外源酶对发酵羊肉香肠挥发性风味物质的影响

研究外源酶对发酵羊肉香肠挥发性风味物质的影响.通过顶空固相微萃取-气相色谱-质谱联用技术测定发酵羊肉香肠中的挥发性风味物质.结果表明,发酵羊肉香肠中的主要挥发性风味物质为醛类、烃类、醇类和酯类等.对照组和试验组发酵香肠挥发性风味物质的种类和含量存在着一定的差别.     

IDENTIFICATION AND QUANTITATION OF SEVERAL NONVOLATILE ORGANIC ACIDS OF COCOA BEANS

SUMMARY— Organic acids precipitated as lead salts from water extracts of cocoa beans were converted to trimethylsilyl ethers. TMS ethers were then separated and identified using a combined gas chromatograph-mass spectrometer. Citric, phosphoric, lactic, oxalic, malic, tartaric, succinic and gluconic acids were present in every sample examined, irrespective of geographic origin. Five of the acids were quantitated using a GLC procedure which involved the preparation of methyl esters from freeze-dehydrated, water extracts. Concentration ranges found, g/100g beans, were: lactic, 0.11–0.71; oxalic, 0.24–0.43; succinic, 0.02–0.07; malic, 0.02–0.10; citric, 0.56–1.32. Concentrations of lactic acid were lowest and citric acid levels tended to be highest in commercial samples from countries where cocoa beans usually are not subjected to a planned fermentation. These trends were confirmed in an experiment involving beans from Trinidad which had undergone a carefully controlled fermentation. Only minor differences were found in organic acid concentrations between roasted and unroasted cocoa beans.     

ASSESSMENT METHODOLOGY TO PREDICT QUALITY OF COCOA BEANS FOR EXPORT

The existing quality assessment methods for cocoa such as the cut-test and sensory test were evaluated. The results were compared with the fermentation index and color measurement as indirect quality assessment methods. Results of the cut-test score and sensory evaluation methods indicated variability in results and therefore were not adequate to assess bean quality. The fermentation index method was useful to distinguish different bean samples from 5 color categories. The fermentation index related well with other quality parameters, such as pH, reducing sugars, free amino acids, and cocoa color pigments. Direct color measurement had a good relationship with fermentation index, pH, reducing sugars, and free amino acids, as evidenced by high correlation values. Color measurement was appropriate to estimate cocoa bean quality.     

INFLUENCE OF ODOR SOURCES ON THE ODOR AND FLAVOR OF BEEF

Research was conducted to determine the influence of odor sources present in the vicinity of meat during slaughter, storage, shipping and handling, on the odor and flavor of beef. In most cases, outside samples and ground composites scored higher in off-flavor intensity than did inside samples. Fat sample results were similar but exhibited greater variation. Odor scores followed a similar pattern. Ammonia was found the easiest source of odor and flavor to detect; cigarette smoke, butts and ashes, automobile exhaust, kerosene and paint were also easily detected. Spoiled meat could be detected as imparting an off-odor and off-flavor, but the source was not easily identified. Other variables (e.g., silage, soap, rancid grease) showed little evidence of causing off-flavor or off-odor to the meat. The influence of storage time and exposure pre- or post-rigor seemed negligible in most cases.     

INFLUENCE OF FREEZE-DRYING PARAMETERS ON THE RETENTION OF FLAVOR COMPOUNDS OF COFFEE

Freeze-dried coffee powders were evaluated to determine the effect of freezing method and chamber pressure during drying on the retention of coffee flavor components. Headspace gas chromatography revealed at least 14 components of coffee aroma, but minor chromatograph peaks were re moved from consideration, and evaluation was based on the total area of the eight remaining peaks. The results showed that volatile retention was greatest when slowly frozen samples were dried at low chamber pressure. Samples that were foamed prior to slow freezing showed sizably reduced retentions. Slowly frozen samples showed gradually decreasing volatile retention as the pressure increased up to 0.7 torr, and drying at 0.8 torr resulted in a large reduction. Samples which were processed at different chamber pressures so as to give the same powder color showed significant differences in their flavor retention. Almost all the test samples had higher volatile contents than the commercial samples which were tested, though it cannot be sure that this does not reflect differences in coffee extracts.