Charles F. Shoemaker

Physical and Antimicrobial Properties of Peppermint Oil Nanoemulsions

The mixture of peppermint oil (PO) with medium-chain triacylglycerol was emulsified in water and stabilized with a food-grade biopolymer, modified starch, to form PO nanoemulsions. The effects of emulsifying conditions including homogenization pressure, the number of processing cycles, and oil loading on the mean diameters and viscosities of nanoemulsions were characterized by dynamic light scattering, optical microscopy, and rheological measurements. The formulated PO nanoemulsions with mean diameters normally <200 nm showed high stability over at least 30 days of storage time. Their antimicrobial properties related to those of PO have also been evaluated by two assays, the minimum inhibitory concentration (MIC) and time-kill dynamic processes, against two Gram-positive bacterial strains of Listeria monocytogenes Scott A and Staphylococcus aureus ATCC 25923. Compared with bulk PO, the PO nanoemulsions showed prolonged antibacterial activities. The results suggest that the nanoemulsion technology can provide novel applications of essential oils in extending the shelf life of aqueous food products.

Antioxidants and antioxidant activity of several pigmented rice brans.

This study investigated the antioxidant content and activity of phenolic acids, anthocyanins, α-tocopherol and γ-oryzanol in pigmented rice (black and red rice) brans. After methanolic extraction, the DPPH free radical scavenging activity and antioxidant activity were measured. The pigmented rice bran extract had a greater reducing power than a normal rice bran extract from a long grain white rice. All bran extracts were highly effective in inhibiting linoleic acid peroxidation (60-85%). High-performance liquid chromatography (HPLC) analysis of antioxidants in rice bran found that γ-oryzanol (39-63%) and phenolic acids (33-43%) were the major antioxidants in all bran samples, and black rice bran also contained anthocyanins 18-26%. HPLC analysis of anthocyanins showed that pigmented bran was rich in cyanidin-3-glucoside (58-95%). Ferulic acid was the dominant phenolic acid in the rice bran samples. Black rice bran contained gallic, hydroxybenzoic, and protocatechuic acids in higher contents than red rice bran and normal rice bran. Furthermore, the addition of 5% black rice bran to wheat flour used for making bread produced a marked increase in the free radical scavenging and antioxidant activity compared to a control bread.

Stability and Bioaccessibility of β-Carotene in Nanoemulsions Stabilized by Modified Starches

Oil-in-water nanoemulsions stabilized by food-grade biopolymer emulsifiers (modified starches) were fabricated using high-pressure homogenization in an effort to improve the stability and bioaccessibility of β-carotene. Physicochemical and biological properties of β-carotene nanoemulsions were investigated considering the particle size, β-carotene retention, and in vitro digestion. During 30 days of storage at different conditions, the mean diameters of the emulsion systems were increased by 30-85%. The retention of β-carotene in nanoemulsions was significantly higher compared to that of the β-carotene dispersed in bulk oil. After in vitro digestion, the bioaccessibility of β-carotene was increased from 3.1% to 35.6% through nanoencapsulation. The results also indicated that modified starch with high dispersed molecular density led to a higher retention but lower bioaccessibility of β-carotene in nanoemulsions. This could be due to the thick and dense interfacial layer around the oil droplets. This result provides useful information for developing protection and delivery systems for carotenoids.

Optimization of liquid phase mixtures

Abstract The concept of window diagrams has been used to predict what lengths of dissimilar fused-silica capillaries should be serially coupled to achieve the optimum separation of two “real world” samples whose separation on a single column has not yet been reported. Complicating factors, including the role of the solute partition ratio and the velocity gradient of the carrier gas, are discussed. Separations of mixtures of (a) volatiles produced by yeast fermentation, and (b) solvents used in the preparation of food packaging films, were achieved in single passes on properly configured serially coupled columns composed of two precise lengths, one coated with polymethylsiloxane, and the other with polyethylene glycol.

The use of capillary viscometry, reducing end-group analysis, and size exclusion chromatography combined with multi-angle laser light scattering to characterize endo-1,4-β-d-glucanases on carboxymethylcellulose: a comparative evaluation of the three methods

Abstract Three methods were used to characterize seven purified endo-1,4-β- d -glucanases derived from different microbial sources (Trichoderma reesei, Thermomonospora fusca, and Acidothermus cellulolyticus) on carboxymethylcellulose (CMC). The methods included capillary viscometry, reducing end-group analysis, and high performance size exclusion chromatography combined with multi-angle laser light scattering (HPSEC-MALLS). The investigation was performed with the objective of comparative evaluation of the different methods for characterizing endoglucanases, particularly in relation to their endo- and exomode of action. The measurement of the initial rate of reducing end-group formation using disodium 2,2′-bicinchoninate (BCA) was found to be the most accurate method for determination of endoglucanase activity. The BCA method was highly sensitive, simple to perform, and directly gave the number of bonds broken, thus allowing for expression of endoglucanase activity in international units (μmol of β-1,4-glucosidic bonds hydrolyzed in 1 min during the initial period of hydrolysis). The viscometric method was simple to perform and highly sensitive for the internal bonds cleaved, but did not account for the hydrolysis of CMC near the chain end, and thus only allowed for expression of endoglucanase activity in arbitrary viscometric units. The HPSEC-MALLS technique provided the number-average molecular weight (Mn) of CMC, thus allowing the quantification of the number of the bonds broken during degradation of CMC; however, reproducibility of the method was low, especially for the high-molecular weight fragments of CMC at the beginning of hydrolysis. As hydrolysis proceeded to the more advanced stages, the HPSEC-MALLS method gave an overestimated (compared to the reducing end-group analysis) values for Mn, probably due to insufficient sensitivity of the light-scattering detector for the low-molecular weight products of CMC degradation. The combined use of the three methods allowed characterization of endoglucanases according to their selectivity for hydrolysis of internal bonds within a CMC molecule which was expressed as the ratio of the initial rate of viscosity decrease to the initial rate of glucosidic bonds broken. This ratio was found to be unique for each endoglucanase, and, therefore, no universal equation could be established for all endoglucanases for conversion of arbitrary viscometric units to international units of activity.

Properties of Chitosan-Microencapsulated Orange Oil Prepared by Spray-Drying and Its Stability to Detergents

Fragrance encapsulated in small particles of <20 μm diameter is preferred for use in textiles. This study demonstrated that the proper combination of surfactants could produce small and heat-stable emulsion droplets with chitosan that could be spray-dried to produce microcapsules. The microcapsules were able to be deposited onto cotton using water or detergents. It was found that stable emulsion was obtained when Tween 40 and Span 20 were used as compound emulsifiers with the ratio of 4:1 (w/w). The optimum conditions were 1% (w/w) chitosan in acetic acid with the compound emulsifiers of 3-7% (w/w) in the oil, and the inlet temperature for spray-drying was 150 °C. The encapsulation efficiency for orange oil was >90% with a 1:2 (w/w) ratio of oil to chitosan. Microcapsules had a mean diameter of <20 μm and regular particle morphology. The orange oil in the microcapsules was well retained in cotton fabrics after washing in normal detergent solution. The process and products are low in cost, nontoxic, biocompatible, and biodegradable.

Effect of polysaccharides on the gelatinization properties of cornstarch dispersions.

Konjac glucomannan (KG, neutral), carboxymethylcellulose (CMC, negatively charged), and chitosan (positively charged) were added to cornstarch dispersions to study the effect of polysaccharide-starch interactions on starch gelatinization properties. Pasting and retrogradation properties were measured with a rheometer and DSC. Swelling properties of the starch granules were determined by solubility index, swelling power, and particle size distribution. Depending on the nature of the different polysaccharides, viscosities of cornstarch dispersions were affected differently. The particle size distributions were not influenced by the addition of any of the polysaccharides. Swelling results showed that the KG and CMC molecules interacted with the released or partly released amylose in the cornstarch dispersions. This was correlated with the short-term retrogradation of the starch pastes being retarded by the additions of KG and CMC. However, the chitosan molecules appeared not to associate with the amylose, so the retrogradation of the chitosan-cornstarch dispersions was not retarded.

The effect of high moisture heat-acid treatment on the structure and digestion property of normal maize starch.

The objective of this study was to analyze the influence of thermal-acid treatment on the formation of resistant starch (RS). The maximum RS content in citric acid-heat treated starches (CAHT) reached 36.55%, which was 7 times higher of that in native starch. According to HPSEC-MALLS-RI analysis, amylopectin was more susceptible to hydrolysis than amylose during citric acid-heat treatment (CAH). X-ray measurement revealed that even though the starch crystalline pattern was changed from A-type to a more resistant B-type after CAH, the fraction of crystalline region decreased from 21.16% to 8.37%. The hydroxyls on the starch chains were substituted by the citric acid anhydrides during CAH according to FT-IR analysis, which led to the formation of ester bond cross-linking structures in starch granules, and it could be the main contribution to the increase of RS content in CAHT samples.

Effect of dry heat treatment with xanthan on waxy rice starch.

Waxy rice starch was impregnated with xanthan and heat-treated in a dry state. The effects on the pasting and rheological properties of the treated starch-xanthan mixture were evaluated. Swelling of the granule was restricted, and a continuous rise of the viscosity during pasting was provided for the treated sample. After pasting, the gel forming ability of the treated starch was strengthened, as both storage and loss modulus increased and tan δ decreased. The paste also owned the highest zero order Newtonian viscosity and yield stress. An increase in starch particle size of the dry heated starch-xanthan mixture suggested a cross linking of the starch granules by the xanthan polymers. An increase of crystallinity was observed for the starch after dry heat treatment, but with the addition of xanthan the amorphous region of the granule became more resistant to dry-heating. The melting enthalpy was found to be correlated with the crystallinity.

Mechanical properties of composite gels consisting of fractionated whey proteins and fractionated milk fat

Abstract Properties of composite gels with 13% protein consisting of 0:1-to-1:0 α-lactalbumin (α-Lac) to β-lactoglobulin (β-Lg) and 10 or 30% filler consisting of fractionated milk fat as well as properties of matrix-only gels with 10–15% proteins were investigated at 4–50 °C. Maximum compressive force and elastic modulus of the composites were proportionately related to the proportion of β-Lg and proportion of solid lipids included in the matrix and filler, respectively. Details of the compressive behavior, microstructure and extent to which filler affected the mechanical properties were significantly influenced by protein composition. Results obtained with matrix-only gels indicated a protein composition-specific power law relationship ( n =2) between protein content and mechanical properties of the gels.