Kirk D. Dolan

Total phenolics, antioxidant activity, and functional properties of ‘Tommy Atkins’ mango peel and kernel as affected by drying methods

Mango processing produces significant amount of waste (peels and kernels) that can be utilized for the production of value-added ingredients for various food applications. Mango peel and kernel were dried using different techniques, such as freeze drying, hot air, vacuum and infrared. Freeze dried mango waste had higher antioxidant properties than those from other techniques. The ORAC values of peel and kernel varied from 418-776 and 1547-1819 μmol TE/g db. The solubility of freeze dried peel and kernel powder was the highest. The water and oil absorption index of mango waste powders ranged between 1.83-6.05 and 1.66-3.10, respectively. Freeze dried powders had the lowest bulk density values among different techniques tried. The cabinet dried waste powders can be potentially used in food products to enhance their nutritional and antioxidant properties.

Confidence intervals for modeling anthocyanin retention in grape pomace during nonisothermal heating.

Degradation of nutraceuticals in low- and intermediate-moisture foods heated at high temperature (>100 degrees C) is difficult to model because of the nonisothermal condition. Isothermal experiments above 100 degrees C are difficult to design because they require high pressure and small sample size in sealed containers. Therefore, a nonisothermal method was developed to estimate the thermal degradation kinetic parameter of nutraceuticals and determine the confidence intervals for the parameters and the predicted Y (concentration). Grape pomace at 42% moisture content (wb) was heated in sealed 202 x 214 steel cans in a steam retort at 126.7 degrees C for > 30 min. Can center temperature was measured by thermocouple and predicted using Comsol software. Thermal conductivity (k) and specific heat (C(p)) were estimated as quadratic functions of temperature using Comsol and nonlinear regression. The k and C(p) functions were then used to predict temperature inside the grape pomace during retorting. Similar heating experiments were run at different time-temperature treatments from 8 to 25 min for kinetic parameter estimation. Anthocyanin concentration in the grape pomace was measured using HPLC. Degradation rate constant (k(110 degrees C)) and activation energy (E(a)) were estimated using nonlinear regression. The thermophysical properties estimates at 100 degrees C were k = 0.501 W/m degrees C, Cp= 3600 J/kg and the kinetic parameters were k(110 degrees C)= 0.0607/min and E(a)= 65.32 kJ/mol. The 95% confidence intervals for the parameters and the confidence bands and prediction bands for anthocyanin retention were plotted. These methods are useful for thermal processing design for nutraceutical products.

Total phenolics, antioxidant properties and quality of fresh-cut onions (Allium cepa L.) treated with mild-heat

This study investigated the effect of mild-heat on fresh-cut onion slices by treating in hot water (50, 60, 70°C) for 1 min. Total phenolics (TP), antioxidant properties, colour, and weight loss of slices were evaluated during 4°C storage at 7-day intervals (21 days total). The 60°C heat treatment resulted in a significant increase in TP, from 44.92 to 52.32 mg GAE/100g. Except for 50 and 70°C treatments, TP in control and 60°C treated fresh-cut onions decreased during storage. The antioxidant properties of fresh-cut onions were 1.31, 0.99, and 62.49 μM TE/g using ABTS, DPPH, and ORAC assays, respectively. The mild-heat treatments did not affect ABTS and DPPH antioxidant activities and the colour of fresh-cut onions. The storage time had mixed effect on the antioxidant properties (ABTS decreased; DPPH and ORAC remained fairly stable). The 50°C samples exhibited the lowest weight loss during 21-day storage.

Parameter Estimation in Food Science

Modeling includes two distinct parts, the forward problem and the inverse problem. The forward problem-computing y(t) given known parameters-has received much attention, especially with the explosion of commercial simulation software. What is rarely made clear is that the forward results can be no better than the accuracy of the parameters. Therefore, the inverse problem-estimation of parameters given measured y(t)-is at least as important as the forward problem. However, in the food science literature there has been little attention paid to the accuracy of parameters. The purpose of this article is to summarize the state of the art of parameter estimation in food science, to review some of the common food science models used for parameter estimation (for microbial inactivation and growth, thermal properties, and kinetics), and to suggest a generic method to standardize parameter estimation, thereby making research results more useful. Scaled sensitivity coefficients are introduced and shown to be important in parameter identifiability. Sequential estimation and optimal experimental design are also reviewed as powerful parameter estimation methods that are beginning to be used in the food science literature.

Effect of Defatted Maize Germ Addition on the Functional and Textural Properties Of Wheat Flour

The objective of this study was to assess functional properties of wheat flour blends with defatted maize germ flour (DMGF), a byproduct of the corn oil industry, at 5–25% levels. The bulk density, oil, and water absorption capacities, emulsion/foaming capacity and stability, objective color, least gelation concentration, and rheological properties (apparent viscosity and dough compression) were determined in control and flour blends. With DMGF addition, bulk density and foaming capacity decreased from 0.62 g/mL to 0.55 g/mL and 33.7% to 25.7%, respectively, both at 25% level. In general, when compared to control, oil and water absorption and emulsion capacities increased significantly in flour blends with >10% DMGF. Overall, regardless of the DMGF level, complete or partial gelling was observed at ≥ 8% gelation concentration. The apparent viscosity increased with increasing DMGF levels (0–25%) in all flour blends and also at all 4 concentrations from 5% to 20%. The control flour dough had a hardness value of 7.56 N, which increased significantly to 84.6N, when the DMGF level increased to 25% in the flour blend. These results indicate that most of the functional properties of wheat flour blends improved with DMGF addition, thus DMGF has a great potential to be used in a variety of food products.

Effects of Spray Drying on Antioxidant Capacity and Anthocyanidin Content of Blueberry By‐Products

UNLABELLED The effect of spray drying on degradation of nutraceutical components in cull blueberry extract was investigated. Samples collected before and after spray drying were tested for antioxidant capacity using oxygen radical absorbance capacity (ORAC(FL) ) and total phenolics; and for individual anthocyanidins. In Study 1, four different levels of maltodextrin (blueberry solids to maltodextrin ratios of 5: 95, 10: 90, 30: 70, and 50: 50) were spray dried a pilot-scale spray dryer. There was significantly higher retention of nutraceutical components with increased levels of maltodextrin indicating a protective effect of maltodextrin on the nutraceutical components during spray drying. In Study 2, the air inlet temperature of the spray dryer was kept constant for all runs at 150 °C, with 2 different outlet temperatures of 80 and 90 °C. The degradation of nutraceutical components was not significantly different at the 2 selected outlet temperatures. ORAC(FL) reduction for blueberry samples after spray drying was 66.3% to 69.6%. After spray drying, total phenolics reduction for blueberry was 8.2% to 17.5%. Individual anthocyanidin reduction for blueberry was 50% to 70%. The experimental spray dried powders compared favorably to commercial blueberry powders. Results of the study show that use of blueberry by-products is feasible to make a value-added powder. PRACTICAL APPLICATION Results can be used by producers to estimate final nutraceutical content of spray-dried blueberry by-products.

Characterization of New Tart Cherry (Prunus cerasus L.): Selections Based on Fruit Quality, Total Anthocyanins, and Antioxidant Capacity

Tart cherries (Prunus cerasus L.) are rich in anthocyanins and possess high antioxidant activity. The objective of this study was to evaluate six Michigan tart cherry selections for different quality attributes; fruit weight, firmness, total soluble solids (TSS), titratable acidity, instrumental color parameters, total anthocyanins, and antioxidant capacity, determined as Oxygen Radical Absorbance Capacity (ORAC). Generally, significant (p < 0.01) differences were observed across tart cherry selections for fruit weight, firmness, total soluble solids, titratable acidity, and color values. As compared to 13.7°B for Montmorency (control), the TSS contents of all the tart cherry selections were significantly higher; ranging from 15.8 °B in selection 27–10(50) to 20.2°B in Erdi Jubileum. Fruit weight also showed significant differences, which were in the range of 3.95–8.17 g/fruit. In comparison to Montmorency, other tart cherry selections showed significantly higher titratable acidity (1.20–1.41% vs. 1.132%); higher anthocyanins (78.9–391.4 μg/g vs. 33.1 μg/g, as gallic acid equivalent); and higher ORAC values (up to 145.4% more). With respect to cost and better marketability, the results of this study could be useful for the cherry juice/concentrate industry.

Optimization of inverse algorithm for estimating the optical properties of biological materials using spatially-resolved diffuse reflectance

Determination of the optical properties from intact biological materials based on diffusion approximation theory is a complicated inverse problem, and it requires proper implementation of inverse algorithm, instrumentation and experiment. This article was aimed at optimizing the procedure of estimating the absorption and reduced scattering coefficients of turbid homogeneous media from spatially-resolved diffuse reflectance data. A diffusion model and the inverse algorithm were first validated by Monte Carlo simulations. Sensitivity analysis was performed to gain an insight into the relationship between the estimated parameters and the dependent variables in the inverse algorithm for improving the parameter estimation procedure. Three data transformation and the relative weighting methods were compared in the nonlinear least squares regression. It is found that the logarithm and integral data transformation and relative weighting methods greatly improve estimation accuracy with the relative errors of 10.4%, 10.7% and 11.4% for the absorption coefficient, and 6.6%, 7.0% and 7.1% for the reduced scattering coefficient, respectively. Further statistical analysis shows that the logarithm transformation and relative weighting methods give more reliable estimations of the optical parameters. To accurately estimate the optical parameters, it is important to study and quantify the characteristics and properties of the mathematical model and its inverse algorithm.

Characterization of polyphenol oxidase from blueberry (Vaccinium corymbosum L.).

Polyphenol oxidase (PPO) was extracted and characterized from high-bush blueberries. PPO showed an optimum activity at pH 6.1-6.3 and 35°C, with the enzyme showing significant activity over a wide temperature range (25-60°C). Catechol was the most readily oxidized substrate followed by 4-methylcatechol, DL-DOPA, and dopamine. Blueberry PPO showed a Km of 15mM and Vmax of 2.57 ΔA420nm/min×10-1, determined with catechol. PPO was completely inactivated in 20min at 85°C, however, after 30minat 75°C it showed about 10% residual activity. Thermal treatment at 55 and 65°C for 30min resulted in the partial inactivation of PPO. Ascorbic acid, sodium diethyldithiocarbamic acid, L-cysteine, and sodium metabisulfite were effective inhibitors of PPO at 1.0mM. Benzoic acid and cinnamic acid series inhibitors showed relatively weak inhibition of PPO (21.8-27.6%), even at as high as 2.0mM concentration.

Modeling the Effect of Temperature and Water Activity on the Thermal Resistance of Salmonella Enteritidis PT 30 in Wheat Flour

Salmonella continues to be a problem associated with low-moisture foods, particularly given enhanced thermal resistance at lower water activity (aw). However, there is a scarcity of thermal inactivation models accounting for the effect of aw. The objective of this study was to test multiple secondary models for the effect of product (wheat flour) aw on Salmonella enterica Enteritidis phage type 30 thermal resistance. A full-factorial experimental design included three temperatures (75, 80, and 85°C) and four aw values (~0.30, 0.45, 0.60, and 0.70). Prior to isothermal treatment, sample aw was achieved by equilibrating samples in a humidity-controlled conditioning chamber. Two primary models (log linear and Weibull type) and three secondary models (second-order response surface, modified Bigelow type, and combined effects) were evaluated using the corrected Akaike information criterion and root mean squared errors. Statistical analyses of the primary models favored the log-linear model. Incorporating the three secondary models into the log-linear primary model yielded root mean squared errors of 2.1, 0.78, and 0.96 log CFU/g and corrected Akaike information criterion values of 460, -145, and -19 for the response surface, modified Bigelow, and combined-effects models, respectively. The modified Bigelow-type model, which exponentially scaled both temperature and aw effects on thermal inactivation rates, predicted Salmonella lethality significantly better (P < 0.05) than did the other secondary models examined. Overall, aw is a critical factor affecting thermal inactivation of Salmonella in low-moisture products and should be appropriately included in thermal inactivation models for these types of systems.