Joan M. King

Using Ozonation and Amino Acids to Change Pasting Properties of Rice Starch

In this study, the effects of ozonation and the addition of amino acids on rice starches were determined in terms of pasting properties using a rapid visco-analyzer. Results from viscosity analysis showed that 30-min ozone treatment on commercial rice starch exhibited the greatest swelling extent among the treatments and least retrogradation tendency. The control pure oxygen treated sample had the best cooking stability. The addition of lysine (6%) to 30-min ozonated commercial rice starch significantly reduced peak viscosity (PV), minimum viscosity (MV), and final viscosity (FV) by 918, 1024, and 1023 cP, respectively. Moreover, it decreased Ptime, resulting in the faster swelling upon heating and less rigid gel formation upon cooling. Furthermore, the presence of lysine in 30-min ozonated starch isolate (WSI) also significantly reduced PV, MV, FV, pasting time, and total setback (TSB) and produced starch gel with the best cooking stability and the least retrogradation tendency. Ozonated starch exhibited similar pasting properties to those from oxidized starches treated with low concentrations of chemical oxidizing agents. The combination of lysine with ozonation resulted in pasting properties similar to starches treated with high levels of chemical oxidizing agents. The ozonated starch could be used as a thickening agent, whereas ozonated starch with lysine might be an alternative for a highly chemically oxidized starch. Therefore, ozonation alone or the combination of ozonation and addition of lysine might be used to develop new starch ingredients with various functionalities without using typical chemical modifications.

Effect of preservatives on microbial safety and quality of smoked blue catfish (Ictalurus furcatus) steaks during room-temperature storage

The microbial safety and quality of smoked blue catfish (Ictalurus furcatus) steaks treated with antimicrobials and antioxidants were examined during 6-week ambient storage. Five pre-smoking soaking treatments were applied: 25% NaCl and 1% ascorbic acid for 30 min or 1h, 3% sodium lactate with or without 5% rosemary extract for 30 min, and 5% sorbic acid alone for 30 min. After smoking, cooled catfish steaks were packed and analyzed at 0, 2, 4, and 6 weeks of ambient storage. Neither Listeria nor Salmonella was recovered from the smoked catfish steaks. Significant reductions (P<0.05) in total plate counts were observed in all treated samples, with those treated with 3% sodium lactate carrying the lowest microbial load. The rosemary extract-treated samples were the most stable against oxidation. All treated smoked catfish steaks had water activities less than 0.85; however, neither pH nor water activity changed significantly within each treatment group during storage (P> or 0.05). In conclusion, smoking/cooking effectively reduced microbial populations, and the use of antimicrobial agents and antioxidants, particularly 3% sodium lactate, could aid the control of microbial safety during storage, resulting in safe products for up to 6 weeks without refrigeration.

Comparison of the activities of hydrophilic anthocyanins and lipophilic tocols in black rice bran against lipid oxidation.

The antioxidant capabilities of anthocyanin and tocol extracts from black rice bran were evaluated using an emulsion system containing either cholesterol (1.0mg/ml) or fish oil (10mg/ml). The cholesterol oxidation product, 7-ketocholesterol, increased to 180.1 μg/ml in the control emulsion after 168 h of oxidation, while it was only 15.4 and 39.0 μg/ml in the emulsions containing 1 μg/ml of the anthocyanin and tocol extracts, respectively; but below 1.2 μg/ml in the emulsion having 5 μg/ml of anthocyanins or tocols. In the fish oil emulsion, over 80% of C20:5 and C22:6 were oxidised after a 48 h incubation at 37°C, while they were retained above 38% and 65% in the emulsions containing 10 μg/ml of anthocyanins and tocols, respectively, and above 85% in the emulsion containing 20 μg/ml of anthocyanins or tocols. Compared with the tocols extract, the capability of the anthocyanin extract was relatively greater in stabilising cholesterol but lower in inhibiting fatty acids oxidation.

Resistant Starch, Fermented Resistant Starch, and Short-Chain Fatty Acids Reduce Intestinal Fat Deposition in Caenorhabditis elegans

Obesity is a growing global public health dilemma. The objective of this project is to develop and validate a screening mechanism for bioactive compounds that may reduce body fat and promote health. Resistant starch (RS) reduces body fat in rodents. Amylose starch that has a high content of RS, endogenous compounds obtained from the ceca of amylose starch fed mice (fermented RS), and individual short-chain fatty acids (SCFA) were tested. The Caenorhabditis elegans model and Nile red staining were selected to determine the intestinal fat deposition response to bioactive components. The fluorescence intensity of Nile red was reduced to 76.5% (amylose starch), 78.8% (fermented RS), 63.6% (butyrate), or 28-80% (SCFAs) of controls, respectively (P < 0.001). The reduced intestinal fat deposition suggests reduced food intake or increased energy expenditure. C. elegans is a practical animal model to screen for bioactive compounds that may prevent or treat obesity.

Altering Pasting Characteristics of Sweet Potato Starches through Amino Acid Additives

This study assessed the effects of amino acid additives, aspartic acid, leucine, lysine, and methionine, on the pasting and thermal characteristics of white- and orange-fleshed Beauregard sweet potato starches. A rapid visco analyzer 3D was used to determine pasting properties. In comparing pasting characteristics, starch from orange-fleshed sweet potato was found to be easier to cook, had a lower potential for retrogradation, and was less stable during heating than the white-fleshed sweet potato starch. The RVA analysis showed that the charged amino acids, aspartic acid and lysine, altered pasting characteristics of the 2 starches more than the neutral amino acids, leucine and methionine. Aspartic acid had similar effects on both starches, making them less stable during cooking and lowering the potential for retrogradation. Lysine, when added to the orange-fleshed sweet potato starch, decreased the breakdown, allowing for more stability during cooking. This study showed that pasting properties of sweet potato starches can be altered by the addition of amino acids.

Evaluation of green tea extract as a glazing material for shrimp frozen by cryogenic freezing.

Solutions of green tea (Camellia sinensis) extract (GTE) in distilled water were evaluated as a glazing material for shrimp frozen by cryogenic freezing. Total of 2%, 3%, and/or 5% GTE solutions (2GTE, 3GTE, 5GTE) were used for glazing. Distilled water glazed (GDW) and nonglazed shrimp (NG) served as controls. The GTE was characterized by measuring color, pH, (o) Brix, total phenols, and % antiradical activity. Individual catechins were identified by HPLC. The freezing time, freezing rate, and energy removal rate for freezing shrimp by cryogenic freezing process were estimated. The frozen shrimp samples were stored in a freezer at -21 °C for 180 d. Samples were analyzed for pH, moisture content, glazing yield, thaw yield, color, cutting force, and thiobarbituric acid reactive substances (TBARS) after 1, 30, 90, and 180 d. The HPLC analysis of GTE revealed the presence of catechins and their isomers and the total polyphenol content was 148.10 ± 2.49 g/L. The freezing time (min) and energy removal rate (J/s) were 48.67 ± 2.3 and 836.67 ± 78.95, respectively. Glazed samples had higher moisture content compared to NG shrimp after 180 d storage. GTE was effective in controlling the lipid oxidation in shrimp. Glazing with GTE affected a* and b* color values, but had no significant effect on the L* values of shrimp.

Comparisons of Chemical and Physical Properties of Catfish Oils Prepared from Different Extracting Processes

Four different catfish oil extraction processes were used to extract oil from catfish viscera: process CF1 involved a mixture of ground catfish viscera and water, no heat treatment, and centrifugation; process CF2 involved ground catfish viscera (no added water), heat treatment, and centrifugation; process CF3 involved a mixture of ground catfish viscera and water, heat treatment, and centrifugation; process CF4 involved ground catfish viscera, enzymatic hydrolysis, and centrifugation. Chemical and physical properties of the resulting of catfish oils were evaluated. The CF4 process recovered significantly higher amounts of crude oil from catfish viscera than the other 3 extraction methods. The CF4 oil contained a higher percent of free fatty acid and peroxide values than CF1, CF2, and CF3 oils. Oleic acid in catfish oil was the predominant fatty acid accounting for about 50% of total fatty acids. Weight loss of oils increased with increasing temperatures between 250 and 500 degrees C. All the catfish oil samples melted around -32 degrees C regardless of the extraction methods. The flow behavior index of all the oil samples was less than 1, which indicated that the catfish oils exhibited non-Newtonian fluid behavior. The apparent viscosity at -5 and 0 degrees C was significantly higher (P < 0.05) than those at 5, 10, 15, 20, 25, and 30 degrees C. The average magnitude of activation energy for apparent viscosity of the oil was higher for CF2 than CF1, CF3, and CF4.

Antibacterial Activity of Ozone‐Depolymerized Crawfish Chitosan

Antimicrobial activities of chitosan samples with different molecular weights (1333, 432, 201, 131, and 104 kDa) prepared by ozone treatment were examined against 2 Gram-positive bacteria (Listeria monocytogenes and Staphylococcus aureus) and 2 Gram-negative bacteria (Escherichia coli and Pseudomonas fluorescen) to investigate the effect of chitosans molecular weight and concentration on the inhibition of bacterial growth. Antimicrobial activity of chitosan varied depending on the molecular weight, concentration of chitosan, and type of microorganism. Generally, the effectiveness of the chitosans significantly increased with increasing chitosan concentration, regardless of molecular size and types of bacteria. Chitosan with molecular weights ranging from 104 to 201 kDa showed relatively greater antimicrobial activity against L. monocytogenes, S. aureus, and P. fluorescen; whereas for E. coli, intermediate molecular weight chitosan was more effective in growth inhibition than lower or higher molecular weight chitosan particularly at 0.1% concentration.

Comparison of soybean oils, gum, and defatted soy flour extract in stabilizing menhaden oil during heating.

Capabilities of crude soy oil, degummed oil, gum, and defatted soy flour extract in preventing the oxidation of menhaden oil and its omega-3 fatty acids, DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid), during heating were evaluated. The menhaden oil mixed with defatted soy flour extract demonstrated the greatest stability by producing the lowest TBA reactive oxidation products and retaining the highest concentrations of DHA and EPA after heating at 150 degrees C for 30 min. A range of 62.8% to 71.5% of DHA and 67.7% to 75.9% of EPA remained in the fish oil with defatted soy flour extract, while only 29.9% of DHA and 37.2% of EPA were retained in the fish oil with no addition. Stabilizing capability from highest to lowest was defatted flour extract > gum > degummed oil = crude oil. The defatted flour extract had the highest level of total phenolic content (11.3 microg catechin equivalent/g), while crude oil, degummed oil, and gum contained 7.1, 6.1, and 6.0 microg catechin equivalent/g, respectively. The level of isoflavones in the defatted soy flour extract was 55 mg/g, which was over 100 times higher than in the crude oil or gum. Although isoflavones were not detected in the degummed oil, it contained the highest level of tocopherols (414 mug/g), whereas the lowest level (215 microg/g) was found in the defatted flour extract. The order of free radical scavenging capability measured from high to low was the defatted soy flour extract, crude oil, degummed oil, and gum.

Selected quality characteristics of fresh-cut sweet potatoes coated with chitosan during 17-day refrigerated storage.

Selected quality characteristics of fresh-cut sweet potatoes (FCSP) coated with chitosan were evaluated during 17-d refrigerated storage. The FCSP cubes were coated with a solution (1%, w/v) of chitosan having 470 or 1110 kDa. Color (L*, a*, b*) values of uncoated and chitosan-coated FCSP during storage were generally affected by storage time as well as coating treatments (P < 0.05). No significant changes in color lightness (L*) of 470 kDa-coated FCSP were observed during the 17-d storage. During days 3 to 17, 470 kDa-coated FCSP had significantly higher redness (a*) and yellowness (b*) values than did uncoated and 1110 kDa-coated FCSP. Texture firmness of uncoated and chitosan-coated FCSP exhibited minimal changes during the 17-d storage. Although actual weight loss values (%) of uncoated and chitosan-coated FCSP were not significantly different at day 17, the weight loss difference (%) between day 3 and day 17 for uncoated FCSP (3.02%) was slightly higher compared to those (2.24% to 2.26%) of chitosan-coated FCSP. The initial total aerobic count was 4.7 log(10) CFU/g which then gradually increased to 8.54 and 9.67 log(10) CFU/g after 17 d of storage for 470 kDa-coated and uncoated FCSP, respectively. After day 6, the total aerobic counts of uncoated FCSP were higher than those of 470 kDa-coated FCSP. The yeast and mold count of chitosan-coated FCSP was about 2.5 log(10) CFU/g at day 17. Overall, consumers could not differentiate between 470 kDa-coated FCSP at day 17 and uncoated FCSP at day 0.