Ready-to-eat shelf-stable food compositions based on aerogel and xerogel technology

Abstract

Solid, storage-stable, crispy food compositions comprising a plurality of aerogels or xerogels are provided. The aerogels / xerogels comprise a crosslinked hydrogel-forming biopolymer and a functional ingredient entrapped into the aerogels / xerogels, said functional ingredient comprising the solid and solute components of a liquid carrier. The liquid carrier is selected from the group consisting of fruit juices, vegetable juices, edible liquid by-products of the food industry, plant- or animal-based drinks, soft drinks and any combination thereof. These compositions are useful as healthy snacks, food, food ingredients, food additives or dietary supplements. Said compositions promote the feeling of satiety which, combined with their appealing sensory characteristics, particularly taste and texture, make them healthy alternatives to high-calorie snacks. Methods for preparing the aerogels / xerogels of the invention are also provided, which ensure that the food compositions are storage-stable without added preservatives and that the functional ingredient entrapped into the aerogels / xerogels retains its dietary value.

Description

[0001] READY-TO-EAT SHELF-STABLE FOOD COMPOSITIONS BASED ON AEROGEL AND

[0002] XEROGEL TECHNOLOGY

[0003] Description

[0004] TECHNICAL FIELD

[0005] The present invention relates to food compositions comprising aerogels and xerogels and their uses as healthy snacks, food ingredients, food additives and dietary supplements among others. It also relates to methods for production of said compositions.

[0006] BACKGROUND OF THE INVENTION

[0007] Overweight and obesity are defined as abnormal or excessive fat accumulation that presents a risk to health. Overweight and obesity are major risk factors for a number of chronic diseases, including cardiovascular diseases such as heart disease and stroke, which are the leading causes of death worldwide.

[0008] Both overweight and obesity are largely preventable and manageable, as long as healthier lifestyle changes are adopted, namely limiting consumption of energy-dense foods and promoting other healthy eating behaviour, limiting energy intake from total fats and sugars and increasing consumption of fruit and vegetables, in conjunction with regular physical activity.

[0009] The food industry can play a significant role in promoting healthy diets by reducing the fat, sugar and salt content of processed foods, ensuring that healthy and nutritious choices are available and affordable to all consumers, restricting marketing of foods high in sugars, salt and fats, especially those foods aimed at children and teenagers, and ensuring the availability of healthy food choices (World Health Organization, March 1st, 2024).

[0010] According to the World Health Organization, a major factor determining the obesogenic environment exacerbating the likelihood of obesity in individuals and populations is related to structural factors limiting the availability of healthy sustainable food at locally affordable prices (https : / / www .who .int / news-room / fact-sheets / detail / obesitv-and-overweight) .

[0011] Therefore, a need remains for healthy, appetizing and safe food compositions that would help maintain a healthy diet and assist in weigh management while at the same time preferably also being sustainable and cost-effective.

[0012] SUMMARY OF THE INVENTION The invention described herein provides solid food compositions comprising aerogels or xerogels according to claim 1 and their use as foods, healthy snacks, food ingredients, food additives and dietary supplements among others.

[0013] The products disclosed herein are suitable for use as healthy dietary products, toppings for salads, yoghurt and other foods, or as nutritious ready-to-eat snacks and food supplements to name a few of their uses.

[0014] Another advantage is that the proposed compositions are useful for promoting the feeling of fullness and satiety, thus enabling the individuals consuming these compositions to better control their caloric intake.

[0015] An additional and related advantage is that the claimed compositions can make use of edible liquid by-products of the food industry, very ripe fruits or vegetables and / or fruits or vegetables with a bad appearance that are unattractive for consumption, thus can make effective use of food that would have otherwise been lost from the food chain or wasted. This results in a product that is cost- effective to produce and makes best use of the available resources.

[0016] Taking into account the aforementioned factors, the compositions disclosed herein are designed as alternative food products, combining healthy eating, quick and easy consumption, and reduced food waste using an eco-friendly technology for the production of aerogels and xerogels.

[0017] The present invention also provides methods for the production of said aerogels and xerogels, as claimed herein.

[0018] Other aspects and benefits of the present invention will become apparent from the detailed description to follow.

[0019] BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will now be described with reference to certain embodiments thereof which are illustrated in the accompanying drawings. It should be noted that the accompanying drawings illustrate preferred embodiments of the invention, therefore should not be considered as limiting the scope of the invention.

[0021] Fig. 1 is a schematic presentation of the synthesis of Ca-alginate aerogel food compositions in the form of beads via freeze-drying.

[0022] Fig. 2 shows optical photos of Ca-alginate hydrogels (top rows) and aerogels (bottom rows) of samples A (control), B (prepared with strawberry juice), C (prepared with mixed berry juice), D (prepared with extract from espresso coffee residues) and E (prepared with oat drink), as indicated.

[0023] Fig. 3 shows ATR-FTIR spectra of aerogel samples A (control), B (prepared with strawberry juice), C (prepared with mixed berry juice), D (prepared with extract from espresso coffee residues) and E (prepared with oat drink), as indicated.

[0024] Fig. 4 shows the behavior of (A) aerogel sample A (control) and (B) aerogel samples C (prepared with mixed berry juice) and E (prepared with oat drink), after being immersed in water for 1 hour. The corresponding dry aerogel samples are also shown for comparison.

[0025] DETAILED DESCRIPTION OF THE INVENTION

[0026] The present disclosure provides food compositions comprising aerogels or xerogels for a variety of uses and applications, such as healthy snacks, food ingredients, food additives and dietary supplements among others.

[0027] The term “aerogel” as used throughout the description and claims refers to a class of materials comprising an open non-fluid colloidal network or polymer network that is expanded throughout its whole volume by a gas and is formed by the removal of all swelling agents (i.e., pore-filling solvents) from a hydrogel without substantial volume reduction or network compaction.

[0028] The term “hydrogel” as used throughout the description and claims refers to gels in which the swelling agent contains water.

[0029] The term “xerogel” as used throughout the description and claims refers to open networks formed by the removal of all swelling agents from a hydrogel with unconstrained shrinkage.

[0030] Prior art biopolymer aerogels, i.e, aerogels derived from natural polymers, have been used for biomedical applications like tissue engineering scaffolds, drug delivery carriers, and wound dressings, due to their biodegradability and biocompatibility. Moreover, their eco-friendly nature and sustainability has promoted their use in food packaging, cosmetics, and agriculture.

[0031] The inventors have found that aerogels and xerogels can be made into compositions suitable as food products. The solid food compositions of the present invention comprise a plurality of aerogels or xerogels. Each aerogel or xerogel comprises a crosslinked hydrogel-forming biopolymer and a functional ingredient entrapped into the aerogel or xerogel, said functional ingredient comprising the solute components of a liquid carrier as well as its solid components (if present in the liquid carrier) . Put in different words, each aerogel or xerogel comprises a crosslinked hydrogel-forming biopolymer and a functional ingredient entrapped into the aerogel or xerogel, said functional ingredient comprising the components of a liquid carrier after the removal of water during the process of drying the hydrogels. The liquid carrier according to the invention is selected from the group consisting of fruit juices and vegetable juices (e.g., juices from berries, kiwi, melons, watermelons, tomatoes), edible liquid by-products of the food industry (e.g., beetroot or broccoli water, extract from espresso coffee residues), plant- or animal-based drinks, such as oat, almond, soy drinks or milk, soft drinks, liquid extracts or solutions of natural aromatic spices (such as cinnamon, clove, ginger among others) or of natural aromatic resins (such as mastic), and any combination of the above. As an example, the solid components of fruit juice include the pulp, if present, whereas the solute components include any of the antioxidants, vitamins, flavonoids, water soluble fibers, minerals, etc., that are naturally found dissolved in the fruit juice. “Fruit juice” is understood to encompass both fruit juice with pulp and fruit juice without pulp. “Vegetable juice” is understood to encompass both vegetable juice with pulp and vegetable juice without pulp. The term "liquid aqueous extracts" refers to liquids containing extracts obtained by extracting the soluble components of a substance using water as a solvent. Aqueous extracts are commonly made by soaking or boiling a solid substance in water, then filtering out the solid material to obtain the liquid extract.

[0032] The hydrogels of the invention can also be made in forms denser than aerogels, such as in the form of xerogels, so that they provide an enhanced feeling of getting full without the calories.

[0033] Importantly, the aerogels and xerogels of the invention have a crispy texture. Crispiness is a property that is directly related to the mechanical properties of the structure, particularly its rigidity, stiffness and brittleness. In turn, those properties are related to the morphology and texture of the micro / nanostructure. Crispiness is not related to porosity. For example, a sponge is very porous, but it is resilient, not crispy. Crispiness is a glass-like property. Indeed, the aerogels and xerogels of the present invention are characterized by a strong network formed by the crosslinked hydrogel-forming biopolymer and the functional ingredient entrapped into the aerogel or xerogel. The increased crispiness observed in the compositions of the present invention, apparently arises from the presence of the functional ingredient, which reinforces the structural network, making it more rigid and mechanically stronger. This increased stiffness leads to a sharper fracture behavior when bitten or broken, which is perceived as crispiness. The inventors have found that this network has been rigidized in the presence of the functional ingredient and the resulting aerogels and xerogels are much stronger and crispier compared to control aerogels prepared with water as the liquid carrier, as shown in Example 3. The rigidification of the network and the crispiness of the aerogel and xerogel products is apparently linked to the incorporation of the solute component and of the solid component (if present) of the liquid carrier on the biopolymer network. An advantage of achieving food compositions with enhanced crispiness, apart from enhancing their appetizing characteristic, is that they are particularly resilient to moisture and do not become soggy when used as food toppings or food additives.

[0034] As shown in Figure 2, said compositions have additional characteristics that differentiate them from aerogels prepared using water instead of the liquid carrier of the invention and used as control samples. Specifically, the optical photos (Figure 2) show that the claimed food compositions have a different appearance from the control sample, primarily due to differences in colour. These colour variations are attributable to the presence of the functional ingredient, which alters the visual characteristics of the final product.

[0035] Furthermore, said compositions are rich in dietary fiber and / or proteins. As an example, the alginates and cellulose that may be included in the compositions are classified as dietary fiber that is not digestible by humans. In addition, they have been shown to inhibit digestive enzymes and thus they can be used as adjuncts in the treatment of obesity. Moreover, the functional ingredient is retained entrapped in the skeleton of the aerogels or xerogels of the present invention, enriching the compositions with dietary components naturally present in the liquid carrier, including, but not limited to, antioxidants, vitamins, flavonoids, water soluble fibers and minerals. Therefore, the food compositions of the invention are particularly useful as diet foods that also retain the nutrients of the liquid carrier. Additionally, the functional ingredient provides the food compositions with enhanced flavor coming from the components of the liquid carrier after the removal of water. Therefore, the aerogels / xerogels can be converted into food that is tasty and appealing to the consumer, thus acquiring properties that are important for dietary products.

[0036] The hydrogel-forming biopolymer is selected from polysaccharide (s) and protein(s) such as gelatin, alginate, pectin, starch, starch sodium octenyl succinate, carrageenan, cellulose, locust bean gum, xanthan gum, guar gum, agar, chitosan, casein, whey protein isolate, soy protein isolate, pea protein isolate, potato protein isolate, zein, derivatives thereof, copolymers thereof, or mixtures thereof. Preferably, said biopolymer is selected from the group consisting of gelatin, alginate, pectin, starch, carrageenan, cellulose, gums, agar, chitosan, derivatives thereof, copolymers thereof, or mixtures thereof. Most preferably, said biopolymer is selected from the group consisting of gelatin, alginate, pectin, cellulose, starch, chitosan, gums, derivatives thereof, and mixtures thereof. In the most preferred embodiment, said biopolymer is alginate.

[0037] The food compositions of the invention are free (or essentially free) from organic solvents. As will be explained below, the absence of organic solvents is ascertained by the manufacturing process selected for preparing the compositions. This quality makes the disclosed compositions suitable for consumption as safe and healthy diet alternatives. The disclosed food compositions have different characteristics from other competitive products in the “fillings and toppings” sector that include dried fruits, freeze-dried fruits and hydrogels made of fruits. Hydrogels made of fruits are not solid products, they have a short shelf-life, and they have to be kept in the refrigerator. Dried fruits are produced via dehydration of fruit at low temperature, a methodology different from the one applied for the disclosed food compositions. Lyophilized fruits are produced via freeze-drying (lyophilization). As will be explained in Example 1 below, the food compositions of the invention are produced via lyophilization not of the whole fruit, but of the hydrogel formed from a biopolymer and a liquid carrier such as fruit juice. This preserves the aroma, taste as well as the characteristics of fresh fruits, while at the same time the product is porous, lightweight, with porous or foamy texture, which is different from that of lyophilized fruits, and can be prepared in any shape and size. Most importantly, the step of lyophilization yields products that retain the nutrients of the fresh fruit.

[0038] The disclosed aerogel and xerogel compositions have a high porosity, thus are characterized by low caloric density, which enhances the feeling of satiety. As shown in Example 1, the aerogels disclosed herein have porosities in the range of 70-91 v / v and bulk densities within the range of 0.09-0.3 g / cm3. Bulk densities are higher and porosities are lower compared to the control sample.

[0039] The aerogels of the invention preferably have water activity <0.4. Water activity of the control sample is also below 0.4, which characterizes them as dried and shelf-stable products. The inventors have found that compositions according to the present invention having a water activity below 0.4 are advantageous as it ensures microbial safety, thereby preventing spoilage and pathogenic contamination. Additionally, such low water activity slows down undesirable chemical reactions preserving the flavor, color, texture, and nutritional quality of the food while maintaining its characteristic crispness. This extreme dryness also prevents moisture absorption from the environment, thus supporting long shelf life and product stability, a key factor in quality assurance for shelf-stable food products.

[0040] The inventors have found that the disclosed food compositions advantageously exhibit a long shelf life without requiring refrigeration. This allows them to be stored or transported for a long period of time without a decrease in their physical and chemical integrity. Indeed, Example 2 shows that the disclosed compositions have a shelf life at room temperature of at least a year.

[0041] For a dietary product it is important that the sensory aspects, and particularly the taste and texture, are appealing to the consumer. Sensory tests regarding color, taste, aroma and texture detailed in Example 4 show that, compared to control Ca-alginate aerogels, the new food products revealed sweet, fruity and aromatic notes combined with a satisfying crunchy and light, airy texture. Due to the unique synthetic methodology and composition, the new food products give consumers a unique taste and texture option that is not available in other competing products.

[0042] In a preferred embodiment, the liquid carrier used for the preparation of the disclosed food compositions is selected from the group consisting of juices from fruits or vegetables (e.g., berries, kiwi, melons, watermelons, tomatoes), edible liquid by-products of the food industry (e.g., beetroot or broccoli water, extract from espresso coffee residues), plant- or animal-based drinks, such as oat, almond, soy drinks or milk, liquid aqueous extracts or solutions of natural aromatic spices or resins, and any combination of the above. The food compositions that comprise the above-mentioned liquid carrier have the additional advantage that they comprise no preservatives or artificial sweeteners. Many preservatives and preservation methods have undesirable side effects, such as toxicity, allergenicity, and / or carcinogenicity, and are often not accepted by the consumers, especially for products in the healthy food sector. The absence of preservatives does not compromise the long shelf life of the disclosed compositions, including their good microbiological quality as well as their longlife taste and texture. In addition, these compositions do not comprise artificial sweeteners. These qualities, i.e., the absence of preservatives and artificial sweeteners, make the compositions suitable as safe and healthy food choices.

[0043] In a more preferred embodiment, the liquid carrier of the food compositions is selected from the group consisting of juices from fruits and vegetables (e.g., berries, kiwi, melons, watermelons, tomatoes), edible liquid by-products of the food industry (e.g., beetroot or broccoli water, extract from espresso coffee residues), plant-based drinks, such as oat, almond or soy drinks, and any combination of the above. The food compositions that comprise the above-mentioned liquid carrier also have the additional advantage that they can be prepared from sustainable and natural resources. As an example, when the liquid carrier is fruit juice, very ripe fruits and / or fruits (e.g., strawberry, raspberry, kiwi, tomato) with a bad appearance that are unattractive for consumption and therefore rejected (while being safe for consumption) can also be used, thereby helping to reduce food waste. The same principle can be applied when the liquid carrier is vegetable juice where use can also be made of ripe and / or rejected vegetables (e.g., carrot, cucumber, beetroot), or a plant-based drink, or an edible liquid by-product of the food industry (e.g., beetroot water, extract from coffee residues), thus helping reduce food loss.

[0044] In certain embodiments, the food compositions comprise additional ingredients. In preferred embodiments, said ingredients are dietary fibers, proteins, peptides, amino acids minerals / trace minerals, vitamins, polyphenols, antioxidants, to name a few, or any combination of the above. Suitable fibers are water-soluble dietary fibers such as alpha cellulose and hemicellulose, glucomannan and glucan, pectin, carrageenan, locust bean gum, guar gum, gum arabic, fructooligosaccharides such as inulin, and mucilages, any derivative thereof and any combination thereof. The protein may be dairy-based protein, plant-based protein, animal-based protein, artificial protein, and combinations thereof. Preferably, the protein is plant-based or artificial, making the disclosed compositions suitable for vegetarian or vegan diets.

[0045] Minerals such as calcium, zinc, phosphorus, iron, copper, manganese, magnesium, cobalt, iodine, selenium among others, essential for humans, can be incorporated in the products and in well- defined amounts, making the disclosed compositions suitable for use as food supplements.

[0046] In other preferred embodiments, the additional ingredients comprise excipients suitable for use in food. Suitable excipients are fillers or texturing agents such as inulin or celluloses such as microcrystalline cellulose, natural sweeteners such as fructose, honey, high fructose com syrup, molasses, maple syrup, stevia, and the like.

[0047] In other preferred embodiments, the compositions disclosed herein do not contain additives such as food colourings, processed sugars or artificial sweeteners, making them a healthy alternative to popular high-calorie snacks.

[0048] The compositions disclosed herein can be formulated in any suitable form, for instance powders, granules, spheres, pellets or monoliths, i.e., having the shape of rice crispies. They can be consumed as an additional topping in any food, as a snack, food supplement, and are suitable for consumers of all ages.

[0049] The present disclosure also provides a method for the preparation of said aerogels and xerogels. The prior art methods of preparation of biopolymer aerogels usually include the following steps: (a) dissolving a suitable biopolymer in water, (b) inducing crosslinking (gelation) by metal ions (via coordination) or acids (via hydrogen bonding) or any other crosslinking agent (monomeric or polymeric) which leads to formation of hydrogels, (c) aging of the hydrogels, and (d) drying the hydrogels to obtain the corresponding aerogels. A number of different methodologies have been used in the prior art for drying the hydrogels. The main methodologies used include supercritical drying, oven drying, air drying, ambient-pressure drying, spray drying (e.g., Ikizler BK et al, ACS Omega 2023, 8(12): 11479-11491) and air frying.

[0050] In the present invention, the edible aerogels / xerogels are fabricated via sol-gel synthesis and aerogel / xerogel technology. Specifically, (a) water has been replaced with a liquid carrier selected from the group consisting of fruit juices, vegetable juices, edible liquid by-products of the food industry, plant- or animal-based drinks, soft drinks and any combination thereof), (b) non-toxic, safe and essential for humans metal ions (e.g., Ca2+, Zn2+, Fe2+, Mg2+) are used whenever needed, and (c) acids, whenever needed, have been replaced by natural acids that can be found in fruits and vegetables (e.g., citric acid, ascorbic acid or mixtures thereof). To dry the hydrogels, freeze-drying was applied, as no organic solvents are needed in this process. The organic solvents used in supercritical drying can leave residues in the final food products. In addition, with freeze-drying or oven / air drying the aroma, flavor, taste and color of the food compositions can be retained, in contrast to supercritical drying, for which organic solvents are used (e.g., ethanol) to exchange / replace the pore-filling water / liquid of the hydrogels. The organic solvents would dissolve / remove some of the components of the liquid carrier, which would affect / reduce the aroma, flavor, taste and color of the food products.

[0051] In addition, the inventors have found that, if the hydrogel-forming biopolymer is dissolved in water and the resulting hydrogels are soaked in the liquid carrier afterwards, the amount of the liquid carrier retained in the hydrogel would be less than the maximum. Therefore, according to a separate embodiment, a method is provided for producing the aerogels or xerogels according to the present invention, said method comprising the following steps in the order mentioned: (i) a hydrogelforming biopolymer is dissolved in a liquid carrier to yield a solution; (ii) the resulting solution is subjected to conditions that allow the hydrogel-forming biopolymer to form hydrogels, whereby the liquid carrier is entrapped in the hydrogels; (iii) the resulting hydrogels are left to age for at least 3 hours depending on the shape and size of the hydrogel, in order to obtain the maximum degree of crosslinking and the strongest possible hydrogel; (iv) the aged hydrogels are washed; and (v) the washed hydrogels are freeze-dried to form aerogels, or they are oven- or air-dried to form xerogels.

[0052] The liquid carrier is selected from the group consisting of fruit juices, vegetable juices, edible liquid by-products of the food industry, plant- or animal-based drinks, soft drinks, liquid aqueous extracts or solutions of natural aromatic spices or of natural aromatic resins, and any combination thereof. Preferably, the liquid carrier is selected from the group consisting of fruit juices, vegetable juices, edible liquid by-products of the food industry, plant- or animal-based drinks, liquid aqueous extracts or solutions of natural aromatic spices or of natural aromatic resins, and any combination thereof. Most preferably, the liquid carrier is selected from the group consisting of fruit juices, vegetable juices, edible liquid by-products of the food industry, plant-based drinks, and any combination thereof.

[0053] In preferred embodiments, step (ii) comprises adding in a dropwise fashion the solution resulting from step (i) to a solution of a crosslinking agent (monomeric or polymeric). The crosslinking agent includes, but is not limited to, multivalent cations such as Ca2+, Zn2+and Fe2+, or natural acids such as citric acid, ascorbic acid, malic acid, tartaric acid, formic acid, oxalic acid, quinic acid, or mixtures thereof.

[0054] Most preferably, the crosslinking agent is dissolved in the liquid carrier. The inventors have found that, in order to optimize the production process, both the solution of the hydrogel-forming biopolymer prepared in step (i) and the solution of the crosslinking agent prepared in step (ii) have to be prepared in the liquid carrier. This ensures that the maximum amount of the liquid carrier will be retained in the hydrogel, yielding the maximum aroma, flavor, color, taste and nutrients in the final product. In addition, it allows for aging of the hydrogels for long-enough time to provide hydrogels with the maximum possible degree of crosslinking. If only one of the solutions is prepared in the liquid carrier and the other in water, then the liquid carrier would diffuse out of the hydrogel. Also, as mentioned above, if the hydrogel-forming biopolymer is dissolved in water and the resulting hydrogels are soaked in the liquid carrier afterwards, the amount of the liquid carrier retained in the hydrogel would be less than the maximum.

[0055] The aging time must be at least as long as the time required for the crosslinking agent to diffuse from outside the hydrogel into the bulk (inside) the hydrogel. The aging time was experimentally found to be at least three hours.

[0056] Typically in the prior art drying methods, the hydrogels are exhaustively washed prior to drying, until the solution filling their pores is fully replaced by a pure solvent (in this case, pure water). However, the inventors have found that prolonged washing with water leads to the removal of the functional ingredient from the hydrogels, thus leading to considerable loss of the aroma and taste, as well as of the rigidity of the network and of the crispiness of the aerogel or xerogel. Therefore, in a preferred embodiment, the washing in step (iv) consists of one or more washes of a total duration that does not exceed thirty seconds, preferably twenty seconds, more preferably 10 seconds.

[0057] The hydrogel-forming biopolymer is selected from polysaccharide (s) and protein(s) such as gelatin, alginate, pectin, starch, starch sodium octenyl succinate, carrageenan, cellulose, locust bean gum, xanthan gum, guar gum, agar, chitosan, casein, whey protein isolate, soy protein isolate, pea protein isolate, potato protein isolate, zein, derivatives thereof, copolymers thereof, or mixtures thereof. Preferably, said biopolymer is selected from the group consisting of gelatin, alginate, pectin, starch, carrageenan, cellulose, gums, agar, chitosan, derivatives thereof, copolymers thereof, or mixtures thereof. Most preferably, said biopolymer is selected from the group consisting of gelatin, alginate, pectin, cellulose, starch, chitosan, gums, derivatives thereof, and mixtures thereof.

[0058] The concentration of the hydrogel-forming biopolymer in the liquid carrier in step (i) is preferably within the range from 0.1 to 15% w / w. Most preferably, said concentration is within the range from 0.5 to 5% w / w. The latter concentration range is particularly suitable when the hydrogel-forming biopolymer is an alginate.

[0059] In the embodiments where multivalent cations such as Ca2+, Zn2+or Mg2+are used as crosslinking agents, these are used in the form of a food grade salt, such as calcium chloride, calcium carbonate, calcium citrate, calcium lactate, zinc citrate, zinc lactate, magnesium chloride, magnesium carbonate, magnesium sulfate, magnesium citrate or magnesium lactate, to name a few.

[0060] In the embodiments where the food compositions of the invention comprise additional ingredients, such as dietary fibers, proteins, peptides, amino acids, minerals / trace minerals, vitamins, polyphenols, antioxidants, fillers and others, as detailed above, these ingredients are added in the solution of the hydrogel-forming biopolymer prepared in step (i) and, if applicable, also in the solution of the crosslinking agent prepared in step (ii), by dissolving them into the liquid carrier.

[0061] In a preferred embodiment, a method of production of the aerogels of the invention is provided. The aerogel technology was implemented in order to “solidify” fruit or vegetable juice, edible liquid byproducts of the food industry, plant- or animal-based drinks, soft drinks, liquid aqueous extracts or solutions of natural aromatic spices or of natural aromatic resins, or any combination of the above, in a way that the nutrients such as vitamins, as well as the original aroma, flavor, taste and color are preserved. To accomplish that, the drying process chosen for the food compositions was freeze- drying. Before freeze-drying, the edible liquid carrier (such as fruit or vegetable juice or coffee or plant- or animal-based drink, soft drink, liquid extract or solution of natural aromatic spices or resins, or any combination of the above) fills the pores of the hydrogels. After freeze-drying, the functional ingredient remains on the skeleton formed by the biopolymer. As disclosed in Example 1, these aerogels have a water activity <0.4 making them shelf-stable products, requiring no refrigeration. Indeed, the results shown in Example 2 indicate that the disclosed compositions have a shelflife at room temperature of at least a year.

[0062] Most importantly, the present method results in compositions that retain their nutrients, as well as the original aroma, flavor, taste and color, as shown in the Examples and particularly in Example 5. This important attribute is a result of the freeze-drying process used for the drying of the hydrogels to yield aerogels.

[0063] The synthetic procedure for production of representative aerogels of the invention in the form of beads via freeze-drying is schematically presented in Figure 1.

[0064] Xerogels according to the invention are prepared via the same procedure used for preparing aerogels, the only difference being that the hydrogels are dried using air-drying or oven-drying instead of freeze-drying, until the water activity reaches a constant value lower than 0.4.

[0065] An advantage of the methods described herein is that the synthetic procedures are eco-friendly, as no toxic chemicals or organic solvents are used. In addition, the freeze-drying process used for preparing aerogels and the oven- or air-drying process used for preparing xerogels ensures the long shelf-life and microbiological safety of the product without the need to add chemical preservatives. A related advantage of the disclosed methods is that the drying step applied ensures that the functional ingredient entrapped into the aerogels or xerogels retain their dietary value. Even more, the drying step imparts desirable texture characteristics to the compositions, namely crispiness, thus enhancing their appetizing characteristics.

[0066] EXAMPLES

[0067] Hereinafter, the present invention is described in more detail with reference to examples and comparative examples. It will be apparent to one of ordinary skill in the art that these examples are for illustrative purposes only and should not be construed as limiting or altering the scope of the present invention.

[0068] Example 1

[0069] Preparation of representative examples of calcium alginate hydrogels and aerogels.

[0070] An aqueous solution of sodium alginate (1.5% w / w) was prepared by dissolving sodium alginate (1.50 g) in 98.5 g of liquid carrier (Table 1). The solution was added dropwise, using a 25-mL burette, to a 0.2 M solution of CaCl2dissolved in liquid carrier A to E (three times the volume of the sodium alginate solution) under mild magnetic stirring. Spherical Ca-alginate hydrogel beads were formed instantly and were left to age for 18 h. Afterwards, they were washed with H2O (four times, each for a few seconds), they were either frozen in liquid N2(-196 °C) for 30 min or in the freezer (-18 °C) for 18-24 h and they were freeze-dried to produce the corresponding (referred to as Ca- alginate) aerogel beads A to E. Figure 2 presents selected optical photos of Ca-alginate hydrogels and aerogels. Experimental data are presented in Table 1.

[0071] Table 1. Compositions tested and corresponding bulk density, porosity and water activity.

[0072] ATR-FTIR spectra (Figure 3) show the characteristic peaks of Ca-alginate aerogel sample A (control), B (prepared with strawberry juice), C (prepared with mixed berry juice), D (prepared with extract from espresso coffee residues) and E (prepared with oat drink), as indicated. The spectra of samples B to E display a number of differences that include the appearance of new peaks (denoted with asterisks in Figure 3), showing the different chemical composition of the different food compositions.

[0073] Example 2

[0074] Stability tests conducted on calcium alginate aerogel samples B to E,

[0075] In order to examine the stability of the compositions during storage, the inventors have performed accelerated shelf-life studies, in which a variety of quality indicators, including sensory assessment, microbiological examination, and water activity were tracked over time. Freshly produced aerogels were kept at four different isothermal temperatures (15, 20, 25, and 35°C) following the principles of the accelerated shelf-life testing procedure. The shelf-life of the proposed product is longer than six (6) months if stored at temperatures lower than 25 °C as total counts of bacteria, yeasts and moulds analysis results in the absence of these indicators (below detection limit, i.e., <10 CFU / gr). Using data extrapolation it is estimated that the shelf life will be at least one year.

[0076] Example 3

[0077] Resilience testing of the compositions of the invention

[0078] In order to examine the resilience and the mechanical strength of the aerogels of the invention, aerogel samples C and E and control samples (samples A) are kept in water. The aerogels of the present invention (samples C and E) were stable for at least 1 h, while control samples (sample A) shrank within seconds, as shown in Figure 4, as a result of the mechanically weak biopolymer skeleton of the control aerogels.

[0079] Example 4

[0080] Sensory and aroma tests conducted on calcium alginate aerogel compositions B, C and E,

[0081] The inventors have conducted sensory tests regarding color, taste, aroma and texture. A 21 -person sensory panel used a nine-grade hedonic scale to rate the samples color, flavor, texture, scent, and overall impression. The acceptance / non-acceptance range was set between 1 to 5. The results are shown in Table 2.

[0082] Table 2. Results of the sensory tests conducted using the samples B, C and E.

[0083] The results show that, compared to control aerogels, the new food compositions revealed sweet, fruity and / or aromatic notes along with satisfying crunchy and light, airy texture. The appealing sensory aspects and particularly the taste and texture are important for a dietary product in order for the consumer to select them over alternative, high-calorie choices.

[0084] Example 5

[0085] Nutritional and aromatic profile of calcium alginate aerogel compositions B and C.

[0086] In order to examine the nutritional and aromatic profiling of the composition, the inventors have performed analysis of the produced samples during their storage. Macronutrients, vitamin C, total polyphenols and antioxidant activity were analysed. For aromatic profiling, volatile organic compounds were analysed with chromatography-mass spectrometry (GC-MS).

[0087] The nutritional analysis of the compositions showed high protein (> 6.2 g / 100 g), carbohydrates (>71 g / 100 g), dietary fiber levels (>8 g / 100 g), while vitamin C content was more than 300 mg per 100 g. Aromatic profiling revealed that the two compositions were rich in fruity esters like methyl butanoate, sweet fiiranones such as fiiraneol, and floral terpenes, ketones and y-decalactone, contributing to a layered, fruit-forward, and creamy scent. These results evidence the fact that the employed methods of obtaining aerogels yield compositions that retain their nutrients as well as the original aroma.

[0088] Materials & Methods

[0089] Sodium alginate (food grade El 04) was purchased from JRS and CaCE (food grade) was purchased from Chimcomplex S.A. and they were used without further modification. Fruit juices were prepared from fresh or frozen fruit. Oat drink was purchased from a grocery store. Coffee extract was prepared from espresso coffee residues.

[0090] ATR-FTIR spectra: ATR-FTIR spectra were obtained with a Shimadzu FTIR IRAffinity-1 spectrometer equipped with an ATR Shimadzu QATR10 single-reflection attachment.

[0091] Bulk density measurements: Bulk densities of the samples were calculated from their weights and natural dimensions.

[0092] Porosity measurements: Porosities were calculated according to formula: (ps-pb) / ps, where ps: skeletal density and pb: bulk density. Skeletal densities were determined by helium pycnometry using a Micromeritics AccuPyc II 1340 pycnometer.

[0093] Water activity: The water activity of the samples was measured using water activity meters (Rotronic A2 Hygromer) at 22 °C, based on the dew point. After analysis calibration, the sample was placed without pre-treatment in the container and the measurement was taken after the levels had been stabilized.

[0094] Macronutrient quantification: Protein, fat, and carbohydrates were quantified by reference methods including Kjeldahl combustion, Soxlet extraction and AOAC standard protocol, respectively.

[0095] Vitamin C quantification: Vitamin C quantification was performed using high-performance liquid chromatography (HPLC), with the use of Reverse-phase C18 and the use of ultraviolet (UV) absorption detection method.

[0096] Total polyphenols and antioxidant activity: Spectrophotometric assays were performed by the use of Folin-Ciocalteu which includes spectrophotometrical analysis of the prepared samples at 760 nm and DPPH method including absorbance measurements of the prepared samples at 517 nm.

[0097] Volatile organic compounds: Headspace solid-phase microextraction (HS-SPME) and subsequently separation, identification, and quantification were performed using gas chromatography-mass spectrometry (GC-MS).

Claims

CLAIMS1. Solid, storage-stable, crispy food composition comprising a plurality of aerogels or xerogels, wherein each aerogel or xerogel comprises a crosslinked hydrogel-forming biopolymer and a functional ingredient entrapped into the aerogel or xerogel; wherein said functional ingredient comprises the solute components of a liquid carrier as well as its solid components (if present in the liquid carrier), said liquid carrier selected from the group consisting of fruit juices, vegetable juices, edible liquid by-products of the food industry, plant- or animal-based drinks, soft drinks, liquid aqueous extracts or solutions of natural aromatic spices or of natural aromatic resins, and any combination thereof; and wherein said composition is free from organic solvents.

2. The composition according to claim 1, wherein said liquid carrier is selected from the group consisting of fruit juices, vegetable juices, edible liquid by-products of the food industry, plant- or animal-based drinks, liquid aqueous extracts or solutions of natural aromatic spices or of natural aromatic resins, and any combination thereof; and wherein said composition further does not comprise preservatives or artificial sweeteners.

3. The composition according to claim 1 or 2, wherein said biopolymer is selected from the group consisting of gelatin, alginate, pectin, cellulose, starch, chitosan, gums, derivatives thereof and mixtures thereof.

4. The composition according to claim 3, wherein said biopolymer comprises alginate.

5. The composition according to any one of the preceding claims, wherein said plurality of aerogels or xerogels have a water activity below 0.4.

6. The composition according to any one of the preceding claims, wherein said plurality of aerogels or xerogels have a bulk density within the range from 0.09 to 0.3 g / cm3, and / or a porosity within the range from 70 to 91 v / v.

7. The composition according to any one of the preceding claims, wherein the composition is in the form of powders, granules, spheres, pellets or monoliths.

8. Use of the compositions according to any one of claims 1 to 7 as food, food ingredients, food additives or dietary supplements.

9. A method for producing the aerogels or xerogels of any one of claims 1 to 7, the method comprising the following steps:(i) a hydrogel-forming biopolymer is dissolved in a liquid carrier to yield a solution;(ii) the resulting solution is subjected to conditions that allow the hydrogel-forming biopolymer to form hydrogels, whereby the liquid carrier is entrapped in the hydrogels;(iii) the resulting hydrogels are left to age for at least 3 hours;(iv) the aged hydrogels are washed; and(v) the washed hydrogels are freeze-dried, thereby forming aerogels, or air- or oven-dried to form xerogels; wherein said liquid carrier is selected from the group consisting of fruit juices, vegetable juices, edible liquid by-products of the food industry, plant- or animal-based drinks, soft drinks, liquid aqueous extracts or solutions of natural aromatic spices or of natural aromatic resins, and any combination thereof.

10. The method according to claim 9, wherein said biopolymer is selected from the group consisting of gelatin, alginate, pectin, starch, carrageenan, derivatives thereof, copolymers thereof, and mixtures thereof.

11. The method according to claim 9 or 10, wherein step (ii) comprises adding in a dropwise fashion the solution resulting from step (i) to a solution of a crosslinking agent (monomeric or polymeric), said crosslinking agent including, but not limited to multivalent cations or acids; wherein said crosslinking agent is dissolved in the same liquid carrier used in step (i); and wherein the volume of the solution of the crosslinking agent is from one to three times the volume of the solution resulting from step (i).

12. The method according to any one of claims 9 to 11, wherein in step (i) the hydrogel-forming biopolymer is present in the liquid carrier at a concentration within the range from 0.1 to 15% w / w.

13. The method according to any one of claims 9 to 12, wherein step (iv) consists of one or more washes of a total duration that does not exceed thirty seconds, preferably twenty seconds, more preferably ten seconds.

14. Solid, storage -stable, crispy food composition comprising a plurality of aerogels or xerogels, wherein said aerogels or xerogels are obtainable by a process according to any one of claims 9 to 13; and wherein said composition is free from organic solvents.

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