Effect of roasting degree on the antioxidant activity of different Arabica coffee quality classes.

BACKGROUND: Coffee is one of the most widely consumed beverages in the world, because of its unique sensory properties and physiological properties. Coffee beverages represent a significant source of antioxidants in the consumers' diet and contribute significantly to their daily intake. The aim of this research was to investigate the effect of different roasting degrees on the content of biologically active compounds and antioxidant activity in different quality classes of Arabica coffee. METHODS: Samples of green Arabica coffee (Rio Minas) of two quality classes from two production batches were used for the research. Roasting was carried out at temperatures of 167, 175 and 171°C. The total phenol content (TPC), total flavonoid content (TFC), flavonol content (FC) and antioxidant activity (DPPH, ABTS) in the coffee extracts was determined. RESULTS: This research shows that TPC was significantly higher (P < 0.05) in green coffee compared to TPC in roasted coffee, and TPC decreases as the roasting temperature increases. TFC and FC were significantly lower (P < 0.05) in green coffee than in roasted coffee. Differences in TPC between the 1st and 2nd classes of Arabica coffee were not significant (P > 0.05), while differences in TFC were significant (P < 0.05) only for green coffee from the second production batch and differences in FC were significant (P < 0.05) for green coffee and for coffee roasted at 175°C. Roasting temperatures have different influences the antioxidant activity (DPPH, ABTS) of coffee and the highest antioxidant activity was determined in coffee roasted at 171°C. An exception was 1st class Arabica coffee roasted at 167°C (ABTS). All samples of 1st class Arabica coffee had higher antioxidant activity (DPPH, ABTS) compared to 2nd class Arabica. CONCLUSIONS: This research shows that the bioactive compounds content and antioxidant activity of different quality classes of Arabica coffee are dependent on the degree of roasting. TPC decreases when the roasting temperature increases, while TFC and FC also increase. These results indicate that the antioxidant activity of coffee depends on a variety of bioactive components in coffee beans. Antioxidant activity largely depends on the class of coffee. The coffee samples of 1stclass quality (maximum 8 black beans/300 g from the sample and large bean size) had higher antioxidant activity compared to samples of 2nd quality class (maximum 19 black beans/300 g in the sample and medium-sized beans).

Effects of rapid chilling of carcasses and time of deboning on weight loss and technological quality of pork semimembranosus muscle.

The effect of rapid air chilling of carcasses in the first 3 h of chilling at -31°C (then at 2-4°C, till 24 h post-mortem) and the possibility of earlier deboning (8 h post-mortem) after rapid air chilling, compared to conventional air chilling (at 2-4°C, till 24 h post-mortem) on weight loss and technological quality (pH value, tenderness, drip loss, cooking loss and colour - L(∗)a(∗)b(∗) values) of pork M. semimembranosus was investigated. Under the rapid chilling conditions, weight loss was 0.8% at 8 h post-mortem and increased to 1.4% at 24 h post-mortem when weight loss was 2.0% under conventional chilling. Carcasses that were rapid chilled had significantly lower (P<0.001) internal temperature in the deep leg at 4 (25.7°C), 6 (13.0°C), 8 (6.2°C) and 24 h (3.8°C) post-mortem compared to conventional chill treatment (32.7, 24.2, 19.1 and 5.1°C, respectively). Rapid chilling reduced significantly (P<0.05) the rate of pH value decline at 8 h (6.02) post-mortem in M. semimembranosus compared to conventional chill treatment (5.88). Compared to conventional chilling, in M. semimembranosus deboned in different time post-mortem, rapid chilling had a positive significant effect on drip loss (P<0.05, muscles deboned 8 h post-mortem), cooking loss (P<0.001) and incidence of pale colour (L(∗) value). Rapid chilling i.e. rapid chilling and earlier deboning had neither positive nor negative significant effects (P>0.05) on other investigated technological quality parameters of M. semimembranosus (tenderness, a(∗) value and b(∗) value) compared to conventional chilling.