Abstract
The objectives of this thesis were to develop formulations and processing specifications for two types of cooked meat patties made with novel mixtures of squid and beef, and to design and verify a safe thermal processing regime that could be achieved under the available manufacturing conditions.
Locally sourced Arrow Squid (Nototodarus sloanii) was trialled for process suitability in patty mixtures. Lower cost squid fins were unsuitable due to presence of skin pigments causing pink discoloration and the presence of hard textured fragments of squid pen material. Second grade frozen skinned squid tubes with uniform white colour and absence of pen were selected and used in formulations.
Two types of cooked squid and beef patty products were developed: Squid and Beef Nuggets were produced by mixing together ground beef and ground squid tubes with other ingredients and forming into slightly oval shaped pieces (nuggets). Product dimensions were approximately 55mm x 40mm x 15mm thick and 24g per piece. The formulation was composed of ground squid tubes (39.0%), ground beef (23.8%) and a mixture of other non-meat ingredients (37.2%).
Squid and Beef Bites were produced by co-extruding an outer casing mixture of ground squid tubes and other ingredients with an inner filling of ground beef patty mixture. The Bites were co-extruded on a Rheon forming machine and formed into bite sized pieces. Product dimensions were approximately 60mm x 60mm x 23mm thick and 60g per piece. The formulation was composed of ground squid tubes (44.9%), ground beef (21.2%) and other non-meat ingredients (33.9%).
Both Nuggets and Bites were cooked on an electrically heated continuous contact belt grill cooker. Cooking was followed immediately by cooling and individually quick freezing the Nuggets or Bites in a blast spiral freezer. Products were packed as free flow pieces in polyethylene lined cardboard boxes and stored frozen below -18 ºC.
A consumer acceptance study was conducted with 85 consumers. The squid and beef Nuggets and Bites were evaluated after reheating for overall liking, appearance, smell, texture and taste. A 90mm anchored line scale (where 1 = dislike extremely and 9 = like extremely) was used to rate the products. The mean overall liking scores for Bites and Nuggets were 6.63±SD2.48 and 5.9±SD2.02 respectively. A Student t-test determined there was a significant difference at the 95% confidence level for overall liking. Similar ratings were found for other attributes in the test, with appearance scoring higher for the Bites than for the Nuggets. The results indicated a ‘like slightly’ response. Further analysis of the distribution frequency of the scores revealed 69.2% of respondents rated Bites with scores of 6 or higher on the scale, while 50.6% rated Nuggets with scores of 6 or higher. This was considered a reasonable level of liking for the novel products with the Bites being slightly more preferred than Nuggets.
Nutritionally, the squid and beef formulations had a low fat content of 4 - 6%, protein content of 14-15% and carbohydrate content of 9-11%. Squid and beef mixtures were found to have low cooking losses (not more than 5%). Costing analysis showed that wholesale prices for the Bites and Nuggets compared favourably with other frozen food service products. Bites and Nuggets were estimated to wholesale for around $7/kg while other available frozen convenience seafood products wholesale prices were found to be between $7.50/kg for ‘crab and fish bites’ to $ 11.25/kg for seafood finger food. Despite the positive competitive position of the indicative wholesale costings for the squid and beef products, the second grade squid tube raw material priced at $4.50/Kg was expensive for use in patty products, especially when compared to the cost of beef trimmings which ranged from $1.75/kg for fatty grade to $3.00/kg for lean grade. Optimization for cost reduction purposes was recommended.
A safe thermal regime specifically designed for the squid and beef mixture used in the Nuggets was determined. Thermal death time (TDT) experiments were conducted to determine D values for Listeria spp. in the Nugget mixture. Listeria was selected because it had been detected on the raw material and because it is reported to have higher heat resistance than other pathogens of concern in meat patties, such as E.coli and Salmonella spp. Thermal inactivation of Listeria therefore is indicative of destruction of other pathogenic microorganisms. The D60 value determined for L.monocytogenes in the Nugget mixture was 6.14 minutes and the z value was 6.16 ºC. The values obtained for D60 and z in the Nugget mixture concurred with a typical range reported in the scientific literature for 11 different meat products.
Based on the results of the TDT experiments, the thermal regime was specified for the safe processing of squid and beef patties as 69.4οC for a minimum of 97 seconds. This regime was sufficient to provide a 9.0-D thermal reduction treatment. A verification trial conducted under factory processing conditions with a variety of meat patty products confirmed the required 9.0-D thermal regime for Listeria spp. was achievable.
A process capability index (Cp) for the critical end-point core temperature achieved during patty manufacturing using the continuous belt grill cooker was calculated using data from a previous study. The resulting Cp was found to be unacceptably low at 0.44. Consequently, a wide tolerance for patty endpoint core temperatures for the squid and beef products was specified at 75 ºC ± 6 ºC. A major source of variability associated with the belt grill cooker was identified and it was recommended that the process capability be re-determined after problem rectification. A Cp of 1.33 or higher was recommended which would enable tighter temperature tolerances to be specified.
Formulations for two new pre-cooked frozen squid and beef patty products, design and verification of a safe thermal process for the patties and improved understanding of the performance aspects of a belt grill cooker’s thermal processing capability were the technical achievements resulting from this project. Further research into how to lower the cost and investigate how the composition and functional properties of Arrow Squid (Nototodarus sloanii) could be utilized in further processed meat product mixtures was recommended.