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.     

Quality Evaluation of an Ohmically Cooked Ham Product

Selected parameters (cooking loss, instrumental colour and texture and sensory quality) of a brine-injected pork muscle cooked by a novel and rapid ohmic cooking protocol were examined and compared with those obtained in conventionally cooked samples. Ohmic samples were cooked using either a low-temperature long-time (LTLT) protocol (2 min equilibration, 5 min ohmic heating to 70 °C, 8 min holding) or a high-temperature short-time (HTST) procedure (2 min equilibration, 6 min ohmic heating to 95 °C) performed within a hot air cabinet set at 80 °C (LTLT) and 100 °C (HTST). Conventional cooking (steam oven at 80 °C for 120 min) was conducted to a core temperature of 70 °C. The LTLT treatment gave a much lower cooking loss value (4–5% lower, p < 0.05) than the other treatments, though the full magnitude of this difference was not completely reflected in the proximate composition of the cooked products. Ohmically cooked ham showed a significantly (p < 0.05) lighter surface colour with Hunter L values of 65.3 (LTLT) and 63.5 (HTST) relative to the control (61.4). Texture profile analysis (TPA) indicated a significant difference (p < 0.05) in hardness (N) especially between the HTST surface (82.1 N) and the conventional centre (58.8 N). Although the ohmic cooking protocols yielded products with quite acceptable eating qualities, sensory evaluation found the overall quality of the conventionally cooked ham to be significantly (p < 0.05) superior, indicating that further optimisation of the ohmic cooking protocols would be required prior to any commercial adoption.     

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.     

The effects of different cooking regimes on the cook yield and tenderness of non-injected and injection enhanced forequarter beef muscles

The aim was to investigate the effect of different cooking regimes on the cook yield and tenderness of non-injected and brine injected (0.5% residual NaCl) bovine M. triceps brachii caput longum (TB), M. supraspinatus (SP) and M. pectoralis profundus (PP). Injected and non-injected TB, SP and PP muscle sections (400 g) were (a) conventionally oven cooked to 72 °C or cooked slowly (using a Δ10 programme) to 72 °C or (b) cooked in a water bath to 72 °C or cooked in a water bath to 55 °C and held at this temperature for 2 h before heating to 72 °C. In addition, injected PP muscle sections were oven cooked to 69 °C and held at this temperature for up to 12 h. Slow cooking using a Δ10 programme had no significant (P < 0.05) effect on WBSF values of injected or non-injected SP and TB muscles but significantly (P < 0.05) decreased the WBSF values of injected and non-injected PP muscles when compared to conventional cooking. Slow cooking significantly (P < 0.05) increased % cook yield of injected PP, SP and TB muscles. Staged cooking significantly (P < 0.05) decreased the WBSF values and had no significant effect on sensory tenderness ratings of non-injected TB, SP and PP muscles and injected PP muscles. Staged cooked injected or non-injected PP, SP and TB muscles had lower % cook yield values than those cooked straight to 72 °C. Increasing the cooking time of injected PP muscles at 69 °C to 8 and 12 h decreased % cook yield, decreased WBSF values and increased sensory tenderness ratings. It also alleviated the problem of residual chewiness which was evident in PP muscles cooked using the other regimes.     

Colour and sarcoplasmic protein evaluation of pork following water bath and ohmic cooking

The objective of this study was to investigate the effects of ohmic (OH) and waterbath (WB) cooking on colour attributes and sarcoplasmic changes of porcine longissimus dorsi muscle at the same endpoint temperatures (EPTs; range 10 °C–80 °C). The OH treatment was carried out at 10 V cm^− 1, and the WB temperature at 85 °C. The colour parameters, deoxymyoglobin% (DeoMb) and metmyoglobin% (MetMb) of the OH-cooked meat were significantly lower (P < 0.05) than those obtained by WB-cooking at the same EPTs (range 60 °C–80 °C). SDS-PAGE analysis showed that the meat treated with WB-cooking had a lower sarcoplasmic protein solubility (5.97 mg/g vs.14.89 mg/g, P < 0.05) and fainter protein bands than that of OH-cooking thus, indicating paler colour, and lower water-holding capacity especially in WB-cooked meat at EPTs above 40 °C. Strong correlations among lightness, browness, metmyoglobin% and soluble proteins were observed in meat following OH-cooking.     

Physico-chemical, textural and structural characteristics of sous-vide cooked pork cheeks as affected by vacuum, cooking temperature, and cooking time

This paper describes the influence of different factors on sous-vide cooked pork. Pork cheeks were cooked at different combinations of temperature (60 °C or 80 °C), time (5 or 12 h) and vacuum (vacuum or air packaged). Weight losses were lower and moisture content higher in samples cooked for a shorter time (P = 0.054) and at a lower temperature (P < 0.001). Samples cooked at 60 °C showed more lightness (L*) and redness (a*) (P < 0.001). Lipid oxidation showed an interaction between cooking time and temperature (P = 0.007), with higher TBARs values for samples cooked for 12 h at 60 °C and lower for those cooked for 12 h at 80 °C. Samples cooked at 80 °C for 12 h showed lower (P < 0.05) values for most textural parameters than all the other types of samples. Vacuum packaging showed no influence on any of the studied variables. For the treatments evaluated, cooking temperature × time combination seems to be more important than vacuum packaging in the textural and colour parameters of pork cheeks.     

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.     

Acidification,crushing and thermal treatments can influence the profile and stability of folate poly-γ-glutamates in broccoli (Brassica oleracea L. var. italica)

The influence of different treatments, i.e., crushing, high temperature short time (90 °C/4 min) (HTST) and low temperature long time (60 °C/40 min) (LTLT) blanching, acidification (pH 4.3), and sequences of these treatments on the folate poly-γ-glutamate profile and stability were investigated. In this study, broccoli was used as a case study. Regarding the folate poly-γ-glutamate profile, endogenous folate poly-γ-glutamates in broccoli florets were found predominantly as hepta- and hexa-γ-glutamates. Crushing raw broccoli, acidification and LTLT blanching enhanced folate deconjugation resulting in monoglutamate, di- and tri-γ-glutamates. Compared to other treatments, HTST blanching preformed prior to crushing resulted in the highest concentration of long chain poly-γ-glutamates. Regarding folate poly-γ-glutamates stability, acidification combined with LTLT blanching decreased folate stability whereas HTST blanching combined with different sequences of blanching and crushing did not affect folate poly-γ-glutamates stability. It was concluded that crushing (prior to heating), acidification and blanching could be strategically applied to increase the folate monoglutamate content of broccoli.     

Ohmic heating of meats: Electrical conductivities of whole meats and processed meat ingredients

The ohmic heating rate of a food is highly influenced by its electrical conductivity (σ). A survey of σ values of commonly used meat ingredients when dispersed as 5% (w/w) aqueous solutions/suspensions was undertaken. A subset was further investigated at typical usage levels in solution/suspension, and/or when incorporated into beef blends, while σ of selected cuts from five meat species (beef, pork, lamb, chicken and turkey) was also measured. Measurements were made from 5 to 85 °C and showed a linear increase in σ values with increasing temperature. In processed beef, addition of sodium chloride and phosphate (P22) caused a significant increase in σ which in turn would lead to an increase in ohmic heating rates. Furthermore, whole meats with lower endogenous fat or processed meats with the least added fat displayed higher σ and reduced ohmic heating times. In beef maximum σ was observed when fibres were aligned with the current flow.     

Effect of green tea marinades on the formation of heterocyclic aromatic amines and sensory quality of pan-fried beef

The effect of a green tea marinade on the formation of heterocyclic aromatic amines (HAs) was examined in pan-fried beef cooked at 180–200 °C for 4 min each side. Different marinating times were assayed and unmarinated samples cooked in similar conditions provided reference HAs levels. A green tea marinade catechin rich was prepared taking 1 g of green tea and infusing with 125 ml of boiling tap water during 10 min. Four HAs were quantified in unmarinated and marinated meat samples during 1, 2, 4 and 6 h at 5 °C. Compared with the unmarinated samples, marinating in green tea resulted in a significant decrease (p < 0.05) of levels of PhIP and AαC. Person correlation indicated that the reduction of the levels of these HAs in meat marinated with the increase of marinating time was significant (respectively, r = −0.799, p < 0.0001; r = −0.631, p < 0.05). No reduction was observed for 4,8-DiMeIQx and MeIQx.     

A Weibull model to describe antimicrobial kinetics of oregano and lemongrass essential oils against Salmonella Enteritidis in ground beef during refrigerated storage

The antimicrobial effect of oregano (Origanum vulgare L.) and lemongrass (Cymbopogon citratus (DC.) Stapf.) essential oils (EOs) against Salmonella enterica serotype Enteritidis in in vitro experiments, and inoculated in ground bovine meat during refrigerated storage (4 ± 2 °C) for 6 days was evaluated. The Weibull model was tested to fit survival/inactivation bacterial curves (estimating of p and δ parameters). The minimum inhibitory concentration (MIC) value for both EOs on S. Enteritidis was 3.90 μl/ml. The EO concentrations applied in the ground beef were 3.90, 7.80 and 15.60 μl/g, based on MIC levels and possible activity reduction by food constituents. Both evaluated EOs in all tested levels, showed antimicrobial effects, with microbial populations reducing (p ≤ 0.05) along time storage. Evaluating fit-quality parameters (RSS and RSE) Weibull models are able to describe the inactivation curves of EOs against S. Enteritidis. The application of EOs in processed meats can be used to control pathogens during refrigerated shelf-life.     

Application of thermal inactivation of enzymes during vitamin C analysis to study the influence of acidification,crushing and blanching on vitamin C stability in Broccoli (Brassica oleracea L var. italica)

The effectiveness of heat inactivation of oxidative enzymes e.g., ascorbic acid oxidase (AAO) to stabilise vitamin C during extraction and analysis was evaluated. The influence of different sequences of performing treatments including acidification (pH 4.3 vs. pH 6.5), crushing, high temperature short time (90 °C/4 min–HTST) and low temperature long time (60 °C/40 min–LTLT)) blanching on vitamin C stability in broccoli florets and stalks was also investigated. Heat inactivation of enzymes prior to matrix disruption resulted in higher vitamin C values mainly in L-ascorbic acid (L-AA) form, while lack of enzyme inactivation resulted in high vitamin C losses resulting from conversion of L-AA to dehydroascorbic acid. Various treatments and their sequence of application influenced vitamin C stability as follows: (i) crushing prior to blanching reduced vitamin C stability and (ii) in the absence of heating, acidification increased vitamin C stability (iii) blanching prior to crushing resulted in higher vitamin C retention, with HTST blanching retaining more vitamin C than LTLT blanching.     

Tenderness profiles of ten muscles from F1 Bos indicus x Bos taurus and Bos taurus cattle cooked as steaks and roasts

Twenty Bos taurus (Hereford x Angus crosses) and 20 F1 Bos indicus x Bos taurus heifers of the same age, management and feeding regimen, were harvested and evaluated at 2 days postmortem for carcass and meat traits. Ten muscles were obtained from the right sides and aged until 10 days postmortem. Bos indicus carcasses were lighter, had less fat cover, smaller ribeyes, and less intramuscular lipid (all p ≤ 0.05). Bos taurus longissimus lumborum, gluteus medius, triceps brachii, and semimembranosus muscles cooked as steaks and roasts had a lower Warner-Bratzler shear force (WBSF) (p ≤ 0.05) than those from Bos indicus. Bos taurus deep pectoral and semitendinosus muscles cooked as roasts had a lower WBSF (p < 0.05) than Bos indicus. Infraspinatus, longissimus lumborum, and semitendinosus muscles were more tender (p < 0.05) as roasts than steaks, whereas the opposite was true for the deep pectoral and semimembranosus muscles. Seven of the 10 muscles had lower WBSF (p ≤ 0.05) for Bos taurus when cooked as steaks, roasts or both.     

Effects of ohmic thawing on histological and textural properties of beef cuts

The changes in the histology and the texture of beef cuts during ohmic thawing were compared with those during conventional thawing method. The beef cut samples were thawed from −18 to 10 °C by applying different voltage gradients (10, 20 and 30 V/cm) during ohmic treatment whereas conventional thawing was applied at constant temperature (25 °C, 95% RH) in the controlled incubator. There were significant differences between the effects of thawing methods in terms of hardness, chewiness, gumminess of beef cut samples (p < 0.05). The sample treated ohmically at 30 V/cm voltage gradient was significantly different from the other thawed samples in terms of springiness, cohesiveness and resilience (p < 0.05). The change in the textural properties was explained by investigating the histological changes of beef cuts for both thawing method. Ohmic thawing provided the thawed meat sample having lower textural and histological changes rather than conventionally thawed ones.     

Decomposition kinetics of umami component during meat cooking

We developed a kinetic model for the decomposition reaction of inosine monophosphate (IMP), which is a umami component, and obtained kinetic parameters based on the amount of IMP in an isothermal experiment. The amount of remaining IMP decreased with heating time, and its reduction rate was the highest at 40 °C. We assumed that the activity of IMP decomposition enzyme is temperature-dependent above 40 °C, and constant below 40 °C. The predicted results using this kinetic model are in good agreement with the experimental ones. Unsteady-state three-dimensional heat transfer analysis of meat during sous-vide cooking was conducted, and the distribution of remaining IMP was predicted. By the end of sous-vide cooking, the ratio of the amount of IMP in the interior of the meat decreased, whereas at the surface region, it was almost the same as the initial value, because the surface temperature reached the inactivation temperature immediately.     

Sensory characteristics of meat cooked for prolonged times at low temperature

The present study evaluated the sensory characteristics of low temperature long time (LTLT) treated Semitendinosus from pork and beef and Pectoralis profundus from chicken. Semitendinosus and Pectoralis profundus muscles were heat treated at 53°C and 58°C for T_c + 6 h, T_c + 17 h, and T_c + 30 h (only Semitendinosus from pork and beef). T_c was the time for the samples to equalize with the temperature in the water bath. Tenderness increased with increasing heating temperature and time in pork and beef, but not in chicken. Juiciness decreased with increasing heating temperature and time in all species, and cooking loss increased with increasing temperature. A done appearance was developed with increasing heating time at 58 °C in pork and beef, while in chicken the done appearance was only affected by temperature. Flavor attributes were less affected by the LTLT treatment for all species.     

Effects of succinate and pH on cooked beef color

Two experiments were conducted to assess the effects of succinate and pH on cooked beef color. In experiment 1, ten strip loins (M. longissimus lumborum) were divided in half and assigned to either non-enhanced control or 2.5% succinate. Each half-loin was cut into steaks, packaged in vacuum or 80% oxygen, and stored at 1 °C for 0, 6, or 12 days. Steaks were cooked to either 66 °C or 71 °C. Succinate increased (P < 0.05) steak pH, raw a* values, and interior cooked redness when packaged in high oxygen. In experiment 2, to assess the role of succinate in raw and cooked color, succinate or ammonium hydroxide was added to ground beef patties to result in a common meat pH (5.9). At a similar pH, succinate had greater metmyoglobin reducing activity and internal cooked redness compared with ammonium hydroxide (P < 0.05). In addition to ingredient-based changes in muscle pH, succinate may influence color by regenerating reducing equivalents.     

Enhancing the thermal destruction of Escherichia coli O157:H7 in ground beef patties by trans-cinnamaldehyde

The effect of trans-cinnamaldehyde (TC) on the inactivation of Escherichia coli O157:H7 in undercooked ground beef patties was investigated. A five-strain mixture of E. coli O157:H7 was inoculated into ground beef (7.0 log CFU/g), followed by addition of TC (0, 0.15, and 0.3%). The meat was formed into patties and stored at 4 °C for 5 days or at −18 °C for 7 days. The patties were cooked to an internal temperature of 60 or 65 °C, and E. coli O157:H7 was enumerated. The numbers of E. coli O157:H7 did not decline during storage of patties. However, cooking of patties containing TC significantly reduced (P < 0.05) E. coli O157:H7 counts, by >5.0 log CFU/g, relative to the reduction in controls cooked to the same temperatures. The D-values at 60 and 65 °C of E. coli O157:H7 in TC-treated patties (1.85 and 0.08 min, respectively) were significantly lower (P < 0.05) than the corresponding D-values for the organism in control patties (2.70 and 0.29 min, respectively). TC-treated patties were more color stable and showed significantly lower lipid oxidation (P < 0.05) than control samples. TC enhanced the heat sensitivity of E. coli O157:H7 and could potentially be used as an antimicrobial for ensuring pathogen inactivation in undercooked patties. However detailed sensory studies will be necessary to determine the acceptability to consumers of TC in ground beef patties.     

Electrical conductivity changes of minced beef–fat blends during ohmic cooking

Minced beef–fat blends having different fat level (2%, 9% and 15%) and full meat-fat samples were ohmically cooked by different voltage gradients (20, 30 and 40 V/cm). Main factors affecting the electrical conductivity were the temperature and the composition of the blends. Although the effect of initial fat content on electrical conductivity was statistically significant, voltage gradient did not affect the electrical conductivity changes during cooking treatment (p > 0.05). The electrical conductivity of the samples increased with increasing temperature up to the critical initial cooking temperature (60–70 °C) depending on the fat level, and then decreased due to structural changes and the increase in the bound water during cooking. The results of the nonlinear mathematical model including the effects of initial fat level and the temperature on the electrical conductivity changes had good agreement (r = 0.952; SEM = 0.009) with the experimental data. The determination of electrical conductivity changes being affected by process variables is crucial to characterize the ohmic cooking of meat products and design of ohmic systems.     

Effects of dry,vacuum, and special bag aging; USDA quality grade; and end-point temperature on yields and eating quality of beef Longissimus lumborum steaks

This study evaluated the effects of three aging methods: (dry (D), wet (W), and special bag (SB)); two quality grades [USDA Choice((≥ Small⁵⁰ marbling) and Select); and two cooked end-point temperatures (62.8 °C and 71.1 °C) on physico-chemical traits of instrumental tenderness, color, and sensory properties of Longissimus lumborum beef muscle. Dry-aged loins had higher (P < 0.0001) weight loss than W or SB aged loins. However, D and SB aged loins had similar (P > 0.05) combined losses. W aged loins had higher (P < 0.01) L* values than D or SB aged loins. Warner–Bratzler shear force of steaks was not affected (P > 0.05) by aging method or quality grade but increased (P < 0.0001) as end-point temperature increased. Sensory panel evaluation also showed no effect (P > 0.05) of aging method or quality grade on myofibrillar tenderness, juiciness, connective tissue amount, overall tenderness or off flavor intensity. Steaks cooked to 62.8 °C were juicier (P < 0.05) than those cooked to 71.1 °C. Neither D nor SB aging had advantages over W aging.