Woo-Young Son

The gelation ability of gelatin is useful for improving texture and stabilizing food structure, but excessive gelation may limit its application in liquid and high-moisture food systems. Therefore, this study compared the effects of Alcalase and pepsin hydrolysis on the gel-forming ability, viscosity, and functional properties of porcine skin gelatin. o-Phthaldialdehyde (OPA) analysis showed that the Alcalase hydrolysate had a higher free amino group content (0.77 meqv/g protein) than the pepsin hydrolysate (0.23 meqv/g protein), indicating more extensive peptide bond cleavage (p < 0.05). The control formed a stable gel structure after 60 min at 25 °C, whereas both hydrolysates showed reduced gel-forming ability. In particular, the Alcalase hydrolysate was found to maintain high fluidity, completely inhibiting gel formation. Furthermore, 17.5% (w/v) Alcalase hydrolysate solution showed no measurable viscosity. In contrast, 17.5% (w/v) pepsin hydrolysate solution exhibited a viscosity of 653.88 cP. In contrast to the Alcalase hydrolysate, the pepsin hydrolysate also showed the highest oil absorption capacity (8.81 g/g), emulsion stability index (854.09 min), and a slightly higher in vitro digestibility (29.36%) (p < 0.05). These results demonstrate that enzyme-specific hydrolysis can differentially modify the balance between gel suppression and techno-functional properties of porcine skin gelatin.

Porcine blood meal is a protein and iron-rich animal by-product, but its use in companion animal diets is often limited by poor solubility and variable digestibility caused by thermal processing. This study evaluated whether enzymatic hydrolysis could improve the physicochemical properties, digestibility, iron-related characteristics, and antioxidant capacity of porcine blood meal for potential use in canine diets. Porcine blood meal was hydrolyzed using alcalase or pepsin under controlled conditions, and the resulting hydrolysates were characterized by degree of hydrolysis, electrophoretic peptide profiles, techno-functional properties, in vitro digestibility using a simulated canine gastrointestinal model, heme and non-heme iron fractions, and antioxidant activities. Alcalase treatment produced a higher degree of hydrolysis and more extensive peptide fragmentation than pepsin. Consistent with these structural changes, the alcalase hydrolysate exhibited significantly higher in vitro apparent digestibility. Enzymatic hydrolysis increased extractable heme iron while reducing ferrozine-reactive non-heme iron, suggesting changes in iron binding forms after proteolysis. Hydrolyzed samples also showed enhanced radical scavenging activity and ferric-reducing capacity, whereas superoxide dismutase (SOD)-like activity decreased following hydrolysis. These findings indicate that controlled enzymatic hydrolysis, particularly with alcalase, could improve apparent digestibility and non-enzymatic antioxidant capacity of porcine blood meal, supporting its potential as an iron-containing ingredient in canine diets. Further in vivo studies would be required to confirm iron availability and nutritional efficacy.

Korean native black goat is commonly consumed as thermally processed extracts and is widely perceived to exhibit health-promoting properties; however, the contribution of intrinsic muscle proteins to these functional characteristics remains unclear. This study evaluated the effects of thermal processing on the antioxidant activity of myofibrillar and sarcoplasmic protein fractions using a screening-based approach. Protein fractions were extracted and subjected to various thermal conditions (60–121 °C), followed by analyses of extractable protein, α-amino group content, and antioxidant activities, including 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, hydroxyl radical scavenging, iron-chelating ability, and ferric reducing antioxidant power (FRAP). Thermal processing increased α-amino group content, particularly in the myofibrillar fraction, indicating enhanced protein degradation. Antioxidant activities improved with increasing temperature, with myofibrillar proteins showing stronger activity than sarcoplasmic proteins. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) indicated fragmentation in myofibrillar proteins and aggregation in sarcoplasmic proteins. Cluster analysis supported fraction-dependent differences in antioxidant responses. These findings suggest that thermal processing enhances antioxidant activity in a protein fraction-dependent manner and provide practical insights for optimizing processing conditions of Korean native black goat extracts.

Polyphenol conjugation has emerged as a promising approach to enhance the technological properties and physiological benefits of food proteins. This study investigated the effects of polyphenol conjugation on the technological properties, antioxidant capacity, and in vitro digestibility of chicken breast (CB) proteins. Conjugation with (-)-epigallocatechin 3-gallate (EGCG) and tannic acid (TA) significantly reduced sulfhydryl content. EGCG conjugates exhibited higher turbidity and greater molecular weight aggregates (>245 kDa). Fourier-transform infrared spectroscopy (FTIR) revealed alterations in protein secondary structures, with shifts in amide I and II bands. Polyphenol conjugation significantly enhanced the water-holding capacity of chicken muscle proteins, particularly for CB-TA (3.29 g/g) and CB-EGCG (3.13 g/g) compared to the control (2.25 g/g). The emulsion stability index improved notably in CB-EGCG (96.23 min) and CB-TA (87.24 min) compared to the control (69.05 min). Color analysis revealed darker and more intense hues for CB-EGCG, while CB-TA maintained a lighter appearance, making it potentially preferable for industrial applications requiring neutral-colored powders. Moreover, polyphenol conjugation could enhance antioxidant capacity, particularly in conjugates with EGCG (p < 0.05). In vitro protein digestibility remained comparable across treatments (p > 0.05). Our findings could indicate the potential of chicken muscle protein–polyphenol conjugates as innovative ingredients for high-quality protein supplements.

자원과학연구(Resources Science Research)

Porcine by-products have garnered attention as an excellent material for producing antioxidant peptides; however, understanding the antioxidant characteristics of protein hydrolyzates derived from specific parts remains limited. In this study, we compared the antioxidant properties of protein hydrolyzates derived from major porcine organs (heart, kidney, spleen, liver, and lung) and performed classification based on their antioxidative potential. Their chemical composition exhibited significant variations, with a high protein content ranging from 15.90 to 20.30 g/100 g. Alcalase achieved higher hydrolysis efficiency than trypsin, which induced limited degradation of some proteins, such as porcine serum albumin. The hydrolyzates exhibited superior radical scavenging activities compared to the raw materials, although their reducing power remained unaffected or, in some instances, decreased. Hierarchical and k-mean cluster analyses revealed distinct antioxidant profiles and Alcalase-hydrolyzed kidney and trypsin-hydrolyzed lung hydrolyzates were deemed the most promising candidates, with strong radical scavenging activities and reducing power. Our findings indicate that, even when processed in bulk rather than being obtained from specific parts, porcine by-products can produce hydrolyzates rich in antioxidant peptides through enzymatic hydrolysis. However, selectively processing porcine kidneys with Alcalase and lungs with trypsin is recommended to produce premium products with enhanced and balanced antioxidant properties.

The non-destructive and rapid monitoring system for residual nitrite content in processed meat products is critical for ensuring food safety and regulatory compliance. This study was performed to investigate the application of hyperspectral imaging in combination with machine learning algorithms to predict and monitor residual nitrite concentrations in emulsified pork sausages. The emulsified pork sausage was formulated with 1.5% (w/w) sodium chloride, 0.3% (w/w) sodium tripolyphosphate, 0.5% (w/w) ascorbic acid, and sodium nitrite at concentrations of 0, 30, 60, 90, 120, and 150 mg/kg, based on total sample weight. Hyperspectral imaging measurements were conducted by capturing images of the cross-sections and lateral sides of sausage samples in a linescan mode, covering the spectral range of 1000–2500 nm. The analysis revealed that higher nitrite concentrations could influence the protein matrix and hydrogen-bonding capacities, which might cause increased reflectance at approximately 1080 nm and 1280 nm. Machine learning models, including XGBoost, CATboost, and LightGBM, were employed to analyze the hyperspectral data. XGBoost demonstrated the best performance, achieving an R² of 0.999 and a root mean squared error of 0.095, highlighting its high predictive accuracy. This integration of hyperspectral imaging with advanced machine learning algorithms offers a non-destructive and real-time method for monitoring residual nitrite content in processed meat products, noticeably improving quality control processes in the meat industry. Additionally, real-time implementation in industrial settings could further streamline quality control and enhance operational efficiency. Further research should focus on validating these findings with larger sample sizes and more diverse datasets to ensure robustness.

자원과학연구(Resources Science Research)

This study aimed to isolate the proteolytic fraction from the silkworm thorn fruit (Cudrania tricuspidata) through ethanol precipitation at different ratios, and to determine its proteolytic activity and optimal activity conditions. Furthermore, the hydrolysis characteristics and antioxidant activity of soy protein isolate (SPI) and whey protein concentrate (WPC) hydrolyzates obtained through the enzymatic hydrolysis of freeze-dried silkworm thorn fruit powder (SF) were evaluated. For isolation and partial purification of proteolytic fraction, the water-solubilized fraction of the silkworm thorn fruit was purified through ethanol precipitation at four different ratios of 1:1, 1:2, 1:4, and 1:6 (v/v). The protein recovery rate, caseinolytic activity, protein pattern, and optimal activity (pH, temperature, and inhibitors) of fractional ethanol precipitate obtained from the silkworm thorn fruit (ESF) were evaluated. The proteolytic fraction obtained from silkworm thorn fruit exhibited a major protein band around 65–70 kDa and showed the highest proteolytic activity at a 1:4 ratio of ethanol precipitation (p < 0.05). The optimal activity of the measured enzyme fraction was determined to be at pH 9.0 and 50 °C, and the proteolytic activity of ESF was almost inhibited by phenyl methyl sulphonyl fluoride (PMSF, 2 mM), a serine protease inhibitor. Compared to Alcalase and papain, extensively used as commercial enzymes, the silkworm thorn fruit powder was less effective in hydrolyzing SPI and WPC. Nevertheless, SPI and WPC hydrolyzates mediated with silkworm thorn fruit powder showed even better antioxidant activities than those mediated with Alcalase and papain. Thus, our results show the potential application of silkworm thorn fruit as a novel source of plant protease for producing human-grade protein hydrolyzates.