Comparative study on the effect of acid- and alkaline-aided extractions on mechanically separated turkey meat (MSTM): Chemical characteristics of recovered proteins

A Comparative Study on Changes in Protein, Lipid and Meat-Quality Attributes of Camel Meat, Beef and Sheep Meat (Mutton) during Refrigerated Storage

An in-depth characterisation of protein and lipid fractions and changes in the physicochemical and meat-quality attributes of camel meat, beef and mutton over 9 days of refrigerated storage was investigated. The lipids of all the meat samples, especially those in camel meat, underwent significant oxidation in the first 3 days of storage. A decrease in pigment and redness (a* value) with an increase in the storage time was noticed in all the meat samples, suggesting the oxidation of the haem protein. The mutton samples displayed greater protein extractability, while the protein solubility values in all the meat samples were similar, and these varied as storage progressed. The drip loss percentage in camel meat and mutton were two times higher than in beef, and it increased during storage period. The textural properties of fresh camel meat were higher than mutton and beef, and these decreased during day 3 and 9, respectively, indicating the proteolysis and the degradation of the structural proteins, which were also evident from the SDS-PAGE pattern.

Improving myofibrillar proteins solubility and thermostability in low-ionic strength solution: A review

The development of myofibrillar proteins drinks (MPDs) can provide meat protein nutrition to specific groups of people. However, one major challenge is that myofibrillar proteins (MPs) are insoluble in solutions with a low ionic strength. Another functional constraint is the susceptibility of MPs to heat-induced aggregation. Currently, the primary approach used to improve the water solubility of MPs is to inhibit the assembly of myofilaments. Increasing the thermostability of MPs primarily inhibits the aggregation of myosin or oxidizes myosin to soluble substances. This review focuses on the description of several chemical and physical strategies, with an emphasis on the advantages, disadvantages, and recent progress. Under the myosin filament assembly process and the cross-linking aggregation mechanism, this summary helps improve our understanding of the solution and thermostability of MPs in low-ionic-strength solutions, thus providing new ideas to the development of MPDs.

Recovery of emulsifying and gelling protein from waste chicken exudate by using a sustainable pH-shifting treatment

The inevitably generated chicken exudate was usually unconsciously discarded, leading to protein waste and environmental pollution. The study is performed to reveal the loss and constitute of different sourced exudate (purge exudate/defrozen exudate, PE/DE), investigate the efficiency of various pH-shifting strategies (Method I: NaOH-HCl, Method II: Ca(OH)₂-Critric acid, and Method III: Ca(OH)₂-Glucono δ-lactone) in recovering selected exudate, and evaluate the functionality of these recovered protein isolates. Accordingly, PE and DE shared greatly similar (P > 0.05) lipid and ash content. Despite sarcoplasmic protein, there are a small amount of functional myofibrillar protein in the exudate samples. During extraction, Method III had higher recovery yield (85.5%) than other two groups, but the isolates contained higher level of moisture. The protein isolates treated with Method II exhibited highest emulsion ability, while the Method III treated group obtained best gelation properties. Overall, pH-shifting could recover functional protein from chicken exudate for industrial application.

Optimization of Valorization of Chicken MDCM to Produce Soluble Protein and Collagen Peptides

This study aimed to utilize enzymatic treatment and pressurized hot water extraction (PHWE) to recover soluble food-grade protein and collagen peptides from mechanically deboned chicken meat (MDCM), a side-stream from the meat industry. Food-grade enzyme blends Ermitase 1 and Ermitase 2 were used to fractionate the mechanically deboned meat into fat, soluble protein, and solids. Response surface methodology was utilized to optimize treatments to maximize the protein yield. At the optimum conditions (hydrolysis time 240 min, E:S 0.27%, and a hydromodule 1 L/kg), the enzymatic treatment produced high protein yield, approximately 90%. The protein hydrolysates showed a good solubility index, but weak gelling properties. The PHWE of the bones resulted in a high nitrogen yield, approximately 87%, at the optimum conditions of 190 °C and 83 min. Peptides in the bone extract were in the range of 0.5–13.7 kDa. Overall, our study highlights the importance of response surface methodology to optimize parameters for mechanically deboned chicken meat enzymatic and PHWE treatments to achieve high yields of protein for food applications and low-molecular-weight collagen peptides for cosmetic applications. The crucial role of protein and peptide prices was observed in preliminary profitability analysis.

Impact of Processing Technology on Macro- and Micronutrient Profile of Protein-Enriched Products from Fish Backbones

Impacts of processing technology (mechanical separation and pH-shift processing) on protein recovery from salmon, herring and cod backbones and the content of macro- and micronutrients in the recovered protein enriched products were investigated. Mechanical separation led to higher protein recovery compared with the pH-shift process and using both techniques, recovery ranked the species as herring > salmon > cod. However, the pH-shift process up-concentrated protein from herring and salmon backbones more efficiently than mechanical separation by removing more fat and ash. This consequently reduced n-3 PUFA and vitamin D content in their protein isolates compared with the backbones and mechanically separated meat (MSM). Cod protein isolate, however, contained higher levels of these nutrients compared with MSM. Mechanical separation concentrated vitamins E and C in salmon MSM but not for cod and herring. Opposite, pH-shift processing reduced levels of these two vitamins for cod and herring backbones, while vitamins D and C were reduced for salmon. For minerals, selenium, calcium, magnesium, and potassium were lower in protein isolates than MSM, while copper, zinc, iron and manganese were similar or higher. Overall, there is a major potential for upcycling of fish backbones to food ingredients, but processing technology should be carefully balanced against the desired nutrient profile and final application area.

Effect of pH regulation on the components and functional properties of proteins isolated from cold-pressed rapeseed meal through alkaline extraction and acid precipitation

Cold-pressed rapeseed meal with high protein content (38.76% protein dry weight basis) was used to prepare rapeseed protein isolates (RPIs) by alkaline extraction (pH 8.0, 9.0, 10.0, 11.0, 12.0 and 13.0) and acid precipitation (pH 3.0, 3.5, 4.0, 4.5, 5.0 and 5.5). The protein with an intact structure and the highest yield (65.08%) was obtained at extraction pH 9.0 and precipitation pH 4.5, accompanied by the lowest D-amino acid content, the lightest colour and the lowest contents of glucosinolates (2.85 mmol/kg), phytic acid (1.05 mg/g) and sinapine (0.68 mg/g). Additionally, water/oil absorption, foaming and emulsifying capacities decreased with decreasing precipitation pH, while the solubility showed the reverse trend. During gastric simulation digestion, the α-polypeptide of cruciferin and napin in the RPIs showed digestive resistance. Overall, pH regulation might be an effective method to isolate high quality RPIs for use in the food processing industry.

Hybrid Bionanocomposites from Spent Hen Proteins

Spent hens, a poultry by-product, have little economic value for processing and mostly end up in landfills. However, there are concerns over disposal of spent hens; therefore, it is pertinent to find out alternative uses that are environmentally sound. On the other hand, single-use plastic packaging is leading to a global environmental crisis. In this study, proteins were extracted from spent hen, plasticized, and processed into films by compression molding. The hybrid bionanocomposite films were successfully prepared using glycerol as a plasticizer, chitosan as a cross-linker, and varying concentrations of nanoclay as a nanoreinforcement. The effects of nanoreinforcements, plasticization, and cross-linking were then evaluated on thermal, mechanical, and barrier properties of the prepared bionanocomposite films. Various concentrations of nanoclay and chitosan were dispersed in the protein matrix. However, with the same plasticizer loading, the optimum addition of chitosan and nanoclay led to almost twofold increase in the mechanical strength, compared to neat protein films. The results indicated that at optimal conditions, a good intercalation and/or exfoliation of the protein biopolymers into clay interlayer galleries was observed leading to improved thermal, thermomechanical, and barrier properties. These hybrid bionanocomposite films have great future potential to be used in packaging and other applications.

Protein and cell wall polysaccharide carbonyl determination by a neutral pH 2,4-dinitrophenylhydrazine-based photometric assay

A new 2,4-dinitrophenylhydrazine (DNPH)-based photometric assay is developed for the quantification of carbonyls in protein samples from any biological source by protein carbonyl-DNPH hydrazone formation at acidic pH in the presence of denaturing urea, and subsequent hydrazone solubilization in the presence of SDS and stabilization from acid hydrolysis at pH 7.0. At this neutral (ntr) pH, interfering unreacted DNPH is uncharged and its thus increased hydrophobicity permits its 100% effective removal from the solubilizate with ethyl acetate/hexane wash. The ntrDNPH assay is more reliable and sensitive than the standard (std) DNPH photometric assay because it eliminates its main limitations: (i) interfering unreacted DNPH (pKa 1.55) that is nonspecifically bound to the TCA (pKa 0.7)-protein pellet is not effectively removed after wash with EtOH: ethyl acetate because it is positively charged, (ii) acid (TCA-induced) hydrolysis of the protein carbonyl-DNPH hydrazone, (iii) sample protein concentration re-determination, (iv) loss of sample acid (TCA)-soluble proteins, (v) DNA interference, and (vi) requires high protein quantity samples (≥ 1 mg). Considering ntrDNPH assay's very low protein limit (1 µg), its cumulative and functional sensitivities are 2600- and 2000-fold higher than those of the stdDNPH assay, respectively. The present study elucidates the DNA interference mechanism on the stdDNPH assay, and also develops a standardized protocol for sample protein treatment and fractionation (into cytoplasmic/aqueous, membrane/lipid-bound, and histone/DNA-bound proteins; see Supplement section V) in order to ensure reproducible carbonyl determination on defined cell protein fractions, and to eliminate assay interference from protein samples containing (i) Cys sulfenic acid groups (via their neutralization with dithiothreitol), and (ii) DNA (via its removal by streptomycin sulfate precipitation). Lastly, the ntrDNPH assay determines carbonyl groups on cell wall polysaccharides, thus paving the way on studies to investigate cell walls acting as antioxidant defense in plants, fungi, bacteria and lichens.

Preparation of Substrate for Flavorant from Chicken Bone Residue with Hot-Pressure Process

Hot-pressure extraction (HPE), which is regarded as a "green" technology, was applied to extract nutrients (protein, collagen, and minerals) from chicken bone residue (CBR). Amino acids (AA), color, and volatile flavor compounds of chicken bone extract (CBE) were also investigated. Results showed that contents of protein, total soluble solids, minerals, and collagen of CBE were positively correlated with extraction time and temperature. High ratios of protein (83.51%) and collagen (96.81%) were obtained with 135 °C and 120 min. Essential AA accounted for 31.03% to 47.73% of total AA in CBE. The percentage of bitter AA in TAA decreased from 28.94% to 25.02% at 0 min to 20.19% and 21.41% at 120 min, although fresh AA increased from 46.35% to 50.84% (0 min) to 53.14% (120 min) at 130 and 135 °C, respectively, indicating CBE was nutritionally beneficial with good flavor. Color and volatile flavor of CBE improved significantly after extraction, although calcium in CBE (4.2 to 4.8 mg/100 g) was relatively low compared with that of CBR (1078 mg/100 g). It can be concluded that HPE is a promising way to transform CBR into a nutritious flavorant substrate, but it is not an efficient way to extract calcium.

Physicochemical and functional properties of gelatins extracted from turkey and chicken heads

Gelatins were prepared from chicken and turkey heads in a series of batch extractions at 2 different temperatures (50 and 60°C), and their composition and functional properties were evaluated. Gelatin yield from chicken and turkey heads was 52.29 and 62.76%, respectively, on a dry weight basis relative to the total collagen content in the raw materials. The gel strength of turkey gelatins varied from 332.7 to 368.4 g, which was significantly (P < 0.05) higher than that of chicken gelatins. Both chicken and turkey head gelatins had high solubility at acidic and alkaline pH values. However, turkey head gelatins showed better emulsifying and foaming properties compared with chicken gelatins.

Nutritional properties of spent duck surimi-like material prepared by conventional and acid-alkaline solubilization methods

The nutritional properties of surimi-like materials produced from spent duck meat processed conventionally (CDS) and processed with acid and alkaline solubilization (ACDS and ALDS, respectively) were studied. The essential amino acids (EAAs) content was significantly higher (p < 0.05) in the ACDS and ALDS than in control (CON) and CDS, with values of 436.78 ± 13.67, 450.30 ± 9.72, 377.29 ± 7.20 and 400.61 ± 14.7 mg/g protein, respectively. All duck surimi-like materials had a higher chemical score, amino acid score and EAA index than the CON. The saturated fatty acid compositions of the ACDS and ALDS samples were significantly lower (p < 0.05) than that of the CDS sample, whereas the opposite pattern was observed for the polyunsaturated fatty acid content. ACDS samples had significantly higher (p < 0.05) contents of minerals than ALDS samples. The results indicated that acid-alkaline solubilization permitted recovery of high-quality surimi-like material from spent duck meat, which has potential for human food uses.