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.     

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.     

Characterization of Spaghetti Prepared Under Different Drying Conditions

Spaghetti dried at low (max. 50 °C), high (max. 70 °C), and very high (max. 85 °C) temperatures were characterized by their color, surface structure, rupture strength, texture analysis, and sauce retention capacity. The texture and sauce retention capacity were estimated for cooked spaghetti. The color of the spaghetti's methanol extracts, as evaluated through absorbance at 440 and 466 nm, did not depend on the drying temperature. A trend was observed in the surface texture of spaghetti, as estimated by atomic force microscopy and mercury intrusion porosimetry, where the surface was rougher when dried at higher temperatures than at low temperatures. Furthermore, the rupture strength was also higher for the spaghetti dried at higher temperatures. This result can be ascribed to the formation of stronger gluten networks, promoted by denaturation of gluten at the higher temperatures. However, the hardness of cooked spaghetti was not affected by the drying temperature, a result attributable to the action of water sorption to offset any differences in hardness among the spaghettis dried at the 3 different temperatures. The sauce retention capacity of cooked spaghetti was evaluated using a dextran solution as a simulated sauce, and by this method, the capacity of the spaghetti dried at a low temperature was shown to be significantly lower than that of the spaghetti dried at higher temperatures. This can be ascribed to the smoother surface of cooked spaghetti dried at the lower temperature and also to the leakage of amylose onto the surface during cooking.     

Initial work on developing a cooking protocol for producing re-structured meat under controlled conditions

Restructured meat is made by binding individual pieces of meat together. To study the effect of mechanical work on the meat binding process, a standard cooking protocol must be established. This paper details the establishment of a standard cooking protocol for the cooking process using untreated beef semitendinosus muscle. The effect of different cooking temperatures and applied loads during cooking were investigated. Meat samples were cut in 20 mm cubes size from beef semitendinosus muscle and two pieces were held together with the muscle fibre parallel to each other by wrapping them with a plastic food wrap. Then the samples were placed inside square steel tubes, that act as a mold for cooking, and different weights (0, 250, 500, 750 and 1000 g) were placed on top of the meat cubes during cooking. The temperatures used for cooking were 60, 70 and 80 °C. There was a significant temperature effect, with increases noted between 60 °C and 70 °C and between 70 °C and 80 °C. At 60 °C neither myosin nor collagen has gelatinized, leading to low binding strengths. At 70 °C the myosin component will have gelatinized. At 80 °C the collagen component will be contributing to the bond. To keep the collagen effect to a minimum the meat should be cooked at 70 °C. The effect of applied cooking load was significant at all cooking temperatures once sufficient load had been applied against no load to ensure good contact at the joint. There was a significant effect of applied load noted at 80 °C with increases up to 750 g and a drop occurring between the 750 and 1000 g loadings. The drop has been attributed to collagen being squeezed out of the joint as a bead of white material was noted around the joint.     

Heat transfer modeling of chicken cooking in hot water

To calculate the slowest heating point and optimum cooking time of whole chicken cooking in hot water, a 2-dimensional heat transfer model was developed to predict temperature profile and history of the chicken cooked in hot water at 85, 90 and 95 °C. Chickens were divided into 12 sections and the heat transfer model was applied to each cross section. These models were solved with an I-DEAS program. Specific heat and thermal conductivity were measured at temperatures ranging from 25 to 95 °C. The temperature of chicken did not significantly affect the thermal properties. The average values of specific heat of white and dark meats were 3.521 and 3.654 kJ/(kg K), respectively, and the average thermal conductivity values were 0.5093 and 0.4930 W/(m K), respectively. The model was validated against experimental results, and provided an average root mean square error of 2.8 °C. Temperature distributions showed that the slowest heating point was deep in the breast part of the second cross section (3.6 cm far from shoulder) at the symmetric line of the chicken, around 2.1–2.5 cm deep from breast skin. For food safety consideration, the recommended cooking times, for whole chickens in weight range of 2.3–3.2 kg with different initial temperatures (5–30 °C), were around 74–84, 64–74 and 57–67 min for cooking temperatures of 85, 90, and 95 °C, respectively.     

Low‐field nuclear magnetic resonance analysis of the effects of heating temperature and time on braised beef

We investigated the characteristics of water mobility and distribution in Chinese braised beef after treatment at different temperatures for different times using low‐field nuclear magnetic resonance (LF‐NMR). The beef was heated at 45, 55, 65, 75, 85 or 95 °C for 30, 60, 90 and 120 min. Results showed that T₂ changed significantly with heating temperature. T₂₁ and A₂₁ decreased significantly with increasing temperature below 65 °C, with a steady phase from 75 to 95 °C, which agreed with cooking loss. Inversely, T₂₂ had no changes below 65 °C and changed apparently from 75 to 95 °C. The change in T₂₁ below 65 °C may be related to proteins denaturation and shrinkage and, above 65 °C, T₂₂ possibly induced by the dissolution of connective tissue. The characteristics of braised beef at 65 °C were different from those at other temperatures in T₂ distributions. The findings could provide a theoretical basis for the processing of Chinese braised beef.     

Collagen of the skin of ocellate puffer fish (Takifugu rubripes)

Collagens (acid-solubilized and pepsin-solubilized collagens) were prepared from ocellate puffer fish skin and partially characterized. With respect to the pepsin-solubilized collagen, it was a heterotrimer with a chain composition of (α1)₂α2. The patterns of peptide fragments were different from skin collagens of other species. The denaturation temperature was 28 °C, about 9 °C lower than that of porcine skin collagen. On the other hand, the yields of acid-solubilized and pepsin-solubilized collagens were very high, 10.7% and 44.7%, respectively, on a dry weight basis. These results suggest that ocellate puffer fish skin has potential as an alternative source of collagen for use in various fields.     

Effect of Gradual Heating and Fat/Oil Type on Fat Stability,Texture, Color,and Microstructure of Meat Batters

The effects of endpoint cooking temperature (40, 50, 60, 70, 80, and 90 °C) on emulsion stability, texture, color, and microstructure of meat batters prepared with different fats/oils were studied. Canola oil treatments showed the highest cooking loss whereas hydrogenated palm oil provided the most stable meat batters. Rendered beef fat was less stable than regular beef fat. Increasing endpoint cooking temperatures resulted in a progressive reduction of water holding capacity in all treatments. As temperature was raised, meat batters showed higher hardness and cohesiveness values, but no appreciable changes in cohesiveness above 60 °C. Canola and hydrogenated palm oil treatments showed the highest hardness and chewiness values. Lightness (L^*) values of all meat batters increased significantly with increasing temperature from 40 to 60 or 70 °C; no major changes observed above 70 °C. Light microscopy revealed no substantial changes in the microstructure of all the stable meat batters cooked to between 50 and 70 °C. Heating to 90 °C changed the microstructure in all meat batters except the hydrogenated palm oil treatments, which still showed nonround fat particles and a less aggregated protein matrix.     

Distinctive characteristics of collagen and gelatin extracted from Dosidicus gigas skin

Squid skin, often discarded as processing by-product, is a good resource of collagen/gelatin. In this study, acid soluble collagen (ASC), pepsin soluble collagen (PSC) and water soluble gelatin (WSG) were extracted from squid (Dosidicus gigas) skin and physicochemically examined. The lowest yield of 33.5% was obtained for ASC extracted at 4 °C, and the addition of pepsin increased the collagen yield by around 35.0% (PSC). The highest yield of 81.9% (WSG) was achieved by thermal extraction at 60 °C. A low temperature can largely retain the native helix structures of ASC and PSC, contrariwise, thermal treatment converted collagen into gelatin with unordered and renatured structures. The proline and hydroxyproline contents of ASC, PSC and WSG were 183/1000 residues, 194/1000 residues and 175/1000 residues, respectively. In addition, WSG showed a denaturation temperature at 80.7 °C which was much higher than that of ASC (24.2 °C) and PSC (26.2 °C), while a significant lower resistance towards enzymatic digestion.     

Influence of CMC‐ and guar gum‐based silver nanoparticle coatings combined with low temperature on major aroma volatile components and the sensory quality of kinnow (Citrus reticulata)

Aroma profile and organoleptic quality of CMC‐ and guar gum‐based silver nanoparticle‐coated kinnow (Citrus reticulata cv. Blanco) was evaluated for 120 days at 4 °C and 10 °C, 85–95% relative humidity. Loss in three major aroma‐active volatile compounds (limonene, linalool and γ‐terpinene) was determined after every 15 days by GC‐MS. Sensory quality of coated and uncoated fruit stored at 10 °C was declined during storage. Twenty five volatile aroma compounds were identified in fresh kinnow juice. Guar gum‐Ag coatings and 4 °C storage has significantly reduced losses of limonene, linalool and γ‐terpinene contents from 91 to 23%, 99 to 10% and 97 to 29% respectively as compared to uncoated fruit stored at 10 °C. Study suggests that CMC‐ and guar gum‐based silver nanoparticle‐coated kinnow stored at 4 °C has preserved the fruit aroma and sensory quality for 120 days.     

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.     

Effect of high‐pressure treatments prior to cooking on gelling properties of unwashed protein from barramundi (Lates calcarifer) minced muscle

Heat‐induced gelling properties of barramundi minced muscle with 1.5% and 2% added salt were assessed after application of pressures at 300, 400 and 500 MPa at 4 °C (initial temperature) for 10 min and subsequent cooking at 90 °C for 30 min. Whiteness, gel‐forming ability, water‐holding capacity, hardness and springiness of the barramundi gels increased as applied pressure and salt concentration increased. At 2% salt concentration, high‐pressure treatment results in barramundi gels with higher gel strength, mechanical properties and smoother texture as compared to conventional heat‐induced gels (0.1 MPa, 90 °C for 30). At a reduced salt concentration (1.5%) and pressure ≥ 400 MPa, the quality (gel strength, water‐holding capacity, hardness and springiness) of pressurised cooked gels is comparable to those heat‐induced gels with 2% added salt, but the microstructure is smoother. Scanning electron microscope images of pressurised cooked gels showed dense and compact network with smoother surface than those of heat‐only‐induced gels. Thus, application of high‐pressure treatment prior to cooking could be an effective method to enable reduced salt concentration in barramundi gels.     

Preparation and partial characterization of collagen from paper nautilus (Argonauta argo,Linnaeus) outer skin

To make more effective use of limited-resources, collagen was prepared from the outer skin of the paper nautilus. As a result, the outer skin was hardly solubilized in 0.5 M acetic acid (yield: about 5.2% on a dry weight basis). The insoluble matter was easily digested by 10% pepsin (w/v), and a large amount of collagen was obtained with about a 50.0% yield (pepsin-solubilized collagen). The pepsin-solubilized collagen had a chain composition of α1 α2 α3 heterotrimer similar to Callistoctopus arakawai arm collagen. Although the paper nautilus collagen has a denaturation temperature of 27 °C, that is about 10 °C lower than that of the porcine one, this result indicates that it is possible to use the paper nautilus outer skin as an important collagen source.     

Cooking loss and juiciness of pork in relation to raw meat quality and cooking procedure

The study comprised two experiments with the aim to investigate the influence of raw meat quality and cooking procedure on cooking loss and juiciness of pork. The first experiment determined the cooking loss at 60, 70 and 80 °C centre temperature of 10 raw meat qualities (defined according to ultimate pH, drip loss, breed and rearing conditions) when cooked as steaks on a pan or as a roast in oven at a oven temperature of 90 or 190 °C. The differences in cooking loss between the raw meat qualities and the cooking procedures did decrease as the centre temperature increased and were almost negligble at 80 °C. Low water holding capacity (WHC) and low pH resulted in high cooking loss while no difference in cooking loss was observed between meat having medium or high WHC and pH. In the second experiment four raw meat qualities (standard, Duroc, low pH and heavy carcass weight) chosen from the first experiment to ensure a wide variation in cooking loss, were cooked in oven at 90 or 190 °C oven temperature. Juiciness was assessed three times during the chewing process. The results suggested that juiciness experienced initially in the chewing process depended only on the water content of the meat, whereas juiciness experienced later in the chewing process was determined by a combination of the water and intramuscular fat contents and the saliva production during chewing.     

High-temperature air fluidization improves cooking and eating quality and storage stability of brown rice

Brown rice contains many valuable active ingredients; but due to its long cooking time, hard texture, heavy rice bran taste, and short shelf life, it is not widely accepted by consumers. Herein, we developed a novel processing technology so-called high-temperature air fluidization (HTAF) to treat brown rice. The effects of the HTAF treatment at 120 °C, 130 °C, and 140 °C for 60 s at a feed rate of 80 kg/h on the quality of brown rice were investigated. The results showed that the treatment with HTAF caused fissures to form on the surface and the interior of brown rice, and these fissures appeared to facilitate the penetration of water into the rice kernels during soaking. The optimal HTAF treatment temperature was 130 °C, the water adsorption of HTAF-treated brown rice at 130 °C (TBR-130) was increased to 25.3% after soaking for 160 min, which was higher than that of white rice and untreated brown rice (UBR; 13.7%). The optimal cooking time for TBR-130 was also 5 min shorter than that for UBR. The results further showed that TBR-130 had a larger degree of volume expansion compared to that of UBR, and cooked TBR-130 had softer texture than cooked UBR. The cohesiveness and sensory quality of TBR-130 were also higher than those of UBR, and the content of flavor compounds in TBR-130 was similar to that of white rice. HTAF caused no obvious damages to the main active components or nutritional components of TBR-130. Finally, TBR-130 had better chromaticity and higher storage stability than UBR. These results demonstrate that the HTAF treatment can improve cooking and eating quality and storage stability without causing obvious damages to nutritional quality of brown rice. This technology may play important roles in an attempt to promote the use of brown rice as staple foods.     

Comparison of microwave-assisted induction heating system (MAIH) and individual heating methods on the quality of pre-packaged white shrimp

Microwave-assisted induction heating (MAIH) is a novel heating technology that combines microwave heating in the upper section and induction heating at the bottom. Our previous study demonstrated that optimal cooking in white shrimp can be achieved by MAIH either at 130 °C for 80 s or at 90 °C for 100 s. The objective of this study was to compare the cooking of white shrimp using microwave heating or induction heating alone with that using MAIH under the optimum cooking condition. The following three methods for cooking white shrimp were analyzed: (1) induction heating (IH) at 90 °C for 100 s or at 130 °C for 80 s; (2) microwave heating (MW) at 1300 W and 2450 MHz for 80 or 100 s; and (3) MAIH at 90 °C for 100 s or at 130 °C for 80 s. The results showed that using only induction or microwave heating gave the shrimp an uncooked or undercooked appearance; meanwhile, cold spots and non-uniform temperature distribution were observed in the thermal image of the shrimp. On the contrary, the shrimps processed by MAIH were found to be fully cooked, and a uniform temperature distribution was observed in the corresponding thermal image. Furthermore, no detectable aerobic plate count (APC), psychrophilic bacteria count (PBC), and coliform were found in the shrimp samples processed by MAIH. The color (L*, a*, b*, W, and ΔE), hardness, cohesiveness and chewiness of the samples processed by MAIH were all significantly greater (p < 0.05) than those of shrimp processed by induction or microwave heating alone, indicating that MAIH cooking shrimp exhibited better color and texture than MW or IH alone. The results showed that the shrimps heated with MAIH at both 130 °C or 90 °C had better microbiological, physical and chemical quality, as compared to MW or IH heating alone.Industrial relevanceThis novel MAIH technology allows shrimp to be heated and pasteurized after being packed, thereby eliminating the post-pollution issue. Therefore, it has a great potential for developing short-time in-package pasteurization processes in food industry.     

Influence of cooking conditions on cooking loss and tenderness of raw and marinated chicken breast meat

The influence of different cooking treatments on tenderness and cooking loss, as main quality characteristics of chicken breast meat, was investigated. Industrial skinless chicken breast meat samples were designated as raw and marinated and cooked in the oven by hot air and hot air-steam mixture at 130, 150 and 170 °C, for 4, 8 and 12 min. Cooking losses were evaluated by weight changes before and after cooking, and tenderness changes were determined on cooked samples by measuring shear force using instrumental texture analysis. Results showed that marination, followed by air-steam cooking is the best combination to obtain the most tender chicken breast slices. The time and temperature of cooking showed similar effects on cooking loss and tenderness: short cooking time (4 min) and temperatures of 130–150 °C resulted in lower cooking losses and best meat tenderness, in both not marinated and marinated meat. Statistically significant correlations between tenderness and cooking loss indicated that the cooking loss correlated better with cooking time than with cooking temperature. An opposite phenomenon was observed for meat tenderness.     

Rheological and physico‐chemical properties of gelatin extracted from the skin of a few species of freshwater carp

The physico‐chemical and rheological properties of gelatin from the skins of three different freshwater carp species, namely Catla catla, (catla) Cirrhinus mrigala (mrigal) and Labeo rohita (rohu), have been assessed and compared with that of gelatin from porcine skin. The average solids yield from the three species of carp varied in the range of 11.8–14.1%. The amino acid profile showed that the porcine gelatin had a higher proportion of imino acids and glycine than carp skins gelatin. The average molecular weight of carp skins gelatin as determined using a gel filtration technique was 233 kDa, while that of porcine skin gelatin was 282 kDa. The gelling temperature of carp skins gelatin was in the range of 6–15.7 °C, and the melting temperature was 17.9–23.7 °C as determined using a controlled stress rheometer. A higher gelling and melting temperature was observed for porcine skin gelatin.     

Effects of High‐Hydrostatic Pressure on Inactivation of Human Norovirus and Physical and Sensory Characteristics of Oysters

The purpose of the study was to determine the effect of high‐hydrostatic pressure (HHP) on inactivation of human norovirus (HuNoV) in oysters and to evaluate organoleptic characteristics of oysters treated at pressure levels required for HuNoV inactivation. Genogroup I.1 (GI.1) or Genogroup II.4 (GII.4) HuNoV was inoculated into oysters and treated at 300 to 600 MPa at 25 and 0 °C for 2 min. After HHP, viral particles were extracted by porcine gastric mucin‐conjugated magnetic beads (PGM‐MBs) and viral RNA was quantified by real‐time RT‐PCR. Lower initial temperature (0 °C) significantly enhanced HHP inactivation of HuNoV compared to ambient temperature (25 °C; P < 0.05). HHP at 350 and 500 MPa at 0 °C could achieve more than 4 log₁₀ reduction of GII.4 and GI.1 HuNoV in oysters, respectively. HHP treatments did not significantly change color or texture of oyster tissue. A 1‐ to 5‐scale hedonic sensory evaluation on appearance, aroma, color, and overall acceptability showed that pressure‐treated oysters received significantly higher quality scores than the untreated control (P < 0.05). Elevated pressure levels at 450 and 500 MPa did not significantly affect scores compared to 300 MPa at 0 °C, indicating increasing pressure level did not affect sensory acceptability of oysters. Oysters treated at 0 °C had slightly lower acceptability than the group treated at room temperature on day 1 (P < 0.05), but after 1 wk storage, no significant difference in sensory attributes and consumer desirability was observed (P > 0.05).     

Study on the self‐assembly property of type I collagen prepared from tilapia (Oreochromis niloticus) skin by different extraction methods

Type I collagen was prepared from tilapia (Oreochromis niloticus) skin by acetic acid and pepsin process at 4 °C, respectively (ASC and PSC), and hot‐water method separately at 25, 35 and 45 °C (C‐25, C‐35 and C‐45). Their structure and self‐assembly property were discussed. SDS‐PAGE patterns suggested that pepsin hydrolysis and the 35 and 45 °C extraction produced collagen with much reduced proportions of α‐ and β‐chains. Fourier transform infrared spectroscopy spectra revealed that pepsin hydrolysis did not change the conformation of collagen, but higher extraction temperature did. Self‐assembly curves and atomic force microscopy (AFM) observations showed that only ASC, PSC and C‐25 could self‐assemble into fibrils with D‐periodicity, but the reconstruction rate of C‐25 was lower. Besides, PSC had relatively higher resolution ratio compared with others. Overall, pepsin‐extracted collagen displayed higher solubility and better fibril‐forming capacity, having the potential of applying in biomaterials and food‐packaging materials.