Abstract
Preparation method may influence acid diffusion and buffering capacity of foods, which will consequently influence food breakdown and nutrient release during gastric digestion. The objective of this study was to determine the acid uptake into red beets during in vitro gastric digestion and characterize the buffering capacity of red beets as a result of different preparation methods. Red beets were cut into cylinders and they were examined as raw, steamed (15 min at 105°C) or pickled (steamed 15 min at 105°C, 7 days immersed in 2% acetic acid). Cylinders were covered to insulate their sides and back to have a one-dimensional diffusion system, before soaking in simulated gastric juice for up to 96 h (37°C). Before digestion, buffering capacity was measured by adding 0.2 M HCl to blended raw, steamed, or pickled beets until the pH value was below 1.5. After digestion, acidity measurements were performed. Acidity was significantly influenced by preparation method and digestion time (p < 0.05). Acidity of raw beets had the greatest increase from 0.46 mmol H+/g dry matter to 3.71 mmol H+/g dry matter during 96 hours of incubation. On the contrary, decrease of acidity was observed in pickled beets during 96 hours of incubation (15.28 mmol H+/g dry matter to 7.50 mmol H+/g dry matter). Preparation method significantly influenced buffering capacity (p < 0.001). Pickled beets had a higher buffering capacity of 0.051 mmol H+/(pH g) compared to raw and steamed beets which had buffering capacity values of 0.035 and 0.034 mmol H+/(pH g), respectively. Beet resistance to changes in pH, or buffering capacity, may cause differences in acid uptake of red beets in the gastric environment after different preparation methods. Higher acid uptake (3.25 mmol H+/g dry matter) was observed in raw beets with respect to steamed beets (2.35 mmol H+/g dry matter) during 96 hours of incubation as a result of higher buffering capacity and structural changes due to preparation method. The study of the relationship between food preparation and behavior during digestion can be important for development of innovative functional food products for specific consumer groups.
