquid dairy product, more preferably from 30 to 45 wt%. Preferably sugars (generally regarded as mono and disaccharides) may be selected from the group consisting of glucose, sucrose, fructose, galactose, lactose, maltose, isomaltose, sugar hydrates (such as dextrose monohydrate), and combinations thereof. Preferably, oligosaccharides may be selected from the group consisting of dextrin, galactooligosaccharides and oligofructose, and are preferably soluble indigestible fibres (i.e. indigestible dietary fibre). Preferably, polysaccharides may be selected from the group consisting of inulin, wheat starch and corn starch (and equally are preferably soluble indigestible fibres). It will be appreciated that a liquid dairy ingredient used in the method of manufacture typically comprises lactose as a naturally occurring sugar such that the final liquid dairy product may comprise lactose (e.g. less than 5 wt%, less than 2 wt%, and/or at least 0.1 wt% by weight of the final product). Lactose is generally present in small amounts such that the amounts described herein of saccharides and sugars may apply equally to the total amount present in the final product or alternatively to the amount of added sugars added as an adjunct ingredient during manufacture. In some preferred embodiments, the liquid dairy product comprises the disaccharide sucrose and/or the polysaccharide dextrin. In exemplary embodiments, the liquid dairy product may comprise from 5 to 15 wt% sucrose and/or from 1 to 8 wt% oligofructose, together with 20 to 30 wt% dextrin, and in other embodiments simply from 20 to 40 wt% sucrose. That is, in some preferred embodiments, a lower amount of sugars (e.g. in an amount of 5 to 15 wt%) may be combined with oligo and/or polysaccharides (e.g. in an amount of 20 to 50 wt%). It can be nutritionally beneficially to provide a product with reduced sugar content and high soluble dietary fibre.
The liquid dairy product may also comprise a non-saccharide sweetener such as stevia glycosides, aspartame or acesulfame potassium. Typically, such sweeteners are included as minor components with respect to the total sugars/sweeteners, such as less than 5 wt% by weight of the liquid dairy product, preferably less than 1 wt%.
The liquid dairy product may further contain one or more additional adjunct ingredients (additives).
Preferably, the liquid dairy product further comprises one or more stabilisers, such as gum arabic. The stabiliser is preferably provided in an amount of from 0.6 to 1.5 wt% of the concentrate, such as 0.8 to 1.2 wt%.
The liquid dairy product may contain salt (NaCI). Salt is preferably provided in an amount of from 0.8 to 1.4 wt% of the product. The liquid dairy product may contain added dairy minerals. Dairy minerals preferably provided in a total amount of from 0.1 to 1.5 wt% by weight of the liquid dairy product. Dairy minerals are well-known adjunct ingredients and various suitable blends are readily commercially available. Dairy minerals are generally powdered sources of minerals that are naturally present in milk, the most predominant mineral of which is calcium. Dairy minerals may be added to contribute to dairy flavour. Preferably, dairy minerals comprise or consist of calcium and one or more of magnesium, potassium, sodium, phosphate, and iron. As such, the presence of added dairy minerals in a liquid dairy product can generally be seen by a higher than expected amount of calcium. WO 2013/116687 discloses exemplary commercial dairy mineral profiles in a table and this is incorporated herein by reference. The liquid dairy product may contain up to 1 wt% of other flavourings (i.e. non-mineral based flavourings such as caramel).
Preferably, the liquid dairy product further comprises one or more buffering salts. Examples of suitable salts include sodium and/or potassium salts of phosphates, citrates and EDTA. Dipotassium phosphate is a preferred buffering salt for a liquid dairy product, which may be combined with trisodium citrate, for example. The total amount of such buffering salts may be at least 0.05 wt% and/or at most 1 wt%, for example, from 0.10 wt% to 0.20 wt%.
The liquid dairy product comprises fat originating from the liquid dairy ingredient. In some preferred embodiments, the liquid dairy ingredient is the sole source of fat in the liquid dairy product. It is also preferred that the fat in the liquid dairy product consists of dairy fat. Preferably, the liquid dairy product has a total fat content of from 5 to 30 wt% by weight of the liquid dairy product, such as from 8 to 20 wt%.
The liquid dairy product comprises protein originating from the liquid dairy ingredient. In some embodiments, the liquid dairy ingredient is the sole source of protein in the liquid dairy product. In other preferred embodiments, the liquid dairy product may further comprise added sodium caseinate (known as a type of dairy protein which may be used to supplement the protein content of the product). It is preferred that the protein in the liquid dairy product consists of dairy protein. Preferably, the liquid dairy product has a total protein content of from 1 to 10 wt% by weight of the liquid dairy product, preferably from 1.5 to 5 wt%. Where sodium caseinate is added, this may be added in an amount of 0.8 to 1.4 wt% of the product, for example. In one exemplary embodiment in accordance with the examples below, the recipe for the liquid dairy product may consist of: Ingredient Amount Cream (25 to 45 wt% fat content) 25 to 45 wt% Sugar 5 to 15 wt% Dairy minerals 0.1 to 1.5 wt% Gum arabic 0.6 to 1.5 wt% Buffering salts 0.05 to 0.2 wt% Salt (NaCI) 0.8 to 1.4 wt% Sodium caseinate 0.8 to 1.4 wt% Oligofructose 0 to 8 wt% Dextrin 20 to 30 wt% Reverse Osmosis (RO) Water 15 to 25 wt% Antioxidants 100 to 400 pg/mL Total 100 wt% The liquid dairy product may have a nutritional profile of fat, protein, lactose and total sugars as described by: Nutrient Amount Fat 8 to 20 wt% Protein 1.5 to 5 wt% Lactose 0.1 to 1.5 wt% Total sugars 10 to 20 wt% The method described herein for the manufacture of a container comprises a first step of heating a liquid dairy ingredient. In some embodiments, the liquid dairy ingredient is pasteurised before processing to form the liquid dairy product. A pasteurised liquid dairy ingredient may have been subjected to a heating step by heating to a temperature below 100 °C, for example from 70 °C to 80 °C, for less than 1 minute. Generally, the liquid dairy ingredient is immediately then cooled to less than 8 °C, such as about 4 °C for storage before use in the present method. As described herein, cream is a particularly preferred liquid dairy ingredient, and may preferably have a fat content of from 25 to 45 wt%.
The first step of heating the liquid dairy ingredient provides a heated liquid dairy ingredient to which, in the subsequent step, water and adjunct ingredients are added. The adjunct ingredients include the TBHQ and the propyl gallate, thereby forming the liquid dairy product. Preferably, the liquid dairy ingredient is not concentrated before the step of adding the adjunct ingredients (e.g. by evaporation or filtration).
In some embodiments, the liquid dairy ingredient is heated to a first temperature that is less than °C (e.g. 64 °C or less) and the TBHQ and the propyl gallate antioxidants are added at the heated temperature. The first temperature may be at least 50 °C, preferably at least 60 °C. Preferably, the method further comprises further heating the liquid dairy ingredient from the first temperature to a second temperature that is more than 65 °C (e.g. 66 °C or more) and adding the adjunct ingredients, such as any saccharide (and optional sweetener), together with the water.. Both antioxidants dissolve poorly in water and the inventors have found that is therefore preferred to add the antioxidants to the heated liquid dairy ingredient and then to add water and other adjuncts. Preferably, the second temperature is less than 80 °C, preferably less than 78 °C. As will be appreciated, the first and second temperatures may each be a range within which the liquid dairy ingredient/product is maintained during the addition and need not necessarily remain a static value.
The adjunct ingredients may preferably be dissolved in the water to be added to the liquid dairy ingredient. In some embodiments, sodium caseinate may be dissolved in one portion of water and the saccharides and sweeteners may be dissolved in a second portion of water. These may be heated to ensure substantially complete dissolution of the adjunct ingredients, and they may optionally be cooled, prior to addition to the liquid dairy ingredient which is preferably maintained at below 80 °C, preferably below 78 °C, for the entire addition step. Readily soluble ingredients such as salts (e.g. salt, citrates and phosphates) may be added as dry ingredients.
Any further water, as required to be added to achieve the desired solids levels taking into account the water content of the other ingredients, may otherwise be added at any time prior to the final heat-treatment (sterilising or retorting) and filling a package (i.e. an empty container) with the liquid dairy product. Whilst the amount of added water will be dependent on the water content of primarily the liquid dairy ingredient, the amount of added water where the liquid dairy ingredient is cream may be in the range of 15 to 25 wt%. As described herein, heat-treatment may comprise heating to an appropriate temperature and for a time effective to destroy bacteria and micro-organisms, for example to achieve an Fo value of at least 5. In a preferred embodiment, the liquid dairy product is heated to 120 °C to 150 °C.
The method may further comprise homogenising the liquid dairy product before and/or after the step of heat-treating the liquid dairy product. Homogenisation is a process used to ensure the homogeneity of two immiscible liquids. It is well known to homogenise dairy compositions to ensure that the fat content is evenly distributed in the aqueous portion of the composition. Homogenisation breaks the fat into smaller sizes so it no longer separates, allowing the sale of non-separating products at any fat specification. Homogenisation is preferably a two-stage high-pressure homogenisation, such as a first step at from 100 to 400 Bar (preferably from 200 to 350 Bar) and a second step at from 10 to 60 Bar (preferably about 40 Bar).
It is a further advantage of the present invention that the liquid dairy product may be (aseptically) filled into the packaging at a non-refrigerated temperature when the heat-treating has taken place before filling (as well as hermetically sealing to provide an aseptic product). Typically, heat-treated liquid dairy products are chilled after heat-treating before being filled into packages (e.g. to less than 8 °C). The liquid dairy product may therefore be cooled to, and filled and packaged at, ambient temperatures, such as from 15 °C to 40 °C. In other embodiments the liquid may be filled into the package and then in-pack retorted to provide the heat-treated liquid dairy product.
Examples
Six combinations of antioxidants were tested in two different liquid dairy product formulations having high and low solids contents (including low and high water activity, respectively), together with a control of each formulation without any antioxidant. Samples were incubated for up to 168 hours at °C and monitored for growth of seven different microbes, namely: Bacillus cereus (b); Clostridium perfringens (cp); Clostridium sporogenes (cs); Escherichia coli (e); Listeria monocytogenes (I); Salmonella enterica (s); Staphylococcus aureus (a). Samples were inspected at 7 hours, 24 hours, 48 hours and 168 hours to determine the efficacy of bacterial growth inhibition.
Strains were inoculated directly from frozen stocks in Brain Heart Infusion (BHI) medium at 37 °C and an array of samples were prepared by introducing overnight cultures of said strains into individual quantities of sterile liquid dairy product in a microtiter plate, each to an initial inoculation level of 103 CFU/mL. The samples were incubated at 25 °C under aerobic conditions for B. cereus, E. coli, L. monocytogenes, S. enterica, and S. aureus, and under anaerobic conditions for C. perfringens and C. sporogenes. At each timepoint of 0, 7, 24, 48 and 168 hours of incubation, one microtiter plate per strain was sacrificed and used for CFU analysis using a High Throughput Screening (HTS) method.
Each sample was diluted and spotplated on BHI-agar. Agar microtiter plates were incubated at 37 °C for at most 24 hours before CFU analysis. After incubation, the plates were photographed and pictures analysed using imaging software.
The recipe for the high solids liquid dairy product is given in Table 1 below. Each sample of the high solids formulation had a solids content of about 57 to 59 wt%, an A. of about 0.93 to 0.94, and a pH of about 6. The amounts are approximate, but the sum of the ingredients listed is 100 wt%.
Table 1
Ingredient Amount Cream (35 wt% fat content) -35 wt% Sugar -10 wt°/0 Dairy minerals H wt% Gum arabic -1 wt% Dipotassium phosphate -0.1 wt% Salt (NaCI) -1 wt% Sodium caseinate H wt% Oligofructose -5 wt% Dextrin -25 wt% Reverse Osmosis (RO) Water -20 wt% Antioxidant(s) 0 (control) or 200 kg/mL Total 100 wt% The low solids liquid dairy product is a commercially available evaporated semi-skimmed milk product -Café Milc -whose ingredients are listed as: sweetened condensed partly skimmed milk (milk, sugar 2%), emulsifiers (E452, E339), acidity regulator (E451). Each sample of the low solids formulation had a solids content of about 32 to 35 wt%, an Aw of about 0.98, and a pH of about 6.1 to 6.4.
The six combinations of antioxidants tested were: (i) TBHQ only; (H) Propyl gallate (PG) only; (iii) TBHQ + BHA + BHT; (iv) TBHQ + BHA + PG; (v) TBHQ + PG; and (vi) Nisin + Lysozyme.
The combined total amount of antioxidant(s) is the same in each of the samples (i) to (v) (i.e. 200 pg/mL), and, where relevant, provided in a 1:1 or 1:1:1 ratio. For sample (vi), Nisin and Lysozyme are provided in a ratio of 1:3 in a total amount of 50 kg/mL. BHA is butylated hydroxyanisole (a well-known antioxidant which is a mixture consisting of two isomeric organic compounds, 2-tert-butyl-4-hydroxyanisole and 3-tert-butyl-4-hydroxyanisole). BHT is Butylated hydroxytoluene (another well-known antioxidant -2,6-di-tert-butyl-4-methylphenol). Nisin is a known polycyclic antibacterial peptide produced by the bacterium Lactococcus lactis that is used as a food preservative. Lysozyme is a known antimicrobial enzyme produced by animals that forms part of the innate immune system.
The results of the high solids formulations are shown in Table 2 below, and the results of the low solids formulations are shown in Table 3 below. Entries with an "X" indicate (almost) no growth (<104 CFU/mL), entries with a "1' indicated medium growth (104 to 106 CFU/mL), and entries with an "CY indicate full growth (>1 06 CFU/mL).
As the results show, the most effective combination of antioxidant compounds for the inhibition of seven microbes in liquid dairy products is TBHQ and PG, though only sufficient inhibition at more than 24 hours is achieved in the high solids products. In the high solids products, after 24 hours, some growth was observed in all samples except those which combined at least TBHQ and PG, particularly, listeria and staphylococcus. After 48 hours, only the sample which combined at least TBHQ and PG showed no growth to any of the seven pathogens even though samples which contained TBHQ or PG individually showed full growth of staphylococcus and at least some if not full growth of B. cereus, listeria and salmonella. Indeed, there was still observed no growth of B. cereus, listeria and staphylococcus in the samples comprising TBHQ and PG, and at most medium growth of E. coli, after 168 hours. All other combinations of antioxidants showed full growth of these pathogens.
The results of the low solids formulations follow an equivalent trend, though there is an overall greater prevalence of growth within a shorter time period. The combination of TBHQ and PG showed the greatest resistance to growth, and was still effective at inhibiting at least listeria after 168 hours.
Table 2
Time 7 h 24 h 48 h 168 h Bacterial bcpcse Isabcpcselsabcpcselsabcpcse I s a species Control X X /0/0/ X /0/00 X 0 TBHQ X / X / /0 X PG X / X / X /0/00 X TBHQ + / X/ X /0/0 X BHA +
BHT
TBHQ + X X X / X O X BHA +
PG
TBHQ + X OX
PG
Nisin + X / 0 0 X / 0 0 X 0 lysozyme
Table 3
Time 7 h 24 h 48 h 168 h Bacterial bcpcse I s a b cp cs e I s a b cp cs e I s a b cp cs e I s a species Control na X 0 na 0 0 na 0 0 na 0 TBHQ / X na / X 0 na0X 0 0 na 0 0 na 0 PG / X / X 0 X 0 0 / 0 0/ 0 TBHQ + / na / X 0 na 0 0 na 0 0 na 0 BHA +
BHT
TBHQ + / X / X 0 X 0/ 0 0 / X 0 0/ 0 BHA +
PG
TBHQ + / X / X 0 X OXOX 0 X OX0 / 0 / 0 X 0
PG
Nisin + / X / X 0 X 0 0 / 0 0 lysozyme As used herein, the singular form of "a", "an" and "the" include plural references unless the context clearly dictates otherwise. The use of the term "comprising" is intended to be interpreted as including such features but not excluding other features and is also intended to include the option of the features necessarily being limited to those described. In other words, the term also includes the limitations of "consisting essentially of (intended to mean that specific further components can be present provided they do not materially affect the essential characteristic of the described feature) and "consisting of (intended to mean that no other feature may be included such that if the components were expressed as percentages by their proportions, these would add up to 100%, whilst accounting for any unavoidable impurities), unless the context clearly dictates otherwise.
It will be understood that, although the terms "first", "second", etc. may be used herein to describe various features, the features should not be limited by these terms. These terms are only used to distinguish one feature from another, or a further, feature.
Numerical lower and upper limits of features described herein may preferably be combined to provide a closed range.
The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art, and remain within the scope of the appended claims and their equivalents.
For the avoidance of doubt, the entire contents of all documents acknowledged herein are incorporated herein by reference.