Thermal properties of tapioca starch

Thermal properties of native tapioca starch, including thermal conductivity, specific heat, and thermal diffusivity at 4, 15, and 30% moisture contents, and 25, 50, and 75°C temperature levels were studied. Thermal conductivity was measured using a line‐heat source thermal probe equipped with a computerized data acquisition system; specific heat was measured using Differential Scanning Calorimetry (DSC) and thermal diffusivity was calculated from the thermal conductivity, density, and specific heat. Thermal conductivity, specific heat, and thermal diffusivity increased with the increase of temperature and/or moisture content. Prediction models for the thermal properties of tapioca starch were developed for practical applications.     

Dielectric properties of Indian Basmati rice flour slurry

Dielectric properties of Indian Basmati rice samples (dry ground flour and wet aqueous slurry) were measured over the frequency range 500–2500 MHz. Temperature dependence of dielectric properties of rice flour slurries (20, 30 and 50 g flour per 100 g water yielding approximately 1:5, 1:3 and 1:2 flour to water ratio) were studied between 30 and 80 °C. Results indicated that dielectric constants (ε′) generally did not vary with frequency while the loss factor (ε″) showed an increasing trend. A sharp change in dielectric parameters were noted above 70 °C attributable to rice starch gelatinization, an observation confirmed later by differential scanning calorimetry. An increase in flour slurry concentration systematically reduced ε′ during the entire frequency range while variations in ε″ values were mixed. Addition of 1% salt markedly increased ε″ of slurries whereas butter resulted in significant reduction in ε′ values. Rice flour slurry containing both salt and butter exhibited intermediate values of dielectric properties. Both ε′ and ε″ data of rice slurries generally fitted a 2nd order polynomial relationship with temperature. These results suggest that dielectric measurements could be used to study frequency, concentration, ingredient and temperature dependent changes in starch–water systems during heating.     

Thermal Stability and Gel-Forming Ability of Shark Muscle as Related to Ionic Strength

Thermal stability and gel-forming ability of silvertip, hammer-head and thresher shark as affected by ionic strength were investigated. Low temperature endothermic peaks (LTEP, between 30 and 44°C) were observed in differential scanning calorimetric (DSC) thermograms of the shark muscles and surimi samples. Increases in ionic strength reduced the thermal stability of surimi as shown by depression of transition temperature, denaturation enthalpies and LTEP. Although gel strength of heat-treated surimi increased with increasing NaCl concentration, the three species had different sensitivities to ionic strength. The highest NaCl-induced gel-forming ability of surimi was achieved at 0.5M salt concentration for silvertip and thresher; at 1.0M for hammer-head shark.     

Residence time distribution of carrot cubes in starch solutions in a pilot scale aseptic processing system

Residence time distribution (RTD) of carrot cubes flowing in starch solutions was evaluated in a commercial pilot-scale aseptic processing system using a full factorial design of experiments employing flow rate (15 and 20 kg/min), temperature (80 and 100°C), holding tube length (0, 60 and 100%), particle size (6 and 13 mm) and starch concentration (3 and 5% w/w) as factors. All factors were found to be significant (p<0·05) in influencing the fastest particle residence time (FPRT), mean particle residence time (MPRT), particle residence time variance (PRTV) and their normalized versions. While particle size, holding tube length and starch concentration increased the FPRT, fluid flow rate and temperature had the opposite effect. The FPRT was lower than the average fluid retention time under all testing conditions.     

Effect of genetic origin, diet and weaning weight on carcass composition, muscle physicochemical and histochemical traits in the rabbit

Fifty rabbits originating from the crossing of one dam strain with three sire strains, Hy+, INRA 9077 and INRA 3889, were studied. The adult body weights of the sire strains were 5·1, 4·1 and 3·1 kg, respectively. After weaning, the Hy+ and the INRA 9077 rabbits were fed either an H (11·99 MJ DE kg DM⁻¹) or L diet (9·67 MJ DE kg DM⁻¹). The INRA 3889 rabbits were fed only the H diet. In each of these five blocks, two weaning weights were studied and the rabbits were slaughtered when the average body weight of each block reached 2·5 kg. Slaughter yield, carcass fatness and hindleg meat to bone ratio were determined. Muscular tissue was described using (1) physicochemical criteria (ultimate pH, L^*a^*b^* colour) of the biceps femoris (BFE), tensor fasciae latae (TFL) and semimembranosus accessorius (SMA) muscles and (2) histochemical characteristics of the longissimus lumborum muscle (LL) through computerised image analysis (fibre type composition, cross-sectional area). At slaughter, the rabbits of INRA 3889 sire origin, which had the highest degree of maturity (72%), gave the best slaughter yield (p<0·01), the heaviest reference carcass weight (p<0·01), and highest LL proportion (p<0·01), hindleg meat to bone ratio (p<0·05) and fatness (p<0·01); their LL muscle showed the lowest percentage of βR fibres, while the cross-sectional area of their muscular fibres was the highest (p<0·05). When all sire × diet combinations were put together, the heavier the weaning weight, the lower the daily gain (p<0·01) and the lightness (L*) of thigh muscles (p<0·05). The lower the DE content of the diet, the lower the growth rate, the slaughter yield, the reference carcass weight (p<0·01) and the cross-sectional area of all types of muscle fibres of the rabbits of both Hy+ and INRA 9077 sire origin.     

Thermal Transitions of Actomyosin and Surimi Prepared from Atlantic Croaker as Studied by Differential Scanning Calorimetry

Differential scanning calorimetry (DSC) was used to investigate thermal transitions of fish mince (surimi) and actomyosin from croaker. Three endothermic peaks were observed in DSC thermograms of surimi. After addition of salt, transition temperatures shifted to lower temperatures. Preheating samples containing 3% salt at various temperatures showed that 40°C heating caused the first peak to disappear, and preheating at temperatures higher than 50°C caused virtual disappearance of all transition peaks. Low temperature storage (4°C) of samples caused no significant change in thermograms of salted or unsalted surimi over a 5-day storage period. Evidence suggests that changes of fish protein during low temperature “setting” are different from those occurring during high temperature “setting.”     

Temperature Prediction during Thermal Processing of Surimi Seafood

ABSTRACT: An interactive temperature prediction for surimi seafood was constructed and validated. The prediction model showed good agreement with experimental temperature profiles. The heat transfer coefficient (h) decreased with an increase of temperature difference (δT) between the sample surface and the water bath. The h had an effect on the convective heat transfer, resulting in a slower overall heat transfer at the beginning of heating. Thermal diffusivity (α) of surimi seafood was determined from experimental temperature profiles. The α increased slightly as the temperature difference (δT) between sample and water bath increased. The low a observed at small δT reduced conduction, resulting in a slower overall heat transfer.     

Influences of the method of housing bulls on their body composition and muscle fibre types

The influence of the type of housing (loose or tying-type) was studied in relation to body composition and muscular characteristics of bulls. 34 young bulls (18 Salers and 16 Limousins) were divided into two groups with equal breed representation and equal mean growth rates, to 10 months of age. One group was housed in tying-type housing (short stalls 1·8 m² per animal) and the other in loose housing (6·5 m² per animal). Samples of semitendinosus (ST) and longissimus thoracis (LT) muscle were taken at slaughter at 16 months. The lactate dehydrogenase (LDH) and isocitrate dehydrogenase (ICDH) activities were measured. The proportion of isoforms LDH-M and LDH-H were determined for each muscle. Total collagen content and solubility were measured for ST alone. Fibres were classified by ATPase myofibrillar and succinate dehydrogenase activities into SO (slow oxidative), FOG (fast oxidative glycolytic) or FG (fast glycolytic), and by immunohistochemistry by reaction with monoclonal antibodies specific to slow and fast myosin heavy chain reactions into I, IIC, IIA, IIAB and IIB fibres. Compared with animals in tying-type housing, animals in loose housing presented the following: fewer carcass adipose deposits (p<0·01); for ST muscle, more collagen (p<0·01) and a reduced glycolytic metabolism, as indicated by lower LDH activity (p<0·10) and a lower proportion of FG fibres (p<0·10). In both ST and LT muscles, loose housing resulted in an increased percentage of IIC fibres (p<0·05) but did not alter the proportions of fast fibres. Modifications in ST alone were increased percentage of IIA fibres (p<0·10) and IIAB fibres (p<0·01) and a lower percentage of IIB fibres (p<0·01). Thus, for a given rate of growth, the type of housing (loose or tying-type) influenced contractile characteristics, especially in muscles involved in movement.     

The influence of season on quality characteristics of hot-boned beef m. longissimus thoracis

Samples of m. longissimus thoracis (LT) muscle were randomly collected from 70 Omani beef cattle 1 h after slaughter between August 2001 and July 2002 in the Muscat Municipality central slaughterhouse to investigate the effect of seasonal parameters on meat quality during the hot and cool seasons of Oman. The collection period (12 months) was divided into two seasons according to ambient temperatures and relative humidity and termed: Cool Season (November–March with average temperature of 21.2±1.40 °C and 57.9±1.61% relative humidity) and Hot Season (April–October with average temperature of 34.3±1.67 °C and 48.8±7.57% relative humidity). The season had a significant effect on meat quality characteristics of the LT muscle. Muscles collected during the hot season had significantly (P<0.001) higher ultimate pH values (6.24) with significantly (P<0.001) lower Warner–Bratzler (WB) shear force values (10.12) than those collected during the cool season (5.54 and 15.58). In these hot-boned samples, there was a linear relationship between ultimate pH and WB shear values. Cooking loss was significantly (P<0.001) higher for cool season samples (26.01%) than from hot season samples (19.75%). Beef from the hot season group had significantly (P<0.001) darker meat than that of the cold season group, based on L* (31.45 vs 35.58), a* (18.53 vs 23.19) and b* (4.16 vs 6.40) colour measurements. There was a linear relationship between ultimate pH and cooking loss, L*, a* and b*. These results indicated that heat stress (>30 °C) lead to physiological stress in beef cattle, which in turn increased muscle ultimate pH and influenced related meat quality characteristics.     

Functional properties of proteins recovered from silver carp (Hypophthalmichthys molitrix) by isoelectric solubilization/precipitation

Isoelectric solubilization/precipitation at acidic and basic pH ranges was applied to whole gutted silver carp (Hypophthalmichthys molitrix) in order to recover muscle proteins. Thermal denaturation (T_onset, T_max, and ΔH), viscoelasticity (G′), and texture properties (shear stress) of proteins recovered from carp as affected by functional additives (beef plasma protein, potato starch, exogenous transglutaminase, polyphosphate, and titanium dioxide) were determined and compared to Alaska pollock surimi. Proteins recovered from carp showed typical endothermic transitions only when functional additives were used. Similar to endothermic transitions, viscoelasticity in carp proteins increased only when the additives were used. Typical endothermic peaks and viscoelasticity increase were recorded for Alaska pollock surimi. Carp protein-based gels with functional additives had lower (P < 0.05) shear stress than their surimi counterparts, but greater (P < 0.05) or similar (P > 0.05) when compared to surimi gels without functional additives. In addition, generally higher shear stress was measured for carp protein-based gels developed from basic pH treatments than the acidic counterparts. The present study indicates that proteins can be recovered from whole gutted carp using isoelectric solubilization/precipitation. However, if the recovered proteins are used for subsequent development of restructured food products, functional additives should be used.     

Thermal and dynamic rheological properties of wheat flour fractions

A commercial high gluten flour (HGF) was fractionated into prime starch (PS), tailing starch (TS), and gluten (G). Fractions were examined alone or in various combinations. Dynamic rheological properties of samples were measured in an oscillatory rheometer (strain 0.02; frequency 0.1 Hz) during heating at 1°C/min. Thermal characteristics of samples were determined by differential scanning calorimetry (DSC) at a heating rate of 10°C/min. The loss (G″) and storage (G′) moduli of PS and mixed G/PS, G/TS, and G/PS/TS increased after 60°C, reaching peak values (e.g. 81, 301, 313, and 3000 Pa in G′, respectively) around 75°C after which the moduli decreased. HGF showed a steady increase in G′ from 32 to 2490 Pa as temperature increased from 65 to 90°C, indicating continuous formation of elastic networks. Cooling increased G′ for G/PS/TS, decreased G′ for HGF, and produced no rheological transitions for all samples. TS and G alone did not exhibit appreciable viscoelastic responses to the heating and cooling temperatures. DSC measurements revealed a major endothermic transition in HGF. This transition, with a peak around 60°C, was due to starch gelatinization. The presence of G or TS resulted in reduced melting enthalpies of starch in the PS fraction. Gluten or TS fractions alone or in combination did not exhibit any endothermic transitions.     

NMR relaxometry and differential scanning calorimetry during meat cooking

By combining simultaneous nuclear magnetic resonance (NMR) T₂ relaxometry and differential scanning calorimetry (DSC) on pork samples heated to nine temperature levels between 25 and 75 °C, the present study investigates the relationship between thermal denaturation of meat proteins and heat-induced changes in water characteristics. Principal component analysis (PCA) on the distributed ¹H NMR T₂ relaxation data revealed that the major changes in water characteristics during heating occur between 40 and 50 °C. This is probably initiated by denaturation of myosin heads, which however, could not be detected in the DSC thermograms obtained directly on the meat. In contrast, the DSC thermograms revealed endothermic transitions at 54, 65 and 77 °C, probably reflecting the denaturation of myosin (rods and light chain), sarcoplasmic proteins together with collagen and actin, respectively. Simultaneous modelling of DSC and NMR data by partial least squares regression (PLSR) revealed a correlation between denaturation of myosin rods and light chains at 53–58 °C and heat-induced changes in myofibrillar water (T₂ relaxation time 10–60 ms) as well as between actin denaturation at 80–82 °C and expulsion of water from the meat. Accordingly, the present study demonstrates a direct relationship between thermal denaturation of specific proteins/protein structures and heat-induced changes in water mobility during heating of pork.     

Influence of ultimate pH on bovine meat tenderness during ageing

The aim of this work was to evaluate the influence of ultimate pH and ageing at 2±2°C on the tenderness of beef. The m.longissimus thoracis et lumborum from 23 young bulls excised at 28 h post mortem were grouped into: Normal (pH 5.5 to 5.8) moderate DFD (mod DFD) (5.8p<0.05) lower in the DFD group than in the Normal one and a significant (p<0.001) linear relationship was found between ultimate pH and tenderness as evaluated by both methods. The myofibrillar protein solubility (MPS) at pH 7.0 was significantly higher in the DFD group at all post mortem times whereas for myofibrillar fragmentation index (MFI) higher values (p<0.05) were only found in the DFD group at day 1. In all three groups toughness decreased (p<0.05) from 1 to 6 days, with no further decrease to 13 days. This decrease in toughness was associated with an increase of MFI in all pH groups. Collagen solubility in all three groups was not affected by ageing. No significant (p>0.05) differences in soluble collagen and myofibrillar protein solubility (MPS) at pH 5.5 were found between the pH groups at any time. The tenderness evaluated by both methods was significantly (p<0.05) related to MFI, MPS at pH 7.0, cooking loss and juiciness. Total and soluble collagen, sarcomere length, intramuscular fat and MPS at pH 5.5 were not significantly (p>0.05) related with tenderness.     

Characterization of Thermal Properties of Potato Dry Matter–Water and Starch–Water Systems

ABSTRACT: Potato dry matter samples of varying moisture contents were analyzed by differential scanning calorimetry (DSC). One endothermic and one exothermic transition were observed when the moisture content was < 50% (w/w) in the dry matter–water system. Both endothermic and exothermic transitions of potato dry matter were influenced by moisture content. One endothermic transition at about 66 °C was observed when the samples were reheated after 2 wk of storage at 5 °C. Gelatinization and retrogradation of starch are chiefly responsible for the endothermic transitions in the potato dry matter. The exothermic transition may originate from chemical reactions such as Maillard and caramelization during heating of a potato dry matter–water system when water is limited (< 50%, w/w) and at temperatures > 120 °C     

Effect of microwave heat/moisture treatment on physicochemical properties of Canna edulis Ker starch

BACKGROUND: Microwave heat/moisture treatment (MWT) is being used increasingly in food processing, but very little research has been carried out on its effect on tuber starches. In this study, Canna edulis Ker tuber starch was subjected to MWT with moisture contents ranging from 20 to 45% (w/w), and the effects of MWT on the physicochemical properties of the starch, including the extent of amylose leaching, enzymatic digestibility, X‐ray diffraction (XRD) and differential scanning calorimetry (DSC) characteristics, were determined. RESULTS: In the process of MWT, temperature exhibited a positive correlation with microwave power and moisture content. When amylose leaching was used as an index, a moisture content of 40%, a treatment time of 15 min and a microwave power of 800 W were found to be the optimal conditions for MWT of C. edulis starch. The enzymatic digestibility changed under different treatment conditions. Furthermore, XRD measurements revealed a change in crystalline structure from type B to type A and an increased degree of crystallinity. Thermal (DSC) studies showed higher values of T_o, T_p and T_c of endothermic peaks, and exothermic peaks were also observed. CONCLUSION: MWT increased the degree of crystallinity, resulting in more resistant fractions in C. edulis starch, which will be beneficial to human health. Copyright © 2009 Society of Chemical Industry     

Mercury, arsenic, lead and cadmium in fish and shellfish from the Adriatic Sea

The aim was to measure concentrations of total mercury, total arsenic, lead and cadmium in common edible fresh fish and shellfish from various areas of the Adriatic Sea. Estimates of intake of these elements were made through seafood consumption by the general population. Samples were either wet digested for mercury and arsenic, or dry ashed for lead and cadmium analysis. Mercury was measured by cold vapour atomic absorption spectrometry (CV AAS) and arsenic, lead and cadmium by electrothermal atomic absorption spectrometry (ET AAS). Quality control procedures of analytical methods, which included analyses of dogfish muscle-certified reference material DORM-2, confirmed the acceptability of methods. The highest mercury and arsenic concentrations were found in hake ( Merluccius merluccius ) and the lowest in mackerel ( Scomber scombrus ). The respective values in hake were 0.373 ±0.075 and 23.3 ±3.6, and in mackerel 0.153 ±0.028 and 1.06 ±0.29 mg kg -1 fresh weight (mean ±SD). Lead and cadmium concentrations were about 10 times higher in shellfish than in analysed fish. The highest lead and cadmium concentrations were found in mussel ( Mytilus galloprovincialis ) and the lowest in hake. Respective lead and cadmium values in mussel were 0.150 ±0.009 and 0.142 ±0.017, and in hake were 0.007 ±0.004 and 0.002 ±0.001 mg kg -1 fresh weight. The concentrations of analysed elements were below acceptable levels for human consumption set by the Croatian Ministry of Health, except for total arsenic. The estimated intake of those trace elements included in this study through seafood consumption by the general population did not exceed the provisional tolerable weekly intake recommended by the Joint FAO/WHO Expert Committee on Food Additives.     

Muscle composition and fatty acid profile in lambs fattened in drylot or pasture

The effects of two fattening systems on muscle composition and fatty acid profile were determined in an experiment using samples of the longissimus dorsi (LD) muscle of 24 ram lambs (slaughter weight 29–31 kg). The fattening systems were: (i) drylot (a mixture of maize, soybean, wheat and minerals) and (ii) grazing (Cynodon dactylon). The lambs fattened in the drylot system presented higher fat levels (p<0.01), but lower concentrations of moisture (p<0.01) and cholesterol (p<0.05). The lipid content presented a negative correlation with moisture and protein. In lambs fattened in the drylot system increasing levels of fatness of LD muscle were associated with a decrease (p<0.05) in myristic and palmitic acids, but myristic, palmitic and linoleic acids increased (p<0.05) as the cholesterol levels of the muscles increased.     

Thermal inactivation of the frozen thawed traditional meat starter culture, Pediococcus pentosaceus, in a meat model system

The equation, y_(t) = y₍₀₎e^kt, was fitted (R = 0.9281, 0.9220 and 0.9117, respectively) to thermal inactivation data (55, 60 and 65 °C) of the traditional meat starter culture Pediococcus pentosaceus (10⁷ cfu/ml) in a meat model system. The population reduction constant (‘k’) increased (about 2.5- and 3-fold) with an increase in the treatment temperature (from 55 to 60 °C and from 60 to 65 °C, respectively). The Q₁₀ (55–65 °C) for ‘k’ was 7.63. Thermal treatments of 19.1, 9.0 and 3.1 min (55, 60 and 65 °C, respectively) reduced the population of P. pentosaceus by 2.0 logs. The value of ‘k’ and the duration of the thermal treatment played an important role in the extent of the inactivation of the culture. The “zero inactivation” temperature (T₀) for P. pentosaceus was 49.9 °C. About 5 logs of the culture would be destroyed at 63 and 68 °C within about 15.5 and 6.5 min, respectively.     

Digestive proteolytic and amylolytic activities in Trogoderma granarium Everts (Dermestidae: Coleoptera)

The Khapra beetle, Trogoderma granarium is a serious post-harvest pest of wheat. Digestive proteinase and amylase activities of larvae and adult insects were investigated using general and specific substrates and inhibitors. Gut pH in larvae was determined to be slightly acidic in the midgut and more acidic in the hindgut. However, midgut extracts from larvae showed an optimum activity for proteolysis against azocasein and haemoglobin at alkaline pH (broad optimum in the range 8–11). Proteinase extracted from larval guts hydrolyzed the synthetic substrates BApNA(N–benzoyl–L–arginine–p–nitroanilide) and SAAPPpNA (N–succinyl–alanine–alanine–proline–phenylalanine–p–nitroanilide) for trypsin- and chymotrypsin-like activities, respectively. The specific substrate for elastase-like activity SAAApNA (N–succinyl–alanine–alanine–alanine–p–nitroanilide) was not hydrolyzed by midgut extract of larvae. The most effective inhibitors of azocaseinolytic hydrolysis were trypsin and chymotrypsin-like serine proteinase inhibitors. Casein zymogram analysis revealed at least six proteinase bands in the larval midgut extract and showed the presence of trypsin-like serine proteinases. No cysteine proteinases were detected in larval midgut extract using specific cysteine proteinase substrates, inhibitors and activators. Carboxypeptidase A activity also was detected in larval midgut extract using FAPP(N-(3-(2-furyl) acryloyl)-l-phenylalanyl-l-phenylalanine) and showed optimal activity at alkaline pH. Activity of -amylase using starch as substrate, was determined to be maximal around neutral pH (pH 6–8), which is correlated with the pH prevailing in the midgut. No proteolytic and amylolytic activities were detected using conventional substrates in the digestive system of the adult suggesting no significant protein and carbohydrate digestion occurs in the adult beetle which does not need to feed.     

Tenderness and collagen composition of beef semitendinosus roasts cooked by conventional convective cooking and modeled, multi-stage, convective cooking

Beef semitendinosus roasts were cooked in a forced-air convection oven using conventional or modeled, multi-stage cooking. Conventional cooking was defined as cooking at 163°C to a core endpoint of 65°C. The model method was developed using a finite difference heat and mass transfer model optimized for a three-stage cooking process that included preheating, holding, and finishing. Model cooking resulted in lower (P<0.05) Warner–Bratlzer peak shear force values than conventional cooking (3.3 vs 4.7 kg). Collagen total unaltered fraction was lower (44 vs 55%, P=0.05) and enzyme labile fraction was higher (56 vs 45%, P<0.05) in the model-cooked samples than in conventionally cooked samples. The three-stage cooking process results in a more tender product without adversely affecting product yield.