Date of Award

Summer 8-21-2015

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Food Science and Human Nutrition

Advisor

Denise I. Skonberg

Second Committee Member

Vivian Wu

Third Committee Member

Jason Bolton

Abstract

Research studies have reported the effects of low-temperature sous-vide (LTSV) processing on improving tenderness and succulence of mammalian muscle foods. However, its effects on sea scallop have not been reported. The shucked adductor muscle of wild-caught sea scallop (Placopecten magellanicus) is a high-value seafood recognized for its high quality protein, low calorie content, succulence and tenderness. LTSV processing of sea scallop meat is particularly promising since high temperature cooking can cause severe changes in the structure of its muscle, leading to significant toughening and liquid loss.

The primary objective of this research was to better understand the effects of LTSV processing on the quality, shelf-life, and protein structural changes in sea scallops. Treatments were designed to thermally process sea scallop meat to internal temperatures of 55, 60, and 65ºC against equivalent processing time values aimed at reducing the

target food pathogen, Listeria monocytogenes. In a series of three experiments, triplicate (studies 1 and 2) and quadruplicate (study 3) batches of fresh scallop meats were vacuum-sealed in boilable pouches and assigned to one of four treatments: vacuum-packed chilled raw (control); 55ºC/208 min, 60ºC/45 min, and 65ºC/10 min. Thermocouples were inserted into the geometric center of scallop meats to monitor the temperature during processing, and timing began once scallop internal temperature reached the target set-point. Scallops were immediately cooled to ≤ 3.3ºC and subjected to analyses. In study 1, effects of LTSV processing were evaluated on key meat quality attributes (weight loss, moisture, water holding capacity, instrumental color, and instrumental texture). In study 2, the refrigerated (≤ 2ºC) shelf-life of the four treatments was evaluated over 18 days by microbiological (aerobic plate count and lactic acid bacteria), biochemical (total volatile nitrogen and pH); and, over 19 days by physical analyses (weight loss, instrumental color, and instrumental texture). In the final study, the effects of LTSV processing on various measures of protein denaturation and oxidation (salt soluble protein, Ca2+ATPase activity, and sulfhydryl content) were evaluated.

Key scallop meat quality attributes such as weight loss, water holding capacity, lightness, and hardness were significantly affected by LTSV processing. All of the treatments except for the control did not reach total plate counts of 105 cfu/g until 18 days of storage at ≤ 2ºC. Thermal denaturation of myofibrillar proteins occurred with more extreme effects observed in the 65ºC/10 min treatment, as determined by protein solubility, Ca2+ATPase activity, and sulfhydryl content. Protein denaturation and oxidation were strongly correlated with increased hardness and weight loss, and decreased water holding capacity. The 60ºC/45 min treatment was the best method in

terms of quality, shelf-life and minimizing changes in proteins. Consumer testing to evaluate the sensory appeal of the LTSV processed scallop and its perceived quality warrants future investigation. There is also a need to conduct future inoculation studies to verify the thermal inactivation of the LTSV treatments on L. monocytogenes. LTSV processing is a promising method to thermally process sea scallops, however the industry will need to balance safety requirements with maximizing quality, particularly for this high-value specialty product.

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