Effect of Particle Size on Color of Ground Coffee

Introduction: Particle size is one of the main variables that influence coffee brewing process and also most obvious to the consumers. The aim of this study was to evaluate the effect of different particle sizes on the color of ground coffee. Methods: A laser diffraction analyzer was used to determine the particle size distribution of the 14 dry ground coffee samples. The particle size distribution of the roasted ground coffee samples that underwent grinding at different time periods was based on volume distribution. Color measurements of all coffee samples were made using a portable CR-400 tristimulus colorimeter and Spectra-Match software, set to L*, a*, b* mode. Color measurements were recorded for two replicates of each sample. Results: Coffee samples ground for short times of 30s, 20s and 10s, were observed to have coarser particles than those that underwent longer grinding times. The 20s and 30s grinding times did not exhibit any significant differences for the D50 and D90 particle size distributions. There was no significant difference in D50 and D90 values for Colombian 1.3, Leyenda and Tarrazu brands. It was observed that lightness (L*) as well as a* and b* were highly significantly different between the different coffee samples with P < 0.0001. The coffee samples that underwent grinding for 60s had the highest L*, a* and b* values of 30.72, +1.31 and +1.39 respectively. Colombian 1.3 coffee brand had the lowest L* and a* values of 29.8 and +0.67 respectively, with brand 1820a having the lowest b* value of +0.39. Conclusion: The results of this study show that there was no significant effect of particle size distribution of coffee samples on color of the ground coffee particles. L*, a* and b* values decreased during roasting, due to the darkening of the beans resulting from sugar caramelization and Maillard reactions.

Variability of Total Polyphenol Contents in Ground Coffee Products and Their Antioxidant Capacities through Different Reaction Mechanisms

Coffee is one of the most popular non-alcoholic drinks consumed daily by millions of individuals worldwide. It is characterized by varieties and processing, which cause changes in chemical compositions and biological activities. This study aimed to evaluate the effects of roasting degrees during the processing period (light, medium, and dark) on the total polyphenol contents (TPCs) in-ground coffee products of arabica, robusta, and liberica and their trolox equivalent antioxidant capacities (TEACs) through various chemical reaction mechanisms (DPPH, ABTS, FRAP, and CUPRAC). The analytical methods were conducted based on spectrophotometric principle after the microwave-assisted liquid extraction. The results of the TPCs followed the descending order of robusta (34.3-48.23 mg GAE g–1) > liberica (31.5-34.37 mg GAE g–1) > arabica (27.1-44.11 mg GAE g–1). Moreover, robusta coffee generally performed greater TEACs than liberica and arabica. Besides, the TPCs and TEACs varied regarding different roasting degrees, in which the medium roasting mostly exhibited the highest values due to the balance between the degradation of phenolic compounds and the generation of new antioxidant compounds mainly from the Maillard reactions. Strong correlations between TPCs and antioxidant capacities (R2 > 0.6), indicating rich phenolic compounds played key roles in TEACs of coffee.

Maillard reaction products of chitosan and glucosamine: antibacterial and antioxidant activity

Maillard reactions between chitosan and glucosamine were induced by Co-60 gamma irradiation method and the antibacterial and antioxidant activities of resulting products were investigated. Briefly, a mixture of chitosan (1%) - glucosamine (0.5%) was irradiated with a dose range of 0-100 kGy. The Maillard reaction products of chitosan and glucosamine (CTS-GA MRPs) were analyzed by UV spectrophotometry, and residual glucosamine was determined by high performance liquid chromatography (HPLC). Antibacterial and antioxidant activities of the CTS-GA MRPs were investigated with radiation dose and pH by using directly contacted and ATBS•+ free radical scavenging methods. The results indicated that the CTS-GA MRPs formed at 25 kGy exhibited high antibacterial activity at both pH 5 and 7. On the other hand, antioxidant activity of CTS-GA MRPs increased with the increase of dose. The results also revealed that CTS-GA MRPs with high antimicrobial and antioxidant activities are potential candidates as preservative agents in food processing and cosmetics.

Gaseous environment modulates volatile emission and viability loss during seed artificial ageing

Main conclusion Modulation of the gaseous environment using oxygen absorbers and/or silica gel shows potential for enhancing seed longevity through trapping toxic volatiles emitted by seeds during artificial ageing. Abstract Volatile profiling using non-invasive gas chromatography–mass spectrometry provides insight into the specific processes occurring during seed ageing. Production of alcohols, aldehydes and ketones, derived from processes such as alcoholic fermentation, lipid peroxidation and Maillard reactions, are known to be dependent on storage temperature and relative humidity, but little is known about the potential modulating role of the gaseous environment, which also affects seed lifespan, on volatile production. Seeds of Lolium perenne (Poaceae), Agrostemma githago (Caryophyllaceae) and Pisum sativum (Fabaceae) were aged under normal atmospheric oxygen conditions and in sealed vials containing either oxygen absorbers, oxygen absorbers and silica gel (equilibrated at 60% RH), or silica gel alone. Seeds of A. githago that were aged in the absence of oxygen maintained higher viability and produced fewer volatiles than seeds aged in air. In addition, seeds of A. githago and L. perenne aged in the presence of silica gel were longer lived than those aged without silica, with no effect on seed moisture content or oxygen concentration in the storage containers, but with silica gel acting as a volatile trap. These results indicate that the use of inexpensive oxygen absorbers and silica gel could improve seed longevity in storage for some species and suggests a potential, and previously unidentified, role for silica gel in ultra-dry storage.