Stability of Dehydrofrozen Green Peas Pretreated with Nonconventional Osmotic Agents

ABSTRACT: Green peas were submitted to osmotic pretreatments in carbohydrate-salt syrups to evaluate the effect of alternative agents on quality and assess the stabilization accomplished during subsequent storage in a wide temperature range-down to −24°C, including the −3 to −12°C detrimental zone. Green color and L-ascorbic acid loss were kinetically studied, and their temperature dependence was modeled by Arrhenius and Will-iams-Landel-Ferry equations. Dehydrofrozen samples exhibited significantly improved stability, with the rate of L-ascorbic acid loss, being reduced by as much as 3-fold for peas osmotically pretreated with oligofructose, trehalose, and maltitol systems. The cryostabilization results are discussed in relation to glass transition behavior of the modified osmodehydrofrozen food matrix.     

Osmotic dehydration of pomegranate seeds: mass transfer kinetics and differential scanning calorimetry characterization

Osmotic dehydration of pomegranate seeds was carried out at different temperatures (30, 40, 50 °C) in a 55°Brix solution of sucrose, glucose, and mixture sucrose & glucose (50:50, w/w). The most significant changes of water loss and solids gain took place during the first 20 min of dewatering. During this period, seeds water loss was estimated to 46% in sucrose, 37% in glucose and 41% in mix glucose/sucrose solution. The increase of temperature favoured the increase of water loss, weight reduction, solids gain and effective diffusivity. Differential scanning calorimetry data provided complementary information on the mobility changes of water and solute in osmodehydrated pomegranate seeds. The ratio between % frozen water and % unfreezable water decreased from 5 to 0.5 during the process. That involving the presence of very tightly bound water to the sample, which is very difficult to eliminate with this process. It also appeared that glass transition temperature depends on the types of sugar.     

Osmotic Dehydration and Vacuum Impregnation on Physicochemical Properties of Chilean Papaya (Carica candamarcensis)

ABSTRACT: The effect of osmotic dehydration (OD) at atmospheric pressure and vacuum impregnation (VI) treatments on some physiochemical parameters of papaya (aw, pH, color, firmness, and microstructure) was analyzed. Osmotic treatments were carried out on papaya with 55°Brix and 65°Brix sucrose solutions at 30 °C. VI with 65°Brix osmotic solution was the most effective in reducing aw due to the highest sucrose gain during osmotic treatment. Color differences were associated to loss of clarity in line with transparency gain. Scanning electron microscopy observations show that osmotic dehydration caused shape changes and size reduction of papaya cells; also differences in microstructural features were observed between OD-treated and VI-treated samples. Moreover, the largest firmness observed in VI samples compared with OD treatments was associated with the thickness of the middle lamella between cells, which was greater in VI than OD treatments. Improvement in texture and palatability of papaya was obtained with VI rather than OD treatment compared with fresh papaya.     

The effect of sub-zero temperatures on different lifestages of Lasioderma serricorne (F.) and Ephestia elutella (Hübner)

The effect of sub-zero temperatures on different lifestages of Lasioderma serricorne and Ephestia elutella was investigated as a means of disinfesting stored tobacco. Eggs, unacclimated cocoons and acclimated cocoons of L. serricorne were exposed to −10 °C, −15 °C and −20 °C in insulated boxes. There was no adult emergence from eggs or unacclimated cocoons following exposure to the respective temperatures for 4 h, 2 h and 1 h. With acclimated cocoons there was no adult emergence after 2 h at −15 °C and 1 h at −20 °C, but at −10 °C, there was adult emergence after 8, 12 and 24 h exposures.In field-scale experiments, cold acclimated fourth-instar larvae of L. serricorne were inserted into cases of leaf tobacco and boxes of finished product, put into commercial freezers and exposed to minimum temperatures of −10 °C, −18 °C or −25 °C. Critical temperatures were measured at the core of the commodity. No adults emerged from the commodity when exposed to at least −18 °C for periods ranging between 3.75 h and 39.25 h or when exposed to at least −25 °C for between 2.4 h and 3.7 h. At a minimum of −10 °C, 3 live adults emerged after 24 h exposure.With E. elutella, diapausing larvae were inserted into small scale tobacco bales and exposed to −10 °C, −13 °C, −15 °C or −20 °C. No emergence of adults and no larval survival was achieved after 21 d, 3 d and 2 h exposure at −10 °C, −15 °C and −20 °C respectively. At −13 °C, there was no adult emergence after 2 and 5 d exposure, but live larvae remained after 24 weeks incubation at 25 °C.Minimum conditions of −18 °C for 24 h and −25 °C for 4 h are recommended for the control of L. serricorne and −20 °C for 24 h for the control of E. elutella in stored tobacco (to fit with operational logistics).     

DETERMINATION OF GLASS TRANSITION TEMPERATURE OF RAINBOW TROUT (ONCORHYNCHUS MYKISS) AND EFFECTS OF VARIOUS CRYOPROTECTIVE BIOPOLYMER BLENDS ON SOME CHEMICAL CHANGES

Sucrose  +  sorbitol  +  gum arabic (2  +  2  +  0.15%), sucrose  +  sorbitol  +  carrageenan (2%  +  2%  +  0.15%), sucrose  +  mannitol  +  gum arabic (2%  +  2%  +  0.15%), sucrose  +  mannitol  +  carrageenan (2%  +  2%  +  0.15%), sorbitol  +  mannitol  +  gum arabic (2%  +  2%  +  0.15%) and sorbitol  +  mannitol  +  carrageenan (2%  +  2%  +  0.15%) were blended with ground rainbow trout and stored at glass transition temperature ( T _g) of rainbow trout ( − 13C), determined by differential scanning calorimetry at − 9 and − 18C for 6 months. Total volatile basic nitrogen (TVB-N) and thiobarbituric acid-reactive substances (TBARS) were determined at 1st, 3rd and 6th months of storage periods. Biopolymer blends and storage period had a significant effect ( P <  0.05) on the TVB-N and TBARS values. T _g and − 18C showed same effect on TVB-N and TBARS values but − 9C has statistically different effect on them.

PRACTICAL APPLICATIONS

The T_g value was found as −13C for rainbow trout. This value is higher than commercial storage temperature (−18C). This has a great importance in terms of economical viewpoint. It was determined that TVB-N values were same and TBARS values were similar at the end of 6 months storage at T_g and −18C. When considering these two parameters, it can be accepted that −13C could be an indicator of usability instead of −18C.     

Optimisation of osmotic dehydration of 'Tommy Atkins' mango fruit

Osmotic dehydration of mango in sucrose solution as influenced by temperature (30–50 °C), immersion time (60–150 min) and solution concentration (40–60% w/w) was studied through response surface methodology. Responses of water loss and solid gain were fitted to polynomials, with multiple correlation coefficients ranging from 0.72 to 0.95, respectively. The fitted functions were optimised for maximum water loss and minimised incorporation of solids in order to obtain a product resembling non-processed fruit. Optimum conditions to obtain water removal >25% with solid uptake lower than 6% could be obtained using a 44% (w/w) sucrose solution concentration, temperatures up to 38 °C and immersion times up to 80 min.     

Effects of freezing and thawing processes on the quality of Atlantic salmon (Salmo salar) fillets

ABSTRACT:  High-pressure processing is finding a growing interest in the food industry. Among the advantages of this emerging process is the ability to favorably freeze and thaw food. This study aims at comparing the effect of different freezing and thawing processes on the quality of Atlantic salmon fillets. Atlantic salmon ( Salmo salar ) samples were frozen by Pressure-Shift Freezing (PSF, 200 MPa, −18 °C) and Air-Blast Freezing (ABF, −30 °C, 4 m/s). Samples were stored 1 mo at −20 °C and then subjected to different thawing treatments: Air-Blast Thawing (ABT, 4 °C, 4 m/s), Immersion Thawing (IMT, 20 °C), and Pressure-Assisted Thawing (PAT, 200 MPa, 20 °C). Changes in texture, color, and drip loss were investigated. The toughness of the PSF samples was higher than that of the ABF sample. The modification of color was more important during high-pressure process than during the conventional process. The PSF process reduced thawing drip compared with ABF. The presence of small ice crystals in the pressure-shift frozen sample is probably the major reason leading to the reduced drip volumes. The freezing process was generally much more influent on quality parameters than the thawing process. These results show the interaction between freezing and thawing processes on selected quality parameters.     

Influence of Cooling Rate on Glass Transition Temperature of Sucrose Solutions and Rice Starch Gel

ABSTRACT: The study's objectives were to determine the influence of cooling rate through the primary zone of freezing on T_g in sucrose solutions and rice starch gels. The influence of cooling rate, water content, and annealing on T_g were evaluated. Results indicated that the observed T_g values for sucrose solutions were lower after rapid cooling (70% solids: rapid cooling −66.7°C; slow cooling −64.6 °C; 30% solids: rapid cooling −34.6 °C; slow cooling −33.3 °C). The T_g values of annealed samples are higher than the T_g of both rapidly and slowly cooled samples (70%: −44.2 °C; 30%: −32.7 °C). The T_g of the rice starch gel was −9.0 °C after rapid cooling and −7.5 °C after slow cooling.     

How to deal with visco-elastic properties of cellular tissues during osmotic dehydration

In this work, vacuum impregnated apple discs with different isotonic solutions (sucrose and trehalose) were equilibrated during osmotic dehydration (55°Brix glucose at 40 °C). Changes in sample composition (water and soluble solid contents), weight and volume are analysed. A mathematical model is proposed to describe and quantify the outflow of water from the protoplast as well as the visco-elastic behaviour of the cell. Good correspondence between simulated and measured data of non impregnated samples and samples impregnated with isotonic solutions of sucrose or trehalose during long term osmotic dehydration is obtained. Fitted values of the cell permeability correspond well with tabulated values. Furthermore, also the obtained values of the parameters describing the mechanical properties of the cell wall and Hectian strands seem to reflect the observed structural development of these structures for the different treated samples well.     

State Diagram of Freeze-dried Garlic Powder by Differential Scanning Calorimetry and Cooling Curve Methods

ABSTRACT: The state diagram of freeze-dried garlic powder was developed using freezing curve, glass transition line, and maximal-freeze-concentration condition. Freezing points of garlic powder were measured by differential scanning calorimetry (DSC) and the cooling curve method, whereas glass transitions were measured by DSC. The freezing curve and glass transition line were modeled using the Clausius-Clapeyron equation, adjusted with unfreezable water, and the Gordon-Taylor model, respectively. Maximal-freeze-concentrated condition was found as X '_s (characteristic water content) = 0.82 [ X '_g (characteristic solids content) = 0.18] with the characteristic temperature of glass formation being T '_m (characteristic glass transition) =−38.6°C and T '_m (characteristic end point of freezing) =−26.0°C. Other characteristic glass transitions T "_g and T ‴_g equal to −29.3°C and −48.6°C, respectively.     

Osmotic Dehydration of Tomato in Sucrose Solutions: Fick's Law Classical Modeling

ABSTRACT:  Osmotic dehydration of tomato was modeled by the classical Fick's law including shrinkage, convective resistance at the interface and the presence of water bulk flow. Tomato slices having 8 mm thickness were osmotically dehydrated in sucrose solutions at 50, 60, and 70 °Brix and at 35, 45, and 55 °C. Other experiments were done in a 70 °Brix sucrose solution at 35 °C with tomato slices of 4, 6, and 8 mm thickness and at different motion levels (velocities 0, 0.053, and 0.107 m/s). Tomato weight, water content, and °Brix of the products were measured as a function of processing time (20, 40, 80, 160, and 320 min). Results showed that temperature, concentration, thickness, and solution movement significantly influenced water loss and sucrose gain during the osmotic dehydration of tomato. The model predicted the modifications of soluble solid content and water content as a function of time in close agreement with the experimental data. Experimental Sherwood number correlations for sucrose and water were determined as Sh _s = 1.3 Re ^0.5 Sc _s^0.15 and Sh _w = 0.11 Re ^0.5 Sc _w^0.5, respectively. The effective diffusion coefficients of water (4.97 10⁻¹¹– 2.10 10⁻¹⁰ m²/s) and sucrose (3.18 10⁻¹¹– 1.69 10⁻¹⁰ m²/s) depended only on temperature through an Arrhenius-type relationship.     

EFFECT OF SUCROSE ON CRISPNESS OF EXPLOSION-PUFFED APPLE PIECES EXPOSED TO HIGH HUMIDITIES

SUMMARY— Explosion-puffed apple pieces, because of their hygroscopicity, rapidly lose their crispness under humid conditions. A major cause of the loss of crispness is softening of the sugars, present in the glassy or amorphous state, as moisture is adsorbed. Of these sugars, sucrose has the highest softening point. Materials higher in sucrose content can tolerate more moisture at a given temperature before they soften than materials higher in monosaccharides. The sucrose content of apple pieces is 20—30% of the total sugars. The sucrose content of pieces for puffing was increased to 86% of the total sugars by the following treatment before puffing: The pieces were first soaked in tap water 3—6 hr to reduce monosaccharide content, then soaked in 20—40% sucrose solutions several hours to increase sucrose content by osmosis and counter-diffusion of sucrose. The pieces were then partially dried, puffed and finally dried by conventional hot-air drying to 2% moisture content. Comparison of untreated and treated pieces revealed that the untreated pieces lost their crispness at 4.3% moisture and the treated pieces at 6.6%. When exposed to 75% R.H. and 72°F the untreated pieces remained crisp between 1 and 2 hr; at 75% R.H. and 90°F these pieces softened in less than 1 hr. However, the treated pieces exposed to 75% R.H. remained crisp 4—5 hr at 72°F and 2 hr at 90°F.     

Factors influencing the particle size distribution of flaked meat. I. Effect of temperature, aperture size and prebreaking before flaking

Steer chuck and blade were pre-broken by grinding at −3.0°C and −7.0°C, re-tempered to −3.0°C and −7.0°C, respectively, and then flaked through aperture sizes of 6.1 mm, 9.9 mm or 19.0 mm. Meat was also flaked at −3.0°C without being pre-broken.
More ice melted at the lower temperature; the gain in enthalpy was also higher at −7°C than at −3°C. Size measurements, made using video image analysis, showed that particles produced at the lower temperature had a smaller mean diameter and a greater surface area. Of the three factors investigated, temperature was the most important influence on particle thickness. For a given feed material there was a good correlation between mean diameter and aperture size.
High speed photography results showed that pre-broken meat tended to break-up more readily on the impeller than intact pieces, resulting in pieces of smaller mean diameter.     

Effects of Osmotic Agents on Colour,Textural, Structural,Thermal, and Sensory Properties of Apple Slices

Effects of various osmotic agents (i.e., glucose, fructose, sucrose, maltose, sorbitol, and honey) were evaluated in terms of moisture loss and solid gain besides objective measurements of colour, texture, glass transition temperature; subjective sensory profile; and scanning electron microscopic cellular structure of osmotically dehydrated apple slices. Significantly (p < 0.05) higher solid gains were observed in the samples dipped in glucose and fructose solutions, whereas maltose-treated samples showed higher water loss. The glass transition temperatures varied from ?68.4 to ?45.6°C, minimum in the case of glucose and maximum in maltose-treated ones. The sucrose- and maltose-treated samples had significantly (p < 0.05) higher L* showing restricted browning. The a* value was maximum and minimum in the case of sucrose- and fructose-treated samples, respectively. Hardness was found to be significantly (p < 0.05) higher (20.104 N) in sucrose-treated samples, while it was at a minimum (4.441 N) in sorbitol-treated ones. The scanning electron microscope studies revealed that cellular structure was retained in sucrose-treated samples, while the damage was observed to be more in the glucose- and fructose-treated ones. The sensory attributes of the osmo-dehydrated samples were found to be better in the case of sucrose-treated samples. The type of humectant, in terms of molecular size, significantly influences the mass transfer process that could be optimized to make the process versatile to meet the requirements of processors and consumers.     

Evaluation of Mass Exchange During Osmotic Dehydration of Plum Using Response Surface Methodology

Water loss (WL), solid gain (SG), weight reduction (WR) and shrinkage were quantitatively investigated during osmotic dehydration of plum using response surface methodology with the sucrose concentration (30–60g/100 g sample), temperature of sucrose solution (40–60°C) and immersion time (60–240 min). Experiments were designed according to Central Composite Rotatable Design with these three factors. For each response, second order polynomial models were developed using multiple linear regression analysis. With respect to water loss, solid gain, weight reduction and shrinkage, both linear and quadratic effects of four variables were found to be significant. In most cases, an increase of sucrose concentration, temperature and immersion time increased WL, SG, WR and shrinkage, except the increasing of immersion time for osmotic treatment has no effect on shrinkage. It was found that immersion time and temperature were the most significant factors affecting the WL during osmotic dehydration of plum followed by concentration of sucrose solution. This was also true for WR. Effect of temperature and time were more pronounced for SG than the concentration of sucrose solution.     

EFFECTS OF SOY PROTEIN AND FREEZING TREATMENTS ON COOKING LOSS AND COMPOSITION OF BEEF PATTIES

All-beef and soy-extended patties were frozen to −18°C in either 24, 48, 72 or 96h and stored at −23, −18 or −7°C for 6, 9, 12, 18 or 24 months. The addition of soy resulted in a substantial reduction in cooking loss for patties cooked from the frozen state with a greater retention of moisture in cooked patties. Freezing reduced cooking loss for soy-extended patties, but increased cooking loss for all-beef patties. Faster freezing (-18°C in 24 h vs. −18°C in 96 h) reduced cooking loss and produced higher moisture values in all-beef patties. Patties stored at –7°C lost more moisture during cooking. Increased frozen storage time had a minimal effect on cooking losses, moisture and fat levels. Where it is essential for frozen patties to sustain minimal cooking losses with maximal moisture in cooked patties, the inclusion of soy protein concentrate, faster freezing, and storage at –18°C or colder are suggested.     

Effect of crust freezing applied alone and in combination with ultraviolet light on the survival of Campylobacter on raw chicken

The application of crust freezing (CF) applied as a stand-alone treatment or in combination with ultraviolet (UV) light for reducing the level of artificially inoculated Campylobacter jejuni on raw chicken was investigated. CF air temperatures of −5, −15 and −27 °C (±3 °C) with freezing times of 70, 15 and 6 min, respectively, were used. The level of C. jejuni on chicken was also examined following subsequent refrigerated (0–4 °C) storage at 3 and 7 days. All CF treatments resulted in significant reductions compared to untreated controls (P < 0.05). Although combining CF with UV also resulted in significant reductions for C. jejuni, the combined treatments were generally no more effective than treatment by CF alone. Overall, the color of chicken drumsticks was not affected by CF treatments (P ≥ 0.05). In general, CF resulted in increased drip loss (P < 0.05), which increased over storage time and was greater at higher CF temperatures. The current study indicates that CF has potential for reducing the levels of C. jejuni by between 0.5 and 1.5 log₁₀ CFU/g and impacts minimally on the color of treated skin.     

Glass Transition and Crystallization of Amorphous Trehalose-sucrose Mixtures

Our objective was to investigate the glass transition and crystallization of trehalose-sucrose mixtures at various moisture contents. Samples were freeze-dried, rehumidified, and scanned with Differential scanning calorimetry (DSC) to obtain T_g values for all mixtures and pure sugars. Amorphous cotton candy samples for crystallization studies were prepared, humidified, and monitored for crystallinity as a function of time using powder X-ray diffraction (XRD). The T_g of pure dry trehalose was found to be 106 °C, while sucrose had a T_g of 60 °C. Glass transition, as expected, occurred at an intermediate temperature for sucrose-trehalose mixtures. Of the dry samples, only those containing less than 16% trehalose showed sucrose crystallization during scanning. In cotton candy made from a 25% trehalose-75% sucrose mixture, humidified to 33%, sucrose did not crystallize after 30 days, whereas pure sucrose cotton candy at that humidity crystallized completely after 11 days. These data show that trehalose may be a useful crystallization inhibitor in foods with high sucrose content, although small amounts of trehalose did not significantly raise the T_g.     

Application of competitive indirect enzyme-linked immunosorbent assay (Ci-ELISA) for monitoring the degree of frozen denaturation of bovine myosin

The denaturation of myosin on freezing and frozen storage was monitored using competitive indirect enzyme-linked immunosorbent assay (Ci-ELISA) formatted with polyclonal antibodies anti-MWM IgG, anti-S-1 IgG and anti-LMM IgG raised against the antigens (Ags) bovine myosin whole molecules (MWMs), heavy meromyosin S-1 (myosin head part, S-1) and light meromyosin (myosin tail part, LMM) respectively. Beef slices and cuts stored at −20 °C or −50 °C lost immune affinity with all antibodies, in particular anti-LMM IgG. Repeated thawing–refreezing treatment caused more myosin denaturation than simple freezing. Myosin from beef stored at −20 °C was denatured more than that stored at −50 °C. The immune affinities between anti-LMM IgG and thawed samples were similar to those from anti-MWM IgG. We were unable to differentiate reliably between fresh and thawed beef using anti-S-1 IgG. Myosin was denatured by freezing, in particular its tail part (LMM).