330: Cool Hardening of High Moisture Meat Analogs: Effects on Texture and Post-Extrusion Processing

Introduction

Meat analogs produced via high-moisture extrusion are of high scientific and industrial interest. However, challenges remain to transform extrudates into consumer products. As extrudates proceed to subsequent unit operations, understanding of the cooling profile and related extrudate properties is necessary to design appropriate cooling and conveying systems. This study evaluates the cooling profile and properties of extrudate, and the effect on a pertinent unit operation, product dicing.

Methods

Pea protein isolate was extruded through a Coperion® ZSK-27 twin screw extruder with 62% moisture and 20 kg/h throughput. Barrels were heated to 60, 80, 80, 100, 100, 135, 130, and 100°C, respectively, before entering a cooling die at a temperature of 65°C. Extrudate was collected directly from the cooling die in 15 mm lengths and either: (1) evaluated for full cooling temperature using a wireless thermocouple, (2) immediately analyzed, or (3) placed on grated racks and cooled to approximately 55°C, 37°C, or 21°C. For immediate as well as cooled samples, temperature was taken in middle of sample prior to texture profile analysis, shear analysis, dicing, or packaging for moisture content. For diced samples, all the pieces were collected, and the weight of each piece larger than 1 cm in any dimension was recorded. Extrudates destined for moisture content were placed in air and watertight bags until time of measurement.

Results

The temperature of extruded slab rapidly decreased following extrusion, before temperature decrease plateaued at approximately 1.5 h following extrusion. Throughout the cooling period, sample hardness increased by 15 N and shear strength increased by 68 N. This appears to be due in part to the reduction in moisture content of the slab throughout cooling, as moisture decreased from 63% of the product to 61%. Despite this loss, piece weight variability was unaffected by dice temperature.

Significance

Extruded slab cools slowly, and as it cools the product properties changes. This effect has not been previously documented for the dicing behavior immediately following extrusion. Knowledge of these properties can reduce production cost and time for high-moisture extruded products, as products can undergo immediate size reduction without needing to expend time or energy to facilitate cooling.

Authors: Audrey Searing Hettel, Halak Mehta, Sochannet Chheneg, Dharmendra Mishra