Canning may do more than simply preserve mahi-mahi for year-round consumption. A new open-access study published on 3 September 2026 in Food Safety and Risk reports that thermally processed Coryphaena hippurus, the pelagic fish better known as dolphinfish or mahi-mahi, showed better amino acid and fatty acid profiles and higher protein quality indices than fresh or pre-cooked mince from the same species. The work, carried out by M. Rasheeda, C. O. Mohan, S. Remya, Pankaj Kishore and J. Bindu, also found that toxic heavy metals were either absent or well below regulatory limits in all three product forms, with benefit-to-risk ratios below one.
The researchers bought the fish from a local market in Kochi, India, and processed it in three ways. Fresh fillets, with a moisture content of 79.29 percent, fat of 0.46 percent and protein of 15.18 percent, were minced and stored at 2 to 3 degrees Celsius for analysis. For the pre-cooked material, fish chunks were boiled in water at 100 degrees Celsius for 15 minutes, yielding mince with 73.03 percent moisture, 3.57 percent fat and 15.69 percent protein. The canned product was prepared by packing pre-cooked meat into tin-free steel cans with vegetable oil at a fish-to-oil ratio of 70:30, then heat-processing the filled cans at 121.1 degrees Celsius to an F0 value of 9 minutes. The resulting canned mince contained 67.06 percent moisture, 3.62 percent fat and notably 25.89 percent protein, a substantially higher protein concentration than the fresh material.
Fatty acid analysis by gas chromatography revealed a striking shift in composition after canning. In fresh and pre-cooked mince, the predominant fatty acid was the omega-3 polyunsaturated fatty acid DHA, at 22.59 percent and 20.3 percent respectively. Palmitic acid was the major saturated fatty acid in all samples, at 19.88 percent in fresh fish, 22.41 percent in pre-cooked mince and 9.13 percent in canned mince, while oleic acid was the predominant monounsaturated fatty acid, reaching its highest level of 25.4 percent in the canned product. The study reported significantly different levels of EPA and DHA across the three sample types, with canned mince showing very low levels of these omega-3 fatty acids, indicating considerable loss upon thermal processing.
Despite that loss of EPA and DHA, the summed fatty acid categories favoured the canned sample. The total saturated fatty acid values were 24.53 percent for fresh fish, 40.17 percent for pre-cooked mince and 16.79 percent for canned mince, while total monounsaturated and polyunsaturated fatty acid sums were greater in the canned mince than in the other samples. The authors link these shifts to the nutritional lipid quality indices they calculated. The index of atherogenicity, which reflects the balance between saturated and unsaturated fatty acids, was 0.52 for fresh fish, 0.66 for pre-cooked mince and just 0.13 for canned mince, all within the reference range of 0.21 to 1.41 reported for fishes. The index of thrombogenicity followed the same pattern, at 0.35, 0.41 and 0.26 respectively, against a fish range of 0.14 to 0.87.
Other lipid indices reinforced the picture. The hypocholesterolemic to hypercholesterolemic ratio, where higher values are preferred, was 2.24 for fresh fish, 1.8 for pre-cooked mince and 8.31 for canned mince. The health-promoting index was 1.9, 1.5 and 7.34 respectively, and the polyunsaturated to saturated fatty acid ratio was 1.4, 0.74 and 3.24, exceeding the globally recommended dietary threshold of 0.45 in all cases. The nutritive value index reached 49.69 in the canned mince compared with 12.76 for fresh fish and 8.17 for pre-cooked mince. Not every index favoured the canned product, however. The fish lipid quality index, which expresses EPA plus DHA as a percentage of total fatty acids, dropped from 27.94 in fresh fish to 6.2 in canned mince, and the EPA plus DHA value fell from 24.85 to 6.05, both consequences of thermal degradation of the long-chain omega-3 fatty acids. The unsaturation index was slightly higher in fresh fish mince, at 226.63 versus 217.21 for canned mince, and the ratio of omega-3 to omega-6 fatty acids fell sharply from 2.71 in fresh fish to 0.12 in the canned sample, reflecting the influx of linoleic acid from the oil.
On the protein side, the canned mince came out ahead across the board. Glutamic acid was the predominant amino acid in all samples, at 3.19, 4.15 and 4.5 grams per 100 grams of sample for fresh, pre-cooked and canned mince respectively, while leucine was the major essential amino acid at 1.35, 1.75 and 2.01 grams per 100 grams. Significantly different amino acid levels between the three products were observed for threonine, valine, methionine, phenylalanine, isoleucine, proline and tryptophan, and in most cases the canned product contained the higher amounts. The authors suggest this reflects the higher protein content of the canned mince. The ratio of essential to total amino acids exceeded the 40 percent threshold that defines good quality protein under the FAO/WHO reference model in every sample, reaching 43.9 percent in the canned mince, and the essential to non-essential amino acid ratio exceeded 60 percent in all cases, peaking at 78.47 percent for the canned product.
The computed protein quality indices told a consistent story. The essential amino acid index, which measures the resemblance of the sample protein to whole egg reference protein, rose from 16.93 in fresh fish to 26.33 in canned mince. The nutritional index climbed from 2.81 to 6.81, biological value from 6.76 to 16.99, and the three predicted protein efficiency ratio equations all gave their highest values for the canned mince, at 0.19, 0.34 and 1.22 for PER1, PER2 and PER3 respectively. Chemical scoring against the whole egg protein model identified methionine and cystine as the first limiting amino acids in the samples, although all chemical score values exceeded 0.6, and those for isoleucine, leucine, lysine and tryptophan in fresh and canned mince approached one. Under the amino acid score system, which uses the FAO/WHO ideal protein as its reference, every essential amino acid scored above 130, so no limiting amino acid was identified by that method. The authors attribute the discrepancy between the two scoring systems to their different reference models.
Mineral analysis by inductively coupled plasma optical emission spectrometry showed potassium as the predominant macro mineral in all samples, at 4755.63, 3997.75 and 3962.32 parts per million for fresh, pre-cooked and canned mince respectively. Significantly different levels between the sample types were observed for calcium, magnesium and phosphorous, with calcium and magnesium highest in the canned mince and phosphorous highest in the pre-cooked mince. The authors note that thermal processing resulted in some loss of mineral content overall, even though the canned sample retained an optimum mineral profile.
The safety assessment focused on mercury, arsenic, cadmium, lead and tin. Mercury was below detection limits in every sample, well under the USFDA maximum allowable level of 1 part per million in fish. Lead and cadmium were below detection in fresh and pre-cooked mince and appeared only at very low levels in canned mince, at 0.02 and 0.01 parts per million respectively, far beneath the FAO/WHO tolerable cadmium intake of roughly 60 to 70 micrograms per day and the reference dose for lead of 3.57 micrograms per kilogram of body weight per day. Arsenic and tin levels also fell far below their respective permissible limits of 76 and 200 parts per million. When these contaminant levels were combined with essential amino acid and essential fatty acid recommendations into hazard quotient benefit-risk ratios, all values came out below one for all three sample types, the threshold below which intake is considered to confer net benefit rather than hazard. The authors conclude that canning could serve as an efficient technique to deliver the nutritional benefits of this underutilized species throughout the year, while acknowledging that the omega-3 losses mean fresh mahi-mahi remains the richer source of EPA and DHA.
Subject of Research: Thermal processing effects on the nutritional profile and heavy-metal benefit-risk ratios of mahi-mahi
Article Title: Effect of thermal processing on the nutritional profile and benefit- risk ratios of Coryphaena hippurus
Article References: Rasheeda, M., Mohan, C. O., Remya, S., Kishore, P., & Bindu, J. (2026). Effect of thermal processing on the nutritional profile and benefit- risk ratios of Coryphaena hippurus. Food Safety and Risk, 13(1), Article 37. https://doi.org/10.1186/s40550-026-00152-2
Image Credits: AI Generated
DOI: 10.1186/s40550-026-00152-2
Keywords: mahi-mahi, Coryphaena hippurus, thermal processing, canning, protein quality, fatty acid profile, lipid quality indices, heavy metals, food safety, amino acids, omega-3, benefit-risk ratio
News Source: Alan Morgan. (October 29, 2026). Canning Mahi-Mahi Boosts Protein and Lipid Quality Scores While Heavy Metals Stay Low. Scienmag.
