Effect Of Maillard Reaction On Protein Aggregates In High Protein Intermediate Moisture Food

One prominent problem of high protein containing intermediate moisture foods (IMFs) is the hardening of texture during storage, making the products inedible and limiting the shelf life. In high protein IMFs, whey proteins are often used as protein source and high fructose corn syrup is also a common ingredient as sweetener and humectant. Therefore, Maillard reaction is prone to occur in this food system, which would probably induce aggregating of protein and lead to the hardening of texture. The objective of this research was to study the effects of Maillard reaction on the texture of high-protein containing intermediate moisture foods.Firstly, this study tried to reveal the effect of Maillard reaction on the texture of IMFs and illustrate its mechanism. The high protein intermediate moisture model systems contained reducing sugar consisted of whey protein, fructose, glycerol and water, while in the control systems, fructose were replaced by sorbitol. The two model systems were stored at 25℃, 35℃and 45℃for 45 days. Progress of Maillard reaction was measured by the browning assay, the soluble aggregation of proteins was investigated by SDS-PAGE, and the insoluble protein aggregates were calculated by measuring the changes of protein solubility. Meanwhile, textural changes in model systems were studied by texture analyzer throughout the storage period. The results indicated that significant Maillard reaction were occurred in high protein IMFs containing reducing sugar, leading to aggregating of proteins, which further contributed to the hardened texture.Secondly, the effects of whey protein categories on the Maillard reaction of high protein IMFs were investigated. Three model systems consisting of whey protein/β-lactoglobulin /α-lactalbumin, fructose, glycerol and water were established, and stored at 25℃and 45℃for 49 days. Progress of Maillard reaction and aggregation of proteins were measured. Further -more, changes in protein glycation were monitored by LC-ESI/TOF/MS. It showed that the browning rate ofβ-lactoglobulin were higher than that ofα-lactalbumin, andβ-lactoglobulin were more liable to be glycated and form covalent aggregates, which suggested thatβ-lactoglobulin were more reactive thanα-lactalbumin to the Maillard glycation by fructose.At last, the effects of different reducing sugars on the Maillard reaction of high protein IMFs were compared. Two model system composingβ-lactoglobulin, glucose/fructose, glycerol and water were used, while in the control systems, the reducing sugars were replaced by sorbitol. All the three systems were stored at 25℃and 35℃for 49 days. Progress of Maillard reaction, soluble protein aggregates and changes in protein glycation were measured. The results showed that the browning rate of glucose model system was much higher than that of fructose model system, protein aggregation were more intensive in glucose model system and the glycation extents in glucose model system were also higher.