适宜转换点提高罗氏沼虾真空冷冻-微波真空联合干燥速率与品质

    Appropriate conversion point enhancing drying rate and quality attributes of Macrobrachium rosenbergii meat during vacuum freezing-microwave vacuum combined drying

    • 摘要: 罗氏沼虾是一种具有重要商业价值的淡水虾,其营养丰富、肉质鲜美,但其含水率高,富含多种内源酶,极易腐败变质,干燥是水产品高值化加工利用的重要途径。为解决单一真空冷冻干燥(vacuum freeze drying,VFD)效率低、能耗高等缺陷,充分利用微波真空干燥(microwave vacuum drying,MVD)热质传递效率高优势,获得优质罗氏沼虾干制品,该研究以罗氏沼虾虾仁为原料,基于变功率控温微波加载策略,探究不同转换点湿基含水率(70%、60%、50%、40%和30%)对VFD-MVD联合干燥对罗氏沼虾虾仁的干燥速率、比能耗、微观结构和品质特性的影响规律,并以单一VFD的罗氏沼虾虾仁作为对照组(control check,CK)。结果表明,与CK相比,VFD-MVD联合干燥处理组的比能耗降低了35.20%~79.11%,平均干燥速率由0.28 kg/kg/h提高至0.43~1.39 kg/kg/h。VFD-MVD联合干燥处理组中,当湿基含水率为40%时,罗氏沼虾虾仁干制品结构更为疏松、多孔;虾青素含量最高,为2.40 μg/g;蛋白质和脂质氧化程度较低,游离巯基和硫代巴比妥酸值分别为0.91 μmol/g和0.53 mg/kg(以丙二醛含量计);而且虾仁干制品的总色差ΔE(4.43)、孔隙率(10.91%)、收缩率(0.52%~1.89%)、复水比(5.30)和质构特性等方面表现优异。综上,罗氏沼虾虾仁转换点湿基含水率为40%时,VFD-MVD联合干燥所得虾仁与单一VFD干制品品质接近,同时提高了虾仁的干燥速率,降低了干燥系统的能耗。该研究可为罗氏沼虾虾仁“节能、高效、优质”干燥技术提供理论依据。

       

      Abstract: Macrobrachium rosenbergii is commonly recognized as the giant freshwater prawn or Malaysian prawn. M. rosenbergii has also gained much popularity with the extremely important commercial value, due to its rich nutrition and delicious flavor. Nevertheless, M. rosenbergii is highly susceptible to spoilage at room temperature, due to the high moisture content rich in various endogenous proteases and plentiful microorganisms. Among them, drying can be expected to serve as an important way for the high-value processing and utilization of aquatic products. Vacuum freeze drying (VFD) has been commonly used for high-quality dried aquatic products. However, the application of VFD has been limited in the field of aquatic products drying, including the prolonged processing duration and high energy demand. Microwave vacuum drying (MVD) has promising potential in the food drying field, due to its high heat transfer rate and controllability. This study aimed to fully utilize the merits of the high heat and mass transfer efficiency of MVD. The high quality of dried M. rosenbergii products was achieved by improving the high drying efficiency and low energy consumption of a single VFD. Macrobrachium rosenbergii meat was used as the experimental raw material. A systematic investigation was made to explore the effects of different conversion point moisture content (MC) on a wet basis (viz., 70%, 60%, 50%, 40%, and 30%) of M. rosenbergii meat on the drying rate and specific energy consumption, microstructure properties, and quality. The dehydration of M. rosenbergii meat with VFD alone was also performed for comparison. It was regarded as the control check (CK). The results demonstrated that the specific energy consumption of the VFD-MVD combined drying groups was reduced significantly by 35.20%-79.11% (P<0.05), compared with the CK. The average drying rate of the CK was 0.28 kg/kg/h. But there was a significant increase with the ranging from 0.43 kg/kg/h to 1.39 kg/kg/h, in the combined drying groups. Compared with the rest VFD-MVD in the drying treatment groups, the structure of the dried M. rosenbergii meat was much looser and porous, when the conversion point MC was 40% (wet basis). The retention rate of the astaxanthin content was the highest measurement of 2.40 μg/g. There were the lower oxidation degrees of protein and lipid, where the free hydrosulfuryl and thiobarbituric acid values were (TBARS) measured to be 0.91 μmol/g and 0.53 mg/kg (TBARS is expressed on terms of malondialdehyde content), respectively. Moreover, the combined VFD-MVD drying treatment group with the conversion point MC of 40% also produced the dried products with the superior total color difference (ΔE 4.43), porosity (10.91%), shrinkage rate (ranging from 0.52% to1.89%), rehydration ratio (5.30), and texture properties. In conclusion, the combined VFD-MVD drying was achieved in the dried products with the quality attributes resembling those of the products fabricated by VFD alone, when the conversion point MC of M. rosenbergii meat was 40%. The drying efficiency was significantly enhanced for the lowest energy consumption of the drying system. This finding can provide a theoretical basis for the "energy-saving, high efficiency and superior-quality" drying technology of M. rosenbergii meat.

       

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