Research and innovation are increasingly crucial in the evolution of whole sectors of the economy, even more so when, as in the case of hand-crafted gelato, Italy is an undisputed international leader. This reasoning lies behind the agreement which the Gelato Product Group of the Italian Association of the Food Products Industry (or AIIPA) signed in 2013 with SIGEP and DeFENS – Milan University’s Department of Food, Nutrition and Environmental Sciences – to set up a Research and Innovation Centre on hand-crafted gelato (or CRIGA).
CRIGA's main objective is to carry out research in the field of compound ingredients for gelato and raw materials, ranging from microbiology and gelato chemistry to technological properties and food safety.
The DeFENS work team is made up of Ernestina Casiraghi, full professor of Food Science and Technology, Roberto Foschino, associate professor in Food Microbiology, Cristina Alamprese, associate professor in Food Science and Technology, and Agostina Moles, laboratory technician assistant at DeFENS.
The results of the research carried out in the first four years by DeFENS were presented during a workshop held on the 17th October at Milan University, attended by the main players in the gelato supply chain.
Alternative sweeteners: honey, trehalose and erythritol
Sugars are crucial ingredients because, as well as giving the product sweetness, they perform other important functions, such as lowering the freezing point, increasing the viscosity of the mix and reducing both the growth of ice crystals and fat destabilization. The type and amount of sugars to use are two parameters which need to be carefully assessed and balanced, so as to achieve an optimal end product that complies with the required characteristics.
What conclusions did the various research projects on alternative sugars reach?
As regards honey, in hand-crafted gelato formulations it makes the product particularly soft and creamy, also improving its spreadability. These advantages, combined with honey’s nutritional aspects, can be effectively used for gelato formulations that meet the needs of the most health-conscious and demanding consumers. What is more, taking into account the fact that the aromas and flavours of honey strongly characterize the gelato obtained, the availability of honeys of different botanical origin, with different aromas, could be a great opportunity for creating new gelato flavours in original combinations. Honeys with a less intense flavour could be used to make gelatos with good spreadability even when using fat-based core ingredients (e.g. cocoa paste or nuts), which generally make the gelato less soft.
The second study involved trehalose. The results indicate that the use of trehalose in formulations of hand-crafted gelato makes the product particularly resistant to melting, but is also accompanied by a considerable increase in its texture, which makes it difficult to spread the product and reduces its creaminess. Given trehalose’s low sweetening power, it clearly cannot be used as the only sugar, but can be put to good use in gelato recipes to give particular melting and texture properties, as well as in so-called “gourmet” gelatos (for example, those flavoured with vegetables or cheeses) that don’t need to be very sweet, as they’re designed to be eaten with savoury dishes.
The third study focused on the performance of erythritol, a sugar substitute of natural origin with much lower calories. This sweetener gives the gelato more texture, as well as making it more resistant to melting. The results therefore suggest that using erythritol in combination with other sugars would keep the caloric intake in check, while helping with its spreadability and melting properties.
Alternative sweeteners: Stevia
Among the various ingredients that can be used as a sugar substitute, Stevia rebaudiana extract has been the subject of much recent interest, connected mainly with its excellent sweetening properties (approx. 300 times that of sucrose) and zero calories. However, as it is an intense sweetener and has no anti-freezing properties, using Stevia in gelato can make it difficult to get the texture right. The formulations therefore need to be balanced with other substitute ingredients (such as polydextrose, maltodextrin and/or sorbitol).
Both a milk base and a fruit base, previously developed by AIIPA, were assessed, in comparison with the corresponding sucrose-based formulations.
No statistically significant differences between the mixes caused by replacing sucrose with stevia were found, owing to the careful balance between the various ingredients. With regard to the qualitative characteristics of the gelato, both for the fruit and the milk base, the results showed no significant differences in texture, melting behaviour and colorimetric indices after replacing sucrose with stevia.
As for the other parameters, the fruit-based mixes showed a slight but significant (p <0.05) difference in freezing time, which was longer in samples containing stevia than in those made with sucrose.
In the melting tests, performed in a controlled temperature chamber at 20°C for 90 minutes, all the milk-based gelatos showed good shape retention for 45-60 minutes, with the indices being almost identical in the samples containing stevia and in those with sucrose. Similarly, the fruit-based samples showed no significant differences between the two types of formulation, retaining their shape well for the entire duration of the test (90 minutes).
From the results obtained, it can therefore be concluded that as a natural sweetener when making milk- or fruit-based artisanal gelato, stevia can be an effective alternative to sucrose. However, the correct balance of sugars is crucial, using ingredients that give body to the gelato and are able to lower the freezing point of the gelato mixes, neither of which stevia can do. Although the sensory aspect was not specifically studied in this work, it must be emphasized that the use of stevia gives gelato an aftertaste of liquorice, which is difficult to hide. In order to avoid this, instead of using stevia powder extract containing several steviol glycosides, it would be better to opt for pure rebaudioside A or other individual minor glycosides, which have less noticeable or even no off-flavours.
Organogels - sunflower oil
The lipid (or fat) component in hand-crafted gelato is crucial as it helps achieve the typical consistency of the product, giving it its body, creaminess and softness. These properties depend, among other things, on the type of fat used. Generally speaking, the most common fat used in making hand-crafted gelato is cream. However, as consumers and manufacturers increasingly look into healthy eating, where animal fat intake is wherever possible limited, recipes containing vegetable oils are coming to the fore.
The aim of the AIIPA-sponsored research was to verify the effects on the quality of hand-crafted gelato of using virgin sunflower oil in the form of an organogel. To summarize, they attempted to ascertain whether using sunflower oil structured in a physical process can give gelato the right structure and at the same time provide nutritional benefits compared to cream. Indeed, the organogel is characterized by greater unsaturated fatty acid content and by the presence of phytosterols with hypocholesterolemic and antioxidant properties, which are very interesting from a nutritional point of view.
Hand-crafted gelatos containing different quantities (4% or 8%) and types of fat (cream, sunflower oil, both in pure form and as an organogel, using two different phytosterol concentrations) were compared, studying 8 different formulations, in duplicate.
In terms of soluble solids and density, the samples showed significant differences as a function of the percentage of fat used in the mixes: as expected, a level of 8% leads to a decrease in the parameters measured. The apparent viscosity of the mixes was, however, significantly higher in the samples made with cream than in those containing sunflower oil or organogels. Regarding the type of fat, the apparent viscosity of the organogel-containing mix with the highest phytosterol concentration was very similar to that of the cream-based mixture and significantly (p <0.05) higher than that of the other samples. This mixture produced the gelato with the highest overrun (42.4%), while the gelato with unstructured sunflower oil contained a significantly (p <0.05) lower amount of incorporated air (27.5%). Moreover, the organogel delayed the first dripping time, thus making the product more resistant to melting.
When the fat content is higher, i.e. 8%, the gelato overrun (mean = 31.1%) would seem to be poorer, playing an anti-foaming role. With regard to shape retention during melting, no significant effects were found in terms of the amount of fat used.
In general, gelatos containing organogel had better shape retention. No significant differences were found in the colorimetric indices, indicating that the different amounts and types of fat used do not significantly affect this aspect of gelato quality.
The results obtained, therefore, led the researchers to conclude that using organogels in hand-crafted gelato formulations provides nutritional benefits compared to the use of cream and improves quality compared to unstructured oil. Indeed, using a higher phytosterol concentration helps to make a gelato with similar or even better characteristics than ones made with cream.
Alternatives to fatty acid mono- and diglycerides
The aim of this work was to evaluate the effect of replacing fatty acid mono- and diglycerides on the qualitative characteristics of hand-crafted gelato. As alternative ingredients to traditional emulsifiers, whey protein (WP), soy lecithin (LC), soy isolate (SI), pea protein (PP), rice protein (RP), citrus fibre (AF) and lupine protein (LP) were used. Furthermore, a gelato formulation with no emulsifiers (NE) was produced, in order to evaluate its effects on the final product. The samples produced with the various alternatives were compared to a reference formulation containing fatty acid mono- and diglycerides (REF). All the gelatos were produced in duplicate.
All of the tested ingredients, with the exception of LC, produced a significant increase in the apparent viscosity of the mix (p <0.05) compared to the reference. By contrast, the sample with no emulsifiers showed a significant decrease (p <0.05) in apparent viscosity.
The ice creams were evaluated for overrun, instrumental texture, melting behaviour and shape indices during melting. The AF and LP samples showed a markedly lower overrun (respectively 30.3% and 21.6%) compared with the reference formulation (50.8%), indicating a lower incorporation of air during freezing. The instrumental texture profile of samples containing WP (28.83 N), SI (57.23 N) and PP (54.40 N) was significantly worse (p <0.05) than that of REF (17.56 N) . In terms of melting behaviour, the use of AF increased melting resistance compared to REF, both in terms of first dripping time (50.81 min versus 16.90 min for REF), and in terms of melting speed (1.60 g/min as against 2.62 g/min for REF). A significant reduction (p <0.05) in melting speed was also found in samples containing PP, RP and LP, while the sample with no emulsifiers showed a faster melting rate (p <0.05) than the reference. In terms of shape retention during melting, samples containing LC, LP and PP performed better than the reference (p <0.05), while all of the other samples showed characteristics comparable to those of gelato made with fatty acid mono- and diglycerides.
These results indicate that soy lecithin, whey protein, rice protein, citrus fibre and lupine protein have shown, overall, good potential as substitutes of fatty acid mono- and diglycerides when making hand-crafted gelato. Pea protein and soy isolate, on the other hand, had notably poorer texture, suggesting they cannot be used as emulsifiers in gelato, at least at the quantities tested. Further studies could focus on refining the formulations tested and characterizing them from a sensory point of view.
Alternative fats and sweeteners
The research sought to verify whether a “low-calorie supergelato" could be made using alternative sweeteners such as stevia and highly unsaturated fats such as organogels based on phytosterols, which are considered to be beneficial in the fight against cholesterol.
In this case, in order to adjust the sweet point by eliminating sucrose, it was decided to use a combination of a natural zero-calorie sweetener (erythritol), a fibre (polydextrose) and an intensive sweetener, of natural origin, Stevia rebaudiana. The results show that sugars can be completely replaced without affecting structure and sweetness while drastically reducing calories and, above all, maintaining the gelato’s flavours and quality.
In order to reduce the amount of saturated fats, while milk fat could be replaced with unsaturated vegetable oils such as sunflower oil, seed oil or olive oil, the performance of these oils in gelato (in terms of creaminess, drip resistance and sensory characteristics in the finished product) has so far been rather disappointing, and has generally been rather unpopular among consumers.
The research project showed that when we add phytosterols (natural products derived from squalene with antioxidant properties) to vegetable oils, a “solid” fat can be create that is very similar to cream. This “creamy” unsaturated fat is full of hypocholesterolaemic and antioxidant substances which are easier to absorb.
These oils were solidified with phytosterols, known as organogels, and were used in gelato-making instead of cream in a low-sugar mix, sweetened with stevia.
The product, this “gelato of the future”, perfectly balanced from a nutritional standpoint (less sugar, less saturated fat), was comparable to a standard gelato at a structural level. The researchers then set out to ascertain the sensory acceptability of this gelato among consumers, which had not previously been scientifically surveyed.