To test the food application of the dried emulsions, bakery creams were formulated using the dried emulsions as a shortening alternative and compared with a control cream prepared using palm fat. Only the cellulose types A4M and F4M were employed, discarding MX, because of the poor results obtained in the mechanical properties and stability trials.
3.5.1. Spreadability of Creams
Spreadability is the ease with which a product can be spread. It is related to the firmness of a product.
Figure 8 shows the spreadability curves corresponding to creams formulated with the different dried emulsions as fat substitute compared to control cream.
Control cream firmness was higher than the reformulated creams, which indicates that palm fat provides a greater firmness or resistance to spread than the dried emulsions. This result was assumable, since the absence of solid fat crystals in sunflower-based emulsions resulted in a lower consistency of the oil structured systems. Previous studies indicated that structured-oil systems provided softer products compared to the use of shortenings or hydrogenated fats [
9,
12,
13]. Bakery creams formulated with 47% oil dried emulsions showed significant differences depending on the type of hydrocolloid used (
Table 3), being more spreadable those made with F4M. The cream that most closely resembled the spread profile of the control was the one made with 1% F4M. In contrast, A4M cream was the softest at the two concentrations tested.
Using the dried emulsions with more initial oil (
Figure 8 and
Table 4), it was observed that the MC A4M cream had an increase in AUC and the maximum peak of firmness. In contrast, F4M reduced these values compared to creams formulated with dried emulsions with less oil. Looking the creams formulated with the 70% oil systems, we can conclude that there were no significant differences regarding the type of cellulose used.
3.5.2. Rheological Properties of Creams
The values of the storage or elastic moduli (G′) and the loss or viscous moduli (G″) as a function of frequency are shown in
Figure 9.
The percentage of oil in the initial emulsion clearly affect the cream viscoelastic properties. The creams obtained from the 47% emulsion showed a gel-like behaviour, since the G′ moduli were higher than the G″ moduli across the entire frequency sweep. Besides, a low dependence of moduli on the frequency (0.1–10 Hz) was observed. However, bakery cream formulated with 70% oil and 0.5% F4M showed a clear frequency dependence and the end of the plateau area (crossover of G′ and G″) is visualised, revealing their lower viscoelasticity with an increase in the predominance of the viscous component (G″) versus the elastic (G′), reflecting a more liquid consistency, which is less suitable in terms of spreadable applications where some degree of elasticity is required.
Like the spreadability results, control cream showed the highest viscoelasticity compared to all the reformulated creams. Considering creams made from 47% oil dried emulsion, at 0.5% hydrocolloid, A4M creams showed slightly higher values of G′ and G″ than F4M cream, although differences in viscoelastic properties varying the type of cellulose were not significant (
Table 5). However, by increasing the cellulose ratio (1%), F4M cream experienced a marked increase in viscoelasticity.
The shortening replacement with 70% initial oil dried emulsions negatively affected the viscoelasticity of the creams, since it produced a notable decrease in the moduli. The lowest viscoelasticity was found in the F4M cream, in which at 1 Hz G′ and G” moduli are practically matched, confirming the crossing of moduli in the studied frequency spectrum (
Table 6).
To better understand the creams’ rheological behaviour, flow experiments were also carried out (
Figure 10). All creams showed a shear-thinning behaviour, which means that their viscosities decreased progressively as the shear rate increased. This is a consequence of the rearrangement of the molecules into a certain direction under shearing which offered less resistance to flow [
14]. Palm fat control cream showed higher apparent viscosity over the range of shear rates compared to the reformulated creams, and a stronger shear-thinning behaviour. These result coincided with those obtained in spreadability and oscillatory trials. The upward viscosity curve is higher than the downward one, especially in the control cream. The hysteresis area among the up and down curves indicates that the sample’s flow is time dependent. The hysteresis area is positively related to the energy required to break the structure. The highest hysteresis area of the control reflects its most complex structure, also reflected by its higher viscoelasticity and spreadability. In creams formulated with 0.5% hydrocolloid systems, both types of cellulose (A4M and F4M) showed similar behaviour. However, by increasing cellulose concentration to 1%, F4M cream presented an increase in viscosity, placing it above the cream with A4M. This change of F4M cream with the increase in the hydrocolloid concentration was also observed in the oscillation and texture determinations. It should be noted that the behaviour of all the creams became more similar at high shear rates, an aspect to consider from a practical point of view, in relation to spreading of the creams. At lower shear rates, there will be clear differences in the consistency of the samples, but these differences will disappear upon increasing shear rate.
Creams formulated with the dried emulsion with 70% initial oil show a lower viscosity and also a lower area of hysteresis, revealing the weakness of their structure. Although dried emulsions exhibited higher texture values when containing higher oil concentration, when applied to creams, a contrary effect is produced: creams formulated from emulsions with 70% initial oil show a drastic decrease in viscosity compared to emulsions starting from 47% initial oil content. The reduced viscosity of the bakery creams formulated from 70% initial oil could be attributed to the lowest oil retention in the dried emulsion matrix, which will be increased by blending during the processing of the cream.
An alternative topic of study with regard to food application of the dried emulsions could be blending them with shortenings. Previous studies have proved that partial replacement of shortening with oleogel provided much more acceptable quality than total replacement in bakery products [
15,
16].