Showing papers in "Journal of Food Science in 2007"

Food packaging--roles, materials, and environmental issues.

Abstract: The Institute of Food Technologists has issued this Scientific Status Summary to update readers on food packaging and its impact on the environment.

Chemistry of deep-fat frying oils

Abstract: Deep-fat frying produces desirable or undesirable flavor compounds and changes the flavor stability and quality of the oil by hydrolysis, oxidation, and polymerization. Tocopherols, essential amino acids, and fatty acids in foods are degraded during deep-fat frying. The reactions in deep-fat frying depend on factors such as replenishment of fresh oil, frying conditions, original quality of frying oil, food materials, type of fryer, antioxidants, and oxygen concentration. High frying temperature, the number of fryings, the contents of free fatty acids, polyvalent metals, and unsaturated fatty acids of oil decrease the oxidative stability and flavor quality of oil. Antioxidant decreases the frying oil oxidation, but the effectiveness of antioxidant decreases with high frying temperature. Lignan compounds in sesame oil are effective antioxidants in deep-fat frying.

Emulsion-based delivery systems for lipophilic bioactive components.

Abstract: There is a pressing need for edible delivery systems to encapsulate, protect, and release bioactive lipids within the food, medical, and pharmaceutical industries. The fact that these delivery systems must be edible puts constraints on the type of ingredients and processing operations that can be used to create them. Emulsion technology is particularly suited for the design and fabrication of delivery systems for encapsulating bioactive lipids. This review provides a brief overview of the major bioactive lipids that need to be delivered within the food industry (for example, ω-3 fatty acids, carotenoids, and phytosterols), highlighting the main challenges to their current incorporation into foods. We then provide an overview of a number of emulsion-based technologies that could be used as edible delivery systems by the food and other industries, including conventional emulsions, multiple emulsions, multilayer emulsions, solid lipid particles, and filled hydrogel particles. Each of these delivery systems could be produced from food-grade (GRAS) ingredients (for example, lipids, proteins, polysaccharides, surfactants, and minerals) using simple processing operations (for example, mixing, homogenizing, and thermal processing). For each type of delivery system, we describe its structure, preparation, advantages, limitations, and potential applications. This knowledge can be used to facilitate the selection of the most appropriate emulsion-based delivery system for specific applications.

A Comparative Study on Phenolic Profiles and Antioxidant Activities of Legumes as Affected by Extraction Solvents

Abstract: The objective of this study was to investigate how 6 commonly used solvent systems affected the yields of phenolic substances and the antioxidant capacity of extracts from 8 major classes of food legumes. Several antioxidant-related phytochemical compositions, namely, total phenolic content (TPC), total flavonoids content (TFC), and condensed tannins content (CTC), were investigated. In addition, antioxidant activities were tested using 2,2-diphenyl-1-picryhydrazyl (DPPH) free radical scavenging, ferric-reducing antioxidant power (FRAP), and the oxygen radical absorbance capacity (ORAC). The results showed that the 50% acetone extracts exhibited the highest TPC for yellow pea, green pea, chickpea, and yellow soybean. Acidic 70% acetone (+0.5% acetic acid) extracts exhibited the highest TPC, TFC, and FRAP values for black bean, lentil, black soybean, and red kidney bean. The 80% acetone extracts exhibited the highest TFC, CTC, and DPPH-free radical scavenging activity for yellow pea, green pea, chickpea, and yellow soybean. The 70% ethanol extracts exhibited the greatest ORAC value for all selected legumes. These results indicated that solvents with different polarity had significant effects on total phenolic contents, extracted components, and antioxidant activities. High correlations between phenolic compositions and antioxidant activities of legume extracts were observed. The information is of interest to the nutraceutical food/ingredient industries since legumes are a rich source of antioxidants.

Food microstructure affects the bioavailability of several nutrients.

Abstract: There is an increased interest in the role that some nutrients may play in preventing or ameliorating the effect of major diseases (for example, some types of cancer, cardiovascular diseases, eye disorders, among others). In this respect, the bioavailability or the proportion of an ingested nutrient that is made available (that is, delivered to the bloodstream) for its intended mode of action is more relevant than the total amount present in the original food. Disruption of the natural matrix or the microstructure created during processing may influence the release, transformation, and subsequent absorption of some nutrients in the digestive tract. Alternatively, extracts of bioactive molecules (for example, nutraceuticals) and beneficial microorganisms may be protected during their transit in the digestive system to the absorption sites by encapsulation in designed matrices. This review summarizes relevant in vivo and in vitro methods used to assess the bioavailability of some nutrients (mostly phytochemicals), types of microstructural changes imparted by processing and during food ingestion that are relevant in matrix-nutrient interactions, and their effect on the bioavailability of selected nutrients.

Applications of Chitosan for Improvement of Quality and Shelf Life of Foods: A Review

Abstract: Chitosan is a modified, natural biopolymer derived by deacetylation of chitin, a major component of the shells of crustacean. Recently, chitosan has received increased attention for its commercial applications in the biomedical, food, and chemical industries. Use of chitosan in food industry is readily seen due to its several distinctive biological activities and functional properties. The antimicrobial activity and film-forming property of chitosan make it a potential source of food preservative or coating material of natural origin. This review focuses on the applications of chitosan for improvement of quality and shelf life of various foods from agriculture, poultry, and seafood origin.

Yerba Mate Tea (Ilex paraguariensis): A Comprehensive Review on Chemistry, Health Implications, and Technological Considerations

Abstract: Yerba Mate tea, an infusion made from the leaves of the tree Ilex paraguariensis, is a widely consumed nonalcoholic beverage in South America which is gaining rapid introduction into the world market, either as tea itself or as ingredient in formulated foods or dietary supplements. The indigenous people have used it for centuries as a social and medicinal beverage. Yerba Mate has been shown to be hypocholesterolemic, hepatoprotective, central nervous system stimulant, diuretic, and to benefit the cardiovascular system. It has also been suggested for obesity management. Yerba Mate protects DNA from oxidation and in vitro low-density lipoprotein lipoperoxidation and has a high antioxidant capacity. It has also been reported that Yerba Mate tea is associated to both the prevention and the cause of some types of cancers. Yerba Mate has gained public attention outside of South America, namely the United States and Europe, and research on this tea has been expanding. This review presents the usage, chemistry, biological activities, health effects, and some technological considerations for processing of Yerba Mate tea. Furthermore, it assesses in a concise and comprehensive way the potential of Ilex paraguariensis as a source of biological compounds for the nutraceutical industry.

Comparative analyses of phenolic composition, antioxidant capacity, and color of cool season legumes and other selected food legumes.

Abstract: The objective of this study was to characterize the phenolic compounds and antioxidant activities of U.S.-produced cool season legumes. A total of 33 cool season legume samples were selected. Some common beans and soybeans were included for comparisons. Total phenolic content (TPC), total flavonoid content (TFC), and condensed tannin content (CTC) were analyzed. Ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, and oxygen radical absorbance capacity (ORAC) were used for analyzing antioxidant properties. Color of the legume flour and the seed coat was also analyzed. TPC, TFC, CTC, FRAP, DPPH, and ORAC values of legumes were significantly different not only between classes but also among samples within each class. Among cool season legume classes, lentils possessed the highest concentrations of the phenolic compounds and antioxidant activities. Colored common beans and black soybeans exhibited higher TPC, TFC, CTC, FRAP, DPPH, and ORAC values than those of yellow peas, green peas, and chickpeas. Antioxidant activities (FRAP, DPPH, and ORAC) were strongly correlated (r= 0.96, 0.94, and 0.89, respectively, P < 0.01) with TPC. TPC and ORAC were moderately correlated (P < 0.01) with either the seed hull surface color or the flour color.

Multifaceted therapeutic benefits of Ginkgo biloba L.: chemistry, efficacy, safety, and uses.

Abstract: The new age of nutraceuticals is now embracing the centuries old herbal extract of Ginkgo biloba (Mantissa Plantarum Altera, 1771, Ginkgoceae) The standardized preparation of the Ginkgo leaf extract (EGb 761) contained 2 main bioactive constituents, flavonoid glycosides (24%) and terpene lactones (6%), along with less than 5 ppm of the allergenic component, ginkgolic acid The Ginkgo leaf extract has been reported to have neuroprotective, anticancer, cardioprotective, stress alleviating, and memory enhancing effects and possible effects on tinnitus, geriatric complaints, and psychiatric disorders The therapeutic mechanisms of action of the Ginkgo leaf extract are suggested to be through its antioxidant, antiplatelet, antihypoxic, antiedemic, hemorrheologic, and microcirculatory actions, where the flavonoid and the terpenoid constituents may act in a complementary manner Toxicity studies show that the Ginkgo leaf extract is relatively safe for consumption, although a few side effects have been reported, that is, intracerebral hemorrhage, gastrointestinal disturbances, headaches, dizziness, and allergic skin reactions The use of Ginkgo leaf extract may be promising for treatment of certain conditions, although its long-term use still needs to be evaluated

Acid, Bile, and Heat Tolerance of Free and Microencapsulated Probiotic Bacteria

Abstract: Eight strains of probiotic bacteria, including Lactobacillus rhamnosus, Bifidobacterium longum, L. salivarius, L. plantarum, L. acidophilus, L. paracasei, B. lactis type Bl-O4, and B. lactis type Bi-07, were studied for their acid, bile, and heat tolerance. Microencapsulation in alginate matrix was used to enhance survival of the bacteria in acid and bile as well as a brief exposure to heat. Free probiotic organisms were used as a control. The acid tolerance of probiotic organisms was tested using HCl in MRS broth over a 2-h incubation period. Bile tolerance was tested using 2 types of bile salts, oxgall and taurocholic acid, over an 8-h incubation period. Heat tolerance was tested by exposing the probiotic organisms to 65 degrees C for up to 1 h. Results indicated microencapsulated probiotic bacteria survived better (P < 0.05) than free probiotic bacteria in MRS containing HCl. When free probiotic bacteria were exposed to oxgall, viability was reduced by 6.51-log CFU/mL, whereas only 3.36-log CFU/mL was lost in microencapsulated strains. At 30 min of heat treatment, microencapsulated probiotic bacteria survived with an average loss of only 4.17-log CFU/mL, compared to 6.74-log CFU/mL loss with free probiotic bacteria. However, after 1 h of heating both free and microencapsulated probiotic strains showed similar losses in viability. Overall microencapsulation improved the survival of probiotic bacteria when exposed to acidic conditions, bile salts, and mild heat treatment.

Antioxidant activities of different colored sweet bell peppers (Capsicum annuum L.).

Abstract: Antioxidant compounds and their antioxidant activity in 4 different colored (green, yellow, orange, and red) sweet bell peppers (Capsicum annuum L.) were investigated. The total phenolics content of green, yellow, orange, and red peppers determined by the Folin-Ciocalteau method were 2.4, 3.3, 3.4, and 4.2 micromol catechin equivalent/g fresh weight, respectively. The red pepper had significantly higher total phenolics content than the green pepper. Among the 4 different colored peppers, red pepper contained a higher level of beta-carotene (5.4 microg/g), capsanthin (8.0 microg/g), quercetin (34.0 microg/g), and luteolin (11.0 microg/g). The yellow pepper had the lowest beta-carotene content (0.2 microg/g), while the green one had undetectable capsanthin and the lowest content of luteolin (2.0 microg/g). The free radical scavenging abilities of peppers determined by the 2,2'-diphenyl-1-picrylhydrazyl (DPPH) method were lowest for the green pepper (2.1 micromol Trolox equivalent/g) but not significantly different from the other 3 peppers. All 4 colored peppers exhibited significant abilities in preventing the oxidation of cholesterol or docosahexaenoic acid (DHA) (C22:6) during heating. However, these 4 peppers did not show significant differences in their abilities in preventing cholesterol oxidation. The green pepper showed slightly higher capability in preventing the oxidation of DHA compared to the other 3 peppers.

Antibacterial Activity Directed Isolation of Compounds from Punica granatum

Abstract: Chemical investigation of the methanolic extract of pomegranate fruit following antibacterial activity directed isolation led to the isolation of pelargonidin-3-galactose, cyanidin-3-glucose, gallic acid, quercetin, and myricetin. All these compounds exhibited substantial activity against species of corynebacteria, staphylococci, streptococci, Bacillus subtilis, Shigella, Salmonella, Vibrio cholera, and Escherichia coli. However, all these compounds were more active against Gram-positive species. On comparing the activity of all the isolated pure compounds, it was found that gallic acid showed the highest antibacterial activity against all the tested sensitive strains and the activity of the remaining pure compounds was almost same due to the structural similarities of the compounds. The reason for antibacterial activity of all pure compounds was attributed to their phenolic structure.

Inactivation of Escherichia coli on almonds using nonthermal plasma.

Abstract: This study was carried out to investigate the applicability of nonthermal plasma (NTP) technology for the pasteurization of almonds. Almonds were spiked with various levels of Escherichia coli by dipping the almonds in E. coli culture broth followed by drying. The spiked almonds were treated with NTP under different treatment conditions. The pattern of the microorganisms reduction by NTP was analyzed. NTP was found to be effective on reduction of E. coli on almond evidenced by almost 5-log reduction after 30-sec treatment at 30 kV and 2000 Hz. The NTP bactericidal effect on E. coli inoculated on almond increased with the applied voltage and the frequency. The NTP reduction followed the 1st-order reaction kinetics, and the reduction rate constants varied with almond types and grades. The E. coli cells at logarithmic phase were more sensitive to the NTP than those at stationary and declining phases.

Antibacterial activity and mechanical properties of partially hydrolyzed sago starch-alginate edible film containing lemongrass oil

Abstract: Edible films were prepared from a mixture of partially hydrolyzed sago starch and alginate (SA). Lemongrass oil (0.1% to 0.4%, v/w) and glycerol (0% and 20%, w/w) were incorporated in the films to act as natural antimicrobial agent and plasticizer, respectively. The films were characterized for antimicrobial activity, water vapor permeability (WVP), tensile strength (TS), percent elongation at break (%E), and water solubility (WS). Fourier transform infrared (FTIR) spectroscopy was conducted to determine functional group interactions between the matrix and lemongrass oil. The zone of inhibition was increased significantly (P 0.05) difference in percent elongation. The percent elongation at break and WVP values for film with 20% glycerol was found to be increased significantly (P < 0.05) with an increase in lemongrass oil content. Addition of lemongrass oil did not have any interaction with the functional groups of films as measured by FTIR.

Wheat gluten: high molecular weight glutenin subunits--structure, genetics, and relation to dough elasticity.

Abstract: Gluten proteins, representing the major protein fraction of the starchy endosperm, are predominantly responsible for the unique position of wheat amongst cereals. These form a continuous proteinaceous matrix in the cells of the mature dry grain and form a continuous viscoelastic network during the mixing process of dough development. These viscoelastic properties underline the utilization of wheat to prepare bread and other wheat flour based foodstuffs. One group of gluten proteins is glutenin, which consists of high molecular weight (HMW) and low molecular weight (LMW) subunits. The HMW glutenin subunits (HMW-GS) are particularly important for determining dough elasticity. The common wheat possesses 3 to 5 HMW subunits encoded at the Glu-1 loci on the long arms of group 1 chromosomes (1A, 1B, and 1D). The presence of certain HMW subunits is positively correlated with good bread-making quality. Glutamine-rich repetitive sequences that comprise the central part of the HMW subunits are actually responsible for the elastic properties due to extensive arrays of interchain hydrogen bonds. Genetic engineering can be used to manipulate the amount and composition of the HMW subunits, leading to either increased dough strength or more drastic changes in gluten structure and properties.

Alginate- and gellan-based edible films for probiotic coatings on fresh-cut fruits.

Abstract: Alginate- (2% w/v) or gellan-based (0.5%) edible films, containing glycerol (0.6% to 2.0%), N-acetylcysteine (1%), and/or ascorbic acid (1%) and citric acid (1%), were formulated and used to coat fresh-cut apple and papaya cylinders. Water vapor permeability (WVP) was significantly higher (P 10(6) CFU/g B. lactis Bb-12 were maintained for 10 d during refrigerated storage of fresh-cut fruits, demonstrating the feasibility of alginate- and gellan-based edible coatings to carry and support viable probiotics on fresh-cut fruit.

Improving antioxidant capacity of fresh-cut mangoes treated with UV-C.

Abstract: The effect of UV-C irradiation time on total phenol, flavonoids, beta-carotene, ascorbic acid contents, and antioxidant capacity (ORAC, DPPH(*)) of fresh-cut "Tommy Atkins" mango stored for 15 d at 5 degrees C was investigated. Fresh-cut mango was irradiated for 0, 1, 3, 5, and 10 min prior to storage at 5 degrees C. UV-C irradiation for 10 min induced a hypersensitive defense response resulting in the phenols and flavonoids accumulation which was positively correlated with ORAC and DPPH(*) values. However, beta-carotene and ascorbic acid content of fresh-cut mangos decreased with irradiation time during storage. Antioxidant capacity (ORAC, DPPH(*)) was increased in fresh-cut mangoes treated with UV-C irradiation. In conclusion, UV-C irradiation appears to be a good technique to improve the total antioxidant capacity of fresh-cut mango.

The Rheology of Colloidal and Noncolloidal Food Dispersions

Abstract: Rheological data on a food together with data on its composition and structure or microstructure should lead to understanding the interrelationships between them A number of foods are dispersions of solids in liquids, liquids in liquids, or gas in liquids The dispersed particles may be colloidal in nature with dimensions 10 µm) For both colloidal and noncolloidal dispersions (either in dilute or concen- trated regimes), several theoretical equations exist that provide insights into the role of key rheological parameters, such as particle volume fraction and size, interparticle forces, and fractal dimension on their viscosity, yield stress, and modulus When theoretical models cannot be easily applied to foods with complex structures, structural analysis and structure-based models provide insight into the role of solids loading and interparticle bonding on rheological behavior In this review, recent studies on colloidal and noncolloidal food dispersions in which theoretical models as well as structural analysis were employed are discussed

Consumer liking of refined and whole wheat breads.

Abstract: Preference for refined bread is often cited as a reason for the relatively low consumption of whole wheat bread; only a few studies, however, have examined consumer preferences between refined and whole wheat breads, and the results of these studies are inconclusive. Our objective was to determine if refined wheat bread is preferred to whole wheat bread. We hypothesized that people would prefer refined wheat bread. We conducted a taste test with 89 people. They rated their liking of 9 different breads chosen to represent several comparisons between equivalent refined and whole wheat breads. The participants also rated the intensity of 6-n-propylthiouracil (PROP) and completed a questionnaire about their bread preferences and purchasing habits. We classified the participants by their bread preference and their PROP taster status, and then examined the liking patterns of these subgroups. People preferred refined bread to whole wheat bread when both were made using equivalent ingredients and procedures. They liked the commercial samples of refined and whole wheat breads equally well. When people were classified by their bread preference, those who preferred refined bread liked the refined bread better in all comparisons. PROP nontasters liked all refined and whole wheat breads equally. Sensory preferences are a barrier to whole wheat bread consumption, but ingredient or processing modifications can improve liking of whole wheat bread to the level of refined bread.

Inactivation of Staphylococcus aureus in milk using flow-through pulsed UV-light treatment system

Abstract: This study investigated the efficacy of pulsed UV-light for continuous-flow milk treatment for the inactivation of Staphylococcus aureus, a pathogenic microorganism frequently associated with milk safety concerns Pulsed UV light is an emerging technology, which can be used for the inactivation of this pathogen in milk in a relatively short time Pulsed UV light damages the DNA of the bacteria by forming thymine dimers that lead to bacterial death The effect of sample distance from the quartz window of the UV-light source, number of passes, and flow rate was investigated A response surface methodology was used for the design and analysis of experiments Milk was treated at 5-, 8-, or 11-cm distance from a UV-light strobe at 20, 30, or 40 mL/min flow rate and treated up to 3 times by recirculation of milk to assess the effect of the number of passes on inactivation efficiency Log10 reductions varied from 055- to 726-log10 CFU/mL Complete inactivation was obtained in 2 cases and no growth was observed following an enrichment protocol Predicted results were in agreement with the experimental data Overall, this work demonstrates that pulsed UV-light has a potential for inactivation of milk pathogens

Effect of Natural Antioxidants on Oxidative Stability of Cooked, Refrigerated Beef and Pork

Abstract: The effect of grape seed extract (GS; 0.01% and 0.02%), oleoresin rosemary (OR; 0.02%) and water-soluble oregano extract (WS; 0.02%) on oxidative and color stability of cooked beef and pork patties stored at 4 degrees C for 8 d was determined. Fresh beef or pork lean and trim were ground, mixed (30% fat), and divided into 5 portions. Antioxidants mixed with salt (2%) were added. Patties were formed, cooked to an internal temperature of 71 degrees C, overwrapped in PVC, and stored at 4 degrees C. Lipid oxidation, assessed using thiobarbituric acid reactive substances (TBARS) and sensory evaluation, instrumental and visual color, and pH were determined after 0, 2, 4, 6, and 8 d. Based on TBARS values and off-odors associated with lipid oxidation such as rancidity, wet cardboard (for beef patties), and grassy (for beef and pork patties), grape seed extract resulted in the best antioxidant activity in both meat species. It did not change instrumental color measures of redness, yellowness, or color intensity, and appeared to reduce visual green discoloration in beef patties. The higher GS concentration (0.02%) exhibited more antioxidant activity than the lower concentration (0.01%). Therefore, grape seed extract at 0.02% has the potential to reduce oxidative rancidity and improve shelf life of refrigerated cooked beef and pork patties.

Quantification of selected aroma-active compounds in strawberries by headspace solid-phase microextraction gas chromatography and correlation with sensory descriptive analysis.

Abstract: Selected aroma-active compounds in strawberries were quantified using headspace solid-phase microextraction and gas chromatography. Ten strawberry cultivars grown in California and Oregon were studied. The standard curves were built in a synthetic matrix and quantification was achieved using multiple internal standards. Odor activity values (OAVs) of the aroma compounds were calculated to understand their contribution to the overall aroma. Although the concentrations of the aroma compounds varied depending on the cultivars, in general, ethyl butanoate, mesifurane, ethyl hexanoate, ethyl 3-methylbutanoate, hexyl acetate, and gamma-dodecalactone had the highest OAVs. Descriptive sensory analysis was performed by a trained panel of 10 members. A PCA plot was built to understand the aroma contribution of principal components. The chemical results were compared with sensory data. The OAV of esters correlated well with the floral, pineapple, and banana notes. The green notes did not correlate with the concentration or OAVs of aldehydes or C6 alcohols. It is assumed that the higher amounts of green, sulfur, musty, and waxy notes in some cultivars were due to the lack of fruity notes.

The long-term effects of feeding honey compared with sucrose and a sugar-free diet on weight gain, lipid profiles, and DEXA measurements in rats.

Abstract: To determine whether honey and sucrose would have differential effects on weight gain during long-term feeding, 45 2-mo-old Sprague Dawley rats were fed a powdered diet that was either sugar-free or contained 7.9% sucrose or 10% honey ad libitum for 52 wk (honey is 21% water). Weight gain was assessed every 1 to 2 wk and food intake was measured every 2 mo. At the completion of the study blood samples were removed for measurement of blood sugar (HbA1c) and a fasting lipid profile. DEXA analyses were then performed to determine body composition and bone mineral densities. Overall weight gain and body fat levels were significantly higher in sucrose-fed rats and similar for those fed honey or a sugar-free diet. HbA1c levels were significantly reduced, and HDL-cholesterol significantly increased, in honey-fed compared with rats fed sucrose or a sugar free diet, but no other differences in lipid profiles were found. No differences in bone mineral density were observed between honey- and sucrose-fed rats, although it was significantly increased in honey-fed rats compared with those fed the sugar-free diet.

2‐Step Optimization of the Extraction and Subsequent Physical Properties of Channel Catfish (Ictalurus punctatus) Skin Gelatin

Abstract: To optimize the extraction of gelatin from channel catfish (Ictalurus punctatus) skin, a 2-step response surface methodology involving a central composite design was adopted for the extraction process. After screening experiments, concentration of NaOH, alkaline pretreatment time, concentration of acetic acid, and extraction temperature were selected as the independent variables. In the 1st step of the optimization the dependent variables were protein yield (YP), gel strength (GS), and viscosity (V). Seven sets of optimized conditions were selected from the 1st step for the 2nd-step screen. Texture profile analysis and the 3 dependent variables from the 1st step were used as responses in the 2nd-step optimization. After the 2nd-step optimization, the most suitable conditions were 0.20 M NaOH pretreatment for 84 min, followed by a 0.115 M acetic acid extraction at 55 degrees C. The optimal values obtained from these conditions were YP = 19.2%, GS = 252 g, and V = 3.23 cP. The gelatin obtained also showed relatively good hardness, cohesiveness, springiness, and chewiness. The yield of protein and viscosity can be predicted by a quadratic and a linear model, respectively.

Phenolic Acid Content and Composition in Leaves and Roots of Common Commercial Sweetpotato (Ipomea batatas L.) Cultivars in the United States

Abstract: Phenolic acids in commercially important sweet potato cultivars grown in the United States were analyzed using reversed-phase high-performance liquid chromatography (HPLC). Caffeic acid, chlorogenic acid, 4,5-di-O-caffeoylquinic acid, 3,5-di-O-caffeoylquinic acid, and 3,4-di-O-caffeoylquinic acid were well separated with an isocratic elution in less than 25 min compared to about 120 min for analyzing and re-equilibrating the column with a gradient method. The isocratic elution order of these caffeoylquinic acid derivatives was confirmed by LC-MS/MS. Chlorogenic acid was the highest in root tissues, while 3,5-di-O-caffeoylquinic acid and/or 4,5-di-O-caffeoylquinic acid were predominant in the leaves. Steam cooking resulted in statistically nonsignificant increases in the concentration of total phenolics and all the individual phenolic acids identified. Sweetpotato leaves had the highest phenolic acid content followed by the peel, whole root, and flesh tissues. However, there was no significant difference in the total phenolic content and antioxidant activity between purees made from the whole and peeled sweet potatoes.

Production of β-Glucosidase and Hydrolysis of Isoflavone Phytoestrogens by Lactobacillus acidophilus, Bifidobacterium lactis, and Lactobacillus casei in Soymilk

Abstract: The study determined β-glucosidase activity of commercial probiotic organisms for hydrolysis of isoflavone to aglycones in fermenting soymilk. Soymilkmade with soy protein isolate (SPI)was fermented with Lactobacillus acidophilus LAFTI� L10, Bifidobacterium lactis LAFTI� B94, and Lactobacillus casei LAFTI� L26 at 37 ◦C for 48 h and the fermented soymilkwas stored for 28 d at 4 ◦C. β-Glucosidase activity of organisms was determined using ρ-nitrophenyl β-D-glucopyranoside as a substrate and the hydrolysis of isoflavone glycosides to aglycones by these organisms was carried out. The highest level of growth occurred at 12 h for L. casei L26, 24 h for B. lactis B94, and 36 h for L. acidophilus L10 during fermentation in soymilk. Survival after storage at 4 ◦C for 28 d was 20%, 15%, and 11% greater (P < 0.05) than initial cell counts, respectively. All the bacteria produced β-glucosidase, which hydrolyzed isoflavone β-glycosides to isoflavone aglycones. The decrease in the concentration of β-glycosides and the increase in the concentration of aglyconeswere significant (P <0.05) in the fermented soymilk. Increased isoflavone aglycone content in fermented soymilk is likely to improve the biological functionality of soymilk.

Minerals, Phenolic Compounds, and Antioxidant Capacity of Citrus Peel Extract by Hot Water

Abstract: Some dried citrus peels, more familiar as chenpi in China, have been widely used in traditional Chinese medicines from ancient times. This paper reports the efficiency of infusion cooking on extracting minerals and phenolic compounds (flavanone glycosides [FGs], polymethoxylated flavones [PMFs], and phenolic acids), and also antioxidant activity of hot water extract of citrus peels. Peels of 2 citrus varieties, namely, Satsuma mandarin (C. unshiu Marc.) and Ponkan (C. poonensis Hort. ex Tanaka), which belong to C. reticulata, were selected. As a result, hot water extraction was efficient in extracting phenolic acids and some minerals. As for citrus flavonoids, narirutin, nobiletin, and tangeretin were easier to extract than hesperidin. The result of antioxidant capacity assays indicated that for citrus peels, hot water extract had almost the same capacity as the methanol extract. We suggested that Ponkan was more suitable as the source of chenpi, since its hot water extract had much higher content of phenolic acids, FGs and PMFs, and higher antioxidant capacity than those of Satsuma mandarin. Generally, to raise the extraction temperature or to prolong the time could not yield higher content of phenolic compounds and stronger antioxidant capacity, though the content of minerals increased to some extent. Furthermore, a 2nd-time extraction seemed necessary since considerable minerals and phenolic compounds could be obtained by doing so. Finally, we suggested that 2 times extraction at 100 degrees C for 30 min was proper to extract the minerals and phenolic compounds in chenpi.

Roselle (Hibiscus sabdariffa) Seed Oil Is a Rich Source of γ-Tocopherol

Abstract: The antioxidant potential of roselle (Hibiscus sabdariffa L.) extracts was studied. Different plant organs, including seeds, stems, leaves, and sepals, were analyzed with respect to their water-soluble antioxidant capacity, lipid-soluble antioxidant capacity, and tocopherol content, revealing that roselle seeds are a good source of lipid-soluble antioxidants, particularly gamma-tocopherol. Roselle seed oil was extracted and characterized, and its physicochemical parameters are summarized: acidity, 2.24%; peroxide index, 8.63 meq/kg; extinction coefficients at 232 (k(232)) and 270 nm (k(270)), 3.19 and 1.46, respectively; oxidative stability, 15.53 h; refractive index, 1.477; density, 0.92 kg/L; and viscosity, 15.9 cP. Roselle seed oil belongs to the linoleic/oleic category, its most abundant fatty acids being C18:2 (40.1%), C18:1 (28%), C16:0 (20%), C18:0 (5.3%), and C19:1 (1.7%). Sterols include beta-sitosterol (71.9%), campesterol (13.6%), Delta-5-avenasterol (5.9%), cholesterol (1.35%), and clerosterol (0.6%). Total tocopherols were detected at an average concentration of 2000 mg/kg, including alpha-tocopherol (25%), gamma-tocopherol (74.5%), and delta-tocopherol (0.5%). The global characteristics of roselle seed oil suggest that it could have important industrial applications, adding to the traditional use of roselle sepals in the elaboration of karkade tea.

Physicochemical and Bitterness Properties of Enzymatic Pea Protein Hydrolysates

Abstract: The effects of different proteolytic treatments on the physiochemical and bitterness properties of pea protein hydrolysates were investigated. A commercial pea protein isolate was digested using each of 5 different proteases to produce protein hydrolysates with varying properties. After 4 h of enzyme digestion, samples were clarified by centrifugation followed by desalting of the supernatant with a 1000 Da membrane; the retentates were then freeze-dried. Alcalase and Flavourzyme™ produced protein hydrolysates with significantly higher (P < 0.05) degree of hydrolysis when compared to the other proteases. Flavourzyme, papain, and alcalase produced hydrolysates that contained the highest levels of aromatic amino acids, while trypsin hydrolysate had the highest levels of lysine and arginine. Papain hydrolysate contained high molecular weight peptides (10 to 178 kDa) while hydrolysates from the other 4 proteases contained predominantly low molecular weight peptides (≤ 23 kDa). DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical scavenging activity of the Flavourzyme hydrolysate was significantly (P < 0.05) the highest while alcalase and trypsin hydrolysates were the lowest. Inhibition of angiotensin converting enzyme (ACE) activity was significantly higher (P < 0.05) for papain hydrolysate while Flavourzyme hydrolysate had the least inhibitory activity. Sensory analysis showed that the alcalase hydrolysate was the most bitter while papain and α-chymotrypsin hydrolysates were the least. Among the 5 enzymes used in this study, papain and α-chymotrypsin appear to be the most desirable for producing high quality pea protein hydrolysates because of the low bitterness scores combined with a high level of angiotensin converting enzyme inhibition and moderate free radical scavenging activity.

Application of atomic force microscopy as a nanotechnology tool in food science

Abstract: Atomic force microscopy (AFM) provides a method for detecting nanoscale structural information. First, this review explains the fundamentals of AFM, including principle, manipulation, and analysis. Applications of AFM are then reported in food science and technology research, including qualitative macromolecule and polymer imaging, complicated or quantitative structure analysis, molecular interaction, molecular manipulation, surface topography, and nanofood characterization. The results suggested that AFM could bring insightful knowledge on food properties, and the AFM analysis could be used to illustrate some mechanisms of property changes during processing and storage. However, the current difficulty in applying AFM to food research is lacking appropriate methodology for different food systems. Better understanding of AFM technology and developing corresponding methodology for complicated food systems would lead to a more in-depth understanding of food properties at macromolecular levels and enlarge their applications. The AFM results could greatly improve the food processing and storage technologies.