Synergistic effects of processing parameters on the biochemical and physical properties of tofu made from yellow field pea (Pisum sativum), as determined by response surface methodology.

Peas are an underutilized crop that do not require allergen labeling and are rarely genetically modified. Peas contain less protein than soy and vary in protein composition. Because peas contain more starch than soy and less lipids, an alternative procedure for pea tofu production needs to be developed to prevent excessive starch gelatinization while promoting curd development. To accomplish this, a response surface model design was utilized to determine optimal oil addition, cook time, and salt concentration. Treatment ranges were from 0.0% to 4.2% for oil addition, 60-134 min for cook time, and 5.0%-9.2% for MgCl2 addition. Treatments had varying effects on tofu texture. Cook time was directly proportional to the hardness and could be used to match the soft, firm, and extra firm texture targets of conventional soy tofu. Protein secondary structure was not related to gel strength, indicating a system with synergies between multiple components other than protein. This research will help satisfy the growing demand for alternatives to soy-based foods.

Effect of Processing Conditions, Biochemical Properties, and Microstructure on Tofu Production from Yellow Field Peas (Pisum sativum).

Tofu, made by coagulating soy milk, is a nutritious food originating in China and is widely consumed globally. Due to allergenicity and consumer perceptions of genetically modified organisms, consumer demand for soy alternatives is increasing. In this study, tofu was made from yellow split peas (Pisum sativum). Effects of pasteurization, fat addition, and curd disruption followed by repressing were studied. Here, disruption was not a chemical disruption, rather a physical disruption of protein curds. Pasteurization alone led to increased uptake of water and nonviable tofus. Disrupted samples became firmer with pasteurization. Texture profile analysis indicated that disruption followed by pasteurization improved hardness from approximately 175 g force from the control, to approximately 325 g force for disrupted + pasteurizated samples without fat addition. A similar trend was observed for samples with fat added, where hardness increased from approximately 50 g force to approximately 75 g force. Fourier-transform infrared spectroscopy of the amide I region showed that an increase of ß-sheet structures led to increased hardness. The shifts in ß-sheet structures followed the same trends as surface hydrophobicity. Surface hydrophobicity decreased with pasteurization and increased with disruption. Molecular weight analysis showed that shear (from disruption) and heat separately degraded the proteins into smaller polypeptides exposing hydrophobic interiors. Changes to biochemical parameters, such as protein secondary structure and exposure of protein hydrophobic regions, allowed for tofu to be made from yellow field peas. PRACTICAL APPLICATION: This study provides critical information and a means to produce pea-based soy-free tofu.