Date of Award

Spring 5-5-2023

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Food Science and Human Nutrition

Advisor

Denise I. Skonberg

Second Committee Member

Brianna H. Hughes

Third Committee Member

Jennifer J. Perry

Additional Committee Members

L. Brian Perkins

Abstract

Doryteuthis pealeii (longfin inshore squid) and Illex illecebrosus (Northern shortfin squid) are the two most commercially important species of squid harvested in the United States. They are also the only two species of squid in the world certified sustainable by the Marine Stewardship Council. Despite their pivotal role in the U.S. seafood industry, very little research has been performed on their quality in decades. Two common methods of freezing and secondary processing applied to squid in the U.S. industry are blast-freezing either at sea or on land; and leaving the squid whole, or fully cleaning and then brining them. To date, the effects that these different post-harvest treatments have on these species’ physicochemical qualities have not been reported.

The specific objectives of this research included: (1) exploring the effects of freezing and processing treatments on various physicochemical qualities of the mantles and tentacles of D. pealeii and I. illecebrosus; (2) quantifying the yield of edible material from each species; (3) examining differences in the color of the mantle skin and meat; and (4) identifying relationships between the squid meat color and (a) the condition of its internal organs and (b) its skin color.

The first study explored a wide variety of physicochemical characteristics, including instrumental color and texture, crude protein, moisture, and ash contents, water-holding capacity, salt-soluble protein, and in-vitro protein digestibility, as well as the size and weight of squid and their individual parts. Land-frozen squid were found to be significantly softer, with more soluble protein, and higher in extractible peptides than sea-frozen squid, and processed samples had significantly lower water-holding capacity and protein content than whole samples, signifying greater damage to muscle proteins. Based on these results, freezing at sea and leaving the squid whole appeared to better preserve their quality. The wings, disposed as waste in the industry despite their edibility, were found to comprise ~10% of the whole squid mass for both species; as a currently unutilized part of the squid, the wings present many opportunities for novel development of value-added products.

The second study evaluated the instrumental color of squids’ external and internal mantle meat, exploring relationships between meat color and the color of the skin and the condition of select viscera. Meat color is critical in quality assurance for distribution to different markets, and discoloration leads to substantial revenue and product loss. Significant correlations were discovered between the redness (a* values) and yellowness (b* values) of the skin and the mantle underneath, as well as between the condition of the organs (from “good” to “poor”) and the meat color, where worse-quality organs were associated with increased meat redness and yellowness.

The results from these studies suggest that sea-freezing should be prioritized over land- freezing, especially for I. illecebrosus, and that eviscerating and skinning squid may preserve the quality of their meat.

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