Gelling Properties Of Myofibrillar Protein From Abalone Muscle And Effects Of Thermal Processing On Textural Properties Of Muscle

Abalone yield of China has grown rapidly,and the numbers of abalone muscle food on the market has gradually increased.The eating quality of abalone muscle food mainly includes texture,juiciness,flavor and color,among which texture is the key factor affecting customer’s consumption.Since the texture characteristics of abalone muscles undergo some changes during thermal processing,so it is necessary to study the influencing factors of abalone muscle texture during thermal processing.Firstly,the myofibrillar protein from abalone muscle(AMP)was extracted and the gel-forming ability was investigated.The lowest protein solubility of AMP in distilled water was obtained at pH 5.5,but shifted to a lower pH value by ionic strength.The breaking force and deformation of AMP gel formed at pH 7.0 were 48.00 g and 27.70 mm,respectively,but they could not be detected at pH 5.0 and pH 5.5 due to the low gel-forming ability.Scanning electron microscopy data showed that a coarse and disorder gel containing clusters of agglomerates was observed at pH 5.0 and pH 5.5,but gradual compact network structure was observed in the gel formed at increasing pH.The glass transition temperature(Tg)of AMP gel formed at pH 5.5 was higher than that of AMP,and the Tg of AMP gel was increased with increasing the pH of gel-forming solution.It was found that the unfolding of tertiary structure of AMP at pH 7.0 was easier than that at pH 5.5 through the result of infrared spectra.We therefore conclude that both the solubility and gel-forming ability of AMP are pH dependent.Nextly,the effects of thermal treatment on the texture and proteins of abalone muscle were investigated.Increasing cooking temperature led to higher weight loss and lower protein,sugar and ash,whereas the proportion of water content increased slightly.Samples cooked at higher temperature showed lower hardness values,while the hardness changes with increasing cooking time were different from cooking temperature.Optical microscopic imaging showed more broken muscle fibberls in the middle parts of adductor muscle were found at higher cooking intensity,and the collagen fibrils in the hard parts of the foot were aggregated with increasing cooking time.The results of SDS-PAGE showed that the water-soluble protein aggregated to form macromolecule at 65℃-80℃ and then began to disappear at 95℃.The higher wavenumber of amide A of infrared was found at higher cooking temperature in the water-soluble component,and the value of intensity ratio between amide Ⅰ and amide Ⅱ in the salt-soluble component increasesd with improving cooking intensity.Heat treatment resulted in a decrease of the α-helix content,and an increase or decrease of β-sheets and β-turns content in water-soluble component and salt-soluble component.Therefore,heat treatment can affect the texture changes of abalone muscle.However,the proteins in each component of abalone muscle have different responses to heat treatment.Finally,the effects of steam heating on the microstructure and texture of abalone muscle were investigated.The lowest cooking weight loss of abalone muscle was obtained at 120℃,and the corresponding water content is more higher.However,the temperature of steam heating is more higher,the abalone muscle had the lower of water holding capacity.The fresh abalone muscle had the highest hardness value,which was 9777.47 g.With the increased the temperature of steam heating,the hardness of abalone muscle increased first and then decreased.The results of optical microscopic imaging showed that the muscle fibers in the middle parts of adductor muscle of abalone was gradually broken at increasing the cooking temperature,and the collagen in the hard parts of the foot of abalone muscle was aggregated first and then dissolved.The infrared results showed that the higher temperature,the lower content of the hydrogen bonds between proteins.The protein composition of abalone muscle was changed at increasing the steam heating temperature.Therefore,different steam heating temperatures can change the texture of abalone muscle.In conclusion,the texture of muscle food is dependent on the gelation properties of myofibrillar protein.Defining the performance of myofibrillar protein during gelation is beneficial in maintaining quality and developing muscle food.During thermal processing,different behaviors of proteins responsed to the effects of thermal treatment on the texture characteristics of abalone muscle.Thermal treatment alters the texture of abalone muscle by changing the behavioral characteristics of proteins.