Properties and microstructure of blackcurrant powders prepared using a new method of fluidized-bed jet milling and drying versus other drying methods

Assessment of Chokeberry Powders Quality Obtained Using an Innovative Fluidized-Bed Jet Milling and Drying Method with Pre-Drying Compared with Convection Drying

There is a need and great interest among food producers in obtaining powders from fruit and vegetables of both high nutritional value and sensory qualities superior to those hitherto obtained by convection drying (CD) and spray drying methods and cheaper to prepare than the sublimation method. This study is focused on whether powders can be obtained from fruit berries with a sticky structure, using the chokeberry (Aronia melanocarpa) as a test example, by a combined fluidized-bed jet milling and drying (FBJD) of pre-dried fruit by CD to an adequate water activity (a_w). The pre-drying step reduced sticking between fruit particles during the simultaneous drying and grinding processes of the FBJD method in order to obtain powders of desired granulation. Three different pre-drying temperatures of 50, 60, and 70 °C were tested for levels of microorganisms in chokeberries at a water activity of 0.4. Vitamin C content and antioxidant properties were also examined along with polyphenol separation. Fruit pre-dried at 60-70 °C had significantly higher vitamin C and polyphenolic content and greater antioxidant properties than those pre-dried at 50 °C. Further studies were thus undertaken on powders pre-dried at 70 °C in which antioxidant properties, vitamin C, and polyphenols content were also compared with CD obtained powders. The FBJD method combined with CD pre-drying proved superior to just using the CD method, where powders had a greater preservation of vitamin C at 84% (CD powders 35%), a 12% higher total polyphenol content, and a 10% higher antioxidant activity. The test method also uses a much shorter drying time than the CD method, because the grinding of the hard-textured material takes only few minutes.

Effects of high hydrostatic pressure on the binding capacity, interaction, and antioxidant activity of the binding products of cyanidin-3-glucoside and blueberry pectin

In this study, the effects of high hydrostatic pressure (HP) treatment on the binding capacity, interaction, and antioxidant activity of the binding products of blueberry pectin (BP) and cyanidin-3-glucoside (C3G) were assessed. HP was found to significantly improve the adsorption between C3G and BP. After binding, the C3G concentration was found to be the highest (382.1 ± 13.2 μg/mg for BP) when using a C3G-BP mass ratio of 1:2, a pressure of 400 MPa, and a holding time of 15 min. HP processing decreased particle size and altered the characteristics of C3G-BP complexes. The main binding form of the complexes before HP treatment was pectin-wrapped C3G by hydrogen bond interaction, while HP caused charged groups in pectin to be more exposed and improve the electrostatic interaction between C3G and BP. The antioxidant activity results showed that the presence of BP could protect the ferric-reducing antioxidant power of C3G after HP treatment.

Properties of raspberry powder obtained by a new method of fluidised-bed jet milling and drying compared to other drying methods

BACKGROUND

Among food producers, there is a need for and a great interest in obtaining powders from fruit and vegetables characterised by high nutritional values and sensory qualities at favourable prices, preferably lower than those for powders obtained by freeze-drying (FD). The present study assessed the functional properties, including bioactive ingredient contents, of the raspberry powders obtained by a new method of fluidised-bed jet milling and drying (FBJD) which has not been yet used on an industrial scale.

RESULTS

Compared to the powders obtained by FD, the powders obtained by the new method were characterised by a comparable content of vitamin C (~2.70-2.74 mg g^-1 ), approximately 10-15% higher contents of anthocyanins and polyphenols, and higher antioxidant properties. Compared to the powders obtained by convection drying (CD) and spray drying (SD) methods, FBJD powders were characterised by approximately 40% and 80% higher polyphenol contents and 43% and 77% higher antioxidant activities, respectively. The content of vitamin C in FBJD powders was 49% higher than in CD powders, and only 4% higher than in SD powders.

CONCLUSION

Considering the findings outlined above, the method tested is concluded to be competitive with the methods currently used as a result of the high content of bioactive compounds in powders obtained by means of the cheaper, low-temperature process of simultaneous drying and micronisation in FBJD. © 2020 Society of Chemical Industry.

Bioactive, Physicochemical and Sensory Properties as Well as Microstructure of Organic Strawberry Powders Obtained by Various Drying Methods

This study compared the quality of organic strawberry powders, obtained by convective drying (CD), freeze drying (FD) and spray drying (SD) methods. In the study, such analyses were performed: the content of vitamin C and polyphenols by liquid chromatography method, antioxidant activity using ABTS+• radicals, microstructure using a scanning microscope, sensory quality by profile method and the determination of the physicochemical properties. The FD powders were characterised by the highest content of vitamin C and polyphenols, obtained values were close to fresh strawberries after conversion to the dry matter content. The content of these ingredients in CD and SD powders was lower by 55%–80% for vitamin C, and 80% for the polyphenols content. Strawberry flavour was most beneficial for the FD powders, while smoothness and homogeneity of appearance were equally rated for the FD and SD powders. Strawberry powders are a concentrate source of bioactive compounds and, therefore, the FD powders should especially be mainly used as a valuable component of high-value foods, especially functional foods, while CD and SD powders can be used to enrich food with vitamin C and as a valuable natural flavour and colouring component, replacing food additives.