Stability of α-tocotrienol and α-tocopherol in salami-type sausages and curing brine depending on nitrite and pH

We studied the stability of the valuable vitamer nutrients α-tocotrienol and α-tocopherol and options for their protection in salami-type sausages (blended with α-tocotrienol-rich barley oil) and curing brine. Four different sausage formulations were produced containing nitrite curing salt; nitrite curing salt and ascorbic acid (300 mg/kg); nitrite curing salt and carnosic acid (45 mg/kg); or sodium chloride. Initial vitamer contents (100 mg/kg) did not decrease significantly during ripening and decreased only slightly during storage. Ascorbic acid and carnosic acid were found to be effective in preserving the vitamers in fresh sausages. Freeze-drying of sausages resulted in a significant loss of vitamers (97%), particularly after 14-day storage at room temperature, even in the presence of shielding gases. The vitamer content in the curing brine decreased with decreasing pH in the presence of nitrite. A nitrite concentration of 136 mg/L at pH 4 resulted in significant loss (90%) of the vitamers. Sufficient stability of the vitamers in salami-type sausage and curing brine can be achieved by processing, formulation, and storage conditions.     

γ-Oryzanol and tocopherol contents in residues of rice bran oil refining

Rice bran oil (RBO) contains significant amounts of the natural antioxidants γ-oryzanol and tocopherols, which are lost to a large degree during oil refining. This results in a number of industrial residues with high contents of these phytochemicals. With the aim of supporting the development of profitable industrial procedures for γ-oryzanol and tocopherol recovery, the contents of these phytochemicals in all the residues produced during RBO refining were evaluated. The samples included residues from the degumming, soap precipitation, bleaching earth filtering, dewaxing and deodorisation distillation steps. The highest phytochemical concentrations were found in the precipitated soap for γ-oryzanol (14.2 mg g⁻¹, representing 95.3% of total γ-oryzanol in crude RBO), and in the deodorisation distillate for tocopherols (576 mg 100 g⁻¹, representing 6.7% of total tocopherols in crude RBO). Therefore, among the residues of RBO processing, the deodorisation distillate was the best source of tocopherols. As the soap is further processed for the recovery of fatty acids, samples taken from every step of this secondary process, including hydrosoluble fraction, hydrolysed soap, distillation residue and purified fatty acid fraction, were also analyzed. The distillation residue left after fatty acid recovery from soap was found to be the best source of γ-oryzanol (43.1 mg g⁻¹, representing 11.5% of total γ-oryzanol in crude RBO).     

Extraction of γ-oryzanol from rice bran using diverse edible oils: enhancement in oxidative stability of oils

Food Science and Biotechnology - Diverse edible oils including perilla, corn, soybean, canola, sunflower, olive, and grape seed oils were mixed with heat-stabilized rice bran to extract...     

Binding of vitamin A with milk α- and β-caseins

The binding sites of retinol and retinoic acid with milk α- and β-caseins were determined, using constant protein concentration and various retinoid contents. FTIR, UV–visible and fluorescence spectroscopic methods as well as molecular modelling were used to analyse retinol and retinoic acid binding sites, the binding constant and the effect of retinoid complexation on the stability and conformation of caseins. Structural analysis showed that retinoids bind caseins via both hydrophilic and hydrophobic contacts with overall binding constants of K_{retinol-α-caseins} = 1.21 (±0.4) × 10⁵ M⁻¹ and K_{retinol-β-caseins} = 1.11 (±0.5) × 10⁵ M⁻¹ and K_{retinoic acid-α-caseins} = 6.2 (±0.6) × 10⁴ M⁻¹ and K_{retinoic acid-β-caseins} = 6.3 (±0.6) × 10⁴ M⁻¹. The number of bound retinol molecules per protein (n) was 1.5 (±0.1) for α-casein and 1.0 (±0.1) for β-casein, while 1 molecule of retinoic acid was bound in the α- and β-casein complexes. Molecular modelling showed different binding sites for retinol and retinoic acid on α- and β-caseins with more stable complexes formed with α-casein. Retinoid–casein complexation induced minor alterations of protein conformation. Caseins might act as carriers for transportation of retinoids to target molecules.     

Functionalisation of rice bran assisted by ultrasonication and fermentation for the production of rice bran–lingonberry pulp-based probiotic nutraceutical

A probiotic nutraceutical based on functionalised rice bran (RB) supplemented with lingonberry (Vaccinium vitis-idaea L.) pulp (LP) at various levels (10–50 g/100 g d.w.) was developed. Prior to immobilisation of lactic acid bacteria (LAB) cells, RB-LP matrix was structured by ultrasound (US) (850 kHz; power 160 W) for 20 min at 40 °C. Xanthan gum and sodium alginate were used for the stabilisation of RB-LP matrix. Survival and fermentative activity of the immobilised LAB cells was studied by monitoring pH, cell number, antimicrobial activity, lactic acid and acetic acid production. US treatment increased by 17.5% soluble dietary fibre (SDS) contents in RB but reduced on average by 49.9% hyperoside, quercetin, quercitrin and coumaric acid contents in LP material. RB substrate supplemented with LP (20–50 g/100 g d.w.) resulted in higher antimicrobial activity against Escherichia coli, Salmonella typhimurium and Staphylococcus aureus for Lactobacillus brevis, and against Bacillus cereus and Staphylococcus aureus for Pediococcus acidilactici. RB-LP matrix stabilised with alginate–xanthan and alginate maintained 8.09–8.67 log CFU g⁻¹ live cells of immobilised L. brevis after 7 weeks of storage at 4 °C. In the case of protection under simulated in vitro digestion conditions, RB-LP gels with sodium alginate demonstrated the highest cell survival with 4.25 CFU g⁻¹ viable cells remaining in the product and 5.23 log CFU g⁻¹ live cells in the digestion medium.     

Loss of solubility of α-lactalbumin and β-lactoglobulin during the spray drying of whey proteins

A reversed phase HPLC technique has been applied to measure the loss of solubility (at pH 4.6) of α-lactalbumin and β-lactoglobulin resulting from the spray drying of whey protein isolate solution. Spray drying was performed in a pilot-scale co-current spray dryer with different feed concentrations (20-40% w/v) and outlet temperatures (60-120 °C). The study reveals that the solubility of both α-lactalbumin and β-lactoglobulin was not significantly affected at low outlet gas temperatures (60-80 °C), but was strongly affected (up to 40%) at high temperatures (100-120 °C). Significantly higher losses in solubility were observed for β-lactoglobulin compared to α-lactalbumin. Increasing the feed concentration at higher outlet temperatures also caused noticeable increases in insolubility. The reversed phase HPLC results were consistent with those from total protein nitrogen content (Kjeldhal) analyses.     

Composition,industrial processing and applications of rice bran γ-oryzanol

Rice bran oil (RBO) (20–25 wt% in rice bran) is a unique rich source of commercially-important bioactive phytochemicals, most of them of interest in nutrition, pharmacy and cosmetics. The unsaponifiable constituents of RBO include mainly tocols (vitamin E, 0.10–0.14%) and γ-oryzanol (esters of trans-ferulic acid with sterols and triterpenic alcohols, 0.9–2.9%). The following topics concerning γ-oryzanol are reviewed: analytical methods for characterisation and determination; influence of genetic and environmental factors on the composition of rice bran; extraction approaches, including supercritical CO₂ and subcritical water; and biomedical and industrial applications, including food and pharmaceuticals. Concentration ranges of γ-oryzanol, tocopherols and tocotrienols found in rice bran and RBO from different varieties and geographical areas are summarised. This review focuses on the 2003–2008 period, where an average of 13–14 references per year were published; however, some relevant work reported during the 1998–2002 period is also briefly commented upon.     

Formation and stability of α-lactalbumin–lysozyme spherical particles: Involvement of electrostatic forces

The formation and the subsequent stability of spherical microparticles resulting from the self-assembly between two oppositely charged proteins, lysozyme (LYS) and apo α-lactalbumin (apo α-LA), at pH 7.5 and 45 °C were studied under different physico-chemical conditions—ionic strength, type of salts, type of buffer. Increasing the ionic strength reduced the ability of the two proteins to interact together and to form microspheres. The formation of such microparticles was completely abolished at an ionic strength of 100 mM. Increasing salt concentration also allowed destabilisation and dissociation of formed microspheres in salt-dependent manner as assessed by turbidity experiments and microscopic observations. Microparticles were destabilised with either NaCl, MgCl₂ or CaCl₂, but the latter showed the greatest destabilising effect. The higher efficiency of calcium ions in the destabilisation experiment could be attributed to the presence of specific calcium binding site on α-LA. Interestingly, complete disappearance of formed particles was not reached even after adding salt concentrations as high as 250 mM of NaCl or 7.5 mM of divalent cations. Our results suggest that electrostatic interactions are clearly involved in the first events of the two-protein assembly and spherical particles building. Moreover, non-electrostatic forces are also involved in maintaining the integrity and stability of formed microparticles.     

Improving the rheological and thermal properties of wheat dough by the addition of γ-polyglutamic acid

The rheological and thermal properties of wheat dough with the addition of γ-polyglutamic acid (PGA) (0.5, 1.0, 5.0 g kg⁻¹, w/w) was evaluated by the measurements of farinography, rapid visco analysis and differential scanning calorimetry. Adding 5.0 g kg⁻¹ PGA in wheat dough increased the mixing stability and raised the pasting temperature from 75.8 to 84.4 °C, but decreased the peak viscosity and breakdown. The water holding capacity of wheat dough increased with the addition of 5.0 g kg⁻¹ of PGA. At 5.0 g kg⁻¹ level, PGA caused significant declines in the enthalpy, onset and peak temperatures of ice-melting transition of wheat dough. Scanning electron microscopy showed that wheat bread with the addition of 1.0 and 5.0 g kg⁻¹ PGA exhibited microstructures with smoother surfaces. During storage, PGA retarded the staling process of wheat bread.     

Partial extraction method for the rapid analysis of total lipids and γ-oryzanol contents in rice bran

Total lipids and γ-oryzanol in rice bran were determined by a partial extraction method. The results agreed well with the conventional total extraction methods. The proposed method uses fewer hazardous organic solvents, takes a shorter extraction time and requires no special extraction apparatus. Total lipids and γ-oryzanol in nine rice bran varieties were analysed by the developed technique. Daw Dum 5647 had the highest total lipids and γ-oryzanol while the lowest content was found in KD XBT 313-19-1-1 and SP XBT 43-7, respectively. The adsorption coefficient (K_d) of the lipids and γ-oryzanol, between hexane and bran, at 30 °C are between 1.16 and 2.00 and 2.02 and 2.65, respectively (depending on the moisture content of the bran). From the K_d values, it was estimated that about 92–95% of the lipids and 95–96% of the γ-oryzanol were extracted into hexane at a 10:1 (v/w) ratio of hexane to bran. The effect of solvents on the extraction of γ-oryzanol from rice bran was also studied. It was found that isopropanol was the most suitable solvent for extraction and determination of γ-oryzanol in rice bran. It showed better agreement with the total extraction method.     

Hydrolysis of soybean isoflavone glycosides by a thermostable β-glucosidase from Paecilomycesthermophila

The β-glucosidase from Paecilomyces thermophila J18 was found to be capable of hydrolysing daidzin and genistin in a previous study. This report further evaluated the thermostability and hydrolysis of soybean isoflavone glycosides. The enzyme was found to be very stable at 50 °C, and retained more than 95% of its initial activity after 8 h at 50 °C. It converted isoflavone glycosides, in soybean flour extract and soybean embryo extract, to their aglycones, resulting in more than 93% of hydrolysis of three isoflavone glycosides (namely, daidzin, genistin and glycitin) after 4 h of incubation. Also, addition of the β-glucosidase greatly increased the contents of isoflavone aglycones in the suspended soybean flour and soymilk. The results indicate that the thermostable β-glucosidase may be used to increase the isoflavone aglycones in soy products. This is the first report on the potential application of fungal β-glucosidases for converting isoflavone glycosides to their aglycones in soy products.     

Extraction of phenolic compounds from grapes and their pomace using β-cyclodextrin

Use of aqueous cyclodextrins (CD) for recovery of selected bioactive phenolic compounds from grapes and their pomace was evaluated. When α, β and γ forms of CD were compared, β-CD was the most effective in recovering stilbenes, flavonols, and flavan-3-ols from grape pomace. The maximum quantified phenolics were obtained from the powder and the slurry of grape pomace when extracted with 2.5% (w/v) aqueous β-CD solutions at 60 °C for 12–24 h. With β-CD, total quantified phenolics obtained from the dry powder were 123 mg/100 g (DW) while from the slurry, they were 35.8 mg/100 g (FW). Incorporation of β-CD to grape mash prior to pressing for juice enhanced the recovery of phenolics in juice. Incorporation of β-CD was more effective in recovering flavan-3-ols than flavonols. Aqueous CD can effectively be used in recovering phenolics from by-products of fruit processing and therefore for functional foods and nutraceutical applications.     

Optimization of hydroxypropylmethylcellulose,yeast β-glucan,and whey protein levels based on physical properties of gluten-free rice bread using response surface methodology

Response surface methodology (RSM) was used to analyze effects of hydroxypropylmethylcellulose (HPMC), yeast β-glucan, and whey protein isolate (WPI) on physical properties of gluten-free bread baked from formulas based on rice starch. A Box–Behnken design with three independent variables (HPMC, yeast β-glucan, and WPI) and three levels was used to develop models for the different responses (physical properties). Individual contour plots of the different responses produced from the models were compared to the corresponding reference wheat bread data and were superimposed to locate gluten-free bread formulations that met the wheat bread standards for spread ratio, specific volume, hardness, cohesiveness, chewiness, and crumb color L∗ value. The optimal formulation, determined from the data, contained 4.35 g/100 g HPMC, 1 g/100 g β-glucan, and 0.37 g/100 g WPI, rice starch basis. Predicted values of the optimized bread were experimentally tested and compared with the experimental wheat bread data. A good agreement among these data was observed. Moreover, the optimized rice starch bread was found to be acceptable according to the results of sensory analysis.     

Characterization and in vitro bioavailability of β-carotene: Effects of microencapsulation method and food matrix

The objectives of this study were to determine the effect of microencapsulation method on physical properties and in vitro release and bioavailability of three types of β-carotene: a spray-dried powder of β-carotene and maltodextrin, commercially available water-dispersible β-carotene powder, and chitosan-coated β-carotene alginate. In vitro digestion trials were conducted with and without food matrices (yogurt, pudding) to elucidate the effect of food matrix on in vitro release and bioavailability. Microencapsulation method significantly affected (p < 0.05) water activity, moisture content, and particle size. The maltodextrin powder had the lowest moisture content (3.5%) and the smallest volume mean diameter (10.5 μm), whereas the chitosan-alginate beads had the lowest water activity (0.195). The maltodextrin powder had the highest surface β-carotene content (39.5%), while the commercial water-dispersible powder had the highest β-carotene content (10%). The microencapsulation method significantly influenced (p < 0.05) release and incorporation into micelles, regardless of food matrix. Water-dispersible β-carotene achieved the highest release (93.3%) and the highest incorporation into micelles (36.4%) in the absence of a food matrix, and the highest release (34.8%) and the highest micelle content (17.0%) with pudding. Food matrix significantly decreased release and micelle incorporation (p < 0.05), with yogurt decreasing release and micelle incorporation more than pudding.     

Investigation of α-glucosidase inhibitory activity of wheat bran and germ

Postprandial hyperglycaemia is a primary risk factor in the development of Type 2 diabetes. α-Glucosidase inhibitors that reduce postprandial hyperglycaemia have a key role in the treatment of Type 2 pre-diabetic states and also have the potential to reduce the progression to complications of diabetes. Epidemiological studies showed that risk for Type 2 diabetes mellitus was decreased with consumption of whole grains. The bran and germ of whole wheat are major components of whole grain consumption and are widely accepted as important ingredients in many low glycaemic index (GI) foods. In this study, the α-glucosidase inhibitory activity of wheat bran and germ was investigated. The active compounds were screened using an in vitro enzyme-inhibitory assay guided fractionation. Potent α-glucosidase inhibitory compounds from wheat germ were identified as phosphatidic acids, 1,2-dilinoleoylglycero-3-phosphate and 1-palmitoyl-2-linoleoyl-glycero-3-phosphate. The low GI property of whole grain wheat could be attributed to these α-glucosidase inhibitory phosphatidic acids, which have the potential to prevent or treat Type 2 diabetes.     

Extraction of Polyphenolics from Plant Material for Functional Foods—Engineering and Technology

Polyphenolic substances or polyphenols include many classes of compounds ranging from phenolic acids, colored anthocyanins, simple flavonoids, and complex flavonoids. Polyphenolics contribute to the bitterness and astringency of fruits and fruit juices due to the interaction between polyphenolics, mainly procyanidins, and the glycoproteins in saliva. Polyphenols contribute largely to cellular processes within the body. In terms of pharmacological activity, they act against the oxidation of high-density lipoproteins (HDLs). Hence, they help the body retain important HDL while helping it get rid of problematic low-density lipoproteins (LDLs). In addition, polyphenols have also been found to have antiulcer, anticarcinogenic, and antimutagenic activities. The reason behind these activities is polyphenol's strong antioxidant power because they are able to quench free radicals. Green tea and grape seed extracts provide a superior source of monomers that are relatively inexpensive to extract. Comparatively, pine bark and other fruits extracts have low levels of monomers. Therefore, the nutraceutical industry has focused on optimizing extraction processes for green tea leaves and grape pomace, skins, and seeds. During extraction, a solvent is mixed with the plant material (grape seeds, grape skins, pine bark, or tea leaves). Extraction can be either completed by the addition of a solvent to the sample in a container and then removed by drying, or the solvent can be removed by concentration by ultrafiltration (UF). After any one of these processes, the extract must be dried to obtain a powder form. Alternatively, supercritical fluid extraction (SFE) can also be used, which produces the final product as a powder without any use of final drying. Organic solvent extraction is efficient and simple, yet costly. Large amounts of organic solvents are needed. This, in turn, is also detrimental to human use because traces of the organic solvent are present in the polyphenol extract. Polyphenol separation and concentration by membrane separation is even more efficient than organic solvent extraction. Organic solvents are still used but in lower quantities, and UF ensures the purity of the polyphenol extract. The drawback is membrane fouling, which can disrupt the process, and the time it takes to complete the process. The separation process has to be repeated several times. Supercritical fluid extraction is the extraction process of the future. CO₂ is low cost, nontoxic, nonflammable, and noncorrosive, making it the perfect solvent for natural products. In the U.S. market, where $141 million was spent on grape seed products in 1999, it is imperative that safe and efficient extraction procedures are delivered that guarantee a pure polyphenol product.     

Extraction, partial characterization, and storage stability of β-glucosidase from propolis

Extraction and assay conditions for β-glucosidase from propolis were optimized. Highest enzyme activity was obtained in a citric acid-disodium hydrogen phosphate buffer at pH 6.0 with 2.5% insoluble polyvinylpyrrolidone at incubation temperature of 57 °C. β-Glucosidase activities were found in all freshly harvested propolis while β-glucosidase activities were scarcely present in the randomly bought propolis. Propolis was stored at -20 °C and 4 °C for 3 mo with almost no loss of β-glucosidase activity, but at room temperature the activity decreased exponentially with the increase of storage time. These results indicated that the activity of β-glucosidase could be a candidate for propolis-freshness index. β-Glucosidase from propolis was capable of hydrolyzing p-nitrophenyl-β-D-glucoside and p-nitrophenyl-β-D-galactoside, but lacked activity toward p-nitrophenyl-β-D-glucuronide, p-nitrophenyl-β-D-cellobioside, amygdalin, cellobiose, and gentiobiose. These results were consistent with the hypothesis that flavonoid glucosides were hydrolyzed by β-glucosidase during propolis collection and processing and provided a possible explanation for why some flavonoid biosides (that is, rutin and isorhamnetin-3-O-rutinoside) exist in propolis. Practical Application: β-Glucosidase activity was detected and partial characterization of the enzyme was determined in propolis. The enzyme activity decreased exponentially with the increase of storage time at room temperature, which suggested that the activity of β-glucosidase could be regarded as a freshness index of propolis. The research will be useful for studying the chemical constituents of propolis.     

Protease and γ-glutamyltranspeptidase activities of bacillus spp. isolated from rice straw

Bacillus strains were isolated from the rice straw of 7 districts in Korea, and almost all were identified as either B. amyloliquefaciens, B. pumilus, or B. subtilis. The correlation between the protease activity and γ-glutamyltranspeptidase activity produced by the identified Bacillus spp. was positively correlated (R²rF0.747). Statistically, the B. subtilis species might be the most potent producer of protease and γ-glutamyltranspeptidase of 3 identified Bacillus strains.     

Texture properties of rice cakes made of rice flours treated with 4-α-glucanotransferase and their relationship with structural characteristics

Rice flours were treated using a thermostable 4-α-glucanotransferase (GTase) from Thermus aquaticus for 1, 3, and 48 h. Molecular weight of modified rice starch rapidly decreased within 1 h of reaction, then slowed down. As the reaction proceeded, the proportions of short (<DP 11) and long (>DP 30) branched chains of modified starch increased, whereas the proportion of medium chains decreased. Rice cakes were prepared with native and GTase-treated rice flours (substitution at 5%) and kept for 3 and 21 h. Texture profile analysis indicated significantly increased hardness, adhesiveness, chewiness, and resilience in rice cakes containing treated rice flours. Sensory analysis revealed that the rice cakes containing 48 h-treated flour had significantly increased springiness, hardness, toughness, and adhesiveness during both storage periods. Meanwhile, it displayed the lowest starch-like attribute and crumbliness. These results suggested that the substitution for 48 h GTase-treated rice flour could retard the retrogradation of rice cakes.