Chemical and nutritional properties of channel and hybrid catfish byproducts

Utilization of Lumpfish (Cyclopterus lumpus) Skin as a Source for Gelatine Extraction Using Acid Hydrolysis

Lumpfish (Cyclopterus lumpus) is an underutilized marine resource that is currently only being exploited for roe. Lumpfish skin was pre-treated with alkali (0.1M NaOH) and acid (0.1M HCl) at a skin to chemical ratio of 1:10 for 24 h at 5 °C to remove non-collagenous proteins and minerals. The pre-treated skin was washed, and gelatine was extracted with 0.1M of acetic acid at three different ratios (1:5, 1:10, and 1:15), time (12,18, and 24 h), and temperature combinations (12, 28, and 24 °C). The highest total extraction yield (>40%) was obtained with combinations of extraction ratios of 1:15 and 1:10 with a longer time (24 h) and higher temperature (18-24 °C). The highest gelatine content was obtained with an extraction period of 24 h and ratio of 1:10 (>80%). SDS-PAGE analysis confirmed the presence of type-I collagen. A rheological evaluation indicated melting and gelling temperatures, gel strength, and viscosity properties comparable to existing cold-water gelatine sources.

Consumers' Acceptance, Emotions, and Responsiveness to Informational Cues for Air-Fried Catfish (Ictalurus punctatus) Skin Chips

Catfish (Ictalurus punctatus) skins, as filleting byproduct, were developed into a crispy snack food via air-frying. Consumers rated catfish skin chips (CSC) across sensory modalities (9-point hedonic scales, a just-about-right scale, and "yes/no" for purchase intent, PI) for Plain-, Lemon & Pepper-, and Barbecue-flavored samples during two consumer studies (N = 115 each). Paprika- flavored CSC were excluded from Study 2 due to inferior acceptance and emotional ratings. CSC-elicited emotions were evaluated using a 25-term lexicon with CATA (Check-All-That-Apply) scaling (Study 1) and refined with an abbreviated lexicon containing food-evoked sensation-seeking emotions (5-point intensity scale). The two consumer studies differed in delivery format of product benefit information (a health/protein message and a food waste/sustainability message). Presenting two separate cues (Study 1) significantly increased overall liking (by 0.5 units) and PI (by 15%) for CSC compared to a single integrated message (Study 2), perhaps due to consumers' mode of information processing. Magnitude of increases was less for Barbeque CSC despite performing best overall (overall liking reaching 6.62 and PI reaching 61.7%). CSC generated mostly positive emotions, and informational cues increased sensation-seeking feelings, which can motivate trial of new foods. Accordingly, acceptance of CSC improved for 25 repeat-exposure consumers who participated in both Studies 1 and 2. In combination, sensory, cognitive, and emotional data showed favorable responses for flavored CSC as an appropriate application of this seafood byproduct.

Proximate composition and amino acid profile of European eel skin: influence of body weight

Fish processing industries worldwide are discarding million kilograms of fish waste per year. The disposal of these wastes is an important handicap in fish processing industry. The thick eel skin is considered a waste product in the fish processing industry and in the home and is usually converted into low market-value products. The aims of this study were to evaluate the variations in the general chemical composition and amino acid content of eel skin in relation to body weight. The moisture content decreased and the lipid content increased with the weight of the eels. Eel skin had a high protein content, which did not vary significantly with eel weight. Glycine was the most abundant amino acid. The predominant essential amino acid was leucine. The smaller eels contained higher levels of threonine, valine, isoleucine, leucine, lysine, glutamic acid and tyrosine than the other groups. The larger eels contained higher levels of methionine, hydroxyproline, glycine, arginine, alanine and proline than the other groups. The protein indices showed that the skin from smaller eels was of higher nutritional quality.

Graphical abstract

Effects of Catfish (Ictalurus punctatus) Bone Powder on Consumers’ Liking, Emotions, and Purchase Intent of Fried Catfish Strips

Catfish are the predominant U.S. aquacultural product. However, byproducts from filleting, including bones that are high in calcium, typically go to waste or are sold as a low-valued feed. This research evaluated the potential use of catfish bone powder (CBP; 21.07% calcium) as a food ingredient. Catfish fillet strips were dredged with a breading mix (CBPM) containing 0% (0CBPM), 10% (10CBPM), and 20% (20CBPM) CBP before frying. Consumers (N = 211) evaluated sensory liking (nine-point hedonic scale) and attribute intensity (JAR scale), emotions (check-all-that-apply), and purchase intent (PI, yes/no) of samples. Color and texture were measured instrumentally. CBP did not show any negative effects on liking scores, although crispiness was scored higher for 20CBPM (mean = 6.88) than 10CBPM (mean = 6.43). Positive emotions were most relevant to CBP-containing samples, with significantly higher rates of adventurous and understanding. Information about calcium fortification using CBP increased PI to 81.04% for the 10CBPM and 83.89% for the 20CBPM samples and showed a greater effect on Latin Americans/Hispanics than U.S. Americans. Consumers were not averse to the consumption of CBP which can contribute to sustainable nutrition through waste reduction. Successful calcium fortification of fried catfish dredged with 20% CBP did not compromise sensory liking and may be feasible in other products.

Properties of bone from Catfish heads and frames

The objective of this paper was to evaluate methods of producing purified Catfish bone fractions from Catfish frames and heads and determine the composition of the purified bone fraction. Fresh samples of Catfish frames and heads were obtained from a large commercial Catfish processor. Triplicate samples were processed for all treatments. Two methods were developed to remove nonbone tissue from the frames: (a) use of a proteolytic enzyme to digest the nonbone tissues and (b) after boiling the frames, removal of the nonbone tissues with high-pressure water. The ash, protein, and lipid contents of unprocessed dried frames were 17%, 33%, and 41%, respectively. After the enzymatic or high-pressure water treatment processes, the frame bone compositions for the two processes were 62% and 54% ash, 35% and 33% protein, and 9% and 2% lipid, respectively. Bone from both processing treatments had a calcium content of 21%-25%, phosphorus content of 10%-11%, and contents of magnesium, manganese, zinc, and nickel were increased. Hydroxyproline content increased from 4% of the amino acids in the untreated bone to 7%-8% for the processed treatments. Tissues were removed from Catfish heads by digestion with a proteolytic enzyme and collection of the bone with a sieve. After the longest digestion period, dried head bone was 51% ash, 38% protein, and 7% lipid. The amino acid profiles showed high levels of hydroxyproline and lower levels of many essential amino acids. With increased enzymatic hydrolysis time, percent calcium and phosphorus increased. Results from this study will be used in the development of new value-added food and feed ingredients from Catfish bone.

Chemical and nutritional properties of channel and hybrid catfish byproducts

The objective of this study was to chemically characterize both channel and hybrid catfish parts including heads, frames, viscera, skin, and fillet trimming mince. Triplicate samples of channel and hybrid catfish byproduct parts were obtained from a large commercial catfish processor and analyzed for percent moisture, lipid, protein, ash, and amino acid and fatty acid profiles were determined. The content of the off‐flavor compounds, 2‐methylisoborneol (MIB) and geosmin were also determined. The lipid content of samples were 13.6% and 10.0% for channel and hybrid skins, 17.7% and 21.4% for channel and hybrid viscera, 20.0% and 19.1% for channel and hybrid frames, and 9.7% and 9.3% for channel and hybrid heads. The protein content of samples ranged from a high of 22.8% for channel catfish skins, to a low of 13.4% for channel frames. Low levels of geosmin, <1 ppb, were detected in the byproduct samples, while no MIB was detected. Palmitic, oleic, and linoleic acid comprised approximately 80% of the fatty acids in the byproduct tissues. The amino acid profiles indicated that the catfish mince had high levels of lysine and methionine and other essential amino acids. Results from this study will be used in the development of new value‐added products from catfish byproducts.