Effect of composition changes and aeration time on the structure and rehydration of innovative freeze-dried gels

Abstract

This paper seeks to explain the structural effect on selected properties of freeze-dried gels with different compositions and aeration times. Herein, sugars and citric acid were added to gels with low-methoxyl pectin, mixtures of xanthan gum and locust bean gum, as well as xanthan gum and guar gum, in order to obtain a strawberry model. Strawberry pulp was also added to hydrocolloids to develop an innovative strawberry product. All samples were aerated for 3 and 7 min, and freeze-dried. Composition changes were found to modify the structure of the examined samples and properties. Freeze-dried gels with low-methoxyl pectin seemed to reflect the best approach towards obtaining an innovative strawberry product with a tailored structure, as they had the best water absorbent capacity, and the most attractive and delicate structure. Samples with a mixture of hydrocolloids were more compact. Aeration time did not significantly affect the examined parameters, while the addition of sugar and citric acid increased them. The strawberry pulp experiment confirmed the strawberry model (with low-methoxyl pectin gels, and sugar and citric acid), which had the finest structure and the best rehydration properties.

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“…They showed that hydrocolloids can improve the texture of dairy products by increasing their viscosity, but also that they may interact with different components of products, which changes the properties of dairy products. Similar effects may be obtained in freeze-dried vegetables or fruit bars as an effect of sample composition, different ingredients and pH, acid and sugar content [83].…”

“…In the literature there are few publications about dried fruit or vegetable gels. Strawberry pulp added to the low-methoxyl pectin, the mixture of xanthan gum and locust bean gum or mixture of xanthan gum and guar gum allowed obtaining a porous structure attractive for consumers, what was confirmed by e.g., sensory analysis ( Figure 6) [60,83]. The porous structure of gel matrix was also created by different aeration time (3, 5, 7 and 9 min).…”

“…Therefore, properly selecting the right hydrocolloids is invariably important in designing a product with specific characteristics. Such investigations were conducted by Ciurzyńska et al [83][84][85] for freeze-dried strawberry gels on the basic of low-methoxyl pectin, the mixture of xanthan gum and locust bean gum, as well as mixture of xanthan gum and guar gum. The authors showed that hydrocolloids created the structure of freeze-dried samples, which is what influenced the physical and organoleptic properties.…”

“…The authors showed that hydrocolloids created the structure of freeze-dried samples, which is what influenced the physical and organoleptic properties. Ciurzyńska et al [83] showed that freeze-dried gels with low-methoxyl pectin seem to be the best way to obtain an innovative strawberry product with the designed structure. Pectin added to this sample caused the freeze-dried gels to have the best rehydration properties, what was related to the structure, the lowest shrinkage and real density.…”

“…Conducted investigations have shown that the type of hydrocolloid has an important influence on freeze-dried gels properties while aeration time was in most cases insignificant. It was shown that samples obtained on the basis of low-methoxyl pectin were characterized by the best physical properties, the most attractive structure and were the most crispy and fragile [60,83]. Broccoli waste from the sorting of frozen material was used to produce freeze-dried bars with addition of xanthan gum (0.5%) and locust bean gum (0.5%).…”