Alkaline Solubilization Process Research Articles

Food functionality of protein isolates extracted from Yellowfin Tuna (Thunnus albacares) roe using alkaline solubilization and acid precipitation process.

Four types of roe protein isolates (RPIs) were prepared through the alkaline solubilization and acid precipitation (ASAP) process, and their functional properties and in vitro bioactivities were evaluated. Higher buffer capacity in pH‐shift range of 8–12 was found in RPI‐1 (pH 11/4.5), required average 94.5 mM NaOH than that of other RPIs to change the pH by 1 unit. All the samples of 1% dispersion (w/v) showed the lowest buffering capacity near the initial pH. The water‐holding capacities (WHC) of RPIs and casein as controls without pH‐shift were in range of 3.7–4.0 g/g protein, and there were no significant differences (p > 0.05). At pH 2 and 8–12 with pH‐shift, WHC and protein solubility of RPIs were significantly improved compared to those of controls. Foaming capacities of RPI‐1 and RPI‐3 were 141.9% and 128.1%, respectively, but those of RPI‐2 and RPI‐4 were not detected. The oil‐in‐water emulsifying activity index of RPI‐1 and RPI‐3 was 10.0 and 8.3 m2/g protein, which was not statistically different from casein (7.0 m2/g), but lower than that of hemoglobin (19.1 m2/g). Overall, RPIs, casein, and hemoglobin exhibited lower food functionality at pH 4–6 near isoelectric points. Through the pH‐shift treatment, the food functionalities of RPIs were improved over the controls, especially in the pH 2 and pH 8–12 ranges. RPI also showed in vitro antioxidant and antihypertensive activities. Therefore, it has been confirmed that RPI extracted from yellowfin tuna roe has high utility as a protein‐ or food‐functional‐enhancing material or protein substitute resource for noodles, confectionery, baking, and surimi‐based products.

Utilization of freshwater mussel (Lamellidens marginalis) for the isolation of proteins through pH shift processing: characterization of isolates.

Study was conducted touse underutilized freshwater mussel (Lamellidens marginalis) for the recovery of proteins using pH shift method and to study the functionality and characteristics of the recovered isolates. From the pH range tested (pH2.0-13.0), maximum protein yields were obtained during solubilization at pH2.0 and pH13.0 (p < 0.05). During the protein recovery process, pH13.0 was found to have minimal effect on proteins resulting in higher protein yields compared to pH2.0. Isolates obtained by both acidic and alkaline solubilization processes had low stability and poor gel network. Total lipid content, total myoglobin, and pigment contents were reduced significantly (p < 0.05) during pH shift processing, resulting in whiter protein isolates and protein gels. All the essential amino acids were present in the isolates recovered by acid and alkaline solubilization, indicating the complete recovery of amino acids. No microbial counts were observed in any of the isolates prepared using acid and alkaline-aided processing. Acid and alkaline solubilization (pH shift) process was found to be promising for the recovery of proteins from underutilized freshwater mussel thus by reducing the supply demand gap.

Acid and alkaline solubilization (pH shift) process: a better approach for the utilization of fish processing waste and by-products.

Several technologies and methods have been developed over the years to address the environmental pollution and nutritional losses associated with the dumping of fish processing waste and low-cost fish and by-products. Despite the continuous efforts put in this field, none of the developed technologies was successful in addressing the issues due to various technical problems. To solve the problems associated with the fish processing waste and low-value fish and by-products, a process called pH shift/acid and alkaline solubilization process was developed. In this process, proteins are first solubilized using acid and alkali followed by precipitating them at their isoelectric pH to recover functional and stable protein isolates from underutilized fish species and by-products. Many studies were conducted using pH shift process to recover proteins from fish and fish by-products and found to be most successful in recovering proteins with increased yields than conventional surimi (three cycle washing) process and with good functional properties. In this paper, problems associated with conventional processing, advantages and principle of pH shift processing, effect of pH shift process on the quality and storage stability of recovered isolates, applications protein isolates, etc. are discussed in detail for better understanding.

Physicochemical and Functional Properties of Protein Recovered from Fish Waste

ABSTRACTThis work aimed to evaluate the physicochemical and functional properties of proteins recovered from whitemouth croaker (Micropogonias furnieri) and Argentine anchovy (Engraulis anchoita) residues obtained by the process of acid solubilization using HCl at pH = 2 and alkaline solubilization using NaOH at pH = 12 and isoelectric precipitation (pH = 5.5). The proximate composition and functional properties were determined. The solubilization and water holding capacity (WHC) of the recovered protein were studied in the pH range of 3, 5, 7, 9, and 11. The high protein content and lowest lipid reduction presented by the protein recovered from the whitemouth croaker residue and obtained by the acid solubilizing process was 97.1 and 98.4%, respectively. The maximum solubilized protein was at pH 3 and 11, and the minimum solubilized protein was at pH 5 for both species. The greater ability to retain oil was observed for the alkaline solubilization process (8.3 and 7.3). The lower WHC was at pH 5. The acid and alkali residue concentrates of the whitemouth croaker presented higher WHC at pH 3 and 11. These proteins can be used in preparing edible films and have been used to produce bioactive compounds for supplements or functional ingredients.

Physicochemical and rheological parameters changes for determining the quality of surimi and kamaboko produced by conventional, acid and alkaline solubilization process methods from common kilka (Clupeonella cultriventris caspia)

Physicochemical properties of surimi and kamaboko obtained of solubility in acid, alkaline and conventional methods were compared. The results indicated that the highest protein recovery was related to solubility in acid, alkaline and conventional methods, respectively. The highest removal of lipid and myoglobin was observed by solubility in alkali. Excretion of total pigment and sulfhydryl groups was not significantly different between solubility in alkali and acid methods. Whiteness of surimi prepared by acid method was more than the other two methods. Electrophoresis pattern in surimi produced by conventional method indicated loss of myofibril and sarcoplasmic proteins through the washing process. Solubility in acid and alkali methods showed myofibril proteins recovery along a part of the sarcoplasmic proteins and disintegration of myosin heavy chain. Physically, study of kamaboko showed that solubility in alkali generated features such as gel strength, expressible moisture, hardness, gumminess and elasticity was superior to the other two methods. About folding test and cohesiveness factor, there was no significant difference between solubility in alkali and conventional methods. In general, solubility in alkali method was better.

Production and Functional Evaluation of a Protein Concentrate from Giant Squid (D osidicus gigas ) Fins Obtained by Alkaline Dissolution

Two protein concentrates from jumbo squid fins (Dosidicus gigas) were elaborated. One of them was obtained via alkaline dissolution and subsequent isoelectric precipitation (alkaline protein concentrate [APC]) and the other was obtained via the traditional method (neutral protein concentrate [NCP]). The electrophoretic profile of the APC showed that the myosin heavy chain band disappeared, mainly due to the denaturation induced by alkaline solubilization or activation of alkaline protease. Concerning the quality of the gels, the folding test showed that gels obtained using APC were better than those obtained using NPC, but a texture profile analysis detected fracture in the APC gels. Regarding the interfacial properties, low emulsifying capacity was observed for both protein concentrates, and the APC was better than the NPC. Additionally, the foaming properties were excellent for both concentrates and were significantly better for APC. Therefore, the alkaline solubilization process for fin squid was suitable for the production of functional protein concentrates. Practical Applications One of the challenges of the fishing industry is to achieve an integral use of fishing resources. Jumbo squid is an abundant resource in Northwest Mexico and its by-products generate a great of waste, which are an environmental problem. Viscera, heads and fins are the main waste of jumbo squid. Fins are about 10% of the total animal; therefore, their exploitation is a good option for this industry. Hence, this study compares and evaluates the functional properties of the protein concentrates obtained from squid fins via alkaline dissolution and subsequent isoelectric precipitation and the conventional methodology (water washing muscle) to determine the most feasible method of obtaining protein concentrates from squid fins.

Nutritional quality evaluation of Whitemouth croaker (Micropogonias furnieri) protein isolate

Purpose– The purpose of this study was to isolate Whitemouth croaker protein by alkaline solubilization process and evaluate their nutritional quality to evaluate the bioavailability of essential amino acids.Design/methodology/approach– The proximate composition, essential amino acid composition,in vitrodigestibility, apparent bioavailability, chemical score of amino acids and SDS-PAGE were determined for the isolated croaker proteins.Findings– The isolated protein showed a high level of protein 92.21 percent and low amount of lipids 0.57 percent. The protein is rich in lysine and leucine, 108.73 and 96.75 mg/g protein, respectively. The protein isolate had high digestibility, 94.32 percent, which indicates proper utilization of this protein source, while the tryptophan had lower bioavailability (12.58 mg amino acid/mg protein). The high chemical scores were found for the amino acids lysine, methionine+cysteine (6.79 and 5.14). SDS-PAGE of proteins extracted showed appearance of the heavy chain of myosin (220 kDa), actin (50 kDa) and other fractions, with molecular weight between 20 and 50 kDa, such as troponin I, C and T.Originality/value– The products obtained from croaker muscle can be incorporated as a high value supplements in human diets. The isolated protein exhibited a high content of essential amino acids and digestibility, indicating that the protein has a high nutritional quality.

Characteristics of film based on protein isolate from red tilapia muscle with negligible yellow discoloration

The properties of film from fish protein isolate (FPI) prepared by prior washing followed by alkaline solubilization process (ASP) from red tilapia muscle were monitored during the storage of 20 days at 50% RH and 25 °C, in comparison with those of films from washed mince. Lipid, heme iron and non-heme iron contents in FPI were decreased by 98.8, 36.8 and 91.9%, respectively in comparison with those of washed mince ( p < 0.05). Films from FPI had higher tensile strength (TS) and elongation at break (EAB) than those from washed mince for both pH (3 and 11) used for film preparation ( p < 0.05). Film from FPI at pH 3 showed the highest TS, while that from washed mince at pH 11 had the lowest TS ( p < 0.05). Nevertheless, films from FPI had higher WVP than those from washed mince for both pH used ( p < 0.05). At the same pH used for film preparation (3 or 11), films from FPI showed the lower TBARS values than those from washed mince ( p < 0.05). Nevertheless, films from both FPI and washed mince had the higher TBARS values when pH 3 was used for film preparation, compared with pH 11 ( p < 0.05). Among all films, those from FPI prepared at pH 3 had the highest transparency and no yellow discoloration was observed during the storage of 20 days, in comparison with other films ( p < 0.05). Conversely, film from washed mince prepared at pH 3 had the higher increase in b*-value and Δ E*-value than other films. Therefore, FPI could serve as a potential material for film preparation with lower contents of lipid and prooxidants, thereby preventing the yellow discoloration of the fish myofibrillar protein-based film during extended storage.

Alkali-aided protein extraction of chicken dark meat: Composition and stability to lipid oxidation of the recovered proteins

Chicken dark meat has been considered as a major underused commodity due to the increasing demand for further-processed breast meat products. One option to increase the utilization of chicken dark meat is to extract myofibrillar proteins and separate them from fat and pigments to enhance their application for the preparation of further-processed meat products. The objective of the current study was to determine the effect of pH, in the range of 10.5 to 12.0, on the alkaline solubilization process of chicken dark meat. Aspects studied were the effect of the alkali-aided process on protein content, lipid composition, lipid oxidation, and color characteristics of the extracted meat. Each experiment and each assay were done at least in triplicate. Lipid content of the extracted meat showed a 50% reduction compared with the chicken dark meat. Neutral lipids were reduced by 61.51%, whereas polar lipids were not affected by the alkali treatments. There was a higher amount of TBA reactive substances observed in the extracted meat compared with chicken dark meat, indicating that extracted meat was more susceptible to oxidation. Long-chain polyunsaturated fatty acids (22:4n-6, 20:3n-3, 20:5n-3, 22:5n-3, and 22:6n-3), which were detected only in the polar lipids, were responsible for increasing lipid oxidation susceptibility of extracted meat compared with chicken dark meat. Alkali-aided extraction of chicken dark meat lightened the color of the meat. The redness, yellowness, and total heme pigments in extracted meat significantly decreased by 83, 11, and 53%, respectively, compared with chicken dark meat. Even though this process did not remove polar lipids, based on our early findings, the extracted meat had considerable physicochemical and textural properties for product preparation compared with those of raw dark meat. Hence, alkali recovery of protein can be considered a potentially useful method to increase the utilization of dark chicken meat.

Physicochemical and gelling properties of short-bodied mackerel ( Rastrelliger brachysoma) protein isolate prepared using alkaline-aided process

This study demonstrated the characteristics and gel properties of short-bodied mackerel ( Rastrelliger brachysoma) surimi prepared by the conventional washing process and protein isolate prepared by alkaline solubilization process without and with prewashing. A decrease in Ca 2+-ATPase activity ( P < 0.05), with changes in the tryptophan fluorescence intensity of natural actomyosin, was observed in protein isolate from alkaline solubilization process. However, higher reactive sulfhydryl (SH) content was found in protein isolate, compared with that in conventional surimi ( P < 0.05). Generally, the higher amounts of lipid and myoglobin in fish mince were removed by using the alkaline-aided process, compared with the conventional process ( P < 0.05). Protein isolate from the alkaline solubilization process formed gels with higher breaking forces than conventional suirmi, especially with 2-step heating (40 °C, 30 min/90 °C, 20 min) ( P < 0.05). The lowest expressible moisture was found in the gel of protein isolate prepared by alkaline solubilization process ( P < 0.05). However, the highest whiteness was found in the conventional surimi gel prepared by 2-step heating ( P < 0.05). Protein isolate prepared by the alkaline solubilization process yielded superior gels compared with the conventional surimi. Therefore, it can be concluded that the gelling properties of surimi or protein isolate are governed by the physicochemical properties of proteins and are affected by processing conditions.

The Acid and Alkaline Solubilization Process for the Isolation of Muscle Proteins: State of the Art

The acid and alkaline solubilization processes for isolating muscle protein from ground fish raw materials are investigated by scrutinizing the literature. Following an introduction to the processes, with some underlying chemistry, patents related to the acid and alkaline solubilization process are described together with previously patented methods for processing of protein isolates. Focus is then placed on comparing a range of factors important in fish muscle protein isolation between the acid and alkaline solubilization processes, and classic washing-based surimi technology. The factors addressed were: protein yield, gel quality, color, lipid reduction, lipid oxidation, microbial stability, and frozen storage stability. A long series of studies made with different fish/shellfish species have been used for this purpose. Certain results are summarized in table form (protein yields, gel strength, and whiteness), others only in text form. From this part of the review, it is obvious that the acid process often has certain advantages (e.g., protein yield) and the alkaline process other ones (gel strength, whiteness, lipid removal, lipid oxidation, and total microbial count). Thus, the choice of method depends on the application. It is clear that most species respond differently to acid and alkaline solubilization, which is why the two methods are initially compared. In a section about new processing attempts, the use of the acid and alkaline methodology for isolating proteins from whole fish/shellfish and fish by-products is reviewed together with attempts to recover waste water proteins and attempts to modify the process. Tentative uses of the new protein isolates, e.g., as coatings, protein brines, and emulsifiers are finally described together with some conclusions and future opportunities for the acid and alkaline processes.

Recovery of functional proteins from herring (Clupea harengus) light muscle by an acid or alkaline solubilization process.

Proteins from herring (Clupea harengus) light muscle were extracted using acidic or alkaline solubilization; 92 and 89% of the initial muscle proteins were solubilized at pH 2.7 and 10.8, respectively, of which 96 and 94% were recovered during precipitation at pH 5.5. Consistency of the pH-adjusted muscle homogenates increased with increased raw material age and homogenization intensity; it declined following holding on ice. Some hydrolytic myofibrillar protein degradation occurred during cold storage of the acidified (pH 2.7) homogenates. With alkalized homogenates, hydrolysis was negligible. The total lipid content changed from 0.13 g/g of protein in the muscle to 0.04 g/g of protein in both the acid- and alkali-produced protein isolates. Corresponding values for the phospholipid content were from 0.037 to 0.02 g/g of proteins. Acid- and alkali-produced proteins made gels with equal strain and color. Stress values were equal or lower in acid- versus alkali-produced protein gels. When ice-stored raw material was used, strain and stress values of gels were reduced.