Ohmic cooking of whole turkey meat – Effect of rapid ohmic heating on selected product parameters

Intact turkey meat was cooked using low temperature long time (LTLT) and high temperature short time (HTST) protocols in a combined ohmic/convection system and compared to conventional (CONV) steam cooking. Both ohmic protocols gave a significantly lighter (p < 0.05) and a more uniform colour vs. CONV, while no significant differences (p ? 0.05) were found in texture profile analysis attributes between LTLT and CONV though HTST showed significantly higher attributes (p < 0.05). Cook loss was significantly (p < 0.05) different between treatments (25.2%, 27.9% and 31.3% for LTLT, CONV and HTST). Sensory studies largely confirmed these observations. Cook values (p < 0.05) were lowest for LTLT (4.0) followed by HTST (5.4) and control (8.5). Lipid oxidation and sulphur-flavour-compound development (measured over 7 days) were higher for conventional than ohmic treatments. Overall, these results demonstrate considerable industrial potential for ohmic heating, yielding high quality products with an 8–15-fold reduction in cooking time.     

Ohmic cooking of whole beef muscle — Evaluation of the impact of a novel rapid ohmic cooking method on product quality

Cylindrical cores of beef semitendinosus (500 g) were cooked in a combined ohmic/convection heating system to low (72 °C, LTLT) and high (95 °C, HTST) target end-point temperatures. A control was also cooked to an end-point temperature of 72 °C at the coldest point. Microbial challenge studies on a model meat matrix confirmed product safety. Hunter L-values showed that ohmically heated meat had significantly (p < 0.05) lighter surface-colours (63.05 (LTLT) and 62.26 (HTST)) relative to the control (56.85). No significant texture differences (p ≥ 0.05) were suggested by Warner–Bratzler peak load values (34.09, 36.37 vs. 35.19 N). Cook loss was significantly (p < 0.05) lower for LTLT samples (29.3%) compared to the other meats (36.3 and 33.8%). Sensory studies largely confirmed these observations. Cook values were lower for LTLT (3.05) while HTST and the control were more comparable (6.09 and 7.71, respectively). These results demonstrate considerable potential for this application of ohmic heating for whole meats.     

The Impact of Thermosonication and Pulsed Electric Fields on Staphylococcus aureus Inactivation and Selected Quality Parameters in Orange Juice

The effect of thermosonication (TS) and pulsed electric fields (PEF) on inactivation of Staphylococcus aureus (SST 2.4) and selected quality aspects in orange juice was investigated. Conventional pasteurization (HTST, 94 °C for 26 s) was used as a control. TS (10 min at 55 °C) applied in combination with PEF (40 kV/cm for 150 μs) resulted in a comparable inactivation of S. aureus to that achieved by conventional HTST. TS/PEF did not affect the pH, conductivity, or °Brix and had a milder impact on the juice color than thermal treatment. Furthermore, the non-enzymatic browning index was significantly affected by HTST (P < 0.05) but not by TS and PEF. Ascorbic acid retention was almost complete after TS and PEF (96.0%), but it was substantially lower (P < 0.05) after HTST (80.5%). Residual activity of pectin methyl esterase (PME) decreased as PEF field strength and treatment time increased; however, applying TS and PEF in combination left a greater residual PME activity than HTST (12.9 vs 5.0%, respectively).     

Effect of Infrared Blanching on Enzyme Activity and Retention of β‐Carotene and Vitamin C in Dried Mango

The objectives of this work were to evaluate infrared (IR) dry blanching in comparison with conventional water blanching prior to hot air drying of mango to inactivate polyphenol oxidase (PPO) and ascorbic acid oxidase (AAO) enzymes, and to study its effect on color change and retention of vitamin C and β‐carotene. Mango cylinders were blanched under similar temperature–time conditions either by IR heating or by immersion in a water bath during 2 min at 90 °C (high‐temperature‐short‐time—HTST) or for 10 min at 65 °C (low‐temperature‐long‐time—LTLT). After blanching mango was hot air dried at 70 °C. PPO was completely inactivated during the blanching treatments, but AAO had a moderate remaining activity after LTLT treatment (～30%) and a low remaining activity after HTST treatment (9% to 15%). A higher retention of vitamin C was observed in mango subjected to IR dry blanching, 88.3 ± 1.0% (HTST) and 69.2 ± 2.9% (LTLT), compared with water blanching, 61.4 ± 5.3% (HTST) and 50.7 ± 9.6% (LTLT). All‐trans‐β‐carotene retention was significantly higher in water blanched dried mango, 93.2 ± 5.2% (LTLT) and 91.4 ± 5.1% (HTST), compared with IR dry blanched, 73.6 ± 3.6% (LTLT) and 76.9 ± 2.9% (HTST). Increased levels of 13‐cis‐β‐carotene isomer were detected only in IR dry blanched mango, and the corresponding dried mango also had a slightly darker color. IR blanching of mango prior to drying can improve the retention of vitamin C, but not the retention of carotenoids, which showed to be more dependent on the temperature than the blanching process. A reduction of drying time was observed in LTLT IR‐blanching mango.     

Effect of Air Temperature on Drying Kinetics,Vitamin C,Antioxidant Activity,Total Phenolic Content,Non-enzymatic Browning and Firmness of Blueberries Variety O´Neil

Effect of air temperature on drying kinetics, vitamin C, antioxidant capacity, total phenolic content (TPC), colour due to non-enzymatic browning (NEB) and firmness during drying of blueberries was studied. Drying curves were satisfactorily simulated with the Weibull model at 50, 60, 70, 80 and 90°C. The scale parameter (β) decreased as air temperature increased and an activation energy value of 57.85 kJ mol⁻¹ was found. Important losses of vitamin C were reported during drying for all the working temperatures (p < 0.05). Although TPC decreased as air-drying temperature increased (p < 0.05) in comparison to its initial value, the dehydration at high temperatures (e.g., 90°C) presented high values for these antioxidant components. Discoloration due to NEB reaction was observed at all the working temperatures showing a maximum value at 90°C (p < 0.05). The radical scavenging activity showed higher antioxidant activity at high temperatures (80 and 90°C) than at low temperatures (50, 60 and 70°C) (p < 0.05). A tissue firmness reduction was observed with increasing temperature (p < 0.05).     

Effects of Applied Process on the In Vitro Digestibility and Resistant Starch Content of Pasta Products

Resistant starch (RS) included in pasta can have auspicious health benefits and functional properties. The resistance of starch, however, can be greatly influenced by the applied food preparation process. The aim of the present study was to investigate the effects of two different resistant starches on the digestibility of pasta and to predict the impact of the conventional pasta processing (extrusion under standard conditions, 120 bars, 40°C; drying in an air-drying room at 35–40°C and cooking until the optimum cooking time) on the quality of different resistant starch included in products by using an in vitro enzymatic hydrolysis method. Results showed that the applied, conventional pasta extrusion step had only a small effect on the liberated glucose level and did not influence the RS content significantly. The cooking in contrast caused an increased digestibility and the lost of resistance of all pasta products. The digestibility was significantly lower (p < 0.05) in the case of raw and dried samples compared to the cooked pastas. It can be concluded that the resistant starches used in the samples are heat sensitive and their properties change radically during the pasta preparation, mainly during cooking.     

Ohmic cooking of ground beef: Effects on quality

Conventional cooking tends to be slow and the surface of the food always receives a much more severe heating treatment than the rest of the food. Ohmic heating has the potential to be much faster and produces even more cooking. In this work cylindrical ground beef samples having different initial fat contents (2%, 9% and 15%) were cooked ohmically (20, 30 and 40 V/cm) and conventionally. Ohmic cooking was faster than the conventional cooking (p < 0.05). Ohmically cooked samples were firmer than those conventionally cooked but yield and fat retention was similar. However, the reduction in volume during cooking was significantly smaller from 5.36% to 6.97% in ohmic cooking than the conventional system which was measured from 26.01 to 31.59. The voltage gradient applied during ohmic cooking was not related to the quality of the cooked meat. These results show that ohmic cooking could be a fast-alternative method for meat products.     

Effect of tumbling time and cooking temperature on quality attributes of cooked ham

This study evaluates effect of tumbling time and cooking temperature on cooking rate, cooking loss (CL), colour, water activity and water‐holding capacity of cooked restructured ham rolls. In experiment were investigated three tumbling times (2, 4 and 6 h) at constant temperature (+4 °C) and three cooking temperatures (76, 86 and 96 °C). It was observed that CL decreased (P < 0.01) from 5.41% to 3.22% with tumbling time (2 h vs. 6 h) but increased (P < 0.01) from 2.35% to 7.25% along with cooking temperature (76 °C vs. 96 °C). In contrast, pH value increased (P < 0.01) from 6.18 to 6.24 with tumbling time (2 h vs. 6 h) but decreased (P < 0.01) from 6.22 to 6.17 along with cooking temperature (76 °C vs. 96 °C). In addition, high temperature had higher efficiency for thermal lethality than low temperature (F₀ values were 19 and 92 min at 96 and 76 °C, respectively). Intermediate tumbling (4 h) and cooking (86 °C) could be preferential.     

Ohmic cooking of whole beef muscle – Optimisation of meat preparation

Uniform ohmic heating of solid foods primarily depends on the uniformity of electrolyte distribution within the product. Different preparation techniques were tested in an attempt to ensure an even salt dispersion within a full beef muscle (biceps femoris). Meat pieces were soaked, injected and tumbled using a range of procedures before ohmic cooking at pasteurization temperatures. A final preparation method (multi-injection (five points) with a 3% salt solution followed by 16 h tumbling) was validated. Selected quality parameters of the ohmically cooked products were compared to steam cooked products. Ohmically heated meat had a significantly (P < 0.05) uniform lighter and less red colour. Cook loss was significantly lower (P < 0.05) in ohmic samples and in relation to tenderness ohmic heated samples were tougher (P < 0.05) though the difference was only 5.08 N. Comparable cook values were attained in the ohmic and conventionally cooked products.     

Effects on microbial inactivation and quality attributes in frozen lychee juice treated by supercritical carbon dioxide

In this paper, we described the use of high-pressure carbon dioxide (HPCD) for the inactivation of natural microbes in lychee juice and evaluated its effects on lychee juice quality, compared to a conventional high-temperature, short-time (HTST) method. The HPCD treatments were carried out using a HPCD unit (8 MPa, 36 °C, 2 min), and the HTST was performed at 90 °C for 60 s. The results showed that five log reduction for yeasts and molds and total aerobic microorganisms occurred at 8 MPa for 2 min. And effects of the treatments on pH and concentrations of microbes, organic acids, titratable acidity (TA), total soluble solid (TSS), sugars, polyphenols, color, and free amino acids were also investigated. HPCD could efficiently maintain the concentration of polyphenols and original color at 8 MPa, 36 °C for 2 min. Insignificant differences in colors were observed between unprocessed and HPCD juices, while significant differences were observed between unprocessed and HTST juices. Furthermore, HTST decreased the total free amino acids, whereas HPCD caused a significant increase (increased by 45.92% at 8 MPa) (p < 0.05). The increase in total amino acids induced by HPCD treatment is beneficial for nutritional value of commercial ready-to-drink lychee juice. In general, HPCD treatment had less influence on the measured quality parameters of lychee juice than HTST treatment. Therefore, HPCD treatment could be a useful alternative to traditional heat treatment.     

In Vitro Digestibility of Native and Resistant Starches: Correlation to the Change of its Rheological Properties

The broadly investigated and applied resistant starches have several health benefits: they can help, for instance, in the treatment of obesity and prevention of colon cancer; therefore, the accurate knowledge of the properties of these starches is elementary. In our study, the digestibility properties of two native starches (maize and wheat) and two resistant starches (RS2, Hi-maize™260; RS4, Fibersym™70), as well as their stoichiometric mixtures before and after cooking (at 100 °C), were investigated. Moreover, correlations were investigated between two different enzymatic methods and the rapid visco analyzer (RVA) method. Our aim was to prove strong relationship between rheological and enzymatic digestibility characteristics. To conclude the results of our measurements regarding resistant starches, it can be stated that the two resistant starches show different digestibility in raw and cooked form. After cooking, RS2 caused a linear decrease in the initially and the totally liberated glucose concentration in cooked mixtures; thus, these parameters can be predicted in the function of resistant starch addition. Additionally, we did not find any synergistic effects in the mixtures after heat treatment. Significant (p < 0.05) and strong correlations were found between enzymatic digestion and RVA methods in both cases of untreated and gelatinized starches. These results provide promising information for the prediction of in vitro digestibility from RVA results. Our results may confirm the theory that there is a relationship between the physicochemical and enzymatic digestibility properties of starches.     

Foam-Mat Drying of Plantain and Cooking Banana (<Emphasis Type="Italic">Musa</Emphasis> spp.)

Foaming, reconstitution, and sensory attributes of foam-mat-dried plantain and cooking banana were investigated. Plantain and cooking banana pastes mixed with different concentrations (0.005%, 0.01%, 0.015%, and 0.02%) of glyceryl monostearate (GMS) were whipped, and the resulting foams were air dried at 60°C, 70°C, and 80°C. Physical, chemical, and sensory properties of fresh and reconstituted paste from plantain and cooking bananas were determined. Higher GMS concentration and longer whipping time resulted in lower foam densities. Generally, cooking banana foams showed lower foam density compared to plantain foam. Lower drying temperatures and concentration of GMS resulted in longer drying time. pH (4.41–4.80), titratable acidity (0.06–0.08), and water absorption capacity (56.75–64.02%) of the reconstituted pastes varied with commodity, drying temperature, and %GMS concentration. Fresh and reconstituted pastes showed comparable physical and chemical attributes, while the taste and sensory attributes of fresh plantain and cooking banana pastes were significantly (p < 0.05) better than those of reconstituted pastes.     

Study on Thermosonication and Ultraviolet Radiation Processes as an Alternative to Blanching for Some Fruits and Vegetables

The impacts of ultraviolet-C radiation, blanching by heat, and combination of heat/ultrasounds (thermosonication) were studied for Listeria innocua (inoculated) in red bell peppers, total mesophiles in strawberries and total coliforms in watercress, in the temperature range 50–65 °C. Quality attributes such as colour and firmness were studied for all products, and total anthocyanins content was additionally determined for strawberries. Results showed that ultraviolet-C radiation was the least effective treatment in terms of microbial load reduction and was equivalent to a simple water washing. Log reductions were 1.05 ± 0.52 for L. innocua, 0.53 ± 0.25 for total coliforms and 0.26 ± 0.18 for total mesophiles. This treatment had the lowest impact on the quality parameters analysed. Thermosonication treatment was similar to heat blanching for all microorganism/product tested, excepted for total coliforms in watercress at 65 °C, in which thermosonication had a higher effect (p < 0.05). Heat blanching at 65 °C allowed 7.43 ± 0.12 log-cycles reduction, while loads were diminished by 8.24 ± 0.13 log-cycles if thermosonication at the same temperature was applied. Thermosonication also allowed better quality retention, when compared to heat blanching at the same temperatures. The impact of thermosonication on microbial load reductions was statistically significant and thermosonicated samples retained quality attributes better than heat blanched ones at the same temperatures (p < 0.05). Hence, it can be concluded that thermosonication is a promising process and may be a favourable alternative to the conventional thermal treatments.     

A Capillary Electrophoresis Method for the Determination of Hydroxyproline as a Collagen Content Index in Meat Products

The addition of collagen or its hydrolysates as a protein source or water binding agent is a common practice in the production of meat products. However, its level of addition is restricted by international regulations. Glycine, proline, and hydroxyproline are the most abundant amino acids in collagen, which is the main constituent of connective tissue. Thus, the objective of this study was to develop a method for the determination of hydroxyproline content in meat products by capillary electrophoresis (CE) as a collagen content index. Acid hydrolysis of samples and amino acid derivatization with fluorescamine prior to CE analysis were conducted. Separations were carried out using an uncoated capillary at 33 °C, using tetraborate buffer 0.05 M, pH 9.3 with 100 mM SDS. Hydroxyproline was detected at 214 nm. The assay was reproducible (RSD < 3% for normalized peak areas and migration times) and had good correlation (r = 0.975, p < 0.001) with the AOAC official method. From the samples tested (36), commercial ham showed the lowest average collagen content (<7.16 g per 100 g protein) by the CE method. On the other hand, frankfurter and Mexican “chorizo” sausages showed average collagen contents of 12.88 and 11.17 g per 100 g protein, respectively. The CE method developed could be used by regulatory agencies to ensure compliance with maximum levels of collagen addition in processed meats.     

Effects of cooking on thermal-induced changes of Qingyuan partridge chicken breast

Changes in some properties of cooked 22-weekold Qingyuan Partridge chicken breast were investigated. Cooking losses of meat increased significantly in the range 55–85°C (p<0.05). The heated chicken muscle became lighter and yellower. The shear value of meat decreased markedly to a minimum at 65°C, and increased dramatically upon cooking from 65 to 85°C (p<0.05) with a slight increase from 85 to 100°C (p>0.05). The texture profile analysis parameters of meat changed independently with increasing temperature. Muscle fibers decreased to a minimum (p<0.05) at 65°C with an increase from 65 to 75°C. A significant decrease in solubility of salt-soluble myofibrillar proteins (p<0.05) and an increase in the content of heat-soluble collagen in the range 55–65°C were observed. The results demonstrated that cooking temperature had significant effects on the thermal-induced changes of older chicken and marked changes were happened from 55 to 85°C.     

Effects of Soy and Corn Flour Addition on Batter Rheology and Quality of Deep Fat-Fried Shrimp Nuggets

In this paper, the effects of soy and corn flour (5 and 10% w/w) addition to the batter formulation on the quality of deep fat-fried shrimp nuggets were evaluated. Rheological properties of batters, coating pick-up, moisture content, and oil content of the samples were determined. Shrimp nuggets were fried at 150 °C, 170 °C, 190 °C, for 1, 2, 3, 4, and 5 min. The coating pick-up, oil and moisture content were found to be directly proportional to batter viscosity. All batters were found to show shear thinning behavior by exhibiting flow behavior index ≤ 1. The batters were modeled as power law fluids. Batter formulation, frying time, and temperature significantly (p < 0.01) affected moisture and oil content of shrimp nuggets. Soy flour added batters provided the highest consistency index, 7.595 and 10.635 Pa.sⁿ for 5% and 10% soy flour added, respectively. Soy flour was found to be an effective ingredient in decreasing oil content of fried nuggets. Batters containing 5% corn flour showed the lowest moisture content and the highest oil content among all the formulations. The mean moisture and fat content of shrimp nuggets coated with batter contained 10% soy and 5% corn flour, fried at 190 °C, for 5 min were 0.59 ± 0.022, 0.480 ± 0.029 and 0.149 ± 0.035, 0.346 ± 0.024 (g/g db), respectively.     

Stability of polyphenolic extracts from grape seeds after thermal treatments

Five commercial grape seed extracts (GSEs) were put under pasteurisation (HTST and LTLT), cooking, baking and sterilisation conditions. After each treatment, the tannin content, antioxidant activity, browning and characteristics of eight phenolic compounds were determined. For nearly all quantified parameters, significant differences (p < 0.05) were found between at least two treatments. The gallic acid, gallocatechin and browning parameters showed a greater tendency to increase in the treatments, and the antioxidant activity showed a greater tendency to decrease. A positive correlation between the tannin content and browning and a negative correlation between the gallic acid and antioxidant activity were found. The GSEs were clearly grouped based on their composition; nevertheless, a grouping based on the treatments did not exist. It can be concluded that the thermal treatments affected the stability of all GSEs in a different manner depending on the phenolic profile of each extract.     

Stability and Degradation Kinetics of Bioactive Compounds and Colour in Strawberry Jam during Storage

The effect of storage time and temperature on degradation of bioactive compounds such as ascorbic acid, anthocyanins, total phenols, colour and total antioxidant capacity of strawberry jam were investigated. The results indicated that lightness (L) value decreased significantly (p < 0.05) over 28 days of storage at 4 and 15 °C, with lower values measured at higher temperatures. Anthocyanins, ascorbic acid and colour degradation followed first-order kinetics where the rate constant increased with an increase in the temperature. The reaction rate constant (k) increased from 0.95 × 10⁻² day⁻¹ to 1.71 × 10⁻² day⁻¹ at 4 and 15 °C for anthocyanins. Similarly, k increased from 2.08 × 10⁻² day⁻¹ to 4.54 × 10⁻² day⁻¹ at 4 and 15 °C for ascorbic acid. In general, total antioxidant activity for strawberry jam samples stored for 28 days at 4 and 15 °C exhibited lower values as compared to control (day 0). The results showed greater stability of nutritional parameters at 4 °C compared to 15 °C.     

Changes in the texture,microstructures, colour and volatile compounds of pork meat loins during superheated steam cooking

We evaluated changes in the texture, colour, microstructure and volatile compounds of pork loins after superheated steam (SHS) cooking at 120, 140, 160 or 180 °C for 5, 10, 15 and 20 min. Results showed that the texture changed significantly with heating temperature and time. Hardness increased significantly with increasing temperature above 140 °C. Scanning electron microscopy micrographs showed that cooked pork with SHS had more complete muscle fibre bundle structure than that of pork in HA. The L* value indicating colour was significantly increased during the early period and then decreased, whereas the a* and b* values showed a continuous increase. Ninety-five volatile compounds were identified in cooked pork from SHS by gas chromatography/mass spectrometry with solid-phase microextraction. The amount of volatile compounds increased during cooking and decreased as cooking time increased and was well retained at 140 °C. Considering those variations, samples cooked at 140 °C showed better quality attributes.     

Effects of high pressure treatment on physicochemical characteristics of fresh sea bass (Dicentrarchus labrax)

The effects of high pressure (HP) treatment (pressure: 220–250–330 MPA; holding time: 5 and 10 min; temperature: 3, 7, 15 and 25°C) on physicochemical characteristics (colour, thiobarbituric acid, trimethylamine nitrogen values) of fresh sea bass fillets were investigated. HP-treated sea bass fillets had higher lightness (Hunter L*) values than untreated sea bass fillets; the magnitude of changes increased with treatment pressure. HP-induced changes in colour generally imparted a cooked sample. The TBA value of HP treated sea bass samples (except 220–330 MPa, 3°C for 5 min) were found to be insignificant (P > 0.05) or significantly (P < 0.05) lower than the untreated samples. TMA-N content of HP treated at 220–250–330 MPa, 3–7–25°C for 10 min sea bass samples were found to insignificant according to the untreated samples. The results obtained from this study showed that the quality of high pressure treated sea bass is best preserved at 220 MPa, 25°C for 5 min.