TECHNICAL FIELD OF THE INVENTION The present invention relates to systems for the preservation of fresh dairy spun- curd products, for example water buffalo mozzarella, that ensure keeping their physical, organoleptic, and nutritional properties over long periods of time. The invention further relates to a method for the realization of such systems.

PRIOR ART

Fresh dairy products have won a large market share, also abroad Italy. Fresh spun-curd cheeses, particularly mozzarella, more particularly water buffalo mozzarella, are among the most widely appreciated products in the industry. However, they, in particular those produced in the South of Italy, are not among the most widely consumed typical products in Northern Italy and abroad due to their short shelf-life.

Shelf-life of fresh dairy products, particularly mozzarella, is tightly linked to the kind of raw material used (fresh raw milk or fresh pasteurised milk) and to the transformation technology used. The product obtained from raw milk and natural serum-graft is preserved immersed in the preservation liquid, for 3 - 4 days at a temperature of 4 - 10 ⁰ C without losing its features (shiny outer surface, white colour, soft and rubbery texture, particular flavour of fresh milk with a musky hint). Beyond this time interval, the outer surface gets softer, the texture loses its consistency and becomes but- tery, losing completely its structure made of superimposed layers, obtained by stretching the curd during the production process. Conversely, mozzarella obtained with pasteurised milk and a select graft, has a far longer preservation time, suitable for industrial productions. However, these products are not much sought after by consumers since they have poorer physical, organoleptic and nutritional properties than non-sterilised products.

Although the transportation networks allow the delivery of fresh dairy products within 24/48 hours, and in spite of the use of innovative packaging, their wide distribution mainly involves products obtained from sterilised raw materials.

Currently, the most widely used materials for packing fresh spun-curd cheeses are plastic bags and trays, polythene-lined paper containers, such as Tetrapak®, also under vacuum and brick containers containing a preserving solution, usually whey, a by-product of cheese production, in which the product is immersed.

SUMMARY OF THE INVENTION

Therefore, there is an evident need to provide packing systems that allow preserving and transporting fresh dairy products, particularly fresh spun-curd cheeses, for long periods of time. The authors developed food-compatible gel systems which, surprisingly, showed great efficacy in the preservation of dairy products, in particular of spun-curd cheeses, and in their distribution.

The gel-preserved product shows a longer shelf-life as compared to the product kept in the well-known current preserving systems, even longer than 30 days, and it maintains the typical organoleptic and nutritional features of the fresh product. Gels of the invention are obtained mainly using polymer-based products, already used in the food industry, but never used before for the manufacture of dairy products. These macromolecules, either natural, semi-synthetic or synthetic can be obtained in large quantities, from natural renewable sources or by synthesis at particularly low costs that are compatible with the scopes of the invention.

Therefore, it is an object of the instant invention a preserving gel for fresh dairy spun-curd products, made of a aqueous solution and at least one food-compatible polymer.

Preferably, the polymer is water-soluble at temperatures higher than 40 ⁰ C and turns into a gel at lower temperatures. More preferably, the gel further comprises at least one reticulating agent. Most preferably, the polymer is a polysaccharide or a protein, natural or semi-synthetic. Preferably, the polymer is agar, xantan, gel- Ian, polyvinyl alcohol, amide acrylate, hydroxyethylcellulose. More preferably, the polymer is animal o vegetal gelatin. Preferably, the aqueous solution is source water or a saline solution. More preferably, the solute in the saline solution is at a concentration that varies between 3 to 10% in weight. Most preferably, the aqueous solution is whey derived from cheese production processes or preservation liquid used for preserving the products.

Preferably, the gel is further made of at least one food-compatible, antimicrobial compound. More preferably, the antimicrobial compound is a preserving and/or anti-oxidant agent. Even more preferably, the preserving and/or anti-oxidant agent is sorbate, citric acid, ascorbic acid. In one embodiment, the concentration of the polymer in the gel is in the range 0.1 to 40% w/v.

It is an object of the instant invention a gelling solution able to form the gel of the invention. It is a further object of the instant invention a wrapping support for preserving fresh spun-curd dairy products characterized by being made of the gel of the invention. Preferably the support is contained in a container.

It is a further object of the instant invention a container for preserving fresh spun- curd dairy products comprising the wrapping support of the invention and at least one fresh spun-curd dairy product. It is a further object of the invention, a method for preserving fresh spun-curd dairy products comprising the steps of: a) immersing at least one dairy product in a gelling solution able to form the gel of the invention, while the latter is still in the liquid state; b) letting the solution turn into a gel either by cooling or by adding a re- ticulating agent; c) preserving the fresh dairy products immersed in the gel at a temperature between 4 to 3O ⁰ C.

It is a further object of the invention a process for preserving fresh spun-curd dairy products comprising the steps of: a) preparing a gelling solution able to form the gel of the invention b) introducing a first aliquot of the preserving solution in a container and let it turn into a gel to thereby form a layer of gel; c) placing the fresh spun-curd dairy product on top of the gel layer; d) adding a second aliquot of gelling solution at a temperature that does not alter the organoleptic characteristics of the product, to cover up the product and let it turn into a gel; e) keeping the product in the wrapping gel support at a temperature of 0°c to 25°C.

The invention will be herein described by the following non-limiting examples, carried out using fresh water buffalo mozzarella as an experimental model. The skilled person in the art will understand that any fresh spun-curd dairy product can be similarly preserved with the finding of the invention. Figure 1 : Typical appearance of freshly made mozzarellas (A), after 15 days preservation in whey (B) and after 15 days preservation in agar gel at a concentration of 1.5% in weight (C).

Figure 2: Microbial counts, LOG scale, of the colony forming units per gram of sample (ufc/g), of water buffalo mozzarellas kept at +4°C for different time peri- ods.

M: reference mozzarella kept in preservation liquid; MA: mozzarella preserved in agar gel at 1.5% in weight; t: days; CMT: total microbial counts; LAB term (termo- phile lactic acid bacteria); LAB mes (mesophile lactic acid bacteria); Colif Tot..: Total conforms; colif. Faec: Faecal conforms; enteroc. Faec: faecal enterococci. Figure 3: Microbial counts, LOG scale, of the colony forming units per gram of sample (ufc/g), of mozzarellas at time 0, preserved at room temperature for five days.

M: reference mozzarella kept in preservation liquid; MA: mozzarella preserved in agar gel at 1.5% in weight; t: days; CMT: total microbial counts; LAB term (termo- phile lactic acid bacteria); LAB mes (mesophile lactic acid bacteria); Colif. Tot.: Total conforms; colif. Faec: Faecal coliforms; enteroc. Faec: faecal enterococci Figure 4: Microbial counts, LOG scale, of the colony forming units per gram of sample (ufc/g), of water buffalo mozzarellas kept at +4°C for different time periods. M: reference mozzarella kept in preservation liquid; MA: mozzarella preserved in polysaccharide agar gel at 1.5% in weight + potassium sorbate at 2% in weight; t: days; CMT: total microbial counts.

Figure 5: Microbial counts, LOG scale, of the preserving media used with the mozzarellas at different time points. Ufc/g: unit forming colonies per gram of sam- pie; L whey; P: agar at 1.5% in water; t: time in days; CMT: total microbial counts; LAB term (lactic acid bacteria); LAB mes (mesophile lactic acid bacteria); Colif. Tot.: total coliforms; Colif. fee: faecal coliforms; Enteroc. fee: faecal enterococci.

Figure 6: Resiliency behaviour of fresh water buffalo mozzarellas, preserved in whey or as described in Example 1. A) After 5 days; B) After 30 days. Figure 7: Resiliency behaviour of fresh water buffalo mozzarellas, preserved in whey or as described in Example 3. A) After 5 days; B) After 30 days. Figure 8: Resiliency behaviour of fresh water buffalo mozzarellas, preserved in whey or as described in Example 6. A) After 5 days; B) After 30 days.

EXAMPLES

Example 1 - Preserving water buffalo mozzarella in an agar gel in source water at 4!C

In a typical preparation, a solution of agar 1.5% (Sigma Cat. A 1296) in source water was made, dissolving the polymer at 90°C. After dissolution, a layer 3 cm in depth was deposited in a polyethylene tray such as those normally used to commercialize mozzarella, and left to cool to a temperature below 40 ⁰ C to thereby ob- tain a gel. On this gel layer the mozzarellas to be preserved were placed, and a further amount of the agar solution was then poured over at 40 ⁰ C, until the mozzarellas were completely covered. Cooling to room temperature or, if a quicker procedure is desired, to 4°C, complete inclusion of mozzarellas into the gel was obtained, which, kept in these conditions at 4°C, maintain intact their rheological, nutritional and organoleptic features thereof, even for time periods longer than 1 month. This type of packaging makes the marketing of the product possible on a wider market, with totally different distribution modes from current ones, which are limited by the short shelf-life of the product in the currently used packaging types. At use, mozzarellas are recovered by opening the gel wrapping, that detaches perfectly from the product surface, without leaving residues. Alternatively, the agar gel can be solubilized by heating to 40 ⁰ C in warm water or in a microwave oven, recovering the product that, after cooling at room temperature, shows features such that it is not possible to distinguish it from the freshly made product. Example 2 - Preserving water buffalo mozzarella in an agar gel in source water at room temperature

The procedure was as described in Example 1 , but the product was kept at room temperature for 5 days. This was done because it is advisable to keep the water buffalo mozzarellas at room temperature for at least the first 3-4 days after being

made. The mozzarellas show properties undistinguishable from those of the natural product.

Example 3 - Preserving water buffalo mozzarella in an agar gel in source water at very low concentration (0.1 %) In a typical preparation, a solution of agar 0.1 % (Sigma Cat. A 1296) in source water was made, dissolving the polymer at 90 ⁰ C. After dissolution, a layer 3 cm in depth was deposited in a polyethylene tray such as those normally used to commercialize mozzarella, and left to cool to a T <40°C to allow gelling to take place. On this gel layer the mozzarellas to be preserved were placed, and a further amount of the agar solution was then poured over at about 4O ⁰ C, until the mozzarellas were completely covered. Cooling to room temperature or, if a quicker procedure is desired, to 4°C, a complete inclusion of mozzarellas in the gel was obtained. It is to be precised that the gel at this concentration was not compact but had a lumpy appearance. Determination of physical parameters of water buffalo mozzarellas preserved as described above are reported in the Results section.

Example 4 - Preserving water buffalo mozzarella in an agar gel in whey or preservation liguid

The procedure was as described for Example 1 but the agar solution was prepared dissolving the polymer in whey obtained as a by-product of the mozzarella production process, or in the preservation liquid used to preserve the product. The mozzarellas showed properties undistinguishable from those of the natural product.

Example 5 - Preserving water buffalo mozzarella in an agar gel in source water containing kitchen salt The procedure was as described for Example 1 but the agar solution was prepared dissolving the polymer in source water where different kitchen salt concentrations were dissolved (3 to 10% in weight), according to the type of salting (curd salting or preservation liquid salting) carried out before packing the product. Example 6 - Preserving water buffalo mozzarella in a high concentration (40%) gellan gel in source water

In a typical preparation, a gellan 40% solution in source water was prepared dissolving the polymer at 9O ⁰ C. Gellan (Sigma cat. G1910) is a food-compatible polysaccharide. After dissolution, a layer 3 cm in depth was deposited in a polyethyl-

ene tray such as those normally used to ship mozzarella, and left to cool to a T <40°C to allow gelling to take place. On this gel layer the mozzarellas to be preserved were placed, and a further amount of the agar solution was then poured over at about 40 ⁰ C, until the mozzarellas were completely covered. Cooling to room temperature or, if a quicker procedure is desired, to 4 ⁰ C, a complete inclusion of mozzarellas in the gel was obtained. The mechanical tests done on the mozzarellas preserved as describe above are reported in the Results section. Example 7 - Preserving water buffalo mozzarella in a agar and gellan gel in source water More compact gels, thus rigid and releasing lesser preservation liquid to the dairy product, were obtained mixing up agar and gellan, a polysaccharide that is misci- ble with agar.

In a typical preparation, samples of freshly made water buffalo mozzarella were packed as described in Example 1 , using a gel in source water containing 1.5% w/w of a polymer mix of 70% w/w agar (Sigma cat. A1296) and 30% gellan (Sigma cat. G 1910). Gellan by cooling made a gel that, being more densely reticulated with respect to agar, increased agar packing to form a more compact gel which showed a lesser ability to release water to the product surface. Using agar with gellan optimises gel resiliency and its ability to release water, according to the type of spun-curd product used. This is particularly relevant in the case of water buffalo mozzarella made in artisan dairies, which contains a very variable amount of water both in relation with the producer and in relation with seasonality. Example 8 - Preserving water buffalo mozzarella in an agar and polyvinyl alcohol gel in source water Less compact, thus more resilient gels were made by mixing agar and polyvinyl alcohol. The latter possesses the feature of being a highly biocompatible, nontoxic, agar-miscible polymer. Its polyalcohol chemical features (repeating unit CH ₂ CH(OH)) makes it water soluble but unable to gel by cooling. Thus, it remains only physically trapped inside the agar gel that is obtained by cooling, hindering its complete packing, thus allowing to obtain a more resilient gel.

In a typical preparation, water buffalo mozzarella samples were packed according to the procedure described in Example 1, using a gel made with source water containing in total 1.5% w/w of a polymer mix made up by 70% w/w agar (Sigma cat.

A1296) and 30% w/w polyvinyl alcohol (Sigma cat. P1763). The polyvinyl alcohol trapped inside the agar gel obtained by cooling hinders its compact packing, thus leading to a more resilient gel. The use of agar with polyvinyl alcohol represents a feasible strategy to optimise gel resiliency and the ability to be removed from product surface upon use.

Example 9 - Preserving water buffalo mozzarella in a cellulose derivatives gel in source water

Hydroxyethylcellulose gels were prepared at different concentrations (0-40% weight) both in source water and in water and salt (salt concentration in the range 3 to 10% in weight). Cellulose derivatives, particularly hydroxyethylcellulose, do not yield compact gels even at concentrations higher than 5%, thus they must be used mixed with other gelling polymers. They yield less fragile gels with agar, but only if used as the dispersing phase and not as the matrix, e.g., at 0.25% in weight. Example 10 - Preserving water buffalo mozzarella in a polvacrylamide gel in source water

Polyacrylamide (Sigma cat. P2433) gels at different concentrations were prepared (0-40% weight)and used for preserving water buffalo mozzarella for different time periods. Gels were physically characterized. Example 11 - Gel preparation with preserving agents (antioxidants, antimicrobial) Gels were prepared as described in Example 1-8, adding preserving agents and/or antioxidants (sorbates, citric acid, ascorbic acid, and so on) at percentages in the range 0 to 2% w/w with respect to the gelling agent used. Gels obtained showed the same chemical-physical and rheological properties than gels obtained in their absence (see Tables III, IV, V, Vl), since their use does not interfere with the gelling reaction. Moreover, the products used showed a higher bacteriostatic activity with respect to that already showed by gels kept at low temperature (4- 8 ⁰ C), as can be seen from the total microbial counts reported in Figure 4.

RESULTS

1) Visual evaluation of the preserved mozzarellas

At a visual evaluation of the mozzarellas preserved at room temperature, it was possible to notice a big difference between the mozzarella preserved in agar with

respect to the control mozzarella: the texture of the former was good and on cutting the typical oozing of milk from the curd was observed; initially the flavour was less intense as compared to that of freshly made mozzarella, but after a short while the preserved product regained its typical aroma; the control mozzarella was softer and its surface was slightly slimy. Going on keeping the mozzarellas at +4°C in a refrigerator, it can be noticed after 15 day that the differences between those preserved in polysaccharide gels and the controls get smaller, indeed both show a bad texture, are very soft and had an almost rancid smell (Figure 1 ). The second test was carried out placing the mozzarellas during the entire period of the test evaluation in a refrigerator at +4°C. After 5 days the difference between the mozzarellas kept in a polysaccharide gel and the reference mozzarellas was evident; the former were more compact, resilient, with the typical milk oozing, and also on this occasion the smell was not immediately intense, but the typical aroma with a musky hint of the water buffalo mozzarella was evident after a while. A second evaluation, carried out after 10 days, evidenced that the differences became more evident in favour of the mozzarella preserved in polysaccharides, in that it tended to preserve the aforementioned features; conversely, in the controls, the degradation processes were even more evident: the surface was slimy and the mozzarella lost its texture and layered structure; even after fifteen days the moz- zarellas kept in polysaccharide gels were well preserved.

In the third test after 5 days, at a visual examination of the preserved mozzarellas the control ones resulted to have a shiny and slightly slimy surface, with a rather soft consistency and broke up easily; the mozzarella preserved in polysaccharides (agar) had a better texture ed the internal curd was grainy. As seen with the other preserved mozzarellas, their surface was at first dry but after a short while the product regained its humidity; as compared to the former, the latter was much better preserved. After 15 day the results were even more surprising: the differences between reference, which resulted easily broken up, very soft and had a very slimy surface, and polysaccharide (agar) mozzarella, which, conversely, had a very good, elastic texture, with an internal grainy surface and a typical milk oozing upon pressure; the aroma was the typical fresh butter one; the mozzarella preserved in polysaccharides was further compared with a freshly made mozzarella purchased on the morning of the test day and coming from the same dairy, and no

difference was seen between the two products. This test was prolonged to up to 20 days and the differences seen between the two preservation methods were remarkable.

2) Evaluation of microbiological features over time a) Microbiological features of the product preserved according to Example 1 and 2.

Microbiological evaluations were carried out on product samples and gel or preservation liquid taken at day 5 according to Example 2, and at day 5, 10, and 20, according to Example 1 , using standard methods for the determination of total bacterial load, lactic bacteria, both thermophile and mesophile, load, streptococci, lactic cocci, yeast, total coliforms, faecal coliforms, faecal enterococci load in dairy products. As control, water buffalo mozzarella coming from the same production lot was used, bur preserved in whey. The products analysed according to Example 1 , were kept at 4°C starting from the time of packing. The experimental data obtained, showed in Figure 2, showed that the total microbial counts (CMT) of the water buffalo mozzarella preserved in preservation liquid (M) and those of the gel-preserved ones (MA) at 4°C for 5, 10, 15, and 20 days showed minimal variations for the whole preserving period. Conversely, lactic flora showed a small raise starting from day 5 in both preservation media. However, while mozzarella in preservation liquid maintained a population of about 10 ⁶ ufc/g for the whole preservation period considered, the one preserved in gel showed a slight decrease in its lactic flora counts, probably caused by a reduction in nutrients or by formation of an unfavourable environment. In both preserving media, no increase in total coliforms and faecal coliforms was noticed, while a considerable decrease in faecal enterococci was evidenced in the gel- preserved mozzarella.

In Figure 3 the behaviour of the microbial population isolated from mozzarella kept in preservation liquid (M) and from the gel-preserved one (MA) is shown. In this experiment mozzarellas were kept at room temperature (period of the year: May) for five days after packing to evaluate the influence of medium and temperature on the their natural microbial flora. The graph shows evidence that the different microbial components of the starting mozzarella (MTO), i.e., total microbial counts (CMT), lactic flora, total and faecal coliforms, and yeasts were in a 10 ² to 10 ⁶ ufc/g

range. After 5 days of preservation, all the components, but for the faecal coli- forms, of the mozzarella kept in preservation liquid underwent an increase (some of them up to three LOGs), while only some of the components (i.e., lactic bacteria and yeasts) underwent an increase that was anyway lower than the reference, when the mozzarella was preserved in a gel. The results obtained with these samples evidenced that room temperature preservation favours an increase in the microbial flora as compared to the starting point, that is higher than 3 LOG units, thus not meeting the parameters set by the law (D. L. 51/34). Moreover, the gels containing preservative agents showed a further bacteriostatic ability with respect to the one showed by the gels kept at low temperature (4-8°C), as it can be seen from the total microbial counts reported in Figure 4. b) Microbiological features of the preserving media

In Figure 5 the microbial behaviour in two preserving media used during the experimentation, i.e., whey and polysaccharides/whey, is shown. It can be noticed that in the polysaccharides/whey preserving medium there was a gradual, if slow, decrease in the faecal enterococci. Moreover, most of the microbial organisms seen in the novel material tended to undergo a slowing in their growth as compared to the ones found in the whey only.

3) pH measurements in the mozzarella samples and in the preserving system as described in Example 1 and 3.

In Table I pH values over time relating to mozzarellas and their preserving system are reported as function of the preserving times. Table I

Table I - pH of mozzarella samples and preserving system in time, as described in Example 1 and 2. M: mozzarella in whey (Control); MA: mozzarella in agar gel in source water (Example 1 ); MAL: mozzarella in agar gel in whey (Example 3); L: whey; A: agar gel in source water; AL: agar gel in whey; t; time in days.

Variations in the pH of the mozzarella samples are lower than 0,5 units both when they are preserved in whey or agar gel. It is slightly higher in the preserving system (A), and in this case it goes towards an increase in acidity, indicating that the process of going rancid is starting after 20 days of preservation.

4) Physical parameters measurements in water buffalo mozzarellas preserved as described in Example 1 , 3, and 6

Physical properties are extremely important to evaluate the shelf-life of mozzarella. Actually, resiliency, fracture properties, and texture of mozzarella perceived during the act of chewing and the energy associated with this act will generate a series of sensory stimuli that determine the evaluation of its pleasantness. Therefore, mozzarella samples preserved as reported in Example 1 , 3, and 6 were subjected to texture tests by monoaxial pressure. One single mozzarella, about 5 cm in diameter, was placed in a plastic container of 6 cm in diameter positioned on the fixed plate of an lnstron dynamometer (P. Masi and F. Addeo (1984)). A rod was fastened to the top clamp of the dynamometer and at the opposite end a steel ball with a diameter of 1 cm was welded. The ball was brought in contact with the mozzarella and the compression modulus was recorded making the ball penetrate by 50% into the mozzarella diameter, at a 10 mm/min speed. In Figure 5 the experimental data of Example 1 are reported. In Figure 7 and 8 the experimental data of Example 3 and 6 are reported.

After 5 days (i.e., a period of time during which mozzarella is still considered to be fresh), the mozzarella preserved in whey had already been subjected to a remarkable decrease in its compression strength as compared to freshly made mozza- rella. The mozzarella preserved in agar gel showed a compression strength very much similar to the freshly made product (Figure 6A). A surprising result is seen after 30 days from the start of the preservation period. At this experimental time the mozzarella in whey showed very low values of compression strength, while the mozzarella in agar maintained its mechanical properties intact (Figure 6B).

Also the samples of water buffalo mozzarella, preserved as reported in Example 3, were subjected to texture tests by monoaxial compression. After 5 days (i.e., a period of time during which mozzarella is still considered to be fresh), the mozzarella preserved in whey had already been subjected to a remarkable decrease in its compression strength as compared to freshly made mozzarella. The mozzarella preserved in agar gel showed a compression strength very much similar to the freshly made product (Figure 7A). After 30 days from the start of preservation, the mozzarella in whey showed very low values of compression strength, and the mozzarella in 0,1 % agar gel showed mechanical characteristics much more similar to the ones of mozzarella kept in preservation liquid than to freshly made mozzarella (Figure 7B). The accelerated deterioration of the texture features of mozzarella when preserved in a non-compact gel could be explained as follows: water cannot be retained by a gel with a low reticulating density, and is thus too much available, showing the same deterioration phenomena that are shown in the ab- sence of a gel.

Also the samples of water buffalo mozzarella, preserved as reported in Example 6, were subjected to texture tests by monoaxial compression. As it can be seen in Figure 8A, after 5 days (i.e., a period of time during which mozzarella is still considered to be fresh), the mozzarella preserved in whey had already been sub- jected to a remarkable decrease in its compression strength, while the mozzarella preserved in compact 40% gellan gel showed a compression strength very much similar to that of freshly made product. After 30 days from the start of preservation, the mozzarella in whey showed very low values of compression strength, while the mozzarella in 40% gellan showed to still have a good texture and to have mechanical characteristics similar to freshly made mozzarella (Figure 8B). In spite of this under many respects positive response, this composition was not deemed as optimal, due to problems relating to reproducibility of gel preparation, which gel forms too rapidly also at low temperature, often not leaving time enough to place the mozzarella in the preserving liquid. Moreover, it must be considered that such a high concentration of gelling polysaccharide would very much raise packing costs.

5) Weight variation measurements in mozzarellas preserved as described in Example 1

With the purpose of verifying the effects of the gel packing system on the tendency of water buffalo mozzarella to soak up water over a prolonged preservation time, mozzarellas preserved according to Example 1 , i.e., in agar gel, were weighed after 5 and 10 days from packing. For comparison, mozzarellas kept in whey were weighed. Results are reported in Table II: Table Il

Table Il - Weight variation measurements in water buffalo mozzarellas preserved in whey or gel after 5 and 10 days according to Example 1

The weight increase of mozzarella in preservation liquid brings to a collapse in texture over the preserving period, as showed in the mechanical tests reported in the graphs of Figure 7 and 8.

6) Panel test of sensory properties of water buffalo mozzarella preserved as described in the reported examples Sensory properties (colour, smell, texture, resiliency, presence of milk) of water buffalo mozzarella preserved as described in Example 1 , were determined by a panel test carried out before a producer of water buffalo mozzarella and his collaborator. The fresh dairy products, average weight 125 g, made on the same day, were packed at 40 ⁰ C in gels differing in their composition as described in Exam- pies 1-4, and kept in a refrigerator at a temperature between 4 and 8°C, taking samples at day 10, 15 and 20. For comparison, dairy products from the same preparation lot were kept in preservation liquid. Soon after opening, the sensory

evaluations of the trained panellists and of the producer and his collaborator were recorded, who verified the persistency of the typical features of freshness in the dairy products preserved in gel, and the progressive loss of the same features in the dairy products preserved in preservation liquid.

7) Compression strength

Compression strength was evaluated for the gels of Example 7 (agar + gellan) as reported in Table III.

Table III

Table III - Elastic modulus of agar gels in source water made with different agar/gellan ratios. The gel was prepared dissolving at 9O ⁰ C the mixture of the two polymers and cooling at 4°C for 24 hours before measuring the compression strength.

In Table IV the elastic modulus of agar gels made with different percentages of polyvinyl alcohol (Example 8) are reported. Table IV

Sample Agar Polyvinyl alcohol Compression

(% w/w agar in (% w/w in gei) (% w/w in gel) Strength the polymer (kg/cm ² )

Table IV - Elastic modulus of agar gels in source water made with different agar/polyvinyl alcohol ratios. The gel was prepared dissolving at 9O ⁰ C the mixture of the two polymers and cooling at 4 ⁰ C for 24 hours before measuring the compression strength.

Compression strength was also evaluated in the gels of Example 9 (agar + hy- droxyethylcellulose) as reported in Table V. Table V

Table V - Elastic modulus of agar gel in source water and 5% salt alone (Sample 1 ) or in the presence of a significant percentage of hydroxyethylcellulose (27%, Sample 2). The gel was prepared dissolving at 90 ⁰ C the mixture of the two polymers and cooling at 4 ⁰ C for 24 hours before measuring the compression strength. The same values were seen adding either bacteriostatic or antimicrobial agents as described in Example 11.

Compression strength for the gels of Example 10 (polyacrylamide gel) as reported in Table Vl.

Table Vl

Table Vl - Elastic modulus of polyacrylamide gels in source water made with different percentages of polyacrylamide. The gel was prepared dissolving at 9O ⁰ C the polymer and cooling at 4°C for 24 hours before measuring the compression strength. The same values were seen adding either bacteriostatic or antimicrobial agents as described in Example 11.

Based on the results herein described, it can be argued that the preferred formulation is the one described in Example 3 in Table III. As a matter of fact, with this formulation gels that guarantee uniformity among lots, optimum values of compression strength, uniform detachement of mozzarella upon product consumption and a satisfactory organoleptic response are obtained.

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