Abstract:
The present invention provides a dairy based spreadable product that does not need any emulsifying or thickening additives. This shelf stable spread includes sweetened condensed milk having a fat content of 2 to 25% by weight and a water content of 15 to 35% by weight. It is substantially free of emulsifiers and thickeners, not caramelized and thickened by shear so that it has a firmness corresponding to a maximum compression force of at least 20 g measured by a Texture Analyser TA.HDi equipped with a 5 kg load cell.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a food product having a spreadable texture suitable for example for spreading on bread, and to a method of making such a food product. 
       BACKGROUND TO THE INVENTION 
       [0002]    Sweet spreads that can be applied to bread include jams, jellies, fruit preserves, peanut butter, hazelnut spreads made from hazel nuts, cocoa butter and vegetable oil and dulce de leche (also known as doce de leite) caramelised milk spreads. 
         [0003]    EP-A-938848 describes a milk based spreadable product comprising milk, sugar, fat and emulsifier. It is prepared by thermally treating sugar, fat and emulsifier and then mixing with a sugared condensed milk to provide a homogenised paste. 
         [0004]    DE-A-19627054 describes a milk based sweet cream product prepared from sweetened condensed milk with flavourings and a thickener comprising an alkaline earth metal salt such as calcium chloride. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention seeks to provide a dairy based spreadable product without the need for using any emulsifying or thickening additive. 
         [0006]    A shelf stable spread according to the present invention comprises sweetened condensed milk of fat content 2 to 25% by weight and water content 15 to 35% by weight, substantially free of emulsifiers and thickeners, not caramelized and thickened by shear so that it has a firmness corresponding to a maximum compression force of at least 20 g measured at 25° C. by a Texture Analyser, for example of the TA.HDi type, equipped with a 5 kg load cell and a 20 mm diameter cylinder probe with a penetration into the sample at a constant speed 1 mm/s during 10s. 
         [0007]    According to another aspect of the invention a shelf stable spread comprises sweetened condensed milk of fat content 2 to 25% by weight and water content 15 to 35% by weight, substantially free of emulsifiers and thickeners, not caramelized and thickened by shear so that it has a yield point of at least 90 Pa measured by a rheometer, for example of the Haake RS100 type and its vane geometry FL 22 , using a stress sweep from 0 to 560 Pa at 25° C. Preferably the spread has a yield point of at least 90 Pa and also a firmness corresponding to a maximum compression force of at least 20 g measured by the Texture Analyser. 
         [0008]    According to another aspect of the invention a shelf stable spread comprises sweetened condensed milk of fat content 2 to 25% by weight and water content 15 to 35% by weight, substantially free of emulsifiers and thickeners, not caramelized and thickened by shear so that it has a storage modulus G′ for a stress value equal to 1 Pa of at least 400 Pa measured by a rheometer, for example of the Haake RS100 type and its vane geometry FL 22  using a stress sweep from 0 to 20 Pa at a frequency of 1 Hz and at 25° C. Preferably the spread has a storage modulus G′ of at least 400 Pa and also a yield point of at least 90 Pa and/or a firmness corresponding to a maximum compression force of at least 20 g measured by the Texture Analyser. 
         [0009]    According to another aspect of the invention a shelf stable spread comprises sweetened condensed milk of fat content 2 to 25% by weight and water content 15 to 35% by weight thickened by shear, the spread being substantially free of emulsifiers and thickeners and containing lactose crystals visible as distinct and regular crystals of maximum dimension less than 25 microns under optical microscopy in Differential Interference Contrast mode with a magnification factor of 640×. 
         [0010]    According to another aspect of the invention a shelf stable spread comprises sweetened condensed milk of fat content 2 to 25% by weight and water content 15 to 35% by weight thickened by shear, the spread being substantially free of emulsifiers and thickeners and sufficiently homogeneous that discrete fat globules are substantially not distinctly visible under fluorescence microscopy with a magnification factor of 640× when the product is stained with Nile Red dye. Nile Red stains the fat present. The absence or quasi-absence of distinctly visible fat globules in the spread indicates that the shear applied has caused a strong aggregation between the fat and the proteins of the condensed milk. 
         [0011]    In a process according to the invention for the preparation of a shelf stable spread from sweetened condensed milk of fat content 2 to 25% by weight and water content 15 to 35% by weight, the sweetened condensed milk is subjected to high shear, in the absence of added emulsifier or thickener, to thicken the sweetened condensed milk to a spread having a firmness corresponding to a maximum compression force of at least 20 g measured at 25° C. by a Texture Analyser for example of the TA.HDi type equipped with a 5 kg load cell and a 20 mm diameter cylinder probe with a penetration into the sample at a constant speed 1 mm/s during 10s) and/or a yield point of at least 90 Pa measured by a rheometer for example of the Haake RS100 type and its vane geometry FL 22  using a stress sweep from 0 to 560 Pa at 25° C. 
       DETAILED DESCRIPTION OF THE INVENTION  
       [0012]    The sweetened condensed milk generally has a water content of 15 to 35% by weight, preferably 25 to 28%. The total sugar (sucrose) content of the sweetened condensed milk is preferably from about 60% by weight sugar in water up to the solubility of sugar in water which is about 65% by weight. The fat content of the sweetened condensed milk is generally 2 to 20 or 25% fat by weight, preferably 5 to 10%. The sweetened condensed milk preferably has a water activity (defined as the ratio of the water vapour pressure over a food to that over pure water) of lower than 0.86, most preferably between 0.80 and 0.85. 
         [0013]    The sweetened condensed milk (SCM) can be fresh or recombined SCM, that is fresh milk that has been condensed and sweetened or sweetened condensed milk derived from skimmed milk and milk fat that have been recombined and sweetened. For either fresh or recombined SCM, the solid (i.e. non-aqueous) content of the sweetened condensed milk consists of non-fat milk solids, milk fat and added sugar. 
         [0014]    The sweetened condensed milk can be filled SCM wherein the milk fat has been replaced by vegetable fat. The sweetened condensed milk can also be an imitation SCM wherein an additional carbohydrate filler such as maltodextrin, has been added. In imitation SCM the fat can consist of milk fat, or all or part of the milk fat can be replaced by vegetable oil. A typical filled SCM formulation comprises 20% skimmed milk, 45% added sugar, 8% vegetable oil and 27% water. 
         [0015]    The high shear is preferably applied by passing the sweetened condensed milk through a homogeniser, in which the sweetened condensed milk is passed through a narrow gap under pressure. The gap is for example about 0.1 mm wide. Homogenisers are described at pages 115 to 118 of the ‘Dairy Processing Handbook’, 1st edition, published by Tetra Pak in 1995. Examples of suitable homogenisers are shown in FIG.  6 . 3 . 4  on page 117 and FIG.  6 . 3 . 6  on page 118. 
         [0016]    The homogenisation pressure is the pressure applied to the sweetened condensed milk before passing through the narrow gap. This homogenisation pressure is preferably at least 100 bar, more preferably in the range of 150 to 500 bar. The high shear caused by passage through a narrow gap under such pressure causes a strong aggregation between fat and proteins to the extent that discrete fat globules are substantially not distinctly visible under fluorescence microscopy after staining with Nile red dye. By substantially not distinctly visible, it is meant that aggregation between fat and proteins is such that there are nearly no more visible discrete fat globules, only a few isolated fat globules remaining present after the homogenisation treatment. The high shear also causes the sweetened condensed milk to thicken to a consistency suitable for use as a spread. The texture or firmness of the spread produced can be varied as required by varying the degree of shear applied, for example the pressure used in a homogeniser. A greater shear (higher pressure in a homogeniser) tends to form a firmer spread. The high shear mixing can be carried out at any temperature below that causing caramelisation but is usually carried out at ambient temperature. 
         [0017]    The spread formed by high shear from sweetened condensed milk alone has a sweet sugary flavour. The spread can be made without added flavour, but it is generally preferred to add flavour and optionally colouring. Examples of flavours that can be added are honey, vanilla, cocoa, peanut or fruit flavour in the formation of a sweet spread, or curry, chilli or a mix of spices can be added to form a savoury spread. The flavours and/or colours are preferably added as liquid flavours and/or colours before the condensed milk is subjected to high shear. The sweetened condensed milk and the liquid flavours and/or colours are preferably mixed in an in-line mixer, for example a static in-line mixer or an in-line dynamic mixer such as a centrifugal pump or rotor and stator device, before being sheared in a homogeniser. 
         [0018]    After the spread has been sheared to the required consistency, it can be filled into a container such as a glass jar or a plastic tub using single-stream or multi-stream filling apparatus, and the container is then closed and packaged for transport. 
         [0019]    The consistency of the spread can be measured in various ways. The firmness can be measured at 25° C. by a Texture Analyser for example of the TA.HDi type (available commercially from Stable Micro Systems of Surrey, U.K.) equipped with a 5 kg load cell and a 20 mm diameter cylinder probe with a penetration into the sample at a constant speed 1 mm/s during 10s. The measurements are run by means of ‘Texture Expert Exceed’ software supplied with the instrument and installed on a computer linked to the instrument. The maximum compression force is reported. The maximum compression force measured for the spread of the invention is generally at least 20 g, for example 50 to 500 g. By comparison, the maximum compression force measured for the SCM starting material is generally in the range 4 to 10 g. 
         [0020]    Additionally, the yield point and the storage modulus G′ of the spread can be measured by a rheometer. The yield point and the storage modulus G′ of the spread are much higher than the yield point and G′ of the sweetened condensed milk starting material. For a detailed definition of yield point and storage modulus G′ reference can be made to “Handbook of elementary rheology” by Howard A. Barnes ISBN 0-9538032-0-1. 
         [0021]    The spread produced has a texture similar to that of a nut-based spread, but has a lower calorie content and a lower fat content. 
         [0022]    The spread can also be characterised by microscopy. If the spread is examined under optical microscopy in Differential Interference Contrast mode with a magnification factor of 640×, it will be seen that the spread contains lactose crystals visible as distinct crystals. Distinct lactose crystals can also be seen in SCM, but are not seen in some dulce de leche spreads because of hydrolysis of the sugars in such spreads. In dulce de leche that were not hydrolysed, large crystals, of lactose i.e. more that 25 micrometers can be seen. The microscopy can be carried out with or without polarisation, the crystals being clearly visible in the spread of this invention. 
         [0023]    If microscopy is carried out on samples stained with Nile Red dye, which stains the fat present, hardly any distinct fat globules can be seen in the spread of the invention. Using this staining technique, discrete fat globules can be seen in great number both in sweetened condensed milk and in dulce de leche. 
     
    
     
         [0024]    The invention is illustrated by the following Examples, in which parts and percentages are by weight. The Examples will be described with reference to  FIGS. 1 to 14  of the accompanying drawings, of which: 
           [0025]      FIG. 1  is a photomicrograph of the spread of Example 1 under optical microscopy in Differential Interference Contrast mode with a magnification factor of 640×; 
           [0026]      FIGS. 2 to 6  are photomicrographs of comparison products under the same conditions as  FIG. 1 ; 
           [0027]      FIG. 7  is a photomicrograph under fluorescence microscopy of the spread of Example 1 stained with Nile Red dye; 
           [0028]      FIGS. 8 to 12  are photomicrographs of comparison products under the same conditions as  FIG. 7 ; 
           [0029]      FIG. 13  is a photomicrograph of the spread of Example 2 under optical microscopy in Differential Interference Contrast mode with a magnification factor of 640×; 
           [0030]      FIG. 14  is a photomicrograph under fluorescence microscopy of the spread of Example 2 stained with Nile Red dye, and 
           [0031]      FIG. 15  shows a four blade vane geometry used for measuring the yield point and storage modulus G′ of the spread of the invention. 
       
    
    
     EXAMPLE 1  
       [0032]    Filled sweetened condensed milk (FSCM) of water content 27% and fat content 8% was put into a storage tank at 20-25° C. The sweetened condensed milk was pumped through an in-line homogeniser of the type shown in FIG.  6 . 3 . 4  of ‘Dairy Processing Handbook’ with a pressure setting at 400 bar, wherein the sweetened condensed milk flows through a conduit and is forced through a gap defined between the transversal end surface of the conduit and a plate placed opposite said transversal end surface. The product emerging from the homogeniser was filled into containers which were immediately sealed. The thickened texture similar to that of a nut-based spread is achieved a few hours after filling. 
         [0033]    The firmness of the spread was analysed using a Texture Analyser TA.HDi equipped with a 5 kg load cell. Samples were conditioned in a chamber at 25° C. before analysis. An aluminium cylinder probe (P/20) of diameter 20 mm penetrates into the sample at pre-test speed 1 mm/s and test speed 1 mm/s to a penetration distance of 10 mm, with post-test speed 10 mm/s. The compression force in grams is measured as a function of the penetration distance with a trigger value fixed at 1 g. The force at 10 mm (maximum force) was recorded as 142 g. 
         [0034]    The firmness of fresh and aged SCM, and of three Doce de Leite products, was similarly measured using the Texture Analyser TA.HDi and the results are shown in Table 1. 
         [0035]    The yield point of the spread was measured using Rheometer Haake RS100 with a vane geometry FL 22 . A vane of the FL  22  type is shown in  FIG. 15 . The vane consists of a cylindrical rod  1  at one end of which 4 blades 2 extending radially with respect to rod  1  extend. A fitting means  3  are provided at the end of the rod opposite the blades. The respective dimensions of the vane shown in the Figure are as follow: Blade height H: 16 mm; Blade diameter D: 22 mm and blade thickness T: 1 mm. Samples were conditioned in a cup in a chamber at 25° C. before measurement. The FL  22  geometry penetrates into the sample. Then a stress sweep of 0 to 560 Pa is applied to the sample at 25° C. The yield point measured was 438 Pa. 
         [0036]    The storage modulus G′ of the spread was measured using Rheometer Haake RS100 with a vane geometry FL 22 . Samples were conditioned in a cup in a chamber at 25° C. before measurement. The FL  22  geometry penetrates into the sample. Then a stress sweep of 0 to 20 Pa is applied to the sample at a frequency of 1 Hz at 25° C. The G′ measured at a stress value equal to 1 Pa was 4140 Pa. 
         [0037]    Samples of the spread were observed with a Leica DMR microscope in Differential Interference Contrast mode with a magnification factor of 640×. Observations were also made in a polarization mode. In each case distinct sugar_(lactose) crystals of length about 10 μm were visible. The contrast between the sugar crystals and the mass of the spread appears clearly, and  FIG. 1  is a photomicrograph of this. 
         [0038]    Samples of the aged and fresh SCM, and of the three Doce de Leite products were also observed under the same microscopy conditions as for  FIG. 1 , and  FIGS. 2 to 6  are photomicrographs at the same magnification respectively of the aged and fresh SCM and the three Doce de Leite products (see Table 1 for details). Distinct sugar crystals of about 10 μm can be seen in the SCM in  FIGS. 2 and 3 . No sugar crystals can be seen in the Doce de Leite samples of  FIGS. 4 and 5 .  FIG. 6  shows that this Doce de Leite sample contains a few much bigger sugar crystals, formed by uncontrolled crystallisation after heat treatment and cooling. 
         [0039]    Samples of the spread were stained with Nile Red by a film technique. 5 mg Nile Red dye (Sigma N-3013) was added to 100 ml of a 5% solution of polyvinyl pyrrolidone in ethanol. 20 μl of the dyed solution was spread onto a 12 mm diameter cover slide and allowed to dry, and the cover slide was then put onto the sample. The prepared sample was observed with a Leica DMR microscope with a magnification factor of 640× under light of a wavelength causing the Nile Red to fluoresce. A diffuse pattern was seen as shown in the photomicrograph marked  FIG. 7 , with hardly any discrete fat globules being visible. 
         [0040]    Samples of the fresh and aged SCM, and of the three Doce de Leite products were also stained and observed under the same microscopy conditions and  FIGS. 8 to 12  are photomicrographs respectively of the aged and fresh SCM and the three Doce de Leite products (see Table 1 for details). Discrete fat globules in great number are very clearly visible in the SCM in  FIGS. 8 and 9 , and also in the Doce de Leite of  FIG. 10 . Discrete fat globules in great number are also visible in the Doce de Leite samples of  FIGS. 11 and 12 , although these are not quite so distinct as the fat globules in  FIG. 10 . 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Texture Analyser 
                   
                   
                   
               
               
                   
                 TA.HDi 
                 yield 
               
               
                   
                 Maximum force 
                 point 
                 G′ 
               
               
                 Sample 
                 (g) 
                 (Pa) 
                 (Pa) 
                 Microscopy 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Spread of Example 1 
                 142 
                 438 
                 4140 
                 FIGS. 1 
               
               
                   
                   
                   
                   
                 and 7 
               
               
                 Spread of example 2 
                 675 
                 &gt;560 
                 24983 
                 FIGS. 13 
               
               
                   
                   
                   
                   
                 and 14 
               
               
                 Aged SCM 
                 7 
                 21 
                 14 
                 FIGS. 2 
               
               
                   
                   
                   
                   
                 and 8 
               
               
                 Fresh SCM 
                 6 
                 15 
                 5 
                 FIGS. 3 
               
               
                   
                   
                   
                   
                 and 9 
               
               
                 Nestle Moca Doce de 
                 360 
                 &gt;560 
                 9229 
                 FIGS. 4 
               
               
                 Leite Para Corte 
                   
                   
                   
                 and 10 
               
               
                 Nestle Moca Doce de 
                 24 
                 85 
                 1219 
                 FIGS. 5 
               
               
                 Leite Cremos 
                   
                   
                   
                 and 11 
               
               
                 Itambe Doce de Leite 
                 132 
                 460 
                 7810 
                 FIGS. 6 
               
               
                 Pastoco 
                   
                   
                   
                 and 12 
               
               
                   
               
             
          
         
       
     
         [0041]    The calorific value of the spread of Example 1 is 325 Kcal/100 g, whereas a commercial spread of similar texture made from hazel nuts, cocoa butter and vegetable oil has a calorific value of 525 Kcal/100 g. The fat content of the spread of Example 1 is 8%, compared to 30% for the nut-based spread. 
       EXAMPLE 2  
       [0042]    Sweetened condensed milk (SCM) of water content 27.5% and fat content 8% was put into a storage tank at 20-25° C. A separate solution of aroma and color was prepared. The sweetened condensed milk and the aroma/color solution was pumped proportionally through a static in-line mixer followed by an in-line homogeniser of the type shown in FIG.  6 . 3 . 4  of ‘Dairy Processing Handbook’ with a pressure setting at 300 bar. The product emerging from the homogeniser was filled into containers which were immediately sealed. The thickened texture similar to that of a nut-based spread is achieved a few hours after filling. 
         [0043]    The firmness of the spread was analysed using a Texture Analyser TA.HDi equipped with a 5 kg load cell. Samples were conditioned in a chamber at 25° C. before analysis. An aluminium cylinder probe (P/20) of diameter 20 mm penetrates into the sample at pre-test speed 1 mm/s and test speed 1 mm/s to a penetration distance of 10 mm, with post-test speed 10 mm/s. The compression force in grams is measured as a function of the penetration distance with a trigger value fixed at 1 g. The force at 10 mm (maximum force) was recorded as 675 g. 
         [0044]    The yield point of the spread was measured using Rheometer Haake RS100 with a vane geometry FL 22 . Samples were conditioned in a cup in a chamber at 25° C. before measurement. The FL  22  geometry penetrates into the sample. Then a stress sweep of 0 to 560 Pa is applied to the sample at 25° C. The yield point measured was more than 560 Pa. 
         [0045]    The storage modulus G′ of the spread was measured using Rheometer Haake RS100 with a vane geometry FL 22 . Samples were conditioned in a cup in a chamber at 25° C. before measurement. The FL  22  geometry penetrates into the sample. Then a stress sweep of 0 to 20 Pa is applied to the sample at a frequency of 1 Hz at 25° C. The G′ measured at a stress value equal to 1 Pa was 24983 Pa. 
         [0046]    It will be understood that various modifications and/or improvements obvious to those skilled in the art may be made to the examples described in the present description without departing from the scope of the invention defined by the annexed claims. In particular, it will be noted that the spread of the invention can be coextruded with another edible product having different flavours and/or colors such as a spread of the invention mixed with a coloring or/or flavouring agent, fruit paste, honey, chocolate etc. so as to produce a spread having alternating outside stripes, thereby improving the spread&#39;s appearance and/or flavour characteristics.