Journal of Food Science

Published by Wiley
Online ISSN: 1750-3841
Print ISSN: 0022-1147
Paired USDA Select beef strip loins (n = 10), aged 2 d, were injected with either an alkaline-based (3.6% sodium chloride, 1% Herbalox seasoning, adjusted to pH 10 with ammonium hydroxide [approximately 0.1%, FFC grade]) or a phosphate-based (3.6% sodium chloride, 1% Herbalox seasoning, 4.5% sodium tripolyphosphate) brine. Steaks were evaluated for 19 d. Overall, phosphate-injected steaks performed better than alkaline-injected steaks with respect to cook yield, water holding capacity, lipid oxidation, color stability, tenderness, and juiciness. Phosphate-injected steaks also had less purge than alkaline-injected steaks, as confirmed by composition analysis. Phosphate-injected steaks were higher in moisture and ash content, and were nearly 2% lower in protein content. Alkaline-injected steaks had significantly lower aerobic (approximately 1 log lower) and anaerobic (approximately 2 log lower) plate counts. Final meat pH probably contributed to the differences observed between treatments. The final pH of phosphate-injected steak was 5.99 while that of alkaline-injected steak was 5.73. Further research should be conducted to determine the concentration of ammonium hydroxide needed in the alkaline-based brine to increase the final meat pH to similar levels found in the phosphate-injected steaks.
An exopolysaccharide (EPS) producing strain was isolated from Tibetan kefir grains in China, which was identified by 16S rDNA tests and designated as Streptococcus thermophilus 05-34. The high-performance liquid chromatography analysis showed that it was composed of galactose and glucose in a molar ratio of 1.0:0.8 with a molecular mass of 2.5 × 10(4) Da. EPS was further revealed to have α-d-glucose, α-d-galactose, β-d-glucose, and β-d-galactose by Fourier transform infrared spectroscopy combined with 1D (1) H nuclear magnetic resonance spectroscopy. The length of EPS ranged from 10 to 100 nm and the maximal height of lumps was 2.5 nm through atomic force micrograph analysis. Furthermore, yogurt fermented with EPS-producing S. thermophilus 05-34 exhibited lower susceptibility to whey separation, higher viscosity, and sensory scores than those made with non-EPS-producing strain in yogurt production. These results suggested that EPS-producing Streptococcus thermophilus 05-34 provided a potential application in the fermented dairy industry.
HPLC chromatogram of the quinoxaline derivatives of citrus honey. 3-DG, 3-deoxyglucosone; GO, glyoxal; MGO, methylglyoxal.
-Descriptions of the honey samples.
Principal component analysis (PCA) score plot for the honey samples (n > 1). (+) acacia; (▴) chestnut; (▪) citrus; (•) eucalyptus;honeydew; (▾) multifloral.
-Characteristics of the honey samples.
-Linearity of response and response factors (RF) for 1,2- dicarbonyl compounds by HPLC-DAD. Calibration fitting: y = ax + b a .
In this study we conducted a survey of the concentrations of the major 1,2-dicarbonyl compounds in 40 commercial honey samples from 12 different floral origins. 3-Deoxyglucosone (3-DG), glyoxal (GO), and methylglyoxal (MGO) were measured, using their corresponding quinoxaline derivatives, by high-performance liquid chromatography (HPLC). The analytical performance of the HPLC method for the analysis of 1,2-dicarbonyl compounds was evaluated in terms of linearity, limits of detection (LODs), limits of quantification (LOQs), and precision. Linearity over 2 orders of magnitude, LODs (0.01-0.04 mg/kg), and LOQs (0.03-0.12 mg/kg) were calculated. Instrumental precision, as measured by the repeatability relative standard deviation% (RSDr%), was found to be between 0.22% and 0.55%. Furthermore, the concentrations of factors GO and MGO with respect to 3-DG were also calculated for rapid quantification in honey. In honey samples, the concentrations of 3-DG ranged from 75.9 to 808.6 mg/kg and were significantly higher (up to 100-fold) than those of 5-hydroxymethylfurfural (HMF). Values for GO and MGO were 0.1-10.9 and 0.2-2.9 mg/kg, respectively. The chemical characteristics that most influenced the levels of 1,2-dicarbonyl compounds in honey were found to be pH and total phenols. This was supported by multivariate analysis used to classify different honey types with respect to their chemical characteristics. In addition, both dicarbonyls and phenols are believed to contribute to the development of the final color of honey.
Streptomyces sp Mo endo-β-1,3-glucanase was found to have hydrolyzing activity toward curdlan and released laminarioligosaccharides selectively. The molecular weight was estimated to be 36000 Da and its N-terminal amino acid sequence was VTPPDISVTN. The optimal pH was 6 and the enzyme was found to be stable from pH 5 to 8. The optimal temperature was 60 °C and the activity was stable below 50 °C. The enzyme hydrolyzed selectively curdlan containing only β-1,3 linkages. The enzyme had 89% relative activity toward Laminaria digitata laminarin, which contains a small amount of β-1,6 linkages compared with curdlan, while Eisenia bicyclis laminarin with a higher amount of β-1,6-linkages, was not hydrolyzed. Mo enzyme adsorbed completely on curdlan powder. The enzymatic hydrolysis of curdlan powder resulted in the accumulation of laminaribiose (yield 81.7%). Trisaccharide was inevitably released from the hydrolysis of laminarioligosaccharides with 5 to 7 degrees of polymerization (DP). Although the enzyme cleaved off disaccharide (DP 2) from tetrasaccharide (DP 4), the reaction rate was lower than those of DP 5 to 7. The results indicated that the active site of Mo endo-β-1,3-glucanase can efficiently recognize glucosyl residue chain of greater than DP 5 and hydrolyzes the β-1,3 linkage between the 3rd and 4th glucosyl residue.
A spectrofluorometer equipped with a highly sensitive near-IR InGaAs detector was used for the direct visualization of singlet oxygen emission at 1268 nm in olive oil during light irradiation with various different wavelengths. The virgin olive oil in methylene chloride (20% w/v, oxygen saturated) was irradiated at the 301, 417, 454, 483, and 668 nm, then the emission at 1268 nm, singlet oxygen dimole decaying was observed. The result showed the highest production of ¹O2 with light irradiation at 417 nm, and followed by at 668 nm in virgin olive oil, indicating that pheophytin a and chlorophyll a were the most responsible components for the production of singlet oxygen. The UV light irradiations at the wavelength of 200, 250, and 300 nm did not induce any detectable luminescence emission at 1268 nm, but 350 nm produced weak emission at 1269 nm. The quantity of ¹O2 produced with excitation at 350 nm was about 1/6 of that of irradiation at 417 nm. Addition of an efficient ¹O2 quencher, 1,4-diazabicyclo[2.2.2]octane, in virgin olive oil in methylene chloride greatly decreased the luminescence emission at 1268 nm, confirming the singlet oxygen production in olive oil. Singlet oxygen production was more efficient in oxygen-purged virgin olive oil than in oxygen non-purged olive oil. This represents first report on the direct observation of singlet oxygen formation in olive oil as well as in real-food system after visible light illumination.
Nutrient-deprived Listeria monocytogenes have increased resistance to processing control measures. Heat-stressed L. monocytogenes cells produce higher counts under anaerobic conditions and SigB reportedly contributes to the survival of environmentally stressed Gram-positive bacteria. In this study, a wild type (wt) strain, L. monocytogenes 10403S, and a DeltasigB mutant, FSLA1-254, were stressed by starvation in phosphate buffered saline coupled with exposure to chemicals with/without oxygen. In the absence of chemicals, the mutant survived starvation almost as well as the wt, suggesting that the starvation survival response (SSR) in L. monocytogenes was SigB-independent. Conversely, in the presence of chemical stresses the SSR results differed depending on the chemical used. In the presence of sodium chloride (SC), both strains were able to express an SSR under aerobic conditions but not under anaerobic conditions. However, in the presence of sodium propionate (SP), the mutant yielded counts that were 2 log CFU/mL lower than the controls and their aerobic counterparts. In the presence of sodium lactate (SL), the mutant yielded counts that were approximately 3 log CFU/mL lower than the wt under anaerobic conditions. Thus, for the chemical stress produced by SC, the SSR appeared to be SigB-independent. The SSR of L. monocytogenes appeared to be SigB-dependent following exposure to SP or SL under anaerobic conditions. Following exposure to sodium diacetate or lauric acid, both strains were unable to express an SSR. No detectable CFUs were observed after 14 to 21 d under either aerobic or anaerobic incubation. Therefore, these 2 chemicals could be used in biocidal formulations against L. monocytogenes cells under aerobic or anaerobic conditions.
Eleven cultivars of celery, belonging to 2 species, were collected and analyzed for their phenolic compound composition and antioxidant activities. Major phenolic acids identified in the extracts of these celeries were caffeic acid, p-coumaric acid, and ferulic acid, while the identified flavonoids were apigenin, luteolin, and kaempferol. The contents of total phenolics were measured using a Folin-Ciocalteu assay and the total antioxidant capacity was estimated by the 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH) and 2, 2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS.(+)) methods. Apigenin was the major flavonoid in these samples and the most abundant phenolic acid was p-coumaric acid. Many of the investigated cultivars had high levels of phenolics and exhibited high antioxidant capacity. Among these 11 cultivars, Shengjie celery had the highest antioxidant activity whereas Tropica had the lowest. An extremely significant positive correlation between the antioxidant activity and the contents of total flavonoids, total phenolic acids, or total phenolics was observed in this study.
A headspace solid-phase microextraction (HS-SPME) method coupled with gas chromatography-mass spectrometry (GC-MS) was applied for the qualitative or semiquantitative characterization of brandy volatiles. SPME variables (SPME fiber, extraction temperature and time, and ethanol concentration) were optimized. A total of 144 compounds were from the brandies' volatiles, tentatively identified or identified by comparing mass spectra and retention indices of the standards or from literature. Of these, 57 are common to 11 brandies. They were mainly represented by esters and alcohols, such as 2-methyl propanol, 3-methyl butanol, 1-hexanol, ethyl octanoate, and ethyl decanoate, which were quantitatively determined. Chromatographic peaks were integrated using selective ion method (SIM) and the semiquantitative data analyzed using principal component analysis (PCA) and cluster analysis (CA) to study relationships between volatile composition and brandy. Eleven brandies were differentiated into 3 groups: 1 for Hennessy VSOP and XO samples, 1 for Changyu PEGASE VSOP and XO-1, 2, 3 samples, and the other for Changyu PEGASE brandy and VO, Taro brandy, Baiyang River brandy, and Wealth XO samples. The classification of groups is consistent with the brandy samples by variety and grade.
A substantial portion of the human population has immune hypersensitivities to various food materials. Soybean is one of the most common foods involved in such hypersensitivity reactions, especially in younger children. In this study, we investigated the effect of peptic and chymotryptic hydrolysis on the allergenicity of the 11S soybean globulin, which is the primary soybean allergen. The 11S globulin is composed of both acidic and basic polypeptides, and we found that the acidic polypeptide was effectively hydrolyzed, while basic polypeptide was more resistant to hydrolysis. The 11S globulin hydrolysate was size-fractionated by gel filtration, and 9 of the fractions obtained were tested for allergenicity against sera from 6 soybean-allergenic patients. The overall allergenicity of soybean 11S globulin was reduced by peptic and chymotryptic hydrolysis, although a gel filtration fraction with a major peptide of 20 kDa was highly immunoreactive. Hydrolyzed fragments of less than about 20 kDa were not immunoreactive.
During fresh-cut produce processing, organic materials released from cut tissues can rapidly react with free chlorine in the wash solution, leading to the potential survival of foodborne bacterial pathogens, and cross-contamination when the free chlorine is depleted. A reported chlorine stabilizer, T-128, has been developed to address this problem. In this study, we evaluated the ability of T-128 to stabilize free chlorine in wash solutions in the presence of high organic loads generated by the addition of lettuce extract or soil. Under conditions used in this study, T-128 significantly (P < 0.001) decreased the rate of free chlorine depletion at the presence of soil. T-128 also slightly decreased the rate of free chlorine depletion caused by the addition of lettuce extract in wash solution. Application of T-128 significantly reduced the survival of bacterial pathogens in wash solutions with high organic loads and significantly reduced the potential of cross-contamination, when contaminated and uncontaminated produce were washed together. However, T-128 did not enhance the efficacy of chlorinated wash solutions for microbial reduction on contaminated iceberg lettuce. Evaluation of several produce quality parameters, including overall visual appearance, package headspace O2 and CO2 composition, and lettuce electrolyte leakage, during 15 d of storage indicated that iceberg lettuce quality and shelf life were not negatively impacted by washing fresh-cut lettuce in chlorine solutions containing 0.1% T-128. Practical Application: Reported chlorine stabilizer is shown to enhance chlorine efficacy against potential bacterial cross-contamination in the presence of high organic loads without compromising product quality and shelf life.
Differentiating blended sesame oils from authentic sesame oil (SO) is a critical step in protecting consumer rights. Stable carbon isotope ratios (δ13C), color, fluorescence intensity, and fatty acid profiles were analyzed in SO prepared from sesame seeds with different roasting conditions and in corn oil blended with SO. Sesame seeds were roasted at 175, 200, 225, or 250 °C for 15 or 30 min at each temperature. SO was mixed with corn oil at varying ratios. Roasting conditions ranging from175 to 250 °C at the 30 min time point did not result in significant changes in δ13C (P > 0.05). Values of δ13C in corn oil and SO from sesame seeds roasted at 250 °C for 15 min were −17.55 and −32.13 ‰, respectively. Fatty acid ratios, including (O + L)/(P × Ln) and (L × L)/O, where O, L, P, and Ln were oleic, linoleic, palmitic, and linolenic acids, respectively, showed good discriminating abilities among the SO blended with corn oil. Therefore, using different combinations of stable carbon isotope ratios and some fatty acid ratios can allow successful differentiation of authentic SO from SO blended with corn oil. Practical Application: Adulteration of sesame oil with less expensive oils such as corn oil or soybean oil to reduce cost is a common unethical practice in Korea. Due to the unique and strong flavor of sesame oils that may mask other weaker flavors, however, differentiating authentic sesame oils from blended oils is difficult. This study showed that the roasting process did not significantly affect the ratios of the stable carbon isotope (δ13C) in sesame oils. δ13C was confirmed to be a reliable parameter. Moreover, some fatty acid ratios were designed to discriminate between blended sesame oil with corn oil and authentic sesame oil.
Improving the microbial safety while maintaining quality of fresh fruits and vegetables will increase consumer confidence in fresh produce. This study was conducted to investigate the effects of irradiation at 1 kGy, a dose that potentially inactivates E. coli O157:H7 by 5 logs, on the quality of 13 common fresh-cut vegetables: iceberg, romaine, green and red leaf lettuce, spinach, tomato, cilantro, parsley, green onion, carrot, broccoli, red cabbage, and celery. The results showed that the appearance of irradiated samples was similar to the nonirradiated ones except that irradiated carrots, celery, cilantro, and green onions had higher appearance scores than corresponding nonirradiated vegetables. There was no difference in the instrumental texture between irradiated samples and nonirradiated ones. The aroma of several irradiated vegetables was significantly better than controls after 14-d storage, because these control samples decayed or senesced. The 1 kGy irradiation did not affect vitamin C content of most vegetables; however, irradiated green and red leaf lettuce had 24% to 53% lower vitamin C contents than the controls. Our results suggest that most fresh-cut fruits and vegetables tested can tolerate up to 1 kGy irradiation without significant losses in any of the quality attributes.
The dielectric properties must be defined to design efficient radio frequency (RF) and microwave (MW) processes by the food manufacturers. The objective of this study was to understand how frequency, temperature, and muscle fiber orientation influence the dielectric properties. The eye of round (Semitendinosus) muscle was selected because it contains large, relatively uniform muscle cells with similar muscle fiber orientation and relatively uniform chemical composition throughout the tissue. Dielectric properties were measured using an open-ended coaxial probe technique at 27, 915, and 1800 MHz and temperatures between -5 and 130 degrees C. Power penetration depth was calculated. Since many commercially prepared, thermally processed, ready-to-eat entrees are made with frozen meat, dielectric property measurements were started from -5 degrees C. The dielectric constant and dielectric loss factors were often higher for muscle with the muscle fiber measured in a parallel orientation to the probe compared to samples of the same treatment (for example, fresh or frozen) in a perpendicular tissue orientation at the same frequency and temperature. Dielectric constant and loss values for frozen beef tended to be higher than fresh beef at the same temperature and frequency. Tissue orientation appeared to have a greater effect on dielectric loss values at lower frequencies. Penetration depth tended to be greater when the direction of propagation was perpendicular to the muscle fiber.
Pseudomonas fluorescens ATCC 13525 is used as the challenge organism to evaluate the efficacy of the clean-in-place (CIP) process of food equipment (automatic ice-maker) as per NSF/ANSI Standard 12. Traditional culturing methodology is presently used to determine the concentration of the challenge organism, which takes 48 h to confirm the cell density. Storage of the challenge preparation in the refrigerator might alter the cell density as P. fluorescens is capable of growing at 4 °C. Also, background organism can grow on the Pseudomonas F agar (PFA) used for the recovery of P. fluorescens thus affecting the results of the test. Real-time TaqMan assay targeting the cpn60 gene was developed for the enumeration and the identification of P. fluorescens because of its specificity, accuracy, and shorter turnaround time. The TaqMan primer-probe pair developed using the Allele ID® 7.0 probe design software was highly specific and sensitive for the target organism. The sensitivity of the assay was 10 colony forming units (CFU)/mL. The assay was also successful in determining the concentration of the challenge preparation within 2 h. Based on these observations, TaqMan assay targeting the cpn60 gene can be efficiently used for strain level identification and enumeration of bacteria. Practical Application: Pseudomonas fluorescens ATCC 13525 is used as a challenge organism in the efficacy testing of clean-in-place process of food equipments. Currently, culturing technique is used for its identification and estimation, which is not only time-consuming but also prone to error. Real-time TaqMan assay is more specific, sensitive, and accurate along with a shorter turnaround time compared to culturing techniques, thereby increasing the overall quality of the testing methodology to evaluate the clean-in-place process critical for the food industry to protect public health and safety.
Commercial cucumber fermentations are typically carried out in 40000 L fermentation tanks. A secondary fermentation can occur after sugars are consumed that results in the formation of acetic, propionic, and butyric acids, concomitantly with the loss of lactic acid and an increase in pH. Spoilage fermentations can result in significant economic loss for industrial producers. The microbiota that result in spoilage remain incompletely defined. Previous studies have implicated yeasts, lactic acid bacteria, enterobacteriaceae, and Clostridia as having a role in spoilage fermentations. We report that Propionibacterium and Pectinatus isolates from cucumber fermentation spoilage converted lactic acid to propionic acid, increasing pH. The analysis of 16S rDNA cloning libraries confirmed and expanded the knowledge gained from previous studies using classical microbiological methods. Our data show that Gram-negative anaerobic bacteria supersede Gram-positive Fermincutes species after the pH rises from around 3.2 to pH 5, and propionic and butyric acids are produced. Characterization of the spoilage microbiota is an important first step in efforts to prevent cucumber fermentation spoilage. Practical Application An understanding of the microorganisms that cause commercial cucumber fermentation spoilage may aid in developing methods to prevent the spoilage from occurring.
Jeotgal, which is widely consumed as a nutritional supplement in Korea, is traditional type of preserved seafood that is prepared by salting and fermenting. Here, we report on the bacterial community structure and diversity of jeotgal obtained from the Korean island of Jeju, which has a subtropical climate. Two samples of Jeotgal were collected from Jeju, made from either damselfish (Chromis notata; jari-dom-jeot, J1 and J2) or silver-stripe round herring (Spratelloides gracilis; ggot-myulchi-jeot, K1 and K2). The physical characteristics (pH and salinity) were assessed and the bacterial communities characterized using 16S rRNA gene-clone library analysis and cultural isolation. No difference was found in the community composition between the J and K fermented seafoods. Both fermented seafoods had relatively high salinity (26% to 33%) and high pH values (pH 6.08 to 6.72). Based on the 16S rRNA gene sequences, the halophilic lactic-acid bacteria Tetragenococcus halophilus and T. muriaticus were observed to be dominant in the J and K fermented seafoods, accompanied by halophilic bacteria including Halanaerobium spp., Halomonas spp., and Chromohalobacter spp. When compared with 7 other types of fermented seafood from a previous study, the communities of the J and K fermented seafoods were separated by the most influential group, the genus Tetragenococcus. The results suggest that these 2 types of traditional salted fermented seafood from Jeju have distinct communities dominated by Tetragenococcus spp., which are derived from the raw ingredients and are dependent on the physical conditions. This may explain how the seafoods that are made in Jeju may differ from other jeotgals.
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.
The biogenic amines (tyramine, histamine, cadaverine, and puterscine) and microbiological properties (mesophilic, psychrotrophic, and Pseudomonas spp.) of whole pike-perch (Sander lucioperca) was investigated during 2 d prestorage icing and 90 d frozen storage (−24 °C). At the end of ice storage, a noticeable increase only was found for puterscine level (P < 0.05), and microbial loads of fish increased in comparison with fresh fish (P < 0.05). During the frozen storage, as time passed, a continuous increase of biogenic amines and decrease of bacterial load (except for Pseudomonas spp. at the last 30 d) was detected (P < 0.05). The total contents of biogenic amines ranged from 6.24 to 91.76 μg/g during the investigated period. Puterscine was the major amine detected in pike-perch and its concentration varied between 1.75 and 56.95 μg/g; due to a more step-wise increase it was a good quality indicator. At the end of storage, all of the obtained values are below the tolerable maximum amounts based on available regulations. Based on biogenic amines content and microbial load, it could be concluded that pike-perch can be consumed without any health risks after 2 d icing condition and 90 d frozen storage. Practical Application: Biogenic amines as one of the commonest forms of food intoxication occur in protein-rich food such as fish. Short-time icing during transportation is the simplest method to fish preserving for processing or long-term storage. In this study formation of biogenic amines and bacterial changes in ungutted pike-perch as highly demanded fish species for human consumption, during transportation and frozen storage was investigated. The results of the research can be advantageously used by fish industry. These findings suggest that the production and storage practices of fish in the retails condition could have acceptable food quality level.
17beta-19-nortestosterone (17beta-NT) has been illegally used in antifatigue functional foods to promote muscle growth and improve endurance. A rapid and sensitive solid-phase extraction-enzyme-linked immunosorbent assay (SPE-ELISA) method was developed and successfully applied to analyze the levels of 17beta-NT in antifatigue functional foods. A polyclonal antibody against 17beta-NT was produced from rabbits immunized with the 17beta-NT-BSA conjugate, and a competitive direct enzyme-linked immunosorbent assay was developed for the rapid detection of 17beta-NT. The concentration causing 50% inhibition (IC(50)) and the limit of detection (LOD) were found to be 0.08 and 0.0055 ng/mL, respectively; this was better than methods previously reported that had a LOD of 2.4 ng/mL. C(18) cartridges were investigated for use in removing the effects of matrix in foods, and the sample purification protocol was optimized. Using the developed SPE-ELISA method, recoveries of functional food samples were obtained in the range of 71% to 91.5%. Moreover, 2 kinds of antifatigue functional foods were analyzed using the established ELISA and HPLC methods. The correlation coefficient of the results obtained using the 2 methods was greater than 0.98. Thus, the preliminary evaluation of the SPE-ELISA method proved that it is a specific, sensitive, and precise tool that can be used for the practical detection of 17beta-NT in various antifatigue functional food samples.
Aqueous and ethanolic extracts of maize kernels from 18 varieties/strains were prepared for the evaluation of inhibitory activities toward α-glucosidase and scavenging activities toward nitric oxide (NO•) and superoxide (•O(2)(-)). All ethanolic extracts of maize strains tested inhibited yeast (Saccharomyces cerevisiae) α-glucosidase with the highest potency (49% to 54%) found for 2 purple and a yellow strains. However, inhibitory effects of maize extracts on rat intestinal α-glucosidase were as a whole about 10% as effective as with the yeast enzyme. Maize extracts were capable of scavenging NO• at the level of 0.25 mg/mL to extents ranging from 24% to 50% and 26% to 57%, respectively, for aqueous and ethanolic extracts. All tested aqueous extracts were also capable of scavenging •O(2)(-), with efficacies ranging from 8% to 38%, at the level of 1.5 mg/mL, whereas almost none of the ethanolic extracts scavenged •O(2)(-), except for one purple strain (approximately 10% effective). The effectiveness in the enzyme inhibition and antioxidant assays did not correlate with total phenolic and/or anthocyanin levels, nor with the nature of pigmentation among the maize strains evaluated. Practical Application: A diversity of pigmented maize strains was evaluated for biological activities related to mitigating oxidative stress and slowing down glucose absorption from the diet. Certain strains tended to be more abundant in these biological activities and have potential to be used in dietary regimes that are designed to promote human health.
The effect of acoustic energy density (AED) on inactivation of Shigella boydii 18 IDPH and Listeria monocytogenes Scott A in a cell suspension was studied at sublethal temperatures and at AEDs of 0.49, 0.85, and 1.43 W/mL. The effect of temperature on ultrasonic inactivation of L. monocytogenes Scott A at 35, 50, and 65 degrees C was examined at an AED of 1.43 W/mL. Increasing AED increased the rate of inactivation for both S. boydii and L. monocytogenes. The destruction of S. boydii and L. monocytogenes followed 1st order kinetics in a 20-min treatment, except for S. boydii inactivation at 1.43 W/mL where a tailing effect was observed after 15 min. At sublethal temperatures, the D-values of S. boydii were 8.8, 4.3, and 2.5 min for AEDs of 0.49, 0.85, and 1.43 W/mL, whereas those for L. monocytogenes at the 3 AED levels were 31.5, 13.5, and 7.3 min, respectively. Ultrasonic treatment of L. monocytogenes at 35 and 50 degrees C enhanced inactivation. However, at 65 degrees C, application of ultrasound did not result in additional inactivation compared to thermal treatment alone at the same temperature. With the experimental conditions and the ultrasound system used in this study, an upper temperature limit for thermosonication was evident above which no added killing due to ultrasound was observed.
The dielectric constant and loss factor of egg albumen and egg yolk over the frequency range from 10 to 1800 MHz were measured at 24 degrees C at weekly intervals during 5-wk storage at 15 degrees C. Moisture and ash contents of albumen and yolk, as well as Haugh unit and yolk index, were also measured. The dielectric constant and loss factor of albumen were higher than those of yolk. Linear relationships were evident between the log of frequency, below about 1000 MHz, and the log of loss factor of albumen as well as that of yolk. The dielectric constants of albumen and yolk at 10 MHz were lower than those of fresh albumen and yolk when eggs were stored at 15 degrees C for 1 wk. However, after 2 wk in storage these dielectric constants rose and remained at higher levels for the rest of the 5-wk period. At frequencies of 100 MHz and higher, the dielectric constant was essentially constant during the entire storage period. Storage had much less influence on the loss factor of either albumen or yolk. In general, the moisture content and ash content of albumen and yolk decreased slightly as eggs aged. The moisture content of yolk increased somewhat with storage, and there was a corresponding decrease in albumen moisture content. The freshness qualities, Haugh unit and yolk index, also decreased as eggs aged. No obvious correlation between dielectric properties and moisture content, ash content, Haugh unit, or yolk index was observed.
This paper presents the generation of monoclonal antibodies (mAbs) with high specificity against 19-nortestosterone (NT) through cell fusion procedures, and the development of mAb-based heterologous direct competitive enzyme-linked immunoabsorbent assay (dcELISA) methods to detect NT residue using one of these hybridomas (clone 3B8-E6). Under optimal experimental conditions, this assay exhibited a working range of 0.004 to 19 ng/mL with IC₅₀ and limit of detection values of 0.28 and 0.002 ng/mL, respectively, when it was run in 0.01M phosphate-buffered saline (pH 7.4). Except for minor cross-reactivity with β-boldenone (6.9%) and trenbolone (1.2%), other interference to the assay was negligible (<0.05%). No significant differences (P > 0.05) were found for IC₅₀ values when the pH of the assay buffer ranged from 6 to 8 and phosphate ion concentration was less than 20 mM. The dcELISA can tolerate higher concentrations of methanol than other organic solvents tested. When applied to bovine sample, the correlation coefficients (R) of the dcELISA and GC-MS data were 0.9918 in muscle, 0.9834 in liver, and 0.9976 in kidney. Therefore, this assay has the potential to be incorporated into a quantitative monitoring program for the rapid screening of NT residue in food.
Unlabelled: Exposure to high pressure is an efficient method of bacterial inactivation that is particularly important for reducing the microbial load present in foods. In this study, we examined the high pressure inactivation of Aeromonas hydrophila AH 191, a virulent strain that produces aerolysin, a cytotoxic, enterotoxic, and hemolytic toxin. High pressure treatment (250 MPa for 30 min at 25 °C in 0.1 M PBS, pH 7.4) of A. hydrophila grown in milk reduced bacterial viability by at least 9 orders of magnitude. Under these conditions, the enterotoxic, hemolytic, and cytotoxic activities of A. hydrophila culture supernatants were unaltered. These results indicate the need for caution in the use of high pressure for food processing since although truly toxigenic bacteria may be inactivated, their toxins may not be, thus posing a risk to human health. At higher pressure (350 MPa) the inactivation of bacteria was much more effective. Scanning electron microscopy showed a significant decrease in the number of bacteria after higher pressurization (350 MPa for 1 h) and transmission electron microscopy showed irregular shaped bacteria, suggestive of important cell wall and membrane damage, and cytoplasm condensation. Practical application: High pressure inactivates Aeromonas hydrophila efficiently but is enhanced when combined with moderate temperature (40 °C). The biological activities of toxins from this bacterium are unaltered under these conditions.
Cultured shrimp are often exposed to different toxic products during rearing practices that may affect survival and quality of the product. An evaluation of the effects of paralytic shellfish toxins (PSP) from species of Gymnodinium catenatum in white leg shrimp (Litopenaeus vannamei) has been carried out in this study. Death was observed at doses > 5.0 MU (equivalent to 1.1 mug/g of STX), while lower doses provoked paralysis of pereiopods, disequilibrium, and abdominal spasms in the animals. Target organs such as the heart and brain were severely damaged, with cohesion loss and cell density reduction evidenced by histological analysis. Hence, pond productivity and quality of the harvested organisms may be affected by PSP toxins. This is the 1st report on the effect of PSP toxins from G. catenatum in white eg shrimp.
Unlabelled: Food ingredient fraud and economically motivated adulteration are emerging risks, but a comprehensive compilation of information about known problematic ingredients and detection methods does not currently exist. The objectives of this research were to collect such information from publicly available articles in scholarly journals and general media, organize into a database, and review and analyze the data to identify trends. The results summarized are a database that will be published in the US Pharmacopeial Convention's Food Chemicals Codex, 8th edition, and includes 1305 records, including 1000 records with analytical methods collected from 677 references. Olive oil, milk, honey, and saffron were the most common targets for adulteration reported in scholarly journals, and potentially harmful issues identified include spices diluted with lead chromate and lead tetraoxide, substitution of Chinese star anise with toxic Japanese star anise, and melamine adulteration of high protein content foods. High-performance liquid chromatography and infrared spectroscopy were the most common analytical detection procedures, and chemometrics data analysis was used in a large number of reports. Future expansion of this database will include additional publically available articles published before 1980 and in other languages, as well as data outside the public domain. The authors recommend in-depth analyses of individual incidents. Practical application: This report describes the development and application of a database of food ingredient fraud issues from publicly available references. The database provides baseline information and data useful to governments, agencies, and individual companies assessing the risks of specific products produced in specific regions as well as products distributed and sold in other regions. In addition, the report describes current analytical technologies for detecting food fraud and identifies trends and developments.
Proton nuclear magnetic resonance (¹H-NMR) relaxometry was used to study the effects of high pressure and thermal processing on membrane permeability and cell compartmentalization, important components of plant tissue texture. High pressure treated onions were subjected to pressure levels from 20 to 200 MPa at 5 min hold time at initial temperatures of 5 and 20 °C. Thermally treated onions were exposed for 30 min at temperatures from 40 to 90 °C. Loss of membrane integrity was clearly shown by changes in transverse relaxation time (T(2)) of water at temperatures of 60 °C and above. Destabilization effects on membranes exposed to high pressure were observed at 200 MPa as indicated by T(2) measurements and cryo-scanning electron microscopy (Cryo-SEM). T(2) relaxation successfully discriminated different degrees of membrane damage based on the T(2) shift of the vacuolar component. Analyses of the average water self-diffusion coefficient indicated less restricted diffusion after membrane rupture occurred in cases of severe thermal treatments. Milder processing treatments yielded lower average diffusion coefficients than the controls. ¹H-NMR proved to be an effective method for quantification of cell membrane damage in onions and allowed for the comparison of different food processes based on their impact on tissue integrity.
The influence of electrical pulse protocol parameters on cell rupture of onion tissues was investigated in order to improve fundamental understanding and to enhance the processing of plant tissues with pulsed electric fields (PEFs). The impact of PEF parameters on cell integrity of 20 mm dia, 4-mm thick disks of Don Victor onions (Allium cepa L.) was determined by ion leakage measurements. Electric field strength, pulse width, total pulse duration, and frequency effects were determined in relation to their effects on cell damage as a function of pulse protocol. Electric field strengths up to 500 V/cm increased the damage efficiency but there was no significant difference in efficiency beyond this field strength. Larger pulse widths increased the degree of tissue disintegration at a constant pulse number. Higher PEF efficiency was achieved with shorter pulse widths and a larger number of pulses at a constant total treatment time. Lower frequencies caused a greater degree of disintegration at constant number of pulses. ¹H-NMR experiments were performed to determine the proton relaxation components of the PEF-treated onion samples and to obtain cell damage information nondestructively. Paramagnetic ion uptake by the onion sample was used to identify different proton relaxation components. Five different proton relaxation components were observed and changes in the 2 components representing different proton environments showed high correlations with ion leakage results (R²= 0.99), indicating that T(2) distributions can be used to obtain information about cell membrane integrity in PEF-treated samples. 1H-NMR proved to be an effective method for nondestructive quantification of cell membrane rupture in onions.
In order to elucidate the gelation mechanism of surimi, the temperature dependence of water proton spin-spin relaxation time ((1)H T(2)) has been described by a theoretical approach, in which the exposed protein surface is taken into account. Water (1)H T(2) measured for horse mackerel surimi in the presence of 2.5% NaCl was analyzed on the basis of the consideration for the denaturation and the aggregation of protein in order to explain the macroscopic structural change during the heating and the cooling processes. The temperature dependence of water (1)H T(2) and the fraction of rigid component gave a clear explanation for the gelation mechanism of surimi. Differential scanning calorimetry thermogram and dynamic viscoelastic measurements supported the results of nuclear magnetic resonance (NMR) measurements. It has been demonstrated that the measurement of NMR relaxation times is useful to describe the gelation mechanism of surimi.
This study examined the characteristics of the oxidation reaction on the primary alcohol groups in cellulose involving the 2,2,6,6-tetramethyl-1-piperidinyl oxoammonium ion (TEMPO) and determined the optimum conditions for the preparation of oxidized cellulose (OC). The applicability of OC in polysaccharide systems was also investigated. The effects of TEMPO, sodium bromide (NaBr), and temperature on the oxidation reaction time, yield, and selectivity for primary alcohol groups were examined using response surface methodology (RSM). The reaction time decreased with increases in the temperature and the levels of TEMPO and NaBr. The yield increased with the level of NaBr and decreased as the temperature increased. Selectivity increased with the temperature and decreased as the levels of TEMPO and NaBr increased. The optimum levels of TEMPO and NaBr and the optimum temperature for the production of OC were determined as 0.3 mM/100 mM anhydroglucose unit (AGU), 50 mM/100 mM AGU, and 25 degrees C, respectively. The water and oil binding capacity and viscosity of cellulose increased with oxidation. Wheat starch containing OC exhibited a decreased initial pasting temperature and setback, but increased peak viscosity, gelatinization, and retrogradation enthalpy (DeltaH). The hardness of the wheat starch gel decreased significantly upon the addition of OC.
Onion pungency has been routinely measured by determining pyruvic acid concentration in onion juice by reacting with 2,4-dinitrophenylhydrazine (DNPH) since 1961. However, the absorbency of the color adduct of the reaction rapidly decreased in onion samples as compared to that of the pyruvic acid standards, resulting in underestimations of the pyruvic acid concentrations. By measuring the absorbency at 1 min, we have demonstrated that accuracy could be substantially improved. As a continuation, the causes of degradation of the color adduct after the reaction and pyruvic acid itself before the reaction were examined in this study. Alliinase action in juice (fresh or cooked) and bulb colors did not influence the degradation. Some organic acids indigenously found in onion, such as ascorbic acid, proline, and glutamic acid, did not reduce the absorbency. However, fructose within the onion juice or supplemented caused the degradation of the color adduct, whereas sucrose and glucose had a lesser effect. Degradation rates increased proportionally as fructose concentrations increased up to 70 mg/mL. Cysteine was found to degrade the pyruvic acid itself before the pyruvic acid could react with DNPH. Approximately 90% of the pyruvic acid was degraded after 60 min in samples of 7 mM pyruvic acid supplemented with 10 mg/mL cysteine. Spectral comparisons of onion juice containing fructose naturally and pyruvic acid solution with supplemented fructose indicated identical patterns and confirmed that the color-adduct degradation was caused by fructose. Our study elucidated that fructose, a major sugar in onion juice, caused the degradation of color adduct in the onion pungency test and resulted in underestimation of the pyruvic acid concentration.
A part of the "bouquet of wines" can be caused by the presence of odorous heterocycles produced by chemical reactions between S-amino acids and α-dicarbonyl compounds. Under wine ageing physic-chemical conditions (20 ± 2 °C, ethanol/water 12% v/v, pH 3.5), products of the diacetyl (DI) reaction with cysteine include a number of 1,3-N,S and 1-3-N,O 5 member heterocycles having methyl groups attached at C(2). The origin of this methyl-C(2) fragment was not clear; it could be supplied from DI or from cysteine. To explore this question, a parallel reaction was run in which DI was replaced by 3,4-hexanedione. With the C(1) and C(4) carbons of DI thus marked with methyl groups, the product distribution demonstrated that in the DI and cysteine reaction, both DI and cysteine provided the methyl-C(2) to varying degrees in the formation of 2-methylthiazole, 2-methyl-3-thiazoline and 2,4,5-trimethyloxazole but only cysteine supplied this fragment for 2-methylthiazolidine. The results are interpreted in terms of reaction paths appropriate for the mild conditions. These pathways shed light on the mechanisms leading from dicarbonyls to heterocyclic compounds. Like all the chemical pathways, they anticipate the impact of other compounds and physicochemical parameters on heterocyclic generations the generation of heterocyclics. They also suggest the presence of unexplored odorous compounds.
  2,5-Dimethyl-3-methoxypyrazine (DMMP) has been recently identified in both Coccinellidae-tainted (by either Coccinella septempunctata or Harmonia axyridis beetles) and untainted wines; however, little is known regarding its impact on wine aroma and flavor. The aims of this study were to obtain an accurate estimate of both the ortho- and retronasal detection thresholds of DMMP in red wine and to understand how DMMP contributes to the aroma profile of red wine. In the first study, thresholds were determined for 21 individuals using the ASTM E679 ascending forced choice method of limits. The orthonasal group best estimate threshold (BET) was 31 ng/L and the retronasal group BET was 70 ng/L. A moderate variation in individual thresholds was observed for the orthonasal modality (standard deviation (SD) = 19.8) and a larger variation was noted for retronasal thresholds (SD = 111.8). In the second study, a panel of 8 assessors performed descriptive sensory analysis on 3 red wines containing various concentrations of added DMMP (0, 50, and 120 ng/L). Results show significant changes in aroma characteristics in the 120 ng/L wine and smaller effects at the 50 ng/L level. Overall, wines spiked with DMMP generated lower intensity ratings for cherry and red berry descriptors and higher ratings for earthy/musty and green/vegetal descriptors. When considered with other recent results on DMMP concentrations found in wine, DMMP can be considered a hitherto undescribed impact odorant in some wine styles.
Effect of ammonia in acetonitrile to the recovery of xylazine and 2,6-xylidine in fat matrix. The X-axis represents the percentage of ammonia in acetonitrile, and the Y-axis represents the recovery of xylazine and 2,6-xylidine in spiked fat matrix.
Effect of liquid–liquid extraction (No SPE), and 4 types of SPE cartridges (HLB, MCX, C18, and C8) on the recovery of xylazine and 2,6-xylidine spiked at 50 μg/kg in cattle liver matrix.
Effect of acetonitrile content in the initial mobile phase to the peak intensity of xylazine and 2,6-xylidine. The X-axis represents the percentage of acetonitrile in the mobile phase, and the Y-axis represents the peak area intensity of extracted ion chromatograms.
Chromatograms of xylazine (x) and 2,6-xylidine (y) under different concentration of formic acid in mobile phase. Subparts A to G represent the percentage of formic acid added: (A) 0%; (B) 0.01%; (C) 0.02%; (D) 0.05%; (E) 0.1%; (F) 0.15%; and (G) 0.2%. The X-axis represents the retention time of chromatograms, and the Y-axis represents the peak area intensity.
Effect of formic acid concentration in mobile phase to the peak area intensity of xylazine and 2,6-xylidine in extracted ion chromatograms.
Xylazine is a potent α2-adrenergic agonist used in veterinary medicine for sedation, analgesia, muscle relaxation, and so on. Its residue in animal-derived food may cause the food safety problem. Moreover, the metabolite 2,6-xylidine was reported to be a genotoxic and carcinogenic compound. Therefore, it is necessary to develop a high sensitive method for analyzing xylazine and metabolite residue in animal products. Here, we described a LC-MS/MS method for simultaneous determination of xylazine and 2,6-xylidine in 4 animal tissues: liver, meat, kidney, and fat. The samples were extracted by acetonitrile, and further clean up by hexane. The analysis was performed on a C18 reversed-phase column and API 5000 Triple Quadrupole mass spectrometry with positive electrospray ionization interface operating in the multiple-reaction monitoring mode. For all of the investigated sample matrix, the limit of detection (limit of quantitation) for xylazine and 2,6-xylidine were 0.06 (0.2) and 1.5 (5) μg/kg, respectively, the recoveries were between 63.5% and 90.8%. The precision was within the range of required criteria for method development. The presented method is sensitive and reproducible, and thus suitable for accurate quantification of xylazine and metabolite residue in animal-derived food products.
Fruit contributes to dietary nutrient density and consumption of fruit in several forms (whole, dried, or 100% juice) has been reported to be associated with a healthier dietary pattern. The goal of this study was to examine the associations of the consumption of grapes (including fresh grapes, raisins, and 100% grape juice) with diet quality and food group/nutrient intake. A secondary analysis of Natl. Health and Nutrition Examination Survey (NHANES) 2003 to 2008 data was conducted to compare grape consumers (GC) with nongrape consumers (NGC) among children aged 2 to 19 y (n = 9622) and adults 20+ y (n = 12251). GC were defined as those who mentioned the consumption of fresh grapes, raisins, or 100% grape juice during 1 or both 24-h recall interviews. Compared to NGC, GC had higher Healthy Eating Index 2005 (HEI-2005) scores and higher intakes of total and whole fruit along with lower intakes of solid fat, added sugars, and calories from solid fats, alcohol, and added sugars (SoFAAS). Among adults, GC also had higher intakes than NGC of total and dark green/orange vegetables. Among both age groups, GC had higher intake than NGC of several key nutrients including dietary fiber, vitamin A, vitamin C, calcium, magnesium, and potassium. Consumption of grape products is associated with a healthier dietary pattern and higher intake of key nutrients by both children and adults.
Since a high intake of trans fatty acids (TFA) has been associated with the increased risk of developing cardiovascular disease, food regulation worldwide has been amended with respect to nutrition labeling and health claims on TFA. In the present study, the TFA levels of Korean food products were investigated to assess the regulation effect of TFA labeling. Same Korean food products within 7 different categories were purchased in years 2005 and 2008, and the contents of TFA and lipid and fatty acid composition were investigated. Lipid and TFA contents decreased in all food products manufactured in 2008. TFA levels were 0.01 to 6.88 g/100 g food in 2005, but the levels remarkably decreased to nondetectable level or up to 0.5 g TFA/100 g food in 2008. The foods from 2005 contained a various level of TFA ranging 0.6% to 44.6% of total fatty acids; however, the TFA level significantly decreased in most foods up to 3.8% from year 2008. For TFAs, trans C18:1 levels were greater than trans isomers of C18:2, and the levels in 2005 were significantly reduced in 2008 (P < 0.05). TFA levels at the sn-2 position were up to 48.3% of total fatty acids in 2005, but the level considerably decreased up to 5.4% in 2008. The considerably decreased content of TFA in 2008 suggested that food manufacturers recognized the adverse effect of TFA on human health and followed the compulsory trans fat labeling rule by Korean Food and Drug Administration (KFDA), which started December 2007.
Unlabelled: A total of 48 Listeria monocytogenes isolates of different import food products from 8 provinces between 2005 and 2008 were characterized. The serotype and virulence were confirmed for each strain and molecular subtyping were analyzed by multilocus sequence typing (MLST). Twenty five strains were assigned to serotype 1/2a, and 11 isolates to serotype 1/2b, serotype 4b were found in 7 isolate, and the remaining 5 strains were grouped into serotypes 1/2c, 4a, and 4e. Molecular subtyping schemes found thirty two sequence types (STs) among these isolates and the majority of L. monocytogenes strains belonged to lineage II (56%), followed by lineage I (38%), lineage III (6%). Two molecular subtype clusters, cluster A included all isolates of lineage II, while cluster B contained the isolates of lineages I and lineages III. Two L. monocytogenes strains were not grouped in either of the two clusters. Fifty three isolates were as virulent as L. monocytogenes reference strain EGD in mouse virulence assay, while the isolates 22213 and 22265 had low pathogenicity. These results provide the first molecular insight into the L. monocytogenes strains isolated from import food products of 8 provinces in China and indicate the potential risk to cause human disease if intake by contaminated foods. MLST could be used as a routine subtyping method of L. monocytogenes isolates. In China, inspection and quarantine strategies of imported foods should be strengthened. Practical application: There is a potential risk of listeriosis in China and routine subtyping of L. monocytogenes isolates is important. It is necessary for food hygiene management to strengthen the supervision of imported foods.
The objective of this study was to develop an in vitro stomach model, the Human Gastric Simulator (HGS), for studying gastric digestion of foods. The HGS is designed in such a way as to simulate the continuous peristaltic movement of stomach walls, with similar amplitude and frequency of contraction forces as reported in vivo. The HGS mainly consists of a latex vessel, simulating the stomach chamber, and a series of rollers secured on belts that are driven by motor and pulleys to create a continuous contraction of the latex wall. It also incorporates gastric secretion, emptying systems, and temperature control that enable accurate simulation of dynamic digestion process for detailed investigation of the changes in the physical chemical properties of ingested foods. The simulated gastric contraction force demonstrates a similar pattern as in vivo stomach forces. The precise control of gastric secretion and emptying and the adjustable mechanical forces in the HGS provide a useful tool to study transformation of food constituents under simulated physiological conditions. Practical Application: HGS could be used to study changes in the physical and chemical properties of gastric contents, and transformation of food constituents that occur during simulated digestion, and the influence of physiological conditions including acid and enzyme secretion and contraction forces on disintegration kinetics of foods and nutrient release.
The brain areas that represent taste including the primary taste cortex and the orbitofrontal cortex also provide a representation of oral texture. Fat texture is represented by neurons independently of viscosity: some neurons respond to fat independently of viscosity, and other neurons encode viscosity. The neurons that respond to fat also respond to silicone and paraffin oil, indicating that the sensing is texture-specific not chemo-specific. This fat sensing is not related to free fatty acids such as linoleic acid, and a few other neurons that respond to free fatty acids typically do not respond to fat in the mouth. Complementary human functional neuroimaging studies show that the pleasantness of food texture is represented in the orbitofrontal cortex. These findings have implications for the design of foods that mimic the pleasant texture of fat in the mouth but have low energy content, and thus for the prevention and treatment of obesity.
Research suggests that dietary fat is perceived not only by texture, but also by taste. However, the receptors for chemosensory response to fat have not been identified. We report on 2 genes,TAS2R38 and CD36, that may play a role in fat perception and preference in humans. TAS2R38 is a taste receptor for bitter thiourea compounds, including 6-n-propylthiouracil (PROP) and phenylthiocarbamide (PTC). Nontasters of these compounds tend to be poor at discriminating fat in foods, even though they prefer higher fat versions of these foods. CD36, a fatty acid translocase expressed on multiple cell types including taste cells, plays a critical role in fat preferences in animals. In studies conducted in our laboratory with African-American adults, we identified a variant in the CD36 gene, rs1761667, that predicts oral responses to fat. Individuals who have the A/A genotype at this site tend to find Italian salad dressings creamier than those who have other genotypes at this site. In addition, A/A individuals report higher preferences for added fats, oils, and spreads (for example margarine). Assuming these data are confirmed in other populations, screening for CD36 genotype may provide helpful information to food companies for developing fat-modified products.
The objective of this study was to determine glycemic and breath hydrogen responses in 10 healthy men in response to highly cross-linked starch phosphate (HXLS), made of tapioca starch (TS). Plasma glucose concentration was analyzed at baseline and at 30, 60, 90, 120, 150, and 180 min postprandially. In addition, breath hydrogen excretion was measured at baseline and at hourly intervals, over 10 h, after test substance challenge. When compared with unmodified TS easily digested, the area under the curve of plasma glucose of HXLS was 64% smaller, and was almost the same as that of microcrystalline cellulose. When compared with fructo-oligosaccharide rapidly fermented by the microbial bacteria, the area under the excretion curve of breath hydrogen gas of HXLS was 93% smaller, and was almost the same as that of water only. These results show that HXLS is harder to digest and ferment than unmodified TS in men.
Top-cited authors
David Julian Mcclements
  • University of Massachusetts Amherst
Theodore P Labuza
  • University of Minnesota Twin Cities
Ronald E Wrolstad
  • Oregon State University
Tara Mchugh
  • United States Department of Agriculture
Eric A Decker
  • University of Massachusetts Amherst