Roger Stanley

Near-quantitative production of fatty acid alkyl esters by lipase-catalyzed alcoholysis of fats and oils with adsorption of glycerol by silica gel

Abstract A simple solution to the problem of incomplete reaction in lipase-catalyzed alcoholysis of triacylglycerol oils has been found. When immobilized Mucor meihei lipase was used to catalyze the reaction of tallow with three molar equivalents of butanol, the yield of butyl esters did not exceed 70% (w/w). If silica gel was added to the reaction mixture, it adsorbed the glycerol produced during the reaction and the yield increased to up to 98%. The optimum amount of silica gel was 1.25 weight equivalents to the glycerol produced. Other adsorbents were tested, e.g., cellulose, starch, charcoal, and celite, but none was as effective as silica gel. A variety of fats and oils could be used and all gave yields over 90%. Aliphatic alcohols varying in polarity between methanol and dodecanol also gave yields over 90%, although the highest yields were obtained from the most hydrophobic alcohols. The reaction could be carried out by circulating the reaction mixture through columns of enzyme and silica gel. Dehydration of the reaction mixture, and hence of the enzyme, by the silica gel caused loss of activity during repeated reuse of the enzyme. This problem could be minimized by increasing the water content of the initial reaction mixture.

Stability of antioxidants in an apple polyphenol-milk model system

The stability of antioxidants in an apple polyphenol-milk model system was examined. The model system consisted of skim milk fortified with pH-neutralised apple polyphenols (AP, 0-200mg per 100ml milk), with or without ascorbic acid (100mg per 100ml milk). Physical and chemical changes were evaluated after thermal treatment (120°C, 5min) and oxidative storage (20°C and 38°C, up to 12 weeks). Antioxidant capacity was determined using both oxygen radical absorbance capacity (ORAC) assay and ferric reducing antioxidant power (FRAP) assay. Significant antioxidant capacity was detected in the presence of milk. Antioxidant capacity was retained during thermal treatment but decreased slowly during storage. The concentration of ascorbic acid decreased rapidly, and was close to zero after 2-week storage at 38°C or 10-week storage at 20°C. The brownness of the polyphenol-milk system increased over storage duration of 0-12 weeks; this effect was retarded by the addition of ascorbic acid. This high polyphenol-milk has demonstrated good physical stability.

Observation by solid-state 3C CP MAS NMR spectroscopy of the transformations of wheat starch associated with the making and staling of bread

Abstract Wheat starch and wheat starch gels were characterised by 13C CP MAS NMR spectroscopy. It was found that rotating-frame relaxation rates were signif the increase in crystallinity over a period of time. Starch gels were found to contain three distinct components: amorphous regions, crystalline region

Pilot-scale resin adsorption as a means to recover and fractionate apple polyphenols

The purification and fractionation of phenolic compounds from crude plant extracts using a food-grade acrylic adsorbent were studied at pilot-plant scale. A diluted apple juice concentrate served as a model phenolic solution for column adsorption and desorption trials. Phenolic concentrations were evaluated photometrically using the Folin-Ciocalteu assay and by HPLC-DAD. Recovery rates were significantly affected by increasing phenolic concentrations of the feed solutions applied to the column. In contrast, the flow rate during column loading hardly influenced adsorption efficiency, whereas the temperature and pH value were shown to be crucial parameters determining both total phenolic recovery rates and the adsorption behavior of individual polyphenols. As expected, the eluent composition had the greatest impact on the desorption characteristics of both total and individual phenolic compounds. HPLC analyses revealed significantly different elution profiles of individual polyphenols depending on lipophilicity. This technique allows fractionation of crude plant phenolic extracts, thus providing the opportunity to design the functional properties of the resulting phenolic fractions selectively, and the present study delivers valuable information with regard to the adjustment of individual process parameters.

Effects of flavonoid extract Enzogenol® with vitamin C on protein oxidation and DNA damage in older human subjects

In this study a 12 week clinical trial was conducted with Enzogenol®, a commercially available proanthocyanidin-rich flavonoid extract derived from the bark of Pinus radiata that was formulated with vitamin C. The study was to determine whether the oxidative injury markers of protein and DNA damage could be affected by the product. Twenty four (14 males and 10 females) subjects aged between 55-75 years completed the study. The group was given a twice daily dose of 240 mg of Enzogenol® and 120 mg vitamin C for 12 weeks and blood samples were collected at the start of the study before supplementation, 6 weeks and 12 weeks. Plasma samples were analysed for protein carbonyl concentrations as a measure of protein oxidation by an ELISA method. Isolated peripheral blood mononuclear cells were analysed for DNA damage using the alkaline comet assay. Protein carbonyl concentration reductions were highly significant after 6 and 12 weeks of supplementation. DNA damage reduction, as measured by the comet assay, was not significant after 6 weeks but highly significant after 12 weeks of supplementation.

Glycerolysis of tallow with immobilised lipase

SummaryLipozyme (immobilised Mucor meihei lipase) was used to catalyse glycerolysis of melted tallow to synthesise monoglycerides. At a reaction temperature of 50 °C, a maximum 35% yield of monoglyceride was obtained. Cooling the reaction below 42°C resulted in monoglyceride crystallisation which improved the yield to up to 50% but further yield increases were prevented by solidification of the reaction mixture. Enzyme could be easily recovered by filtration after melting the reaction mixture. The reaction could also be carried out by circulating the reaction mixture through a packed column of lipozyme.

Oligosaccharide and alkyl β-galactopyranoside synthesis from lactose with Caldocellum saccharolyticum β-glycosidase

Abstract The synthetic utility of the thermostable β-glycosidase from Caldocellum saccharolyticum was investigated. The ability of the enzyme to catalyze oligosaccharide and β-galactopyranoside synthesis from lactose was compared with that of the readily commercially available, moderately thermostable β-galactosidase (β- d -galactoside galactohydrolase, EC 3.2.1.23) from Aspergillus oryzae. Generally, the C. saccharolyticum enzyme showed significantly greater resistance to inactivation by heat and organic solvent and better yields of product. Although the A. oryzae enzyme gave better oligosaccharide yields at lower lactose concentrations, at higher concentrations (above 50% w/w) the C. saccharolyticum enzyme was significantly better, yielding a sugar mixture containing 42% by weight of tri- plus tetra-saccharides, from a 70% w/w lactose solution, compared with 31% by weight of oligosaccharides with the A. oryzae enzyme. In ethyl galactoside synthesis from ethanol and lactose, neither enzyme appeared to hydrolyze the product to any great extent. Under all conditions tested, the product yield did not peak, even at long reaction times, when most of the lactose had been consumed. The C. saccharolyticum enzyme, however, gave slightly higher product yields and could be used at higher ethanol concentrations without serious loss of activity.

Protease-catalyzed condensation of peptides as a potential means to reduce the bitter taste of hydrophobic peptides found in protein hydrolysates

Abstract Synthetic dipeptides of varying hydrophobicity were used as a model system to investigate the feasibility of reversed protease action as a means of improving the flavor of bitter peptides found in protein hydrolysates. The four different proteases tested were able to convert hydrophobic dipeptides into an insoluble precipitate, but with different efficiencies. Hydrophilic dipeptides did not give detectable condensation or precipitation. Solid-state and solution NMR were used to monitor peptide bond formation in 13C-labelled peptides. NMR and MS analyses showed that the products consisted of higher oligomers of the original peptide. Bitterness decreased in the order starting with dipeptides > whole reaction mixtures ⪢ isolated precipitates. Taste improvement correlated with peptide bond formation and the formation of insoluble material. These observations indicated that the condensation reaction was driven by precipitation of insoluble reaction products and that this process is a potential means to improve the flavor of bitter peptides extracted from protein hydrolysates.

Japanese plums (Prunus salicina Lindl.) and phytochemicals – breeding, horticultural practice, postharvest storage, processing and bioactivity

Previous reviews of plum phytochemical content and health benefits have concentrated on the European plum, Prunus domestica L. However, the potential bioactivity of red- and dark red-fleshed Japanese plums, Prunus salicina Lindl., so-called blood plums, appears to warrant a significant increase in exposure, as indicated in a recent review of the whole Prunus genus. Furthermore, Japanese plums are the predominant plum produced on an international basis. In this review the nutrient and phytochemical content, breeding, horticultural practice, postharvest treatment and processing as well as bioactivity (emphasising in vivo studies) of Japanese plum are considered, with a focus on the anthocyanin content that distinguishes the blood plums.

Separation and concentration of health compounds by membrane filtration

The performance of nano-filtration (NF) for separating phenolic compounds from sugar in apple juice was studied using 1 and 0.25 kDa molecular weight cut-off (MWCO) spiral wound membranes. If these phenolic compounds could be recovered, they could stabilize the juice from haze formation or be added as antioxidants to foods and beverages in order to increase their health properties. Batch experiments were conducted on a pilot scale rig using a diluted clear apple juice concentrate. For the 1 kDa MWCO membrane, the research determined the effect of operating conditions on process efficiency and membrane fouling. The concentration of polyphenolics on the retentate side increased by a factor of up to 4 and the sugar concentration increased by 1.5 times under optimum conditions of lower temperature (30oC), acidic pH (2), lower trans-membrane pressure (5 Bar) and higher initial sugar concentration (20 oBrix). Despite the increase in polyphenolics in the retentate, there was little difference in the phenolic composition between retentate and permeate solutions. As the molecular mass of the rejected phenolics was smaller than the membrane cut-off, this indicated that the rejection was related to the formation of a secondary membrane formed as a result of fouling. A mass balance of polyphenolics in the final retentate and permeate compared with the initial feed solution indicated that up to 4.3 gm of polyphenolics were bound per m2 of membrane. The permeate solutions collected from the 1 kDa MWCO membrane were then filtered using a 0.25 kDa MWCO membrane. Most phenolic compounds were retained by the membrane and the concentration increased by a factor of up to 2. Catechin, rutin, phloridzin and quercetin derivatives were concentrated on the retentate side. However, around 20 - 40% of chlorogenic acid and epicatechin was observed on the permeate side. It is concluded that membrane separation represents a potentially efficient and cost-effective technology to separate the phenolic fraction of fruit juice in a form suitable for use as a functional ingredient.