| Oysters is one of the major aquaculture shellfish in China.It is very popular due to its well taste and high nutritional value.Generally,oysters is mainly consumed without any processing.Because of their meat is soft,easy to corrupt,not freeze-resistant,can not be long-term storage and long-distance transportation.Fresh oysters can only be sold in the main production areas,which limits the development of oyster industrialization.Drying is an important means to prolong the storage period of food.It is urgent to find a drying technology that is low-cost and can obtain quality dry products.Cold-air drying is a technology for processing products in a low-temperature and low-humidity environment.The oysters dried in this way are favored by consumers for their unique flavor,rich nutrition and storage resistance.In this paper,fresh oysters were used as materials to study the cold-air drying process,analyze the main flavoring substances in its dry products,and predict the shelf life of dried oysters by studying the storage stability of the dried products,which provided new information and theoretical support for the exploitation and utilization of oyster resources.The main contents and results are as follows:1.Studied the cold-air drying process of oysters and established the kinetic model.Fresh oysters were dried at different temperatures andrelative humidity conditions.The drying characteristics,rehydration,color,TVB-N value,TBA value and total number of colonies of dried oysters were compared and analyzed.According to the experimental data,the relationship between the moisture ratio and drying time of oyster cold-air drying was established,and the mathematical model from five common thin-layer drying mathematical models was fitted and analyzed.The results showed that when the drying temperature was 20℃ and the ambient relative humidity was 55%,the quality of oyster dried by cold air was the best.The Page model was the most suitable for describing the dynamics of oyster cold-air drying.2.Comparative analysis the non-volatile taste active compounds of oyster cold-air and hot-air dried products.In terms of fatty acids,free amino acids and taste-presenting nucleotides in dried oyster products prepared by two drying methods were analyzed.The content of palmitic acid(C16:0)was the highest among the two kinds of dried products,accounting for more than 65% of saturated fatty acids,followed by stearic acid.The contents of EPA and DHA in polyunsaturated fatty acids were relatively high among the two kinds of dried products,and the total contents of EPA and DHA in oyster cold-air dried products is higher,which is 4558.40 mg/kg.The content of saturated fatty acid and polyunsaturated fatty acid in the two dry products was not much different,but the ∑PUFA/∑SFA value in cold-air dried oyster products was 0.87,which was significantly higher than the hot-air dried products.In free amino acids,two types of dried products more tasty amino acids differ not quite.The content of total amino acids in cold air dried oyster products was higher,and the higher content of taste amino acids were:glutamic acid(Glu),arginine,(Arg),proline(Pro),aspartic acid(Asp),lysine(Lys),its content are in more than 40 mg/100 g,and the TAV values of glutamic acid,lysine and arginine were all higher than 1,Among the taste nucleotide,AMP was found to be up to 80.14 mg/100 g in hot-air dried products and 64.98 mg/100 g in cold-air-dried products,However,the contents of GMP and IMP with strong freshness in cold-air dried products were on the high side,and the TAV values of GMP and AMP were all greater than 1.The EUC values of oyster and hot-air dried products were 69.64 g MSG/100 g and 51.89 g MSG/100 g,oyster cold-air dried products is definitely too high,which indicated that the dried oyster products prepared by cold-air drying method had the rich flavor.3.Studied the storage characteristics of dried oyster products and predict their shelf life.The dried products were stored at different temperatures(25℃,35℃,45℃)to explore the changes of TVB-N value,TBA value and total number of colonies with storage time,and the quality change law was studied to establish the shelf life prediction model of dried oyster products.The results showed that the total colony count and TBA value of oyster dry products increased slowly during storage,and the TVB-N value increased with the increase of temperature and storage time.Therefore,the TVB-N value was selected as the shelf-life prediction index,established the corresponding first-order kinetic equation,and predicted the shelf life of cold-air dried oyster products which stored at 25 ℃,35 ℃ and 45 ℃ was 428 d,158 d,62 d. |
