ABSTRACT
In recent years, China has become an increasingly important and the largest chestnut producer in the world. This study aimed to evaluate the nutritional value and microbiological quality of the roasted freeze-dried Chinese chestnut (Castanea mollissima) (RFDC) coated with dark chocolate (DCC) and milk chocolate (MCC) for industrial use and commercial consumption. Chocolate coating significantly improved the nutritional value of chestnut. RFDC had high levels of starch (66.23%) and fibers (3.85%) while DCC and MCC contained significantly high amounts of sucrose, protein, fat and minerals. Furthermore, the protein content doubled in MCC rather than in DCC. This could be attributed to the different formulations in the two products. Milk powder and whey protein constituted the source of protein in MCC while cocoa powder added to MCC formulation constituted an additional source of minerals. The amino acid profile showed differences in amino acid composition related to the sample's protein content, indicating their good nutritional quality. The moisture contents in all RFDC, DCC and MCC were suitable for industrial processing. These results provide information about the additional nutrients of chocolate-coated chestnut and confirm that the product is an interesting nutritional food. The combination of freeze-drying and chocolate-coating generally results in greater reductions on microbiological loads, extending shelf life of harvested chestnut for commercial application. This is an alternative strategy to add value to chestnut, minimizing the significant losses in harvested fruits and providing a wider range of choices of new products to the consumer disposal.
Subject(s)
Cacao , Chemistry , Microbiology , China , Fagaceae , Chemistry , Microbiology , Food Analysis , Food Handling , Methods , Food Microbiology , Food Packaging , Methods , Fruit , Chemistry , Microbiology , Nutritive ValueABSTRACT
In this paper, a colorimetric method with high sensitivity, reproducibility and low cost for determining glutamate decarboxylase (GAD) activity was developed based on Berthelot reaction. The optimum substrate system is 0.2 mol/L MacIlvaine buffer pH4.7, containing 0.1 mmol/L pyridoxal phosphate (PLP) and 10 mmol/L L-monosodium glutamate (L-MSG). The reaction mixture consisted of 200 ?L substrate solution and 1～100 ?L enzyme preparation from lactic acid bacteria and was incubated at 30℃. The enzymatic reaction was terminated by immersion in ice-water and addition of 200 ?L 0.2 mol/L sodium borate buffer, pH9.0, then 1 mL 6% phenol solution and 400 ?L sodium hypochloride were added. Color development was carried out in boiling water for 10 min then immediately put in ice-water bath for 20 min. The optical density is read at 630 nm. ?-aminobutyric acid (GABA) produced was calculated using the standard curve. Applications of the method in GAD studies were discussed.