Bioactive compounds changes of a green vegetable smoothie after thermal treatments and during shelf life
2018
Smoothies are beverages prepared from fruit and vegetables with excellent health-promoting properties derived from their phytochemical content. The consumers, with reduced time to prepare meals, and specific population groups with special needs (elderly, children, etc.) may find in smoothies an excellent convenient alternative for fruit and vegetables intake. Thermal treatment of such beverages is commonly needed to reduce microbial load and inactivate degradative enzymes. Accordingly, bioactive compounds changes of a green vegetable smoothie (cucumber, broccoli and spinach) after mild processing heat treatment (80°C for 3 min or 90°C for 45 s) during storage were studied. Fresh blended unheated smoothie was used as control (CTRL). Heat-treated smoothies were stored up to 49 days at 5°C and 7 days at 15°C while CTRL smoothie was stored up to 21 days at 5°C and 7 days at 15°C. The initial total phenolic content (TPC - 104.4 mg kg-1 fw of gallic acid equivalent) did not change after the thermal treatment. However, initial chlorophylls content [48.1 (Chla) and 10.8 mg kg-1 fw (Chlb)] and total carotenoids (8.8 mg kg-1 fw) were reduced by 64-77 and 43-47%, respectively, after thermal treatments. TPC in all treatments were well preserved at both storage temperatures showing even an increase of 73% in CTRL samples after 21 days at 5°C compared to initial values. In general, the observed chlorophylls and total carotenoids reductions (23-59%) of CTRL smoothie during storage were avoided in those heat-treated samples. In conclusion, the TPC of the smoothie was not affected by thermal treatments or during storage although heat treatments avoided chlorophylls and carotenoids degradation in the smoothie during storage.
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