Effect of trehalose on the glass transition and ice crystal growth in ice cream

The effects of trehalose and sucrose on the rate of ice crystal growth in ice cream during accelerated shelf‐life were compared. Experimental and theoretical freezing curves were shown to be in good agreement. Glass transition temperatures (T_g) of maximally freeze concentrated trehalose and sucrose solutions (40% w/w) were found to be ?39.5 °C and ?47 °C respectively. For ice cream mixes, the T_g value increased from ?46.4 °C for the 100% sucrose‐based mix to ?42.0 °C for the 100% trehalose sweetened ice cream. However, no differences in viscosity, nucleation rate or inhibition of ice crystal growth were observed with increasing trehalose concentration in ice cream.     

Effect of some additives on the inhibition of lizardfish trimethylamine-N-oxide demethylase and frozen storage stability of minced flesh

Effects of some additives on the inhibition of trimethylamine‐N‐oxide demethylase (TMAOase) from lizardfish (Saurida tumbil) muscle were investigated. Sodium citrate and pyrophosphate could inhibit TMAOase activity in a concentration‐dependent manner, most likely because of their chelating property. Sodium alginate was the hydrocolloid possessing the inhibitory activity towards TMAOase (P < 0.05). During the storage of lizardfish mince at ?20 °C for 24 weeks, the addition of 0.5% sodium alginate and 0.3% pyrophosphate in combination with 4% sucrose and 4% sorbitol as the cryoprotectants resulted in the retarded increase in TMAOase activities with the coincidental lowered formation of dimethylamine and formaldehyde (FA), compared with the control (without additives) (P < 0.05). The loss in solubility of muscle proteins was also impeded with the addition of those compounds, suggesting their role in the inhibition of TMAOase as well as the retardation of protein denaturation induced by FA.     

Purification and characterization of hydroperoxide lyase from amaranth tricolor (Amaranthus mangostanus L.) leaves

Hydroperoxide lyase (HPL) was extracted from amaranth tricolor leaves using Triton X-100, and purified to electrophoretic homogeneity by ammonium sulfate precipitation, ion-exchange chromatography, hydrophobic interaction chromatography and hydroxyapatite chromatography. The purified HPL preparation consisted of a single band and spot with a molecular mass of about 55 kDa as shown in SDS–PAGE and 2-D PAGE, respectively; the isoelectric point was found to be about 5.4. The maximum activity of the enzyme was observed at pH 6.0 and 25 °C, respectively. The HPL showed higher activity against 13-hydroperoxy-linolenic acid compared to 13-hydroperoxy-linoleic acid. K _m value for 13-hydroperoxy-linolenic acid was 62.7 μM, and the corresponding V _max was 178.5 μM min⁻¹. The activity of HPL was significantly inhibited by nordihydroguaiaretic acid, HgCl₂ and 2(E)-hexenal but not by EDTA and hexanal.     

Production of (2E)-hexenal by a hydroperoxide lyase from Amaranthus tricolor and salt-adding steam distillation for the separation

(2E)-Hexenal is widely used in flavors and perfumes; however, it is mainly derived from chemical synthesis. In this study, hydroperoxide lyase (HPL) naturally originated from Amaranthus tricolor was used to catalyze the reaction to generate (2E)-hexenal from 13-hydroperoxy-9Z, 11E, 15 Z-octadecatrienoic acid (13-HPOT), and salt-adding steam distillation was used for the separation of (2E)-hexenal. A maximum yield of (2E)-hexenal that reached 1,156.4?mg?L^?1 was obtained with a high substrate concentration (40?mM 13-HPOT) under the following conditions: 10?min, pH 7.5, 20?°C, HPL 16 U?mL^?1, butylated hydroxytoluene (BHT) 1?mM, and dithiothreitol (DTT) 15?mM. Then the separation of (2E)-hexenal was conducted by salt-adding steam distillation. It was found that AlCl₃ had the greatest effect on the separation of (2E)-hexenal, followed by CaCl₂ and NaCl. The distillate yield with the addition of AlCl₃ was 93.2?%, while the distillate yield without the addition of salt was 81.2?%. The distillate concentration with AlCl₃ was 6,464.2?mg?L^?1, while the distillate concentration without the addition of salt was 4,490.3?mg?L^?1. The addition of salt improved the efficiency of the steam distillation. This study was greatly meaningful for providing a green method to the large-scale production of (2E)-hexenal.     

Fatty acids and sterols of Amaranthus tricolor L.

The fatty acids and sterols of Amaranthus tricolor L. were examined by gas chromatography. The major unsaturated fatty acid in the seeds and stems was linoleic acid, while in leaves it was linolenic. The major saturated fatty acid found in seeds, stems and leaves was palmitic acid. Linolenic, lignoceric and arachidic were also present in seeds but in trace amounts. Five sterols were identified and spinasterol was present in the highest amounts. Among the seeds, stems and leaves a small amount of 24-methylenecycloartenol was found in the seeds only.     

Isolation and Heat Stability of Trypsin Inhibitors in Amaranth (Amaranthus hypochondriacus)

Trypsin inhibitors were isolated from seeds of Amaranthus hypochondriacus by extraction at pH 7.5, heat treatment at 70°C for 15 min and affinity chromatography with trypsin-Sepharose 4B. Inhibitors of trypsin and chymotrypsin were identified in polyacrylamide gels following electrophoresis using a stain procedure that employed the chromogenic substrate acetyl-D, L-phenylalanine-2-napthyl ester. Three of the thirteen trypsin inhibitors identified in the electrophoresis gels, also had antichymotryptic activity. The inhibitor preparation was very thermostable retaining 20% of its original activity after 7 hr at 100°C.     

Volatile compounds and changes in flavour‐related enzymes during cold storage of high‐intensity pulsed electric field‐ and heat‐processed tomato juices

BACKGROUND: The effects of high‐intensity pulsed electric field (HIPEF) processing (35 kV cm^?1 for 1500 µs, using 4 µs bipolar pulses at 100 Hz) on the production of volatile compounds and flavour‐related enzymes in tomato juice were investigated and compared with those of thermal processing (90 °C for 30 or 60 s). RESULTS: Tomato juice treated by HIPEF showed lower residual lipoxygenase (LOX) activity (70.2%) than juice heated at 90 °C for 60 s (80.1%) or 30 s (93.2%). In contrast, hydroperoxide lyase (HPL) was almost completely inactivated when the juice was subjected to 90 °C for 60 s, whereas roughly 50% of the control tomato juice was depleted after HIPEF treatment or thermal processing at 90 °C for 30 s. A slight decrease was observed in the initial LOX activity of treated and untreated samples during storage, whereas initial HPL activity was strongly affected over time. CONCLUSION: HIPEF‐treated juice exhibited higher levels of compounds contributing to tomato aroma than untreated and heat‐treated juices throughout storage. Thus HIPEF processing can preserve flavour quality and stability of tomato juice compared with conventional thermal treatments. Copyright © 2010 Society of Chemical Industry     

Sensory quality of ethylene‐exposed carrots (Daucus carota L,cv ‘Yukon’) related to the contents of 6‐methoxymellein,terpenes and sugars

Carrots were analysed for taste and odour and for contents of terpenes, 6‐methoxymellein and sugars during 3 weeks storage at 15 °C in an atmosphere containing ethylene (1 µl l⁻¹). The ethylene treatment caused an increase in 6‐methoxymellein and the conversion of higher amounts of sucrose to fructose and glucose compared to control carrots stored in air. This corresponded to higher sensory scores for bitterness and terpene flavour and a lower score for sweetness, as measured by an expert taste panel. Principal component analysis showed a more expressed bitter taste, earthy flavour, green flavour, terpene flavour and aftertaste in the ethylene‐treated carrots. Correlations were found between sweet taste and the content of sucrose (r = 0.91, p < 0.005) and between the contents of various terpenes (particularly γ‐terpinene, limonene and caryophyllene) and terpene flavour, green flavour, aftertaste and bitter taste (r ≥ 0.72, p < 0.05). In the air‐stored carrots these off‐flavours seemed to be masked by a high sucrose content. © 2000 Society of Chemical Industry     

Spray‐drying encapsulation of citral in sucrose or trehalose matrices: physicochemical and sensory characteristics

The potential of the disaccharide trehalose as carrier for producing spray‐dried citral was examined. Some physical and sensory characteristics of citral encapsulated in matrices containing either trehalose or sucrose and maltodextrin (MD) were analysed. They included water sorption, glass transition temperatures (T_g), nuclear magnetic resonance (NMR) relaxation and citral retention during spray‐drying. The glassy state at room temperature (25 °C) was maintained as far as 33% relative humidities (RH) for the spray‐dried trehalose formulation and 43% RH for trehalose–MD; however, for sucrose–MD and for sucrose formulations, the glassy state was limited to RHs lower than 33% and 22%, respectively. Sensory evaluation and gas chromatographic analysis indicated that citral retention after spray‐drying was similar for matrices containing either trehalose or sucrose. However, trehalose formulations had improved physical stability as compared to sucrose.     

Enzymatic synthesis of myristoyl disaccharides and their surface activity

The condensation of trehalose, maltose, cellobiose, sucrose, turanose, palatinose, lactose and melibiose with myristic acid by a lipase (triacylglycerol acylhydrolase; EC 3.1.1.3) from Candida antarctica was examined at 60 °C in a mixture of pyridine and 2‐methyl‐2‐propanol (20/80 by vol.). The reactivity of trehalose was the highest among the tested disaccharides, and maltose and palatinose followed. Cellobiose and lactose were poor substrates for condensation. Condensation of all the disaccharides except for cellobiose and lactose with myristic acid was carried out at various initial disaccharide concentrations to estimate the initial reaction rate. Plots of the initial rates for monomyristoyl disaccharide formation versus the initial disaccharide concentration normalized by the solubility of the disaccharide in the mixture indicated that palatinose was the best substrate, and that trehalose, turanose and maltose were the next best ones. The surface activity of the monoacyl disaccharides scarcely depended on the type of disaccharide. Copyright © 2007 Society of Chemical Industry     

Maltose Transport by Brewer's Yeasts in Brewer's Wort

The kinetics of maltose transport by two industrial yeasts were studied. The ale and lager strain each showed both high and low affinity transport. For the lager strain, maltose transport was only weakly inhibited by maltotriose, sucrose and trehalose, suggesting that its dominant maltose transporter is the maltose‐specific type coded by MALx1 genes. For the ale strain, maltose transport was strongly inhibited by maltotriose, sucrose and trehalose, suggesting that its dominant maltose transporter may be the AGT1‐encoded type that also carries these sugars. Also glucose inhibited transport by the ale strain more than that by the lager strain. Instantaneous inhibition by ethanol at concentrations met in brewery fermentations was moderate (about 25% at 50 g ethanol · L^?1). The apparent Vmax for high affinity transport increased about 100‐fold between 0 and 30°C, whereas the Km (3 ± 1 mM) was constant. Standard activities of maltose transport and maltase were followed through pilot fermentations of 11–24°P worts. Rapid (20 s) measurements of the zero‐trans‐rate of maltose uptake were also made with each day's yeast (rapidly harvested and washed) in reaction mixtures containing the same day's wort labelled with tracer ¹⁴C‐maltose. Results suggested that maltose uptake is the dominant factor controlling the rate of maltose utilization in these wort fermentations.     

Diversity in phenotypic and nutritional traits in vegetable amaranth (Amaranthus tricolor), a nutritionally underutilised crop

BACKGROUND: Assessment of genetic diversity in a crop‐breeding programme helps in the identification of diverse parental combinations to create segregating progenies with maximum genetic variability and facilitates introgression of desirable genes from diverse germplasm into the available genetic base. RESULTS: In the present study, 39 strains of vegetable amaranth (Amaranthus tricolor) were evaluated for eight morphological and seven quality traits for two test seasons to study the extent of genetic divergence among the strains. Multivariate analysis showed that the first four principal components contributed 67.55% of the variability. Cluster analysis grouped the strains into six clusters that displayed a wide range of diversity for most of the traits. CONCLUSION: Cluster analysis has proved to be an effective method in grouping strains that may facilitate effective management and utilisation in crop‐breeding programmes. The diverse strains falling in different clusters were identified, which can be utilised in different hybridisation programmes to develop high‐foliage‐yielding varieties rich in nutritional components. Copyright © 2009 Society of Chemical Industry     

Iron bioavailability from Amaranthus species: 1—In vitro dialysable iron for estimation of genetic variation

Green leafy vegetables have the potential to contribute significant amounts of iron to the diet, if the bioavailability of iron from these foods is improved. In order to determine the potential for genetic manipulation of this trait, 46 lines from 12 species of Amaranthus were evaluated for total and bioavailable iron in greenhouse and field experiments. Bioavailable iron was estimated using an in vitro assay for dialysable, low-molecular-weight iron compounds. Significant differences (P < 0·01) were detected among lines and species for total and bioavailable iron. Total iron ranged from 358 to 880 ppm (dry weight) in field-grown plants and 55 to 123 ppm (dry weight) in greenhouse-grown plants. Bioavailable iron ranged from 41 to 63 ppm in field-grown plants and from 24 to 51 ppm in greenhouse-grown plants. Amaranthus tricolor and A lividus had the highest total and bioavailable iron; A hypochondriacus had the lowest levels of the species tested. Although field-grown Amaranthus accumulated higher levels of total and bioavailable iron, a greater proportion of the total iron was sequestered in insoluble, unavailable forms. Generally, species with higher total iron had higher levels of bioavailable iron. These analyses indicated potential for genetic improvement of iron nutritional quality from Amaranthus, especially within the species A tricolor. © 1998 Society of Chemical Industry     

Cryoprotective additives and cryostabilisation effects on muscle fillets of the freshwater teleost fish Rohu carp (Labeo rohita) during prolonged frozen storage

The effects of various cryoprotective additives separately and in combination were studied on the myofibrillar protein integrity, biochemical enzyme activity levels and muscle ultrastructure in the freshwater teleost fish Rohu carp (Labeo rohita). Fish muscle samples were divided into eight groups and immersed in different mixtures of cryoprotective additives (S1–S8), then frozen at ? 20 or ? 30 °C for 24 months. Electrophoretic studies revealed early (within 6 months) alteration of the myofibrillar proteins myosin light chain, α‐actinin and tropomyosin. Reduction of the storage temperature from ? 20 to ? 30 °C slowed down the degradative processes. Sodium dodecyl sulfate polyacrylamide gel electrophoresis indicated that fish muscle treated with cryoprotective mixture S8 (40 g L^?1 sorbitol/3 g L^?1 sodium tripolyphosphate/4 g L^?1 sodium alginate) showed minimal post mortem changes in myofibrillar proteins. Ultrastructural results also revealed post mortem damage to the muscle, seen earliest (within 6 months) in the sample frozen‐stored without additives (S2), as compared with the normal, unfrozen muscle (S1). The influence of cryoprotectants alone and in combination on fish muscle structural proteins, myosin and actin filaments (A and I bands), during prolonged frozen storage was investigated. After 12 months, samples frozen‐stored with various cryoprotective additives (S2‐S7), except S8, showed signs of myofibrillar disintegration. Beyond that time the degradative processes started showing up in all samples, with minimal muscle ultrastructural damage in sample S8. Again, reducing the storage temperature from ? 20 to ? 30 °C slowed down the degradative processes. Ultrastructural results correlated well with levels of biochemical enzymes (Ca²⁺ myofibrillar ATPase and succinic dehydrogenase) during frozen storage. This is the first report of the cryoprotective effects of these additives on this popular edible fish species. Of the various combinations of additives tested, cryoprotective mixture S8 was found to preserve the muscle structure longest under frozen storage conditions. However, even this mixture was only effective for 18 months at ? 30 °C. Beyond that time the myofibrillar degradative processes were apparent with correlative electrophoretic, biochemical and ultrastructural studies. Copyright © 2006 Society of Chemical Industry     

Effect of muscle type and cooking temperature on liver‐like off‐flavour of five beef chuck muscles

Steaks (1.9 cm thick) from the US Department of Agriculture (USDA) Select grade beef chuck muscles (Infraspinatus, Longissimus dorsi, Serratus ventralis, Supraspinatus and Terres major) were cooked to two temperatures commonly applied in US restaurants (71 °C and 82 °C) and evaluated for liver‐like off‐flavour by trained panel. Pigment content of raw muscles were determined to establish its effect on liver‐like off‐flavour. Mean myoglobin content of Serratus (9.26 mg g^?1) was significantly lower than other beef chuck muscles analysed in this study. Infraspinatus had highest (P < 0.05) mean liver flavour of 2.08 where other muscles had <2. Rancid flavour was slightly but significantly increased from 1.34 to 1.58 as internal cook temperature increased from 71 °C to 82 °C; however mean thiobarbituric acid (TBA) values were not affected by cooking temperature. Infraspinatus had small but significant incidence of liver‐like off‐flavour. Cooking temperature had a clear impact on rancidity as evaluated by trained panel but no direct impact on liver‐like off flavour was observed.     

Meaty flavour compounds formation from the submerged liquid culture of Pleurotus ostreatus

The capacity of oyster mushroom (Pleurotus ostreatus) mycelium to produce meaty flavour compounds in the presence of amino acids and sugars was studied. The submerged liquid culture of P. ostreatus mycelium along with base medium made of defatted soybean powder, sucrose, potassium phosphate, and magnesium sulphate was incubated for 3 days at 25 °C. Cysteine, glutamine, or methionine and fructose, galactose, ribose, or xylose were added to the base medium to study the effect of amino acids and sugars on meaty flavour formation by trained panelists. The flavour compounds were isolated and identified by GC–MS and GC retention time of authentic compounds. The base medium required P. ostreatus, cysteine, ribose, and heat treatment to produce meaty flavour. The sulphur containing heterocyclic compounds such as 2,5‐diethylthiophene, 2‐formyl‐5‐methylthiophene, 3‐ethyl‐2‐formylthiophene, and dimethylformyl thiophene were responsible for meaty flavour. These compounds were formed by non‐enzymatic browning reaction between ribose and cysteine during heat treatment.     

Effects of washing and packing on sensory and chemical parameters in carrots (Daucus carota L)

Carrots washed and packed by hand or machine and stored at 2, 10 or 20 °C in three different package types were analysed for taste, flavour and content of sugars, terpenes, 6‐methoxymellein and ethanol as well as for ethylene, CO₂ and O₂ concentrations in the packages. Carrots washed by machine had increased micro‐organism decay and higher sensory scores for bitter taste, aftertaste, terpene flavour and odour, green odour and earthy flavour. The ability of packages to ventilate was important to avoid anaerobic conditions that caused decreased sucrose content, increased production of ethanol and a higher intensity of ethanol flavour and sickeningly sweet taste. Increasing temperature enhanced the concentration of ethanol, CO₂ and ethylene and decreased the O₂ concentration as well as the content of sucrose and total sugar. High temperature also increased the intensity of ethanol flavour and odour, aftertaste, earthy flavour, terpene flavour and bitter taste. Bitter taste was positively correlated with 6‐methoxymellein level, although this level was below the sensory threshold. Bitter taste, earthy flavour and aftertaste were correlated with total terpenes and several individual terpenes. Carrots washed and packed early in the long‐term storage period (November) were more bitter and had a higher level of 6‐methoxymellein and a higher intensity of terpene flavour and odour, green flavour and earthy flavour than those handled in January or March. Copyright © 2004 Society of Chemical Industry     

THE THERMAL STABILITY OF ASPERGILLUS ORYZAE ALPHA-AMYLASE IN PRESENCE OF SUGARS AND POLYOLS

The aim of this study was to test whether it is possible to estimate the heat stability of Aspergillus oryzae alpha‐amylase (α‐amylase) based on the amount of hydroxyl (OH) groups provided in a buffer solution. The thermal stability of the enzyme in a presence of different sugars (sucrose and trehalose) and polyols (mannitol, sorbitol, lactitol and glycerol) was investigated in the temperature range of 62–68C on a kinetic basis. It was investigated if the protective effect of additional substances was correlated to the number of hydroxyl groups (nOH) provided by each of them (per volume unit of the enzyme solution nOH). All additives showed a protective effect on the enzyme's heat stability, which was strongly dependent on the added compound concentration. Among all stabilizing compounds investigated, sucrose exhibited the largest protective effect. The decimal reduction time of α‐amylase activity increased by 33.9 times when 420 mg/mL of sucrose was added to the environment. When the same concentration of trehalose was used, the D‐value increased by 6.4 times compared to the value in the buffer system. The nOH provided in the enzyme solution could not be related to the D‐values for the enzyme thermal inactivation, meaning that the enzyme heat stability was not dependent on the nOH.     

Effect of different storage conditions on coagulating properties and cheese quality of Withania coagulans extract

The effects of different storage conditions on the coagulating properties of extracts of Withania coagulans berries were investigated in terms of coagulation time, pH and quality attributes of cheese prepared from buffalo milk. The extracts were stored under different conditions, viz. room temperature (27 ± 3 °C), refrigerated storage (4 °C), frozen storage (?20 °C) and lyophilisation. The milk‐coagulating activity of the plant extracts was measured on a fortnightly basis for a period of 5 months. There was a nonsignificant change in pH and the milk coagulating properties of the lyophilised extract. Physiochemical analysis revealed that cheese prepared with lyophilised extract retained the highest content of ash (2.3%), fat (23.8%), total solids (48.7%) and crude protein (22.7%), and resulted in the highest cheese yield (17.6%) compared to other tested treatments. Thus, it is concluded that lyophilisation has good potential for storage of vegetable extract coagulants.     

Purification and Characterization of a Lectin from the Seeds of Amaranth (Amaranthus cruentus)

A lectin (ACL) was purified from the seeds of Amaranthus cruentus using affinity chromatography on fetuin-agarose. Apparent homogeneity of the lectin was demonstrated by SDS-PAGE, chromatography on Sephadex G100 and immunoprecipitation. The lectin was a dimer with an estimated molecular weight of 66,000 and a subunit molecular weight of 35,000. ACL-mediated agglutination was inhibited by D-GalNAc and fetuin. Thirty other carbohydrates were non-hibitory. ACL contained 2.2% neutral carbohydrate and relatively high levels of aspartic acid, glutamic acid, serine and glycine. The purified lectin was relatively heat labile retaining approximately 10% of its original activity (titer) after 5 min at 70°C and after just 1 min at 100°C.