Field of the invention

The invention relates to a process for the preparation of a fermented dairy-based snack food product and to the fermented dairy-based snack food product obtainable by such process.

Background to the invention

There is a continuing need for snack food that combine valuable nutrients, such as proteins, with good texture and organoleptic properties, in particular taste and mouthfeel. At the same time the manufacturing of such snacks should not be too cumbersome and costly and should be scalable to enable large scale manufacturing.

Milk is a source of nutrients that have many benefits for humans. Fermented milk products are popular, not in the least because they have a distinct taste and contain many healthy nutrients. Examples are yogurt and quark, either in natural form or with taste -imparting additives such as fruits.

An anonymous disclosure in IP.COM Journal, 2 July 2018, pp. 1-5, entitled“Ready-to-eat yogurt chips containing live probiotics cultures made from fresh yogurt” discloses shelf-stable chips made from fresh yogurt, containing live and/or active probiotic cultures comprising between 40 and 80% by weight of a fermented dairy product, between 10 and 25% by weight of tapioca flour, and having a fat content comprised between 2 and 12% by weight, which has been submitted to drying. An embodiment is disclosed comprising between 40 and 80% by weight of a fermented diary product, between 10 and 25% of tapioca flour, between 4 and 17% by weight of Milk Protein Isolate, and between 2 and 12% by weight of fat.

The method for preparing such ready-to-eat fermented dairy product chips is disclosed to comprise the following steps:

(a) providing an initial mix comprising:

i. between 40 and 80% wt of a fermented dairy

composition containing an ahve culture, for example an alive yogurt culture, for example live probiotics at a concentration of at least 10 ⁶ cfu/g, and

ii. between 10 and 25% wt of tapioca flour, and

iii. and having a fat content comprised between 2 and 10% wt;

(b) extruding and slicing the initial mix of step (a) to obtain chips- precursor dough pieces; and

(c) drying the chips-precursor dough pieces resulting from step (b) using microwave radiation /or oven under vacuum, at a temperature from 10° to 45°C, to obtain ready-to-eat fermented dairy product chips containing the alive culture.

A drawback of such ready-to-eat fermented dairy product chips is that production on an industrial scale would be time-consuming and thus costly. More particularly, especially on a larger scale, there is a risk that the chips will adhere together during production forming larger products, which is undesirable.

The inventors aimed to develop a fermented dairy-based snack food product that would still contain many of the healthy nutrients typically found in fermented dairy products, including the bacterial cultures used to prepare the fermented dairy product. At the same time the snack food product should have an attractive taste, texture and mouthfeel and should be relatively easy to manufacture in a reproduceable and industrially scalable manner.

Summary of the invention

It was found that the aforesaid goals could be met by a product obtainable by a process that involves the preparation of a dough from various ingredients, including a fermented dairy component and a concentrated milk protein component, processing the dough into shaped precursor food products, coating these shaped precursors and finally drying the coated and shaped precursor food products in a vacuum microwave drying device at a temperature below 50 °C. Detailed description of the invention

Accordingly, in a first aspect the invention relates to a process for the preparation of a fermented dairy-based snack food product comprising the steps of:

(a) preparing a dough by mixing

(i) 40-80% by weight, preferably 50-70% by weight, of a fermented dairy component comprising hving fermentation bacteria cultures and having a fat content in the range of 0 to 20% by weight based on total weight of the fermented dairy component;

(ii) 2-20% by weight, preferably 5-15% by weight, of a concentrated milk protein component which comprises at least 40% by weight, based on dry matter, of milk protein;

(iii) 5-30% by weight, preferably 10-28% by weight, of starch;

(iv) 0-20% by weight, preferably 2-10% by weight, of dried fruits;

(v) 0-20% by weight, preferably 1-20% by weight, of edible fibrous

material, preferably oats;

(vi) 0-2% by weight of taste components; and

(vii) 0-5% by weight of sweetener;

(b) processing the dough into shaped precursor food products;

(c) coating the shaped precursor food products, preferably with starch; and

(d) drying the coated and shaped precursor food products in a vacuum

microwave drying device.

Step (a) involves preparation of the dough that will be further processed into the final snack food product. Critical ingredients are a fermented dairy component comprising living fermentation bacteria cultures and a concentrated milk protein component. The fermented dairy component could be a strained fermented dairy product, such as yogurt, Greek style yogurt or quark. Fat percentage of the fermented dairy component could vary from 0 to 20% by weight, suitably 0 to 10% by weight. In one embodiment for preparing a low fat snack food product, a yogurt having a fat percentage of 0 to 2% by weight could be used. Bacteria cultures used for fermenting dairy components are well known. For the purpose of the present invention the yogurt bacteria

Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus are suitably used. Other lactic acid bacteria of the Lactobacillus genus and/or

Bifidobacterium genus may be added too. Examples include Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus plantarum and Lactobacillus fermentum.

The concentrated milk protein component is intended to include additional proteins into the food product. Part of the protein in the final product is already introduced via the fermented dairy component. Total milk protein content of the final product could range from 5 to 50% by weight (based on total weight of product) and would typically be between 10 and 25% by weight. In general, protein content in a milk product can be determined using either the standard Kjeldahl method or the standard Dumas method with a nitrogen conversion factor of 6.38. The concentrated milk protein component comprises a milk protein content of at least 30% by weight (based on dry matter), and preferably at least 40%, and preferably at most 97% by weight, and most preferably at most 95% by weight. The concentrated milk protein component suitably comprises a milk protein content from 50 to 97% by weight and more suitably from 70 to 95% by weight (based on dry matter). The casein: whey protein ratio in the concentrated milk protein component will typically be at least the ratio occurring in raw milk, i.e. approximately 4. Higher casein: whey protein ratios (i.e. higher than 4) are also feasible. Examples of suitable concentrated milk protein components are:

- Milk Protein Concentrates (MPC), such as MPC 80 or MPC 85 (containing respectively about 80% and at least 82.5% by weight protein on dry matter with a casein: whey protein ratio as in milk);

- Milk Protein Isolates (MPI) having protein contents between 85 and 95% by weight (on dry matter) with a casein: whey protein ratio as in milk, such as MPI 80 and MPI 85 (containing respectively about 80% and about 85% by weight protein on dry matter); - Skimmed Milk Powders (SMP) typically having a protein content of 30 to 36% by weight expressed on fat free dry matter, and preferably having a protein content of at least 34% expressed on fat free dry matter, with a casein : whey protein ratio as in milk. Most preferred is SMP having a protein content of 34 to 39% by weight expressed on fat free dry matter, and a casein : whey protein ratio as in milk;

- Caseinates (e.g. sodium caseinate, calcium caseinate, magnesium caseinate); and

- Micellar Casein Isolates (MCI).

The latter two have a casein : whey protein ratio well above 4 and contain casein in an amount of at least 90% by weight based on total protein.

Mixtures of two or more of the concentrated protein components mentioned above could also be suitably used. These protein products are well known and are commercially available. MPI was found to be particularly suitable as the concentrated protein component.

Starch is added to improve the texture and improve processability of the dough. The dough prepared in step (a) should have sufficient elasticity and should not be too sticky. In principle any type of starch able to improve texture and processabihty could be used. Particularly suitable starches comprise 15-30% by weight of amylose (based on total weight of starch) and 80-70% by weight of amylopectin. Such starch could be native or modified. Modified starches that have been approved for use as food additive could be used. The starch used could (partly) consist of resistant starch. For the purpose of the present invention particularly good results have been achieved when using native (or natural) starch. Suitable sources of such native starches include potato, maize, tapioca, rice and wheat. Suitable starches also include pregelatinized starches, i.e.

starched that have been cooked and then dried. For the purpose of the present invention the use of pregelatinized native starch, particularly those derived from tapioca, were found particularly useful for use in step (a). A wide variety of starch products for use in foods are well known in the art and commercially available. The starch content ranges from 5 to 30% by weight of the dough, whilst preferred amounts range from 10 to 28% by weight. The other ingredients of the dough prepared in step (a) are in principle optional ingredients. Dried fruits may be added depending on the desired taste. Amount and type of dried fruit can accordingly vary widely, but typically the amount will range from 0 to 20% by weight. Preferably, the amount of dried fruits used is at least 1% by weight, based on the total weight of the dough. The amount of dried fruits used is preferably at most 15% by weight, based on the total weight of the dough. More preferably, the amount of dried fruits is 1 - 12% by weight, based on the total weight of the dough, more suitably it is 2 to 10% by weight. The dried fruits can be added in any suitable form known to the skilled person. For example, it can be added in the form of a powder or as small pieces of dried fruit (e.g. obtained by drying the fruit and cutting it in small pieces). The dried fruit may consist of one type of fruit only or of a mixture of different types of fruit.

Edible fibrous materials may be added to improve texture, bind moisture and provide a more firm texture in the end product. Preferred edible fibrous materials used include oats and grains, of which oats are preferred. Other edible fibrous materials can be used as well, for example wheat, corn, rice, spelt, quinoa, galacto-oligosaccharides, fructo-oligosaccharides, inuline, chia seeds, sunflower seeds, sorghum, pumpkin seeds, hazelnuts, pecan nuts, walnuts, almonds, pistachio nuts, macadamia nuts, cashew nuts, or brazil nuts. It is also possible to use mixtures of the edible fibrous materials as just mentioned.

The edible fibrous materials are typically used in a total amount of up to 20% by weight, more suitably 0 to 10% by weight. Preferably, the edible fibrous material is added in a total amount of at least 1% by weight. More preferably, it is used in a total amount of at least 1.5% by weight and most preferably in a total amount of at least 2% by weight, based on the total weight of the dough. Preferably, the edible fibrous material is added in a total amount of at most 20% by weight, more preferably, at most 15% by weight and most preferably in an amount of at most 10% by weight, based on the total weight of the dough.

Taste components, i.e. flavouring agents, may be used depending on taste preferences. Natural flavouring agents are preferred. The typical flavouring agents used in yogurt products, such as fruit flavouring agents, could be used. A flavouring agent that imparts a yogurt taste could also be used. Such flavouring agents are well known. The amount in which they are used will be at most 2% by weight, suitably 0.1 to 1.5% by weight. Sweeteners, finally, may be added to improve the taste, if needed and/or desired. Suitable sweeteners are, for example, conventional sweeteners such as sucrose, maltodextrin, glucose and fructose, but artificial sweeteners, such as sucralose or maltitol may also be used. The amount of sweetener to be added will typically vary from 0 to 5% by weight, preferably 0 to 2% by weight.

In step (a) the ingredients are mixed to form a dough. This can be achieved by simply blending all ingredients together. The dough should be elastic and not be too sticky to enable effective further processing. It was, however, found particularly suitable to prepare the dough by the successive steps of (al) preparing a premix of the concentrated milk protein, starch, dried fruits and optionally the oats, taste components and/or sweetener;

(a2) mixing this premix with the fermented dairy component to produce a dough. Typically the ingredients mentioned in step (al) are in powder form, so that this step can be carried out by dry-blending the powder ingredients to form the premix. In step (a2) this premix, in powder form, is then mixed with the fermented dairy component, which will typically have the form of a viscous hquid or gel. Conventional mixing means can be used, in particular those mixers suitable for mixing and kneading dough-like substances. Typically this will be high shear mixers. For the purpose of the present invention the mixer used should anyhow be capable of producing a homogenous dough at a temperature below 50 °C within a reasonable timespan.

Preparation of the dough in step (a) is suitably carried out at a temperature below 50 °C, preferably in the range of 2 to 30 °C, more preferably 5 to 20 °C. This will ensure the fermentation bacteria cultures remain ahve and a processable dough is obtained. In a preferred embodiment the dough prepared in step (a) is stored at a temperature in the range of 1 to 10 °C for at least 10 minutes before being processed into shaped precursor food products in step (b). For process efficiency reasons storage will typically not exceed 1 hour. In step (b) the dough is processed into shaped precursor food products which determine the final shape of the end product. Such processing will suitably comprise portioning the dough into a desired shape that can be easily handled, for example a cylinder- shaped roll. The dough portions thus obtained could then be cut into the desired end shape of the food product. Such portioning and cutting can be achieved by any suitable method known in the art and processing equipment available, depending on desired shape, weight and size of the final snack food product. For example, if popcorn-shaped and -sized snacks are to be prepared the dough portions should be cut accordingly. Likewise, crisp -like shapes could be attained by slicing the dough cylinders and then pressing the slices into flat shapes, possibly using moulds for specific shapes. The result from step (b) are shaped precursor food products.

In step (c) these shaped precursor food products are subsequently coated. Such coating is needed to avoid the shaped precursor food products to adhere to each other before and during subsequent drying step (d), thus forming larger shapes. Since the precursors still contain quite some water, they could still be somewhat sticky. Suitable coating materials are food grade materials that could prevent the shaped precursor food products to stick together. Typically, the coating material is selected from the group consisting of starches; cellulose;

mono- and disaccharides; polyalcohols; silicates; and hydrocolloids. The starches can be native or modified. Preferred examples are starches (same examples and preferences as mentioned hereinbefore in connection with the ingredients of the dough) or cellulose. Starch is most preferred. Native maize starch was found particularly suitable. The amount of coating material should be sufficient to cover the outer surface of the food precursor shapes. It is preferred to have merely a thin coating layer so that it does not adversely affect taste and mouthfeel. Hence, if starch is used, this amount (i.e. the total amount of coating material, most preferably being starch) will typically vary between 0.5 and 5% by weight of total dough, more suitably between 0.5 and 2% by weight.

Once coated, the shaped food precursors are subjected to the microwave vacuum drying treatment in step (d). It is important that this drying step (d) is carried out under such conditions that the fermentation cultures present in the fermented dairy component survive the drying treatment, thereby obtaining the dried fermented dairy food product. The microwave vacuum technology enables drying to take place at relative low temperatures, thus ensuring that the fermentation bacteria cultures used to prepare the starting fermented dairy component will survive the drying treatment. This implies that the material to be dried will typically not exceed a temperature of 50 °C during the drying treatment. Microwave vacuum drying technology and devices for applying such drying technology are known in the art and commercially available. For example, WO 2009/049409 Al, WO 2009/033285 Al, WO

2011/085467 Al and WO 2014/075193 Al all disclose microwave vacuum drying devices and methods that could suitably be used in the process of the present invention. Suitable microwave vacuum drying devices are commercially available from e.g. Enwave Corporation (its Radiant Energy Vacuum or REV™

dehydration technology).

Exact conditions in the microwave vacuum dryer are determined by amount of material to be dried and water content of such material. Generally an average power of between 10,000 and 500 watts (W) could be apphed, suitably between 5000 and 750 W, more suitably between 3500 and 1000 W, with drying times of at least 10 minutes, typically 15 to 100 minutes, when drying 1 to 6 kg of the coated and shaped precursor food product to a water content of 10% by weight or less (based on total weight of product). For the purpose of the present invention it was found particularly suitable to dry the coated and shaped precursor food products obtained in step (c) to a water content of less than 8% by weight. Typically water content would not go below 2% by weight, more suitably not below 4% by weight. The power setting may be varied during the drying step by applying different powers in different stages of the microwave vacuum treatment. For example, in successive stages the power may be decreased or increased with each stage having an equal or different duration. The power ranges given above, accordingly, refer to the average power applied during the entire drying step, whilst the drying time is the total drying time.

Once dried, the resulting fermented dairy-based snack food product is suitably subjected to the step of (e) packaging the fermented dairy-based snack food product.

Suitable packages could have any desired shape, color or size and any suitable packaging material could be used (e.g. card board, paper, plastic, metal).

Examples include plastic buckets with a re-closable lid, sachets or boxes.

In a further aspect the present invention relates to a fermented dairy- based snack food product obtainable by the process as described hereinbefore. Such fermented dairy-based snack food product suitably has a water content in the range of 2 to 10% w/w (based on total weight of product), preferably 5-8% w/w, and a water activity (a _w ) of 0.5 or less, preferably 0.3 or less, at 20 °C. Water (or moisture) content is determined by standard method ISO 5536/IDF 026:2004 - Dried Milk - Determination of moisture content ). Water activity is determined by AO AC Official Method 978.18.

As described above, total (milk) protein content suitably is 5 to 50% by weight (based on total weight of product), more suitably between 10 and 25% by weight. The fermented dairy-based snack food product of the invention the fermentation cultures comprise Streptococcus thermophilus and Lactobacillus bulgaricus and are present in an amount of at least 1 x 10 ⁶ CFU/g (according to NEN-ISO 7889).

The invention will be further illustrated by the following example without bmiting the scope of the invention to this specific embodiment.

Examnle Ί

A premix was prepared by mixing the following powder ingredients, for 2 kg of starting material:

- 440 grams starch (pregelatinized native tapioca starch)

- 80 grams of oat

- 80 grams of Refit® MPI85 ex FrieslandCampina Nederland BV, having milk protein content of 85% by weight on dry matter,

- 92 grams of skimmed milk powder ex FrieslandCampina Nederland BV

- 160 grams of dried fruit (strawberry taste) in the form of a powder,

- 8 grams of a natural flavouring agent. This premix was blended with 1140 grams of yogurt (7.5 wt% fat) in the Stephan UM44 high shear mixer ex Stephan Machinery GmbH for 2 minutes at a temperature of between 15 and 20 °C. The resulting dough was subsequently stored for 2 hours at 4 °C.

After these 2 hours of storage the dough was portioned and cut in a Handtmann VF 628 vacuum filling machine ex Albert Handtmann

Maschinenfabrik GmbH & Co. KG and shaped into balls in the weight range of 1 to 3 grams.

The balls were coated with native maize starch (10 grams/kg) by coating the surface of the dough balls with starch powder by means of a sieve, thereby simultaneously rolling the balls, so that their entire surface was covered with a layer of the starch. The coated balls were subsequently passed into a microwave vacuum dryer (10 kW REV™ microwave vacuum dryer ex Enwave Corporation) and dried. Average power applied was 2500 W, drying time was 1500 seconds.

The resulting dried balls had the properties as indicated in Table 1.

Methods used:

Bacteria count concerned yogurt bacteria Streptococcus thermophilus and

Lactobacillus delbrueckii subsp. bulgaricus and was determined by standard method NEN-ISO 7889.

Protein content was determined according to ISO 16634-2:2016 (Dumas method). Water content was determined according to ISO 5536/IDF 026:2004.

Water activity was determined according to AOAC Official Method 978.18.

Table 1 - Product properties

Comparative Example (no coating layer):

A premix was prepared by mixing the following powder ingredients, for 2 kg of starting material:

- 500 grams of starch (pregelatinized native tapioca starch)

- 80 grams of oat

- 100 grams of Refit® MPI85 ex FrieslandCampina Nederland BV, having milk protein content of 85% by weight on dry matter,

- 114 grams of skimmed milk powder ex FrieslandCampina Nederland BV

- 160 grams of dried fruit (strawberry taste) in the form of a powder,

- 8 grams of a natural flavouring agent.

This premix was blended with 1038 grams of yogurt (7.5 wt% fat) in the Stephan UM44 high shear mixer ex Stephan Machinery GmbH for 2 minutes at a temperature of between 15 and 20 °C. The resulting dough was subsequently stored for 2 hours at 4 °C.

After these 2 hours of storage the dough was portioned and cut in a Handtmann VF 628 vacuum filling machine ex Albert Handtmann

Maschinenfabrik GmbH & Co. KG and shaped into balls in the weight range of 1 to 3 grams. The balls were not coated but were subsequently passed into a microwave vacuum dryer (10 kW REV™ microwave vacuum dryer ex Enwave Corporation) and dried. Average power applied was 2500 W, drying time was 1500 seconds.

During drying, the balls stuck together and big lumps were formed (see

Figure 1).

Example 2

A premix was prepared by mixing the following powder ingredients, for 2 kg of starting material:

- 500 grams of starch (pregelatinized native tapioca starch)

- 80 grams of oat

- 80 grams of Refit® MPI85 ex FrieslandCampina Nederland BV, having milk protein content of 85% by weight on dry matter,

- 74 grams of skimmed milk powder ex FrieslandCampina Nederland BV

- 160 grams of dried fruit (strawberry taste) in the form of a powder,

- 8 grams of a natural flavouring agent.

This premix was blended with 1098 grams of yogurt (7.5 wt% fat) in the Stephan UM44 high shear mixer ex Stephan Machinery GmbH for 2 minutes at a temperature of between 15 and 20 °C. The resulting dough was subsequently stored for 2 hours at 4 °C.

After these 2 hours of storage the dough was portioned and cut in a Handtmann VF 628 vacuum filling machine ex Albert Handtmann Maschinenfabrik GmbH & Co. KG and shaped into balls in the weight range of 1 to 3 grams.

In this experiment the balls were coated with starch subsequently passed into a microwave vacuum dryer (10 kW REV™ microwave vacuum dryer ex Enwave Corporation) and dried. Average power applied was 2500 W, drying time was 1500 seconds. As is clear from Figure 2, the resulting dried balls stayed separate from each other, they did not stick together and no lumping was observed whatsoever.