Nicholas H. Low

Effect of pH, Salt, and Biopolymer Ratio on the Formation of Pea Protein Isolate−Gum Arabic Complexes

Turbidity measurements were used to study the formation of soluble and insoluble complexes between pea protein isolate (PPI) and gum arabic (GA) mixtures as a function of pH (6.0-1.5), salt concentration (NaCl, 0-50 mM), and protein-polysaccharide weight mixing ratio (1:4 to 10:1 w/w). For mixtures in the absence of salt and at a 1:1 mixing ratio, two structure-forming transitions were observed as a function of pH. The first event occurred at a pH of 4.2, with the second at pH 3.7, indicating the formation of soluble and insoluble complexes, respectively. Sodium chloride (<or=7.5 mM) was found to have no effect on biopolymer interactions, but interfered with interactions at higher levels (>7.5 mM) due to substantial PPI aggregation. The pH at which maximum PPI-GA interactions occurred was 3.5 and was independent of NaCl levels. As PPI-GA ratios increased, structure-forming transitions shifted to higher pH.

Nectar-carbohydrate production and composition vary in relation to nectary anatomy and location within individual flowers of several species of Brassicaceae

Abstract. Nectar-carbohydrate production and composition were investigated by high-performance liquid chromatography and enzymology in nine species from five tribes of the Brassicaceae. In six species (Arabidopsis thaliana (L.) Heynh., Brassica napus L., B. rapa L., Lobularia maritima (L.) Desv., Raphanus sativus L., Sinapis arvensis L.) that produced nectar from both lateral nectaries (associated with the short stamens) and median nectaries (outside the long stamens), on average 95% of the total nectar carbohydrate was collected from the lateral ones. Nectar from these glands possessed a higher glucose/fructose ratio (usually 1.0–1.2) than that from the median nectaries (0.2–0.9) within the same flower. Comparatively little sucrose was detected in any nectar samples except from Matthiola bicornus (Sibth. et Sm.) DC., which possessed lateral nectaries only and produced a sucrose-dominant exudate. The anatomy of the nectarial tissue in nectar-secreting flowers of six species, Hesperis matronalis L., L. maritima, M. bicornus, R. sativus, S. arvensis, and Sisymbrium loeselii L., was studied by light and scanning-electron microscopy. Phloem alone supplied the nectaries. However, in accordance with their overall nectar-carbohydrate production, the lateral glands received relatively rich quantities of phloem that penetrated far into the glandular tissue, whereas median glands were supplied with phloem that often barely innervated them. All nectarial tissue possessed modified stomata (with the exception of the median glands of S. loeselii, which did not produce nectar); further evidence was gathered to indicate that these structures do not regulate nectar flow by guard-cell movements. The numbers of modified stomata per gland showed no relation to nectar-carbohydrate production. Taken together, the data on nectar biochemistry and nectary anatomy indicate the existence of two distinct nectary types in those Brassicacean species that possess both lateral and median nectaries, regardless of whether nectarial tissue is united around the entire receptacle or not. It is proposed that the term “nectarium” be used to represent collectively the multiple nectaries that can be found in individual flowers.

Microcapsule production employing chickpea or lentil protein isolates and maltodextrin: Physicochemical properties and oxidative protection of encapsulated flaxseed oil

Flaxseed oil was microencapsulated, employing a wall material matrix of either chickpea (CPI) or lentil protein isolate (LPI) and maltodextrin, followed by freeze-drying. Effects of oil concentration (5.3-21.0%), protein source (CPI vs. LPI) and maltodextrin type (DE 9 and 18) and concentration (25.0-40.7%), on both the physicochemical characteristics and microstructure of the microcapsules, were investigated. It was found that an increase in emulsion oil concentration resulted in a concomitant increase in oil droplet diameter and microcapsule surface oil content, and a decrease in oil encapsulation efficiency. Optimum flaxseed oil encapsulation efficiency (∼83.5%), minimum surface oil content (∼2.8%) and acceptable mean droplet diameter (3.0 μm) were afforded with 35.5% maltodextrin-DE 9 and 10.5% oil. Microcapsules, formed by employing these experimental conditions, showed a protective effect against oxidation versus free oil over a storage period of 25 d at room temperature.

The chemical composition of 80 pure maple syrup samples produced in North America

Abstract A total of 80 pure maple syrup samples received from primary producers in Canada and the United States were analyzed for their chemical composition, pH and oBrix. The major carbohydrates found in maple syrup (sucrose, glucose and fructose) were determined employing anion exchange high performance liquid chromatography (HPLC) with pulsed amperometric detection. The sucrose content was found to range from 51.7 to 75.6%; glucose and fructose contents ranged from 0.00 to 9.59% and 0.00 to 3.95%, respectively. The major organic acid present in maple syrup was malic acid. Trace amounts of citric, succinic and fumaric acid were also present. All organic acids were determined by ion exchange HPLC analysis with UV detection at 210 nm. Malic acid levels ranged from 0.1 to 0.7%. Citric, succinic and fumaric acids were found to be present at levels less than 0.06 ppm. Inductively coupled plasma atomic emission spectroscopy was employed for the analysis of potassium, magnesium and calcium, the main minerals found in maple syrup. Potassium was found to be present in the greatest concentration ranging from 1005 to 2990 mg 1−1. Magnesium and calcium ranged from 10 to 380 mg/l and 266 to 1702 mg 1−1, respectively. The Karl Fischer titration method was employed to determine maple syrup moisture content. The moisture content of maple syrup ranged from 26.5 to 39.4%. The pH and oBrix values for maple syrup ranged from 5.6 to 7.9, and 62.2 to 74.0 °, respectively.

Intermolecular Interactions during Complex Coacervation of Pea Protein Isolate and Gum Arabic

The nature of intermolecular interactions during complexation between pea protein isolate (PPI) and gum arabic (GA) was investigated as a function of pH (4.30-2.40) by turbidimetric analysis and confocal scanning microscopy in the presence of destabilizing agents (100 mM NaCl or 100 mM urea) and at different temperatures (6-60 degrees C). Complex formation followed two pH-dependent structure-forming events associated with the formation of soluble and insoluble complexes and involved interactions between GA and PPI aggregates. Complex formation was driven by electrostatic attractive forces between complementary charged biopolymers, with secondary stabilization by hydrogen bonding. Hydrophobic interactions were found to enhance complex stability at lower pH (pH 3.10), but not with its formation.

Chitosan-tripolyphosphate submicron particles as the carrier of entrapped rutin.

Chitosan (CH)-tripolyphosphate (TPP) submicron particles were formed as carriers of entrapped rutin, and the release properties characterized using simulated gastric juices and fluids of the small intestine. Particle size, charge and entrapment efficiencies were investigated as a function of the CH:TPP molar ratio (2.0:1.0-5.0:1.0). Size was found to decrease from ~814 nm for the 2.0:1:0 mass ratio to ~528 nm for the ratios between 2.5:1.0 and 4.0:1.0, and then again to ~322 nm for the 5:0:1.0 mass ratio, whereas all particles carried a positive surface charge, increasing from +21 to +59 mV as the ratio increased from 2.0:1.0 to 5.0:1.0. The percent entrapment was found to rise from 3.68% to 57.6% as the ratios increased from 2.0:1:0 to 4.0:1:0, before reaching a plateau. Submicron particles (4.0:1.0 mass ratio only) were found to retain rutin in simulated gastric fluids, whereas in conditions which simulated fluids from the small intestine, only 20% of the entrapped rutin was released and 80% remained absorbed to the CH:TPP carriers. Such particles have applications for the delivery of phenolics in food and natural health products.

Encapsulation of flaxseed oil using a benchtop spray dryer for legume protein-maltodextrin microcapsule preparation.

Flaxseed oil was microencapsulated employing a wall material matrix of either chickpea (CPI) or lentil protein isolate (LPI) and maltodextrin using a benchtop spray dryer. Effects of emulsion formulation (oil, protein and maltodextrin levels) and protein source (CPI vs LPI) on the physicochemical characteristics, oxidative stability, and release properties of the resulting capsules were investigated. Microcapsule formulations containing higher oil levels (20% oil, 20% protein, 60% maltodextrin) were found to have higher surface oil and lower encapsulation efficiencies. Overall, LPI-maltodextrin capsules gave higher flaxseed oil encapsulation efficiencies (∼88.0%) relative to CPI-maltodextrin matrices (∼86.3%). However, both designs were found to provide encapsulated flaxseed oil protection against oxidation over a 25 d room temperature storage study relative to free oil. Overall, ∼37.6% of encapsulated flaxseed oil was released after 2 h under simulated gastric fluid, followed by the release of an additional ∼46.6% over a 3 h period under simulated intestinal fluid conditions.

Glucose syrup production from Indonesian palm and cassava starch

Six palm starch samples and one cassava starch sample from Indonesia were converted into glucose syrup with comparison to a commercial corn starch, sample. The conversion was carried out by both liquefaction using α-amylase from B. stearothermophilius and saccharification using glucoamylase from A. niger. The liquefaction time for Metroxylon starch samples was longer than that observed for the other starch samples. Viscosity during liquefaction for palm and cassava starch samples showed the same variation. Based on dextrose equivalent (DE) and high performance liquid chromatography (HPLC) results, starch conversion to glucose for five of the palm and the cassava starch sample was equivalent to that observed for the corn starch sample. Starch conversion to isomaltose and maltose for the palm and cassava starch samples was equivalent to that for the corn starch sample. In general, starch conversion to higher oligosaccharides (DP-3 to DP-7) for the palm and cassava starch samples was higher than that observed for the corn starch sample. Therefore, based on the liquefaction time, percent conversion to glucose and total oligosaccharides, all palm and cassava starch samples, except for one A. pinnata starch sample, could be used for glucose syrup production.

Major Carbohydrate, Polyol, and Oligosaccharide Profiles of Agave Syrup. Application of this Data to Authenticity Analysis

Nineteen pure agave syrups representing the three major production regions and four processing facilities in Mexico were analyzed for their major carbohydrate, polyol, and oligosaccharide profiles, as well as their physicochemical properties (pH, °Brix, total acidity, percent total titratable acidity, and color). Additionally, the detection of intentional debasing of agave syrup with four commercial nutritive sweeteners (HFCS 55 and 90, DE 42 and sucrose) was afforded by oligosaccharide profiling employing both high performance anion exchange liquid chromatography with pulsed amperometric detection (HPAE-PAD) and capillary gas chromatography with flame ionization detection (CGC-FID). Results showed that the major carbohydrate and polyol in agave syrups were fructose and inositol with mean concentrations of 84.29% and 0.38%, respectively. Oligosaccharide profiling was extremely successful for adulteration detection with detection limits ranging from 0.5 to 2.0% for the aforementioned debasing agents. Also, all four of these possible adulterants could be detected within a single chromatographic analysis.

Lentil and chickpea protein-stabilized emulsions: optimization of emulsion formulation.

Chickpea and lentil protein-stabilized emulsions were optimized with regard to pH (3.0-8.0), protein concentration (1.1-4.1% w/w), and oil content (20-40%) for their ability to form and stabilize oil-in-water emulsions using response surface methodology. Specifically, creaming stability, droplet size, and droplet charge were assessed. Optimum conditions for minimal creaming (no serum separation after 24 h), small droplet size (<2 μm), and high net droplet charge (absolute value of ZP > 40 mV) were identified as 4.1% protein, 40% oil, and pH 3.0 or 8.0, regardless of the plant protein used for emulsion preparation.