A NEW EMPIRICAL MODEL TO SIMULATE TRANSIENT SHEAR STRESS GROWTH IN SEMI-SOLID FOODS1

A family of models has been developed which has the ability to simulate transient shear stress growth in foods. The models can be written as follows: Three relaxation terms (seven parameters) are necessary to stimulate transient shear stress growth for stick butter, tub margarine and peanut butter at shear rates of 10 s^?1 and 100 s^?1. At small times the model tends to: which simulates the stress growth part of the curve. At long times the models tend to the power-law. The series of relaxation terms allows for the introduction of several time scales in the relaxation behavior of each food.     

HIGH TEMPERATURE RHEOLOGY OF TOMATO PUREE AND STARCH DISPERSION WITH A DIRECT-DRIVE VISCOMETER

A direct-drive concentric cylinder viscometer in a pressure chamber was used to study the flow behavior of a 11 Brix tomato puree at several temperatures in the range: 76 to 120C. The activation energy of flow of the tomato puree, based on apparent viscosity at 50 s^?1, was: 9.4 kJ mol^?1. The apparent viscosity (η) versus temperature profiles of a 4.0% waxy rice (WR) starch dispersion were determined during continuous heating from 30 to 110C at six shear rates in the shear range: 114 to 644 s^?1; beginning at about 95C, significant increase in η_a was observed at 114 and 160 s^?1. The said profiles collapsed to a single curve when η_a values were converted to reduced viscosity, values of η of the starch dispersion were lower than those of η* at about the same shear rates, γ=5.7 s^?1 and ω=6.3 rad s^?1.     

Fast Determination of Spatially Localized Volume Fractions in Emulsions

A rapid, noninvasive method for determining spatially resolved magnetic resonance (MR) spin-lattice relaxation rates (1/T₁) was developed to study the dynamics of emulsions. The technique acquires data simultaneously along the entire emulsion profile. The observed relaxation rates (1/T_1(obs)) for oil/water emulsions followed the equation: where Volume fractions along the profile of a 40% (v/v) oil/water emulsion were calculated for several times during creaming to establish dynamics of the process. Separation velocities calculated from such profiles may be used to test (or correct) predictions of models for creaming emulsions.     

PREDICTION OF THE TEXTURE OF COOKED POULTRY PECTORALIS MAJOR MUSCLES BY NEAR-INFRARED REFLECTANCE ANALYSIS OF RAW MEAT

Near‐infrared reflectance (NIR) spectra were collected on pectoralis major muscles from 90 broiler carcasses ( from 2 different processing sets) to assess the relationship between the NIR and a cutting‐shear instrumental texture test. For the instrumental razor blade test, two instrumental parameters (maximum shearing force and total shear energy) were calculated. Calibration (R²) and validation () coefficients of determination were obtained for predicting the instrumental measurements using the reflectance and its first and second derivatives. Models obtained with the second derivative were adequate when the two groups of samples were analyzed separately. The R² values ranged from 0.90 to 0.95 and from 0.84 to 0.89 for both maximum shear force and total shear energy. The regressions performed on the two sample sets combined did not yield model statistics that were as satisfactory (R² = 0.85–0.86 and = 0.78–0.77), suggesting that a prediction model accurately predicting poultry breast meat tenderness will need a larger and more varied sample set. The results suggest that NIR could be used to predict poultry meat texture and to classify muscles according to tenderness levels.     

LETHALITY CONTRIBUTION FROM THE TUBULAR HEAT EXCHANGER DURING HIGH-TEMPERATURE SHORT-TIME PROCESSING OF A MODEL LIQUID FOOD

Experiments were conducted using Bacillus stearothermophilus spores in 0.5% w/w carboxymethylcellulose suspension to evaluate come‐up contributions from the tubular heat exchanger. A lab‐scale UHT/HTST simulator that allowed samples to be collected at the exit of the heat exchanger and holding tube was used with operating temperatures up to 270F. The bulk mean residence time in the heat exchanger ranged from 30 to 89 sec, while that in the holding tube ranged from 4 to 14 sec. It was observed that between 40% and 51% of the cumulative lethality ( ) at the exit of the holding tube, was contributed by come‐up in the tubular heat exchanger. This come‐up contribution was determined on the basis of having an of 8.5 min in the holding tube alone. It was evident that come‐up lethality will depend on product initial temperature, residence time and temperature history in the heat exchanger, with higher temperatures obviously contributing more lethality. Therefore, the entire aseptic system becomes even more complex since several critical parameters need to be monitored, controlled and documented. Experimental data compared favorably with computer‐simulated data using the AseptiCAL? software, with the software package giving more conservative results. Ultimately, come‐up credit (CUC) should be tested on a pilot scale or industrial setup by way of reduced residence time (i.e. increased fluid flow rate), reduced holding tube length or temperature in order to determine if CUC can be applied towards the lethality required for the product. Monitoring and control devices become critical to ensure consistency and reproducibility in product residence time and time–temperature history, in the tubular heat exchanger.     

Intrinsic viscosities and apparent specific volumes of amino acids and sugars. ‘Effective size’ and taste of sapid molecules

Intrinsic viscosities ([η]) and apparent specijic volumes (V) are compared for a number of amino acids and simple sugars and their derivatives. While the sugars and their derivatives fit within a narrow range for both parametevs ([η])=2.27–2.61 cm³ g^?1; V=0.60–4.69 cm³ g^?1), the amino acids cover a much wider band ([η]) = 1.29–4.20 cm³ g^?1; V=0.562–0.712 cm³ g^?1). The intrinsic viscosity value of any particular amino acid is always greater than the corresponding apparent specijc volume, and ranges (at 10 mg g^?1) between two and seven times the value of the apparent specific volume. For the sugars and sugar derivatives, on the other hand, the intrinsic viscosities are always three to four times greater than the values of the corresponding apparent specijic volumes. When concentration is increased, all apparent specific volumes increase but they remain relatively constant if they are expressed as parachors (Vγ^1/4). Differences between the sugars and amino acids originate in the greater structural diversification of the latter molecules which in turn accords with their greater range of taste qualities.     

Antioxidant capacities vary substantially among cultivars of rabbiteye blueberry (Vaccinium ashei Reade)

Fruits from forty‐two blueberry cultivars, including thirty‐six rabbiteye (Vaccinium ashei Reade), three V. ashei hybrid derivatives and three northern highbush (V. corymbosum L.) standards, were evaluated for their antioxidant activities against peroxyl free radicals (ROO˙), hydroxyl radicals (OH˙), hydrogen peroxide (H₂O₂), superoxide radicals () and singlet oxygen (¹O₂) radicals. The differences in scavenging capacities for these radicals among forty‐two selected blueberry cultivars were significant. Oxygen radical absorbance capacity values ranged from 33.8 to 118.7 μmol Trolox equivalents (TE) g fresh wt^?1, 196.1 to 518.8 μmol TE g dry wt^?1 and 7.1 to 22.2 μmol cm^?2‐surface area. Extracts from fruit of pure rabbiteye had higher levels of scavenging capacities of oxygen species , ¹O₂ and H₂O₂ compared to V. ashei hybrid derivatives and northern highbush blueberry standards. The rabbiteye cultivars ‘Early May’ and ‘Centurion’ had the highest scavenging capacity for the reactive oxygen species, not only for ROO˙ and ˙OH, but also for , ¹O₂ and a strong oxidant, H₂O_2. In contrast, ‘Pink Lemonade’ (pink‐fruited) had the lowest ability to inhibit free radical activity of ROO˙,˙OH, ¹O_2, and H₂O_2.‘Snowflake’ had the lowest scavenging capacity for . Blueberry cultivars with high antioxidant activity and radical scavenging capacity have potential to improve human health and can possibly be used as parents for future blueberry breeding programs to develop new blueberry cultivars with higher antioxidant activity.     

Kinetics of Chlorophyll Degradation to Pyropheophytin in Vegetables

Pyropheophytins a and b were determined as predominant chlorophyll derivatives in heat processed spinach. Chlorophylls a, b, pheophytins a, b and pyropheophytins a, b were quantitated in fresh, blanched and heat processed spinach at 116, 121 and 126°C. First order degradation rate constants were determined to calculate activation energies of 25.2 and 22.5 Kcal/mole for chlorophylls a and b and 20.7 and 15.7 Kcal/mole for pheophytins a and b, respectively. Based on the results, the suggested mechanism for the decomposition of chlorophyll during heat processing of vegetables is: Chlorophyll Pheophytin Pyropheophytin. Pyropheophytins a and b were major chlorophyll degradation products found in all commercially canned vegetable products surveyed.     

High‐pressure high‐temperature extraction of phenolic compounds from grape skins

This study focused on the use of a non‐conventional extraction technology by employing high‐pressure high‐temperature stirred reactor to extract polyphenols from grape skins. Extraction time (15–330 min) and temperature (30–150 °C) were selected as independent variables, and their effects were studied. A preliminary kinetic study on polyphenols extraction revealed that the second‐order model fitted satisfactorily the experimental results (R² ≥ 0.9798). Total polyphenol yield and total flavonoid (TF) yield, as well as the antiradical power (ARP) of the extracts, were analysed. The use of high‐pressure high‐temperature technology resulted in obtaining extracts rich in polyphenols with high ARP. The highest total polyphenol (60.7 mg_GAE ) and TF (15.1 mg_CE ) yields were obtained at 150 °C for 270 min and 150 °C for 15 min, respectively. HPLC was employed to analyse phenolic compounds. Considerable quantities of single phenolic compounds were extracted. The highest yields of gallic acid, 5‐hydroxymethylfurfural, protocatechuic acid, catechin, vanillic acid, syringic acid, cumaric acid, trans‐resveratrol and quercetin (163.2, 20.0, 69.9, 420.0, 20.6, 603.0, 20.1, 42.4 and 117.1 mg per 100 g_DS, respectively) were found. ARP values were found between 8.45 and 52.17 μg_DPPH .     

DYNAMIC AND STEADY-STATE RHEOLOGY OF AUSTRALIAN HONEYS AT SUBZERO TEMPERATURES

The rheology of 10 Australian honeys was investigated at temperatures ?15C to 0C by a strain‐controlled rheometer. The honeys exhibited Newtonian behavior irrespective of the temperature, and follow the Cox–Merz rule. G″/G′ and ω are quadratically related, and the crossover frequencies for liquid to solid transformation and relaxation times were obtained. The composition of the honeys correlates well (r² > 0.83) with the viscosity, and with 247 data sets (Australian and Greek honeys), the following equation was obtained: The viscosity of the honeys showed a strong dependence on temperature, and four models were examined to describe this. The models gave good fits (r ² > 0.95), but better fits were obtained for the WLF model using T_g of the honeys and µ_g= 10¹¹ Pa.s. The WLF model with its “universal values” poorly predicted the viscosity, and the implications of the measured rheological behaviors of the honeys in their processing and handling are discussed.     

HEAT TRANSFER to and TRANSPORT PROPERTIES of WHEAT GLUTEN IN A TUBULAR REACTOR

The design and modeling of a tubular reactor, similar to an extrusion rheometer, which accounts for reacting flow is described. A numerical study (finite differences) of heat transfer to a flowing and reacting biopolymer melt (wheat gluten), similar to extrusion processing, is described and compared to experimental data. the cylindrical wall is nonisothermal in the axial direction, but is adequately characterized by a third-order polynomial determined experimentally. Convective and viscous dissipation terms are included in the energy equation. the rheological behavior of the melt is described by a power law model, . The consistency coefficient pre-exponential, m₀, is 530,000–2,100,000 Pa-secⁿ and the power law exponent or flow index, n, is 0.38–0.65 for a 25–30% moisture content range and a 110–209 C temperature range. the flow index decreases with increasing conversion due to polymerization reactions occurring at elevated temperatures. Flow curves, bulk temperatures, and temperature profiles are presented for a variety of cylinder wall temperatures and biopolymer moisture contents.     

Effect of nitrogen fertiliser on the nitrate contents of field vegetables grown in Britain

The nitrate and percentage organic nitrogen contents of 14 vegetable and two arable crops were measured after they had been grown with different levels of N-fertiliser. Foliage crops always contained substantial quantities of nitrate which increased with increase in the rate of N-fertiliser application. Grain of legumes and cereals, storage roots of carrots, parsnips and sugar beet, and onion bulbs and leeks contained no detectable amounts of nitrate even when N-fertiliser application rates were very high. Storage roots of red beet, swede and white turnip contained more than 3 mg NON g^?1 dry weight when grown with exceptionally high levels of fertiliser-N but contained very little when grown with the optimum amount of fertiliser-N or less. An equation was developed that linked NON to percentage organic-N for those parts of plants that could accumulate nitrate. It gave good fits to the data from seven crop species grown at a range of different levels of N-nutrition. It is estimated from the foregoing data and a survey of household food consumption that the average British person consumes about 60 mg NON week^?1 in field vegetables. If N-fertilisers were withheld consumption would be about 30 mg and if excess were applied it would be about 120 mg NON week^?1.     

Dissolution of various sources of gypsum in aqueous solutions and in soil

The dissolution of six sources of gypsum in water and 0.01 M CaCl₂ was examined in the presence and absence of soil. The gypsum samples included: analytical grade (AR), three sources of flue-gas desulphurisation (FGD) gypsum, phosphogypsum (PG), and mined gypsum (MG). Dissolution in aqueous solutions was monitored by measuring the concentration of calcium (Ca²⁺) and sulphate (SO) ions. In soils which adsorb small amounts of SO^?2₄, dissolution was estimated from the increase in the concentration of Ca²⁺ and SO in gypsum-treated soil over the control soil. However, in soils which adsorb significant amounts of SO, measurement of solution SO concentration underestimates the extent of dissolution. Gypsum dissolution was larger in water (15.20 mmol litre^?1) than in 0.01 M CaCl₂ (11.12 mmol litre^?1), and this was attributed to the Ca²⁺ common-ion effect. The rate of dissolution decreased in the order: AR > FGD > PG > MG. Dissolution was 2 to 10 times faster for powdered (< 500 .m) gypsum than for the discs obtained by pelletising. The differences in the rate of dissolution between the gypsum sources and between powder and disc samples were related to both surface area and the presence of CaCO₃, impurity. The rate of dissolution was 3 to 8 times faster in the presence than in the absence of soil. Whereas the dissolution of gypsum in the presence of soil followed first order reaction kinetics, it followed second order kinetics in the absence of soil. This difference in reaction kinetics resulted from the continuous removal of Ca2+ and SO by the soil.     

Ion chromatographic determination of inorganic anions in vinegar samples

An ion chromatographic procedure (IC) with chemical suppression is described for the simultaneous determination of the anions Cl^?, NO, HPO and SO at ppm levels in vinegar samples. The moderately strong eluent composed of NaHCO₃/Na₂CO₃ was chosen and sample pretreatment was required to reduce the influence of acetate on the chloride peak. The results obtained by IC were compared to those from standard methods.     

Acceptability of diets containing olive oil fried sardines (Sardina pilchardus) in the prevention of dietary hypercholesterolaemia in rats

Garlic (Allium sativum L) bulb explants produced undifferentiated white globular callus when grown on MS medium having 2,4-dichlorophenoxy-acetic acid (2,4-D) and Kinetin (Kn). Such callus when grown on medium having indole-3-yl-acetic acid (IAA) and/or Kn developed into the differentiating callus which had comparatively more allicin than that of undifferentiated callus. The effect of sucrose, NH/NO ratios and hormone concentrations on growth and allicin development in the callus was investigated. There was a significant increase in allicin development in callus when grown for up to 4 weeks on medium (a) having sucrose at 3% and 5% levels; (b) having NH and NO ratios at 2:1 and 1;1; and (c) with Kn alone at a concentration of 0.5 mg litre^?1, which produced a tenfold increase in allicin content.     

The extraction of radiolabelled inorganic sulphate from blood plasma

A study was conducted into factors governing the efficiency of the ion exchange method for extracting ³⁵S-labelled inorganic sulphate (SO) from blood plasma, using Dowex′1-X8 ion exchange resin. The study compared effects of trichloroacetic acid (TCA) strength as protein precipitant, different HCl strengths as resin eluent, sodium citrate/HCl (SC/HCl) versus HCl as eluents, and evaluated ultrafiltrated (UF) plasma upon the adsorption and recovery of added ³⁵SO. Both adsorption and release of ³⁵SO from the resin were inhibited by the presence of TCA, and HCl was not as effective as 1 M SC/2 M HCl in releasing ³⁵SO adsorbed to resin. The rates of ³⁵SO adsorbed onto resin and recovered were markedly increased by using UF plasma and 1 M SC/2 M HCl as eluent, with the values being 96.3 ± 0.11% and 91.1 ± 0.39%, respectively, where 1 g resin was used. Therefore, the use of UF for deproteinising and 1 M SC/2M HCl as eluent are recommended for extracting ³⁵SO from blood plasma when Dowex′1-X8 resin is used as the ion exchanger.     

Interaction between cow slurry and 15N-labelled calcium nitrate as fertilisers for ryegrass production

A field-plot experiment with ryegrass was carried out to study the interaction between ¹⁵N-labelled calcium nitrate at 0, 25 and 50 kg N ha^?1 and cow slurry supplying 0, 33 and 68 kg NH-N ha^?1. Treatments were applied on a single occasion to a site where first-cut silage had just been removed. The effects of the treatments on dry matter yield, nitrogen offtake and % utilisation of calcium nitrate were measured in two cuts of herbage taken after 5 and 17 weeks. Increases in dry matter yield due to slurry were smaller at the 50 kg N ha^?1 rate of calcium nitrate than at the 0 and 25 kg N ha^?1 rates, possibly due to non-linearity of the yield response curve. Nitrogen offtake data indicated that the two sources of nitrogen were taken up additively by the ryegrass. Rate of calcium nitrate application or slurry treatment had no significant effect on the % utilisation of calcium nitrate in either cut. The average values for % utilisation of calcium nitrate over all treatments were 50 and 7% at cuts 1 and 2, respectively. There was no evidence for enhanced rates of denitrification in the presence of slurry. Recovery values of nitrogen (estimated by difference) were lower for NH-N in slurry than for calcium nitrate. Volatilisation of ammonia from surface-spread slurry is the most likely reason for the low efficiency of NH-N in slurry.     

Thermal Conductivity of Gelatinized Starches

The thermal conductivity (k) of gelatinized high-amylose and high-amylopectin starches was determined, using the heated probe method. The granular starches, mixed with distilled water at 1 to 4 kg water/ kg dry solids, were gelatinized at 120°C. Similar k values which varied from 0.434 to 0.548 W/mK in the temperature range 30 to 70°C were obtained for both starch gels. Experimental data were fitted to six structural models, representing various geometries for mixtures of water and dry starch. The perpendicular model, based on heat conduction in series through layers of dry starch and water, yielded best correlations. The predicted thermal conductivity of dry gelatinized starch (k_s) increased linearly with temperature T (K) according to the equation:      

De la rhéologie des systèmes aqueux à base de gommes

On the Rheology of Aqueous Systems on the Basis of Gums. The water „solutions”︁ of macromolecular carbohydrates (arabic gum, alginate, guaran, starches) often show a non-Newtonian behaviour. Therefore it is impossible to give only one viscosity value for the definition of the rheological behaviour; viscosity changes with the different rheological conditions. But it is possible to speak of an „apparent viscosity”︁ for a given shear rate D_i or stress r_i. To characterize the rheological behaviour it is necessary to establish the relationship between shear rate and shear stress. Sometimes, for limited decades of shear rates, the behaviour may be described by a power law = τ = K D^a: sometimes the Cross relation \documentclass{article}\pagestyle{empty}\begin{document}$ \overline \eta = \eta _\infty + \frac{{\eta _0 - \eta _\infty}}{{1 + \alpha D^{2/3}}} $\end{document} has to be applied; but it may also occur, that one can only give the curve log τ = f (log D). To obtain absolute values it is necessary to apply a correcting factor at the actual values given by Newtonian approximation. Thus it is possible to study the influence of temperature, concentration and ageing on the rheological parameters K, a, η or the graph log τ = f (log D). From the results it seems that the behaviour of this kind of systems is rather like the behaviour of emulsions, than like that of true solutions. Perhaps that is the reason why, the process for the preparation of these systems has to be well defined and rigorously followed in order to obtain reproducible results. To give a sense to rheological studies in the laboratory, it is important to simulate the exact industrial conditions of preparations and of the rheological stresses of these systems. This calls for an exact knowledge of the industrial rheological stress; up to now this knowledge is very rare in most cases.     

Glass Transition Study in Model Food Systems Prepared with Mixtures of Fructose,Glucose, and Sucrose

Abstract: The glass transition temperature of model food systems prepared with several glucose/fructose/sucrose mass fractions was studied using differential scanning calorimetry (DSC). A distance‐based experimental design for mixtures of 3 components was used to establish the proportion of sugars of the model systems. Thus, 32 compositions including individual sugars and sugar mixtures, both binary and ternary were prepared and analyzed. Thermograms showing the complete process of heating–cooling–reheating were used to determine the precise glass transition temperature during cooling () or reheating () in amorphous sugars. The Scheffe cubic model was applied to experimental results to determine the influence of sugar composition on the glass transition temperature (P < 0.05). The final model proved to be appropriate (R² > 0.97, CV < 9%, model significance <0.0001) to predict the T_g values of any dry mixture of amorphous fructose, glucose, and sucrose. Practical Application: The experimental values of T_g and the mathematical model proposed in this work may be of great use for making available T_g data that involves the mixture of more than 2 sugars and thus could be used as a tool for predicting the storage stability and quality of dehydrated products such as fruit powders.