Effects of roasting on phenolics composition and antioxidant activity of peanut (Arachis hypogaea L.) kernel flour.

The effects of roasting on the phenolics composition and antioxidant activity of peanut (Arachis hypogaea L.) kernel flour were appraised. Peanut kernel flour, with and without skin, were roasted at 160 °C for 10, 20, 30, 40 and 50 min. The resultant changes in the antioxidant activity of roasted peanut kernel flour were assessed by the determinations of total phenolics, 1,1-diphenyl-2-picrylhydrazyl free radical-scavenging capacity, percent inhibition of linoleic acid oxidation and thiobarbituric acid test and compared with those of unroasted kernel flour. It was observed that roasting significantly (p 20 min of roasting time). In contrast, over the course of heating, the amounts of phenolics were noted to be slightly increased in the peanut kernel flour with skin; the most significant (p < 0.05) increase occurred in the concentration of p-coumaric acid and quercetin at 30, 40, and 50 min of roasting. The results of this study reveal that optimum roasting time should be sought to enhancing the antioxidant capacity and phenolics concentration in peanut kernel flour

Effect of Roasting Temperature and Time on Precursors, Volatile Components and Flavour Quality of Cocoa Beans During Nib Roasting

The effect of roasting temperature and time on precursors, volatile components and quality of cocoa beans during nib roasting was studied using response surface methodology (RSM) which consisted two independent variables of temperature (110-170˚C) and time (5-65 min). Steam Distillation Extraction (SDE) method was used to extract and gas chromatograph-mass spectrometry equipped with an ICIS data system was used to identity the volatile compounds. The pH linearly increased during roasting period at 120˚C. The colour was used for 1.20-1.80 Fermentation index value. The moisture content of the nib decreased (to 1.1%) as the roasting time and temperature were increased. Fifty three volatile compounds had been detected in roasted nib. Among them, pyrazines and esters were two major groups which constituted of 34 different compounds. Tetramethylpyrazine, trimethylpyrazine, phenethyl acetate, isoamyl acetate, 3-methylbutyl acetate, 2-methylbutyl acetate, phenylacetaldehyde, and benzaldehyde were present in all treatments. The pyrazines formation increased as roasting time and temperature were increased. When roasting time was increased from 5 to 35 and 65 min at 140°C, the number of pyrazines increased from 4 to 10 and 11, respectively. The ratio value of esters increased when the roasting time was increased from 15 to 65 min (at 110-120°C). However, the ratio value of carbonyls linearly decreased with an increasing roasting temperature at shorter time (5-25 min). The ratio value of phenols was enormously reduced at the highest roasting temperature (170°C) with the longest roasting time (65 min) while that of alcohols slightly decreased as roasting temperature and time were increased. With the increase in roasting temperature and time, the concentration of free amino acids, reducing and non-reducing sugars had decreased. The concentration of total free amino acids decreased by 23.0% and 73.3% in the range of 1287.34 - 76.43 mg/100g. Sugars concentration decreased from 24.87 to 12.98 and 11.30 mg/l00g respectively as roasting temperature was increased from 110 to 140 and 170°C. The nib roasted at 140°C had higher response percent of cocoa taste, moderate response of bitter taste and low response of sour; astringent and absent of smoky. However, the nib roasted at 170°C had the lowest percent of cocoa taste but higher in bitter and high roast taste

Online monitoring of coffee roasting by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS): towards a real-time process control for a consistent roast profile

A real-time automated process control tool for coffee roasting is presented to consistently and accurately achieve a targeted roast degree. It is based on the online monitoring of volatile organic compounds (VOC) in the off-gas of a drum roaster by proton transfer reaction time-of-flight mass spectrometry at a high time (1Hz) and mass resolution (5,500m/Δm at full width at half-maximum) and high sensitivity (better than parts per billion by volume). Forty-two roasting experiments were performed with the drum roaster being operated either on a low, medium or high hot-air inlet temperature (= energy input) and the coffee (Arabica from Antigua, Guatemala) being roasted to low, medium or dark roast degrees. A principal component analysis (PCA) discriminated, for each one of the three hot-air inlet temperatures, the roast degree with a resolution of better than ±1 Colorette. The 3D space of the three first principal components was defined based on 23 mass spectral profiles of VOCs and their roast degree at the end point of roasting. This provided a very detailed picture of the evolution of the roasting process and allowed establishment of a predictive model that projects the online-monitored VOC profile of the roaster off-gas in real time onto the PCA space defined by the calibration process and, ultimately, to control the coffee roasting process so as to achieve a target roast degree and a consistent roasting. Figure Online monitoring of coffee roasting by real-time analysis of the roaster off-gas using PTR-ToF-MS. In a first phase, 42 calibration experiments were conducted at three different roasting temperatures and to three final roast degrees, to generate the 3D space defined by the three first principle components PC1, PC2 and PC3. Inverted triangles mark the dark roast degree, square medium and circle light, respectively. The hot-air inlet temperature is marked as follows: high (black), medium (grey), low (white). The different hot-air inlet temperatures and roast degrees are clearly separated. In a second phase, an online monitored PTR-ToF-MS spectrum of a roasting process was projected onto the 3D space, allowing following in real-time the roasting process and halting the roasting with a precision better that ± 1 Colorette roast degre

Espresso coffees, caffeine and chlorogenic acid intake: potential health implications

HPLC analysis of 20 commercial espresso coffees revealed 6-fold differences in caffeine levels, a 17-fold range of caffeoylquinic acid contents, and 4-fold differences in the caffeoylquinic acid:caffeine ratio. These variations reflect differences in batch-to-batch bean composition, possible blending of arabica with robusta beans, as well as roasting and grinding procedures, but the predominant factor is likely to be the amount of beans used in the coffee-making/barista processes. The most caffeine in a single espresso was 322 mg and a further three contained &#62;200 mg, exceeding the 200 mg day−1 upper limit recommended during pregnancy by the UK Food Standards Agency. This snap-shot of high-street expresso coffees suggests the published assumption that a cup of strong coffee contains 50 mg caffeine may be misleading. Consumers at risk of toxicity, including pregnant women, children and those with liver disease, may unknowingly ingest excessive caffeine from a single cup of espresso coffee. As many coffee houses prepare larger volume coffees, such as Latte and Cappuccino, by dilution of a single or double shot of expresso, further study on these products is warranted. New data are needed to provide informative labelling, with attention to bean variety, preparation, and barista methods

Effect of roasting on the Ochratoxin A (OTA) reduction in green coffee beans

Ochratoxin A (OTA) is a mycotoxin with proved carcinogenic (group 2B) effects (1), which is mainly produced by diverse fungus strains such as A. carbonarius, A. niger, A. ochraceus, A. westerdijkiae and A. steynii, as well as Penicillium verrucosum and P. nordicum (2, 3, 4). Coffee has been determined as the third major source of OTA that affect the European population, followed by cereals and wine. The natural occurrence of OTA in green coffee beans has been reported since 1974 in concentrations ranging between 0.2 and 360 ?g.kg-1 (5, 6). Several reports concerning to the roasting impact on OTA content in coffee beans have shown a large range of OTA reduction levels (7, 8). Such variability could be related to the different roasting process conditions. The aim of this work was to assessed the effect of two roasting techniques [Cylinder (C) and fast-Fluidized Bed (FB)]. (Résumé d'auteur

UHPLC-PDA-ESI-TOF/MS metabolic profiling and antioxidant capacity of arabica and robusta coffee silverskin: antioxidants vs phytotoxins

A deeper knowledge of the chemical composition of coffee silverskin (CS) is needed due to the growing interest in its use as a food additive or an ingredient of dietary supplements. Accordingly, the aim of this paper was to investigate the metabolic profile of aqueous extracts of two varieties of CS, Coffee arabica (CS-A), Coffee canephora var. robusta (CS-R) and of a blend of the two (CS-b) and to compare it to the profile of Coffee arabica green coffee (GC). Chlorogenic acids, caffeine, furokauranes, and atractyligenins, phytotoxins not previously detected in CS, were either identified or tentatively assigned. An unknown compound, presumably a carboxyatractyligenin glycoside was detected only in GC. Caffeine and chlorogenic acids were quantified while the content of furokauranes and atractyligens was estimated. GC and CS were also characterized in terms of total polyphenols and antioxidant capacity. Differences in the metabolites distribution, polyphenols and antioxidant capacity in CG and CS were detailed

Changes in Procyanidins and Tannin Concentration as Affected by Cocoa Liquor Roasting

Changes in cocoa procyanidins and tannin concentration as affected by cocoa liquor roasting were studied by heating up cocoa liquor of fermented beans containing 58 g kg-1 of polyphenols and the same liquor which was enriched with crude polyphenols, extracted from freeze-dried unfermented cocoa beans to a final concentration of 170 g kg-1. The liquors were roasted at 120 OC for 15, 25, 35 and 45 min with three replications. Result of the study showed that cocoa bean polyphenol was resistant against high temperature during heating of cocoa liquor 120 OC for up to 45 min. The resistance was stronger with the unfermented cocoa bean polyphenol than with fermented cocoa. High temperature promoted a small quantity of monomers up to pentamers of the fermented cocoa bean polyphenol to polymerize into higher oligomers, but did not with unfermented cocoa bean polyphenol. These results imply that the problem of lack in cocoa flavor in terms high astringency and bitterness due to high polyphenol content cannot be overcome by the application of high temperature during chocolate processing, meanwhile cocoa bean polyphenol could still give beneficial as an antioxidant even after high temperature application

Ferric chloride leaching of the Delta sulfide ores and gold extraction from the leaching residue

Conventional differential and bulk flotation processes have difficulties in achieving high recoveries with acceptable grades far zinc, lead and copper from the complex sulfide ores found at Tok, Alaska. Furthermore, gold and silver, which account for a significant fraction of total value of the ores, are distributed evenly in the flotation tailings and concentrate. Therefore, processing both flotation tailings and concentrate would be necessary to obtain high recoveries of gold and silver. A mineralogical study revealed that the economic sulfide minerals are interstitially associated with a large preponderance of pyrite. The economic sulfide minerals are 10 to 40 microns in size. These mineralogical facts explain the difficulties encountered in the flotation process. A hydrometallurgical method involving ferric chloride leaching and subsequent steps to recover lead, zinc, silver and copper from the leach liquor has been studied at the Mineral Industry Research Laboratory, University of Alaska Fairbanks for the treatment of Delta ores. This alternative is attractive for processing complex sulfide ores which conventional flotation and smelting cannot handle. In addition, the liberation of sulfur in the environmentally acceptable elemental form, rather than as sulfur dioxide, may prove a major advantage of this hydrometallurgical method because of stringent environmental regulations