Influence of rendering methods on yield and quality of chicken fat recovered from broiler skin.

OBJECTIVE: In order to utilize fat from broiler byproducts efficiently, it is necessary to develop an appropriate rendering procedure and establish quality information for the rendered fat. A study was therefore undertaken to evaluate the influence of rendering methods on the amounts and general properties of the fat recovered from broiler skin. METHODS: The yield and quality of the broiler skin fat rendered through high and lower energy microwave rendering (3.6 W/g for 10 min and 2.4 W/g for 10 min for high power microwave rendering (HPMR) and high power microwave rendering (LPMR), respectively), oven baking (OB, at 180°C for 40 min), and water cooking (WC, boiling for 40 min) were compared. RESULTS: Microwave-rendered skin exhibited the highest yields and fat recovery rates, followed by OB, and WC fats (p<0.05). HPMR fat had the highest L*, a*, and b* values, whereas WC fat had the highest moisture content, acid values, and thiobarbituric acid (TBA) values (p<0.05). There was no significant difference in the acid value, peroxide value, and TBA values between HPMR and LPMR fats. CONCLUSION: Microwave rendering at a power level of 3.6 W/g for 10 min is suggested base on the yield and quality of chicken fat.

Optimization of ultrasonic-assisted enzymatic hydrolysis conditions for the production of antioxidant hydrolysates from porcine liver by using response surface methodology.

OBJECTIVE: The objective of this study was to optimize ultrasonic-assisted enzymatic hydrolysis conditions, including enzyme-to-substrate (E/S) ratio, pH, and temperature, for producing porcine liver hydrolysates (PLHs) with the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity by using response surface methodology (RSM). METHODS: The study used RSM to determine the combination of hydrolysis parameters that maximized the antioxidant activity of our PLHs. Temperature (40°C, 54°C, and 68°C), pH (8.5, 9.5, and 10.5), and E/S ratio (0.1%, 2.1%, and 4.1%) were selected as the independent variables and analyzed according to the preliminary experiment results, whereas DPPH free radical scavenging activity was selected as the dependent variable. RESULTS: Analysis of variance showed that E/S ratio, pH, and temperature significantly affected the hydrolysis process (p<0.01). The optimal conditions for producing PLHs with the highest scavenging activity were as follows: E/S ratio, 1.4% (v/w); temperature, 55.5°C; and initial pH, 10.15. Under these conditions, the degree of hydrolysis, DPPH free radical scavenging activity, ferrous ion chelating ability, and reducing power of PLHs were 24.12%, 79%, 98.18%, and 0.601 absorbance unit, respectively. The molecular weight of most PLHs produced under these optimal conditions was less than 5,400 Da and contained 45.7% hydrophobic amino acids. CONCLUSION: Ultrasonic-assisted enzymatic hydrolysis can be applied to obtain favorable antioxidant hydrolysates from porcine liver with potential applications in food products for preventing lipid oxidation.

Determination of the quality of stripe-marked and cracked eggs during storage.

OBJECTIVE: Stripe marks, which occasionally occur on the shell, do not cause breakage to the shell and shell membranes of eggs. This study investigated the quality of intact eggs (IEs), minor stripe-marked eggs (MEs), severe stripe-marked eggs (SEs), and cracked eggs (CEs) during 3-week storage at 25°C. METHODS: Shell eggs were collected the day after being laid and were washed. Among them, eggs without any visual cracks or stripe marks on the shells were evaluated as IEs by the plant employees using candling in a darkened egg storage room; the remaining eggs exhibited some eggshell defects. At day 3, the eggs were further categorized into IEs, MEs, SEs, CEs, and broken eggs (BEs) on the basis of the description given. Except BEs, which were discarded, the remaining eggs were stored at 25°C (approximate relative humidity 50%) and then analyzed. RESULTS: Stripe marks were observed primarily within the first 3 days after washing. At day 3, CEs had significantly (p<0.05) lower Haugh unit values, but all eggs had grades AA or A, according to the United States Department of Agriculture standard. As storage time increased, differences in egg quality between groups were more obvious. IEs had the highest eggshell breaking strength. During storage, the total plate counts and pathogens, namely Escherichia coli, Campylobacter spp., Staphylococcus aureus, and Salmonella spp., were not detectable in the internal content of IEs and SEs. CONCLUSION: In conclusion, cracks degraded egg quality severely and minor stripe marks only slightly influenced the egg quality.

Relationships between Descriptive Sensory Attributes and Physicochemical Analysis of Broiler and Taiwan Native Chicken Breast Meat.

Unique organoleptic characteristics such as rich flavors and chewy texture contribute to the higher popularity of native chicken in many Asian areas, while the commercial broilers are well-accepted due to their fast-growing and higher yields of meat. Sensory attributes of foods are often used to evaluate food eating quality and serve as references during the selection of foods. In this study, a three-phase descriptive sensory study was conducted to evaluate the sensory attributes of commercial broiler (BR) and Taiwan native chicken (TNC) breast meat, and investigate correlations between these sensory attributes and instrumental measurements. The results showed that for the first bite (phase 1), TNC meat had significantly higher moisture release, hardness, springiness, and cohesiveness than BR meat. After chewing for 10 to 12 bites (phase 2), TNC meat presented significantly higher chewdown hardness and meat particle size, whereas BR meat had significantly higher cohesiveness of mass. After swallowing (phase 3), TNC meat had higher chewiness and oily mouthcoat and lower residual loose particles than BR meat. TNC meat also provided more intense chicken flavors. This study clearly demonstrates that descriptive sensory analysis provides more detailed and more objectively information about the sensory attributes of meats from various chicken breeds. Additionally, sensory textural attributes vary between BR and TNC meat, and are highly correlated to the shear force value and collagen content which influence meat eating qualities greatly. The poultry industry and scientists should be able to recognize the sensory characteristics of different chicken meats more clearly. Accordingly, based on the meat's unique sensory and physicochemical characteristics, future work might address how meat from various breeds could best satisfy consumer needs using various cooking methods.

Physicochemical properties and structural changes of chicken breast meat subjected to radio frequency tempering combined with conventional thawing treatments.

Being able to thaw frozen meat in a reasonable time without impairing quality is crucial for industry and households. Radio frequency (RF) techniques have been used to defrost frozen foods. The influences of RF (50 kW, 27.12 MHz) tempering combined with water immersion (WI, 20°C) thawing (RFWI) or air convection (AC, 20°C) thawing (RFAC) on the physicochemical and structural changes of chicken breast meat were investigated, and the results were compared with those of the fresh meat (FM) and the meat samples subjected to WI and AC only. The thawing processes were terminated when the core temperatures of the samples reached 4°C. The results indicated that AC was the most time-consuming technique, whereas RFWI required the least amount of time. The moisture losses, contents of the thiobarbituric acid-reactive substance, total volatile basic nitrogen, and total viable counts of the meat subjected to AC were higher. Relatively less changes in water-holding capacity, coloration, oxidation, microstructure, protein solubility, and high sensorial acceptance were observed for RFWI and RFAC. This study demonstrated that the meat thawed using RFWI and RFAC was of satisfactory quality. Therefore, the RF techniques can be effective alternatives to the time-consuming conventional thawing methods and benefit the meat industry.

The Defeathering Effect by Scalding in Chickens Follows Their Intrinsic Dermal Histologies.

This study aimed to delineate the fundamental skin histology and its association with feathers in broilers and native Red-Feather (RF) chickens and further elucidate their thermal alterations in respect to the defeathering effect by scalding. Comparisons of skin thickness between fresh samples and those after dehydration and fixation, as well as their collagen contents and histological differences, suggested that RF chickens had a thicker dermal layer with more collagen deposition and compact architecture, particularly in the neck and abdominal skin, but a thinner hypodermal layer in the back, chest, and abdomen skin. Despite an adolescent age, RF chickens showed a shorter calamus depth of tail feathers but a larger calamus diameter of wing feathers. Within the feather follicle punch, a very intense follicle sheath layer with compact collagenous matrixes to fulfill the space next to the inner feather root sheath was observed in RF chickens. Under both soft and hard scalding, RF chickens showed a lower degree of denaturation on hip skins and were more resistant to structural disintegration, primarily within the epidermal and dermal layer. Accordingly, a much narrower gap space between the feather sheath and surrounding follicle sheath was observed, and the gap expansion was also resistant to thermal changes. These results suggest that the defeathering effect by scalding follows the intrinsic skin histologies in chickens of various breeds and ages, primarily depending on the interaction of the feather calamus with the surrounding follicle sheath and neighboring cutaneous tissues, reflecting their resistance to thermal denaturation, but is irrelevant to the feathers per se.

Effect of freeze-thaw cycles on the physicochemical properties, water-holding status, and nutritional values of broiler chicken drumstick.

This study aimed to determine the effects of multiple freeze-thaw (FT) cycles (0, 1, 2, and 4) on the physicochemical properties, water-holding status, and nutritional values of broiler drumsticks. The results showed that L* (lightness) and b* (yellowness) values, thiobarbituric acid-reactive substances, total volatile basic nitrogen, and total viable counts significantly increased but pH values, protein solubility, and sensorial acceptance decreased after four FT cycles (P Ë‚ 0.05). The decreases in moisture content thawing loss, centrifugation loss, drip loss, and cooking loss indicated that the water-holding capacities of samples subjected to multiple FT cycles were diminished. Results of cell microstructure analysis and sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed the occurrence of ruptured muscle cells with decreased fiber diameters and changes in myosin heavy chain band intensity after multiple FT cycles (P Ë‚ 0.05). As the number of FT cycles increased, the content of total free amino acids and polyunsaturated fatty acids including linoleic (C18:2), linolenic (C18:3), eicosatetraenoic (EPA, C20:5), and docosahexaenoic (DHA, C22:6) acids decreased (P Ë‚ 0.05). In conclusion, four repeated FT cycles accelerated the deterioration of physiochemical properties, reduced the water-holding status, and considerably impaired sensory characteristics and nutritional values of chicken meat.

Effects of Hard and Soft Scalding on Defeathering and Carcass Quality of Different Breeds of Chickens.

Current soft scalding in broilers is not applicable to various strains of chickens with different market weights and ages. This study aimed to examine the effectiveness of soft (57 °C for 120 s) and hard (60 °C for 60 s) scalding on defeathering and carcass quality of the local strain of Red Feather (RF) country chickens and determine age, breed, and body weight factor in accounting for the defeathering effectiveness using adult layers and juvenile broilers as a reference. Results showed no differences between soft and hard scalding in broilers with 60% and 80% of acceptable defeathering scores, respectively, while a significantly better effect by hard scalding was observed in adult layers, young and old RF chickens with more than 70% of birds exhibiting desirable scores and less than 20% by soft scalding. In contrast to soft scalding, hard scalding had no significant effects on breast meat color but impaired skin color in broilers as assessed by L*, a*, and b* value analysis. Interestingly, hard scalding increased breast skin yellowness and lightness in young RF chickens and lightness in old RF chickens, while there were no significant changes in layers. However, hard scalding decreased skin elasticity in layers and old RF chickens. The effectiveness of defeathering by scalding method was governed by the age to reach a certain threshold in the development of dermal architecture and feather richness, irrelevant to body weight. The alteration of carcass color primarily depends on age, body weight/breed, and their interaction. In conclusion, current soft scalding is suitable for broiler chickens for desirable defeathering effect and carcass color, whereas layers and RF chickens scaled at 60 °C for 60 s showed a better defeathering effect without unfavorable changes of breast meat and skin color.

Molecular identification and relative abundance of microorganisms in douchi koji and salted egg white sufu during processing.

A novel animal protein-based douchi koji-inoculated steamed salted egg white sufu (SEWS) has been developed. This study determined the relative abundance of microorganisms in the douchi koji and semi-finished (5-day fermentation) and finished (5-day fermentation and 14-day ripening) SEWS by using 16S and 18S ribosomal DNA and gene-cloning methods. The results revealed that Bacillus spp. and Aspergillus oryzae were dominant in the douchi koji. In the semi-finished SEWS, the percentages of Bacillus amyloliquefaciens and Bacillus subtilis were considerably lower, whereas those of Enterococcus and Staphylococcus were substantially higher. In the finished SEWS, Bacillus spp. became dominant again and A. oryzae was the only fungus detected. In conclusion, by using molecular techniques, microbial population dynamics in SEWS can be evaluated. During processing, the relative abundance of microorganisms in SEWS changed and Bacillus spp. and A. oryzae remained dominant. This study provides crucial information for designing starter cultures for producing SEWS.

Influence of sucrose level and inoculation of Lactobacillus plantarum on the physicochemical, textural, microbiological, and sensory characteristics of Isan sausage (Thai fermented pork sausage).

The aim of this study was to evaluate the influence of sucrose levels (0.3% and 1.2%) and inoculation of Lactobacillus plantarum on the quality of Isan sausage. The results show that the inoculation accelerated the pH reduction in fermentation. The inoculated samples had significantly (p < .05) lower thiobarbituric acid reactive substances and volatile basic nitrogen values. The total microbial counts and lactic acid bacteria (LAB) counts increased rapidly during fermentation and then decreased during storage. The inoculated samples had significantly higher total microflora and LAB counts. The inoculated samples had a higher hardness texture profile as well as more intense flavor and darker color in sensorial evaluation. Less influence on the quality parameters of the samples due to the different sucrose levels was observed. In conclusion, a combination of 0.3% sucrose and inoculation of L. plantarum (7 log cfu/g) is recommended for producing Isan sausages.

Influences of fermentation and ripening temperatures on the enzymatic activity and physicochemical and sensory properties of salted egg white sufu.

This study developed a novel form of sufu. Salted egg white sufu (SEWS) was produced by fermenting steamed salted egg white with douchi koji and ripening at 25°C, 35°C, or 45°C for 19 days. The results show that the protease activity of the koji reduced pronouncedly during fermentation, whereas the one in the SEWS initially increased but subsequently decreased. The total nitrogen and amino nitrogen contents and degree of protein hydrolysis increased during fermentation and decreased during preripening. SEWS, particularly processed at 35°C, contained more free amino acids, notably glutamic acid and leucine, than steamed salted egg white did. After processing, SEWS had darker colors, particularly when manufactured at higher temperatures, and hardness and springiness decreased. The 35°C and 45°C SEWS had higher sensory acceptability. In conclusion, ripening at 35°C for 19 days is recommended for producing this novel animal protein-based sufu.

Effects of moist- and dry-heat cooking on the meat quality, microstructure and sensory characteristics of native chicken meat.

This study investigates the effects of moist- (water-cooking; WC) and dry-heat (oven-cooking; OC) on the quality, microstructure and sensory characteristics of native chicken breast meat. The results revealed that OC meat had a significantly higher cooking time, cooking loss, and shear force values and lower L* values. Protein solubility decreased after cooking in both cooking methods; however, no statistical difference was observed between WC and OC meats, whereas collagen solubility and myofibrillar fragmentation index (MFI) increased after cooking and WC meat exhibited higher collagen solubility and MFI (P < 0.05). The fiber diameter and sarcomere length decreased substantially after cooking, and fibril shrinkage was noticeable in OC meat (P < 0.05). Descriptive sensory analysis revealed that WC meat exhibited a significantly higher moisture release and lower initial hardness, chewdown hardness and residual loose particles. A darker color and enhanced chickeny flavor were observed for OC meat. Based on the unique sensory and physicochemical characteristics in demand, producers should employ appropriate cooking methods to optimize native chicken meat quality.

Antioxidant properties of porcine liver proteins hydrolyzed using Monascus purpureus.

In this study, the antioxidant activities of porcine liver proteins, hydrolyzed using Alcalase®, papain, pepsin, or a microbial suspension of Monascus purpureus (APLH, PaPLH, PePLH, and MPLH, respectively), were investigated. The results indicated that the yield and degree of hydrolysis (DH) of hydrolysates increased with hydrolysis time. The highest yield and peptide content were obtained from APLH, whereas the DH of PaPLH was higher than that of the others. MPLH exhibited the highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and reducing power, whereas APLH and PaPLH exhibited the higher ferrous ion-chelating ability than that of the MPLH. The molecular weights of all the hydrolysates were <10 kDa. The PaPLH exhibited the highest contents of total amino acids and hydrophobic amino acids. Fifteen antioxidant fractions obtained from MPLH contained one or more of the following amino acids in their sequences: Tyr, Trp, Ala, Pro, Met, Lys, Asp, Cys, Val, Leu, and His.

Validation of feasibility and quality of chicken breast meat cooked under various water-cooking conditions.

Under laboratory conditions, the qualities of boneless chicken breasts are commonly determined by placing them in a bag and cooking them in a water bath. The results are often applied as references for comparing the influences of cooking techniques. However, whether a sample cooked under this "laboratory" condition actually represents the meat cooked under the "real-life" condition in which meat is frequently cooked directly in water without packaging remains unclear. Whether the two cooking conditions lead to comparable results in meat quality should be determined. This study evaluated the influence of cooking conditions, including "placed-in-bag and cooked in a water bath (BC)" and "cooked directly in hot water (WC)" conditions, on the quality of chicken meat. The results reveal that BC samples had a longer cooking time. Deboned-and-skinless BC samples had a higher cooking loss and lower protein solubility (P < 0.01). BC samples with bone and skin had a higher lightness in both skin and muscle. No significant differences were observed in attributes, including shear force, collagen solubility, microstructures, redness, yellowness and descriptive sensory characteristics between treatments. Based on the results, considering the quality attributes that might be influenced, is critical when conducting relevant research.

Effects of egg washing and storage temperature on the quality of eggshell cuticle and eggs.

This study investigated the quality of washed and unwashed eggs stored at 7°C (WC and UC for washed and unwashed eggs, respectively) and 25°C (WR and UR for washed and unwashed eggs, respectively) for 4weeks. The results show that the Haugh unit, albumin pH, thick albumin ratio, yolk index, air cell size, and S-ovalbumin content of UC were significantly the most superior, followed by those of WC, WR, and UR, in that order. Scanning electron microscopy and cuticle staining confirmed the damages and decreased cuticle coverage caused by washing and extended storage. Attenuated total reflection Fourier transform infrared spectroscopy revealed that cuticle composition changed significantly after washing and storage (P<0.05). High correlations were observed between the quality parameters evaluated. In conclusion, storage temperature critically influenced egg quality, and egg washing reduced cuticle coverage.

Lactic acid bacterial population dynamics during fermentation and storage of Thai fermented sausage according to restriction fragment length polymorphism analysis.

This study applied restriction fragment length polymorphism (RFLP) analysis to identify the lactic acid bacteria (LAB) isolated from "mum" Thai fermented sausages during fermentation and storage. A total of 630 lactic acid bacteria were isolated from the sausages prepared using 2 methods. In Method 1, after stuffing, the sausages were stored at 30 °C for 14 days. In Method 2, after stuffing and storage at 30 °C for 3 days, the sausages were vacuum-packed and stored at 4 °C until Day 28. The sausages were sampled on Days 0, 3, 14, and 28 for analyses. The 16S rDNA was amplified and digested using restriction enzymes. Of the restriction enzymes evaluated, Dde I displayed the highest discrimination capacity. The LAB were classified and 7 species were identified For Methods 1 and 2, during fermentation, the Lactobacillus sakei and Lactobacillus plantarum species were dominant. For Method 2, the proportion of Leuconostoc mesenteroides markedly increased during storage, until L. sakei and Ln. mesenteroides represented the dominant species. The identification of LAB in the sausage samples could facilitate the selection of appropriate microorganisms for candidate starter cultures for future controlled mum production.

An innovative method for the preparation of mum (Thai fermented sausages) with acceptable technological quality and extended shelf-life.

Freshly-manufactured mum sausages were assigned to two processing methods (process I: stored at ∼30 °C for 14 days; process II: stored at ∼30 °C for three days, vacuum-packaged, and stored at 4 °C until day 28). Physicochemical, microbial, textural, and sensory properties of samples were analysed. The results showed that dehydration was more intense in process I samples, and resulted in lower moisture content and water activity. Significant decreases in pH values, and increases in lactic acid were observed in both samples by day 3. The total microflora and lactic acid bacteria counts increased rapidly during the fermentation and then decreased while the Enterobacteriaceae counts decreased steadily. Too much dehydration resulted in tough textures and unacceptable sensory qualities for process I samples. In conclusion, after three days of fermentation, with vacuum-packaging, ripening and storage at 4 °C up to 28 days, it is possible to produce mum sausages with better qualities and an extended shelf life.

Synthesis and characterization of collagen/hyaluronan/chitosan composite sponges for potential biomedical applications.

Cells, scaffolds and growth factors are three main components of a tissue-engineered construct. Collagen type I, a major protein of the extracellular matrix (ECM) in mammals, is a suitable scaffold material for regeneration. Another important constituent of the ECM, hyaluronic acid (hyaluronan, HA), has been used for medical purposes due to its hydrogel properties and biodegradability. Chitosan is a linear polysaccharide comprised of beta1- to beta4-linked d-glucosamine residues, and its potential as a biomaterial is based on its cationic nature and high charge density in solution. This study was conducted to evaluate the characteristics of scaffolds composed of different ratios of type I comb collagen and chitosan with added HA in order to obtain the optimum conditions for the manufacture of collagen-hyaluronan-chitosan (Col-HA-Ch; comprising collagen, HA and chitosan mixed in different ratios: 10:1:0, Col10HACh0; 9:1:1, Col9HACh1; 8:1:2, Col8HACh2; 7:1:3, Col7HACh3; 6:1:4, Col6HACh4; and 5:1:5, Col5HACh5) composite porous scaffolds. Microstructural observation of the composite scaffolds was performed using scanning electron microscopy. The mean pore diameters ranged from 120 to 182microm and decreased as the chitosan composition increased. All scaffolds showed high pore interconnectivity. Swelling ratio measurements showed that all specimens could bind 35- to 40-fold of physiological fluid and still maintain their form and stability. For tensile strength, the optimal ratio of collagen and chitosan was 9:1. Thermal stability was investigated using a differential scanning calorimeter and showed that Col5HACh5 and Col6HACh4 were significantly more stable than the other groups. In enzymatic sensitivity, a steady increase in the biostability of the scaffolds was achieved as the chitosan concentration was increased. In biocompatibility testing, the proliferation of the fibroblasts cultured in Co-HA-Ch tri-copolymer scaffolds was high. Overall, we observed the 9:1:1 mixing ratio of collagen, hyaluronan and chitosan to be optimal for the manufacture of complex scaffolds. Furthermore, Col-HA-Ch tri-polymer scaffolds, especially Col9HACh1, could be developed as a suitable scaffold material for tissue engineering applications.