Hung-Min Chang

Antioxidative activity of roasted and defatted peanut kernels

Abstract Peanut kernels were roasted at 180±2°C for various period of times (0–60 min); then grounded and defatted or further hydrolyzed with proteases to test their antioxidative activity (AOA). Samples roasted for 60 min displayed the most remarkable AOA, determined by Ferric-thiocyanate method, on linoleic acid in emulsions prepared with Tween 20 or 80. In reducing power, the absorbance at 700 nm of enzymatic hydrolysates (1 mg/ml) prepared from a 60-min-roasted sample with Esperase (enzyme/substrate=1/200, 60°C, pH 8.0) and with Neutrase (enzyme/substrate=1/200, 50°C, pH 6.0) was 1.24 and 0.81, respectively. The scavenging activity of Esperase and Neutrase hydrolysates on DPPH (α, α′- diphenyl-β-picryldrazyl) radicals was 93 and 89%, respectively, while their chelating activity on Fe+2 was 69 and 52%, respectively. Besides, in vitro, Esperase hydrolysates (⩾100 μg/ml) exhibited the remarkable antioxidative effect on the oxidation of low-density lipoprotein (LDL) induced by copper by showing a lag time of longer than 6 h.

Quantification of racemization of amino acids in alkaline-treated duck eggs by micellar capillary electrophoresis.

Duck eggs were pickled in 4.2% NaOH/5% NaCl solution for 20 days to prepare the traditional Chinese Pidan. The extent of racemization of compositional amino acid in egg albumen and yolk over the alkaline pickling period was investigated with micellar capillary electrophoresis (MCE) using beta-cyclodextrin as chiral selector. The racemization value of amino acids in egg albumen was in the order serine > aspartic acid > glutamic acid > phenylalanine > leucine > valine > threonine = isoleucine, whereas the order in egg yolk was aspartic acid > glutamic acid > phenylalanine > leucine > valine. Therefore, the tendency of amino acid racemization appeared to be closely related to the properties of its residual side chain, as well as the pH and alkaline treating period. Moreover, racemization of most of the amino acids was remarkably induced by the alkaline treatment during the initial pickling period.

Characterization of pectinesterase inhibitor in jelly fig (Ficus awkeotsang Makino) achenes.

Pectinesterase inhibitor (PEI) extract prepared from intact jelly fig (Ficus awkeotsang Makino) achenes was separated by membrane (MWCO 3 and 10 kDa) and fractionated by a Sepharose G-50 gel permeation chromatography. Results from Sepharose G-50 gel permeation chromatography and concanavalin A Sepharose chromatography revealed PEI as polypeptides with molecular weights ranging from 3.5 to 4.5 kDa. Incubation of a PE (1 unit/mL)-PEI (2 mg/mL) mixture for 1 min decreased the PE activity by approximately 50%. On the basis of the results of Lineweaver-Burk double-reciprocal plots, Michaelis constant (K(m)) and V(max) values for jelly fig achenes PE (pH 6.0, 30 degrees C) were 0.78 mM -OCH3 and 1.09 microequiv of -COOH/min, respectively. In addition, PEI competitively inhibited both citrus and jelly fig achenes PEs.

Changes in physico-chemical properties of pectin from jelly fig (Ficus awkeotsang Makino) seeds during extraction and gelling

Degree of esterification of pectin from jelly fig (Ficus awkeotsang Makino) achene seeds and the pH value decreased rapidly during extraction, while apparent reduction of free calcium content in the pectin extract was observed at the gelling stage. Compared to those of the native pectin, total ester linkages and methyl ester linkages of pectin extract decreased, and the bound calcium content increased during pectin gelling. However, non-methyl ester linkages (the difference between the total ester linkage and the methyl ester linkage) increased by approximately 40% during pectin gelling, revealing esterification reaction between C6 carboxyl groups and hydroxyl groups in the presence of pectinesterase. Scanning electron microscopy showed that pectin fragments from jelly curds were large with flake-like structure, while those from hot (85°C) ethanol-treated achenes were small and porous.

Quantification of L-ascorbic acid and total ascorbic acid in fruits and spinach by capillary zone electrophoresis

A standard curve for the quantification of L‐ascorbic acid (L‐AA) by capillary zone electrophoresis (CZE) was established, and the quantification of ascorbic acid and total ascorbic acid in fruits (lemon, Sunkist, and pineapple) and spinach were performed using D‐isoascorbic acid (D‐IAA) as an internal standard. The minimum detection limits (MDLs) for L‐AA and D‐IAA were determined to be 1 and 2 νg/mL, respectively, at 265 nm. Dehydroascorbic acid (DHAA) in fruits and spinach was quantified in the presence of DL‐homocysteine. The recoveries for L‐AA in these juices were between 95 and 105%.

A study on the mechanism of browning in mei liqueur using model solutions

Browning mechanisms of mei liqueur were studied using model solutions containing 28% ethanol in 0.1 M citrate solution (pH 3.0). Catechin alone was stable in the model solution but degraded rapidly to form hydroxymethyl furfural (HMF) in incubation with fructose at 70 °C. The rate of increase in the absorbance at 420 nm also suggested that fructose was more potent than glucose in enhancing browning in acidic ethanolic environment. We propose that the major browning mechanisms in mei liqueur are the oxidation and condensation of tannins and the interactions between tannins and HMF derived from fructose, rather than Maillard reaction, ascorbic acid degradation, or caramelization.

Inhibition of lysinoalanine formation in alkali-pickled duck egg (Pidan)

Abstract Duck eggs were pickled in 4.2% NaOH/5% NaCl solution for 20 days to prepare the traditional Chinese Pidan. Influence of some additives, such as 0.2% CuSO4 0.2% ZnSO4 0.2% PbO, 10 mM l -cysteine or 10 mM reduced glutathione solution, in the pickle solution on the formation of lysinoalanine (LAL) as well as the degradation of lysine in albumen and egg yolk were investigated. It was observed that CuSO4 exhibited the most prevalent inhibition effect on LAL formation in both Pidan albumen and egg yolk, followed by ZnSO4 and PbO. Addition of l -cysteine or reduced glutathione in the pickling solution marked a decreased LAL formation in Pidan.

Isolation of immunoglobulin in yolk (IgY) and rabbit serum immunoglobulin G (IgG) specific against bovine lactoferrin by immunoaffinity chromatography

Abstract Hens were intramuscularly immunized and rabbits were subcutaneously immunized once every two weeks for 6 weeks using bovine lactoferrin (LF) as antigen. Antibody titers of both yolk (IgY) and rabbit serum (IgG) were as high as 1.68×10 8 at the 6th and 8th weeks, respectively, after the initial immunization treatment. However, antibody titer against LF in yolk was 9.4×10 7 at 16 weeks. While antibody titer of rabbit serum declined sharply to 2.1×10 7 at the 12th week and to 2.6×10 6 at the 13th week after the initial immunization. The purification efficiency (specific activity of purified antibody against LF/specific activity of the corresponding antiserum or yolk against LF) of rabbit serum IgG purified by laboratory-prepared LF-Sepharose 4B immunoaffinity column (0.05 mg LF/ml wet gel) was about 2400, similar to that of IgY purified by LF-Sepharose 4B immunoaffinity column. Different amounts (0–15.0 mg) of IgY purified by LF-Sepharose 4B immunoaffinity chromatography were applied to the same column to determine the binding capacity ( q m ) and dissociation constant ( K d ) of LF-Sepharose 4B immunoaffinity gel for IgY specific against LF. It was found that q m was 0.81 mg IgY/ml wet gel (1.620 mg IgY/mg LF) and K d was 6.4×10 −6 M as determined by Langmuir-type adsorption isotherms.

Effect of calcium and thrombin on the turbidity changes and the gelation properties of swine plasma

Abstract Swine plasma solution containing 5.8% protein and 0.4% Na-citrate was supplemented with 800–2000 ppm of calcium to investigate the time-dependent changes of turbidity and gel strength. Maximal absorbance (660 nm) slopes change with time (Sm) were calculated by the first derivatives from the turbidity curves. It was found that plasma solution supplemented with 1200 and 1500 ppm calcium had the maximal Sm value (Max Sm), while that supplemented with 1350 ppm calcium exhibited the minimal Sm value (Min Sm). The minimal time period for activation of blood clotting-related enzymes (Min TSm) was found to be 8.0 min in plasma supplemented with 1200 ppm calcium. Linear relationships of Max Sm and Min TSm between calcium content and 1/protein concentration were observed. Maximal activation of thrombin was obtained by the addition of 800–1200 ppm calcium. Addition of thrombin (0–8 U/ml plasma solution) decreased the gel strength of plasma in the presence of 1000 ppm calcium.