Joseph R. Powers

Determination of total phenolic content and antioxidant capacity of onion (Allium cepa) and shallot (Allium oschaninii) using infrared spectroscopy

Total phenolic content (TPC) and total antioxidant capacity (TAC) of four onion varieties (red, white, yellow and sweet) and shallot from selected locations (Washington, Idaho, Oregon, Texas and Georgia) were determined using Fourier transform infrared (FT-IR) spectroscopy (4000-400cm-1). The Folin-Ciocalteu (F-C) assay was used to quantify TPC and three assays were used to determine TAC, including 2,2-diphenyl-picrylhydrazyl (DPPH) assay, Trolox equivalent antioxidant capacity (TEAC) assay and ferric reducing antioxidant power (FRAP) assay. Partial least squares regression (PLSR) with cross-validation (leave-one-out) was conducted on onion and shallot extracts (n=200) and their corresponding F-C, DPPH, TEAC and FRAP values were employed to obtain four independent calibration models for predicting TPC and TAC for the extracts. Spectra from an extra 19 independent extracts were used as an external validation set for prediction. A correlation of r>0.95 was obtained between FT-IR predicted and reference values (by F-C, DPPH, TEAC and FRAP assay) with standard errors of calibration (SEC) and standard errors of cross-validation (SECV) less than 2.85, 0.35 and 0.45μmolTrolox/g FW of extracts for TEAC, FRAP and DPPH assay, respectively; and 0.36mggallic acid/g FW of extracts for the F-C assay. In addition, cluster analysis (principal component analysis (PCA)) and discriminant function analysis (DFA) could differentiate varieties of onions and shallot based upon infrared spectral features. Loading plots for the various chemometrics models indicated that hydroxyl and phenolic functional groups were most closely correlated with antioxidant capacity. The use of mid-infrared spectroscopy to predict the total antioxidant capacity of vegetables provides a rapid and precise alternative to traditional wet chemistry analysis.

Effect of ultrasound frequency on antioxidant activity, total phenolic and anthocyanin content of red raspberry puree

Ultrasound in the 20-1000 kHz range show unique propagation characteristics in fluid media and possess energy that can break down fruit matrices to facilitate the extraction of valuable bioactive compounds. Red raspberries carry significant amounts of specific antioxidants, including ellagitannins and anthocyanins that are important for human health. The objective of this study was to investigate the effects of ultrasound frequencies associated with cavitation (20 kHz) and microstreaming (490 and 986 kHz) on total antioxidant activity (AOA), total phenolics content (TPC), and total monomeric anthocyanin content (ACY) of red raspberry puree prepared from crushed berries. The pureed fruit was subjected to high-intensity (20 kHz) and higher frequency-low intensity (490 and 986 kHz) ultrasound for 30 min. The temperature of treated purees increased to a maximum of 56 °C with 986 kHz. Sonication at 20 and 490 kHz significantly (p<0.05) affected the AOA, ACY, and TPC of red raspberry puree, while 986 kHz had no significant effect on ACY and AOA (p<0.05). In all cases, ultrasound treatment had significant and positive effect on at least one of the measured parameters up to 30 min. Sonication beyond 10 min (and up to 30 min) using 20 kHz either produced no change or caused a drop in AOA and ACY. However, for 986 and 20 kHz, TPC, increased by 10% and 9.5%, respectively after 30 min (p<0.05) compared to the control. At 20 kHz, AOA and ACY increased by 17.3% and 12.6% after 10 min. It was demonstrated that 20 kHz ultrasound treatment, when limited to 10 min, was the most effective for extraction of bioactive compounds in red raspberry compared to 490 and 986 kHz although the effect could be similar at the higher frequencies if different amplitudes are used.

Extrusion of regular and waxy barley flours for production of expanded cereals

ABSTRACT Grains of two regular and two waxy barley cultivars were milled into break and reduction stream flours using a wheat milling mill, granulated to facilitate feeding and flow through the barrel, and extruded to form expanded products using a modified laboratory single-screw extruder. As moisture content of barley granules decreased from 21 to 17%, the expansion index of extrudates increased from 1.81 to 2.68, while apparent modulus of compression work (AMCW) decreased from 17.1 × 104 to 7.8 × 104 N/m2. Break stream flours of both regular and waxy barley produced extrudates with higher expansion index (2.72–3.02), higher water absorption index (WAI), and lower AMCW than extrudates from reduction stream flours. Extrudates produced from regular barley had generally higher expansion and lower density than those produced from waxy barley. The specific mechanical energy (SME) was greater during extrusion of regular than of waxy barley. Barrel temperatures of 130, 150, and 170°C for the feeding, compressi...

Thermal degradation of anthocyanins from purple potato (cv. Purple Majesty) and impact on antioxidant capacity.

Degradation parameters of purified anthocyanins from purple-fleshed potato (cv. Purple Majesty) heated at high temperatures (100-150 °C) were determined. Purified anthocyanins, prepared by removing salts, sugars, and colorless nonanthocyanin phenolics from the crude extract, were monitored and quantified using HPLC and spectrophotometry for heat-induced degradation products. Separation of colorless phenolics from the anthocyanins was confirmed using HPLC at two wavelengths, 280 and 520 nm. The degradation kinetics of purified anthocyanins followed a first-order reaction with reaction rate constants (k values) of 0.0262-0.2855 min(-1), an activation energy of 72.89 kJ/mol, thermal death times (D values) of 8.06-8789 min, and a z value of 47.84 °C over the temperature range of 100-150 °C. The enthalpy and entropy of activation were 59.97 kJ/mol and -116.46 J/mol·K, respectively. The antioxidant capacity in the purified anthocyanins, measured by DPPH and ABTS assays, was increased after the thermal treatment, indicating antioxidant activities of degradation products in the samples.

Determination of Total Phenolic Content and Antioxidant Activity of Garlic (Allium sativum) and Elephant Garlic (Allium ampeloprasum) by Attenuated Total Reflectance–Fourier Transformed Infrared Spectroscopy

The total phenolic contents and antioxidant activities of garlics from California, Oregon, Washington, and New York were determined by Fourier transform infrared (FT-IR) spectroscopy (400-4000 cm(-1)). The total phenolic content was quantified [Folin-Ciocalteu assay (FC)] and three antioxidant activity assays, 2,2-diphenyl-picrylhydrazyl (DPPH) assay, Trolox equivalent antioxidant capacity (TEAC) assay, and ferric reducing antioxidant power (FRAP), were employed for reference measurements. Four independent partial least-squares regression (PLSR) models were constructed with spectra from 25 extracts and their corresponding FC, DPPH, TEAC, and FRAP with values for 20 additional extracts predicted (R > 0.95). The standard errors of calibration and standard error of cross-validation were <1.45 (TEAC), 0.36 (FRAP), and 0.33 μmol Trolox/g FW (DPPH) and 0.55 mg gallic acid/g FW (FC). Cluster and dendrogram analyses could segregate garlic grown at different locations. Hydroxyl and phenolic functional groups most closely correlated with garlic antioxidant activity.

Effect of Extrusion on the Antioxidant Capacity and Color Attributes of Expanded Extrudates Prepared from Purple Potato and Yellow Pea Flour Mixes

Foods with antioxidant capacity provide protection against cardio-vascular, certain forms of cancers, and Alzheimers diseases caused by oxidative damages and contribute health benefits. The effect of extrusion cooking on the antioxidant capacity and color attributes of extruded products prepared from 3 selected formulations of purple potato and yellow pea flours using a co-rotating twin screw extruder were studied. Expansion ratios of the extruded products varied from 3.93 to 4.75. The total antioxidant capacities (TAC) of the extruded products, using DPPH assay, were 3769 to 4116 μg trolox equivalent/g dry weight sample and not significantly different (P > 0.05) from their respective raw formulations. The total phenolic contents (TP) of the extruded products varied from 2088 to 3766 μg of gallic acid equivalent/g dry weight sample and retained 73% to 83% of the TP from the raw formulations after extrusion. The total anthocyanins contents (TA) in the extrudates were 0.116 to 0.228 mg of malvidin-3-glucosides/g dry weight sample. Compared with their raw formulations, significant losses (60% to 70%) of the TA in the extruded products occurred due to extrusion cooking. Browning indices and color attributes such as brightness, chroma, and hue angle agreed with degradation of anthocyanins in the extruded products. However, extrusion cooking retained antioxidant capacities of the raw formulations in the extruded products either in their natural forms or degraded products with radical scavenging activity. This study demonstrated the potential for the production of puffed extruded food products with the improved antioxidant content from colored potatoes and pulse formulations.

Evaluation of steam pasteurization in controlling Salmonella serotype Enteritidis on raw almond surfaces

Aim:  To investigate the efficacy of steam pasteurization for reducing Salmonella serotype Enteritidis on raw almond surfaces.

Cold Atmospheric-Pressure Plasmas Applied to Active Packaging of Apples

Active packaging of fruits and vegetables uses films that absorb molecules from or contribute molecules to the produce. The pilot application developed in this paper has resulted in the deposition of film to apples. A prospective application relates to replacing hot wax that is expensive and that lowers the textural quality of the apple. This was the early motivation of this paper. Moreover, the focus of this paper will be mostly on the reactor design and film evaluation. The cold-plasma zone was obtained by increasing the voltage on a needle-to-needle electrode structure until the electric field in the feed material (argon + monomer) was sufficiently high to yield electron avalanches and self-propagating streamers. The ¿corona onset criterion¿ was used to design the cold-plasma reactor. The apple was placed in a treatment chamber downstream from the activation zone (cold-plasma zone). Selected physical properties of the film were measured. Environmental scanning electron microscopy and Fourier transform infrared studies of samples were also performed to determine the presence of the film. Electromagnetic modeling was applied to the design of the cold-plasma reactor, and those results are presented in this paper.

Effect of mixing time, freeze-drying and baking on phenolics, anthocyanins and antioxidant capacity of raspberry juice during processing of muffins†

BACKGROUND Consumption of baked products constitutes an important part of a daily breakfast considering that people are continually grabbing meals on the go. Among baked products, muffins rank third in breakfast products and attract a broad range of consumers. Incorporation of red raspberry juice into muffins can add value to the product while preserving health benefits to the consumer. The purpose of this study was to evaluate the effect of mixing time, freeze-drying and baking on the phenolic and anthocyanin contents and antioxidant capacity of raspberry juice during the preparation of muffins. RESULTS Freeze-drying of raspberry batters reduced their phenolic content and antioxidant capacity regardless of mixing time. Non-freeze-dried raspberry batter mixed for 5 min had the highest phenolic content (0.88 mg gallic acid equivalent g(-1) dry matter (DM)). Non-freeze-dried raspberry muffins had the highest antioxidant capacity (0.041 µmol Trolox equivalent g(-1) DM). Freeze-dried raspberry batters mixed for 5 and 10 min had the highest anthocyanin content (0.065 mg cyanidin-3-glucoside g(-1) DM). Baking reduced the anthocyanin content of both non-freeze-dried and freeze-dried raspberry muffins. CONCLUSION Despite the reduction in valuable compounds, muffin is a vehicle for the delivery of these compounds.

Thermal properties of aloe vera powder and rheology of reconstituted gels.

Aloe vera (Aloe barbadensis L.) is a plant from the lily family that possesses therapeutic and antioxidant properties. Extracts from aloe vera leaves are widely used in skin care products, and recently in health drinks and supplements. Substandard aloe products arising from poor processing methods or adulteration with other compounds is a major problem for the aloe industry. Functional properties of aloe vera may be affected by processing procedures that involve heat or shearing action. In this study, aloe vera extract was dried using spray drying (SD), freeze drying (FD), and Refractance Window (RW) drying methods to investigate the effect of those methods on glass transition temperature (Tg), total carbohydrates, reducing groups, particle size distribution, and viscosity of solutions formed after reconstitution with deionized water. The Tg of SD aloe was in the range of 65°C ±3.2°C compared to 70°C to 78°C for the latter two drying methods. Addition of corn maltodextrin contributed to shifts in Tg of aloe powder. Solutions prepared from spray-dried aloe had the lowest viscosity, while freeze-dried and RW-dried counterparts had higher and nearly equal consistency. The activation energy for network formation of solutions reconstituted from SD powder was 23.9 ±0.1 kJ mol-1, which was slightly lower than the 24.6 ±0.3 and 24.7 ±0.4 kJ mol-1 obtained with FD and RW drying, respectively.