Evaluation of qualitative changes of apple-beetroot juice during long-term storage at different temperatures
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ORIGINAL PAPER
Evaluation of qualitative changes of apple‑beetroot juice during long‑term storage at different temperatures Blanka Tobolková1 · Martin Polovka1 · Ľubomír Daško1 · Elena Belajová1 · Ján Durec2 Received: 10 June 2020 / Accepted: 30 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The effect of storage conditions on changes of pH, total soluble solids (°Brix), colour, betalains (betacyanins and betaxanthins), and 5-hydroxymethylfurfural was investigated in apple-beetroot juices stored at 2, 7 and 20 °C for 120 days. The results obtained showed that the quality of apple-beetroot juice is significantly influenced by temperature and storage duration. Increasing storage time and temperature induced an apparent rise (P 0.05) in both parameters among juices stored at 2, 7 and 20 °C. This observation agrees with previous studies [19, 20, 23]. On the contrary, Mahnoori et al. [18] reported increasing total soluble solids and decreasing pH in litchi-beetroot juice blends. According to Bhardwaj and Pandey [24], retention or minimal increase in °Brix values during juice storage is desirable for preserving good juice quality. A gradual rise in °Brix may be associated with a continual increase in the hydrolysis of polysaccharides and acids. On the other hand, the increased pH is accompanied by a decrease in the acidity of juices during storage [18, 25].
Table 1 The changes in total soluble solids content (°Brix) and pH values in apple-beetroot juices stored at different temperatures
°Brix
pH
Temperature (°C)
Time of storage (days) 0
14
28
42
56
70
84
120
20 7 2 20 7 2
11.3 ± 0.2a 11.3 ± 0.2a 11.3 ± 0.2a 4.76 ± 0.05a 4.76 ± 0.05a 4.76 ± 0.05a
11.2 ± 0.1a 11.3 ± 0.1a 11.2 ± 0.1a 4.77 ± 0.04a 4.77 ± 0.06a 4.77 ± 0.04a
11.3 ± 0.1a 11.3 ± 0.1a 11.2 ± 0.1a 4.79 ± 0.03a 4.77 ± 0.06a 4.77 ± 0.05a
11.3 ± 0.1a 11.3 ± 0.2a 11.3 ± 0.1a 4.78 ± 0.03a 4.78 ± 0.03a 4.77 ± 0.03a
11.4 ± 0.1a 11.4 ± 0.1a 11.3 ± 0.1a 4.80 ± 0.04a 4.78 ± 0.05a 4.78 ± 0.05a
11.5 ± 0.2a 11.5 ± 0.1a 11.4 ± 0.1a 4.81 ± 0.06a 4.80 ± 0.05a 4.80 ± 0.05a
11.5 ± 0.1a 11.4 ± 0.1a 11.4 ± 0.2a 4.82 ± 0.04a 4.80 ± 0.05a 4.80 ± 0.04a
11.6 ± 0.2a 11.5 ± 0.1a 11.5 ± 0.2a 4.85 ± 0.04a 4.82 ± 0.04a 4.82 ± 0.03a
Values within a column followed by the same letter do not differ significantly (P > 0.05). The measurements were made in triplicate and are represented as mean values (± SD)
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Colour changes Colour represents one of the most widely measured product quality attributes that affect the preferences of consumers. Figure 1 shows the colour characteristics L* (lightness), a* (redness) and b* (yellowness) of ABJs and how these are affected by storage time and temperature. As seen in Fig. 1a, L* values increased by approximately 6–12% (P
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