Van-Den Truong

Anthocyanin Content, Antioxidant Activity, and Selected Physical Properties of Flowable Purple-Fleshed Sweetpotato Purees

With high levels of polyphenolic compounds, purple-fleshed sweetpotatoes (PFSP) have been utilized as a healthy food commodity and source of natural food colorants in Asia. In the U.S. sweetpotato industry, there are growing interests in exploring these market opportunities for PFSP. A locally grown PFSP cultivar was analyzed for antioxidant properties. The total phenolic content ranged from 313.6 to 1483.7 mg chlorogenic acid equivalent/100 g fresh weight (fw), and anthocyanin contents were between 51.5 and 174.7 mg anthocyanins/100 g fw. The DPPH radical scavenging activities and were 47.0 to 87.4 micromol trolox equivalent (TE)/g fw, and the oxygen radical absorbance capacity (ORAC) values were between 26.4 and 78.2 micromol TE/g fw. Unlike orange-fleshed sweetpotatoes (OFSP), the steamed roots of PFSP formed a thick paste, which required a process modification to produce flowable purees. Rheological testing indicated that adjusting the dry matter of PFSP to 18%-21% produced purees with flow properties similar to the OFSP purees. The PFSP purees had polyphenolic content and antioxidant capacity within ranges reported for various purple-colored fruits and vegetables.

Effect of Type and Content of Modified Montmorillonite on the Structure and Properties of Bio-Nanocomposite Films Based on Soy Protein Isolate and Montmorillonite

The nonbiodegradable and nonrenewable nature of plastic packaging has led to a renewed interest in packaging materials based on bio-nanocomposites (biopolymer matrix reinforced with nanoparticles such as layered silicates). Bio-nanocomposite films based on soy protein isolate (SPI) and modified montmorillonite (MMT) were prepared using melt extrusion. The effect of different type (Cloisite 20A and Cloisite 30B) and content (0% to 15%) of modified MMT on the structure (degree of intercalation and exfoliation) and properties (color, mechanical, dynamic mechanical, thermal stability, and water vapor permeability) of SPI-MMT bio-nanocomposite films were investigated. Extrusion of SPI and modified MMTs resulted in bio-nanocomposites with exfoliated structures at lower MMT content (5%). At higher MMT content (15%), the structure of bio-nanocomposites ranged from intercalated for Cloisite 20A to disordered intercalated for Cloisite 30B. At an MMT content of 5%, bio-nanocomposite films based on modified MMTs (Cloisite 20A and Cloisite 30B) had better mechanical (tensile strength and percent elongation at break), dynamic mechanical (glass transition temperature and storage modulus), and water barrier properties as compared to those based on natural MMT (Cloisite Na(+)). Bio-nanocomposite films based on 10% Cloisite 30B had mechanical properties comparable to those of some of the plastics that are currently used in food packaging applications. However, much higher WVP values of these films as compared to those of existing plastics might limit the application of these films to packaging of high moisture foods such as fresh fruits and vegetables.

Phytochemical changes in phenolics, anthocyanins, ascorbic acid, and carotenoids associated with sweetpotato storage and impacts on bioactive properties

Sweetpotato phytochemical content was evaluated in four genotypes (NCPUR06-020, Covington, Yellow Covington, and NC07-847) at harvest and after curing/storage for 4 or 8 months. Curing and storage for up to 8 months did not significantly affect total phenolic content in Covington, Yellow Covington, and NC07-847, however for NCPUR06-020, a purple-fleshed selection, total phenolic content declined mainly due to anthocyanin degradation during storage. Covington had the highest carotenoid content at harvest time (281.9 μg/g DM), followed by NC07-847 (26.2 μg/g DM), and after 8 months, total carotenoids had increased by 25% and 50%, respectively. Antioxidant activity gradually declined during storage, and freshly harvested sweetpotatoes also demonstrated higher anti-inflammatory capacity as gauged by inhibition of lipopolysaccharide-induced reactive oxygen species (ROS) in SH-SY5Y cells. Gradual changes in sweetpotato phytochemical content and antioxidant and anti-inflammatory capacity were noted during normal long-term storage, but the specific effects were genotype-dependent.

Protein contents, amino acid compositions and nitrogen-to-protein conversion factors for cassava roots

Root protein contents of 15 cassava varieties (Manihot esculenta Crantz) ranged from 5 to 19 g kg -1 dry matter. Intervarietal differences in amino acid profiles of cassava roots were evident. Differences in the levels of aspartic acid, glutamic acid and arginine were most notable. The nitrogen-to-protein conversion factors (k AA ) based on nitrogen recovered from total amino acid analyses including ammonia ranged from 4.75 to 5.87, showing that the traditional conversion factor of 6.25 was not valid for cassava root proteins. Conversion factors (k p ) for 15 cassava varieties based on Kjeldahl nitrogen ranged from 2.49 to 3.67. Therefore an average k p value of 3.24 ± 0.31 may provide a better estimate of the protein content in cassava roots.

Quantitative analysis of linamarin in cassava using a cassava β-glucosidase electrode

Abstract A simple protocol was developed for the quantitative analysis of linamarin in cassava roots using a cassava β-glucosidase (linamarase) electrode. A steady state value could be obtained within 15–20 min and the limit of detection was 0.1 m m linamarin. The linamarin content of 18 cassava varieties determined by this procedure ranged from 24 to 395 mg per 100 g fr. wt. root. These values were comparable to those obtained using a spectrophotometric method. The enzyme electrode method is reliable and simple to perform. Furthermore, it does not require the use of hazardous chemicals like pyridine which is needed by the spectrophotometric procedure.

A Review of Experimental and Modeling Techniques to Determine Properties of Biopolymer‐Based Nanocomposites

The nonbiodegradable and nonrenewable nature of plastic packaging has led to a renewed interest in packaging materials based on bio-nanocomposites (biopolymer matrix reinforced with nanoparticles such as layered silicates). One of the reasons for unique properties of bio-nanocomposites is the difference in physics at nanoscale as compared to that at macroscale. Therefore, the effect of nanoscale on the properties of bio-nanocomposites is discussed. Properties of bio-nanocomposites are governed by the extent of dispersion of nanoparticles in the biopolymer matrix and interaction between nanoparticles and the biopolymer. Selection of proper technique to determine properties of these bio-nanocomposites is very critical in assessing their performance. Experimental techniques (tensile testing, barrier property measurement, dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, rheological measurement) to determine the mechanical, barrier, thermal, and rheological properties of bio-nanocomposites are discussed in terms of methodology, interpretation of results, and application in studying the properties of bio-nanocomposites. Mathematical modeling plays an important role in predicting the properties of bio-nanocomposites and comparing them to the measured properties. This comparison helps in better understanding the mechanism for much improved properties of bio-nanocomposites. Mathematical modeling is also helpful in understanding the effects of different parameters on the properties of bio-nanocomposites. Therefore, the article describes mathematical modeling of mechanical and barrier properties of bio-nanocomposites using analytical micromechanics.

Continuous flow microwave-assisted processing and aseptic packaging of purple-fleshed sweetpotato purees.

Pumpable purees from purple-flesh sweetpotatoes (PFSP) were subjected to microwave heating using a 60 kW, 915 MHz continuous flow system, followed by aseptic packaging in flexible containers to obtain a shelf-stable product. Initial test runs were conducted using a 5 kW 915 MHz microwave system to measure dielectric in-line properties and examine the puree temperature profiles. The results demonstrated uniformity in heating of the puree at sterilization temperatures (>121 degrees C), and the dielectric constants and loss factors were within the range of published values for orange-fleshed sweetpotato purees. The pilot-scale test runs in a 60 kW microwave unit produced shelf-stable puree packages stable at room temperature. Polyphenolic content of the PFSP purees were evaluated and the results showed that while total phenolics increased (5.9%) and total monomeric anthocyanins slightly decreased (14.5%) with microwave application, antioxidant activity determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and oxygen radical absorbance capacity (ORAC) assays did not significantly change as a result of microwave processing. Color values showed that microwave-processed samples differed from fresh puree in saturation and hue angle, but not in overall color change. PFSP purees increased in gel strength when microwave processed, packaged, and stored, but the gel could be easily disrupted into flowable purees. Overall, high-quality retention can be obtained by microwave processing and aseptic packaging of PFSP purees so that they can be used as functional food ingredients.

Dielectric Properties of Sweet Potato Purees at 915 MHz as Affected by Temperature and Chemical Composition

A process for rapid sterilization and aseptic packaging of sweet potato puree using a continuous flow microwave system operating at 915 MHz has been successfully developed. In microwave processing, dielectric properties have a major role in determining the interaction between purees and the electromagnetic energy. The objective of this research was to determine how dielectric properties are affected by temperature and chemical composition of purees derived from thirteen sweet potato cultivars with varying flesh colors. Results indicated that temperature, moisture, sugar and starch content had a pronounced effect (p < 0.001) on dielectric properties measured from 15°C to 145°C at 915 MHz. Dielectric constant decreased with increasing temperature, while dielectric loss factor increased quadratically. Power penetration depth of all cultivars decreased with increasing temperature. Predictive equations were developed for dielectric constant (R2 = 0.82) and dielectric loss factor (R2 = 0.90) as a function of temperature, moisture, sugar, and starch. The predictive equations would be useful in determining the dielectric properties of sweet potato purees for the microwave processing technology.

Processing treatments for mitigating acrylamide formation in sweetpotato French fries.

Acrylamide formation in sweetpotato French fries (SPFF) is likely a potential health concern as there is an increasing demand for good-quality fries from carotene-rich sweetpotatoes (SP). This is the first report on acrylamide formation in SPFF as affected by processing methods. Acrylamide levels in SPFF from untreated SP strips fried at 165 °C for 2, 3, and 5 min were 124.9, 255.5, and 452.0 ng/g fresh weight, which were reduced by about 7 times to 16.3, 36.9, and 58.3 ng/g, respectively, when the strips were subjected to processing that included water blanching and soaking in 0.5% sodium acid pyrophosphate before frying. An additional step of strip soaking in 0.4% calcium chloride solution before par-frying increased the calcium content from 0.2 to 0.8 mg/g and decreased the acrylamide levels to 6.3, 17.6, and 35.4 ng/g, respectively. SPFF with acrylamide level of <100 ng/g or several times lower than that of white potato French fries can be obtained by integrating processing treatments commonly used in the food industry.

Development and Validation of a Near-Infrared Spectroscopy Method for the Prediction of Acrylamide Content in French-Fried Potato

This study investigated the ability of near-infrared spectroscopy (NIRS) to predict acrylamide content in French-fried potato. Potato flour spiked with acrylamide (50-8000 μg/kg) was used to determine if acrylamide could be accurately predicted in a potato matrix. French fries produced with various pretreatments and cook times (n = 84) and obtained from quick-service restaurants (n = 64) were used for model development and validation. Acrylamide was quantified using gas chromatography-mass spectrometry, and reflectance spectra (400-2500 nm) of each freeze-dried sample were captured on a Foss XDS Rapid Content Analyzer-NIR spectrometer. Partial least-squares (PLS) discriminant analysis and PLS regression modeling demonstrated that NIRS could accurately detect acrylamide content as low as 50 μg/kg in the model potato matrix. Prediction errors of 135 μg/kg (R(2) = 0.98) and 255 μg/kg (R(2) = 0.93) were achieved with the best PLS models for acrylamide prediction in Russet Norkotah French-fried potato and multiple samples of unknown varieties, respectively. The findings indicate that NIRS can be used as a screening tool in potato breeding and potato processing research to reduce acrylamide in the food supply.