Lactose and galactose content in cheese results in overestimation of moisture by vacuum oven and microwave methods.

Moisture determination in cheese is a critical test for regulatory compliance, functionality, and economic reasons. Common methods for moisture determination in cheese rely upon the thermal volatilization of water from cheese and calculation of moisture content based on the resulting loss of mass. Residual sugars, such as lactose and galactose, are commonly present in cheeses at levels ranging from trace amounts to 5%. These sugars are capable of reacting with other compounds in cheese, especially under the thermal conditions required for moisture determination, to yield volatile reaction products. The hypothesis of this work is that residual sugars in cheese will be converted into volatile compounds over the course of moisture determination at a level sufficient to result in overestimated cheese moisture. A full-factorial statistical design was used to evaluate the effects of cheese type, sugar type, sugar level, method type, and all interactions. Cheddar and low-moisture, part-skim (LMPS) Mozzarella cheeses were prepared with 1, 3, and 5% added lactose or galactose, and subjected to either vacuum oven or microwave-based moisture determination methods. Browning index and colorimetry were measured to characterize the color and extent of browning. Volatile analyses were performed to provide chemical evidence of the reactions proposed. The presence of residual sugars altered moisture calculations as a function of cheese type, sugar type, sugar level, method type, and numerous interactions. At higher concentrations of residual sugar, the percentage moisture determinations were increased by values of up to 1.8. Measures of browning reactions, including browning index, colorimetry, and volatile profiles demonstrate that the proposed browning reactions played a causative role. This work establishes the need to consider cheese type, sugar type, sugar levels, and method type as a means of more accurately determining moisture levels.

Invited review: Environmental impacts of dairy processing and products: a review.

The objective of this review is to summarize research efforts and case studies to date of the environmental impacts from dairy processing. The pervasiveness of greenhouse gas emission, water use, consumer waste, and other environmental impacts of dairy are described. An outline of the method of choice, the life cycle assessment, for conducting research and deciding appropriate allocation of the impacts is provided. Specific research examples in dairy processing highlight how the representative final product is associated with environmental impacts to air, water, and land. The primary conclusion from the study was the usefulness of life cycle assessment methodology and the need for further research due to limited studies, variable data, and the magnitude of environmental impact.

Gas chromatographic determination of cholesterol in egg products.

A method has been developed for quantification of cholesterol in fresh egg yolks, spray-dried egg yolks, fresh whole eggs, and spray-dried whole eggs. The method uses saponification followed by petroleum ether extraction of cholesterol. Separation of organic and aqueous layers is enhanced by sodium chloride. Petroleum ether extracts are dried under nitrogen and redissolved in chloroform-methanol (2 + 1) for injection into a gas chromatograph. Cholesterol is separated and quantitated on a high temperature capillary column coated with 5% diphenyl and 95% dimethyl polysilicone crosslinked gum. The method was compared with the current AOAC method 17.017-17.022, and results indicated no significant difference (alpha = 0.05). However, the proposed method allowed separation and analysis of 16 samples in 7 h while the current AOAC method allowed separation and analysis of only 4 samples in 9 h.

Effects of exocrine pancreatic secretions on hyperthermic injury of rat small intestine.

The influence of the exocrine pancreatic secretions on development of small intestinal injury following localized hyperthermia was studied. In male Holtzman rats the excretory pancreatic ducts were occluded with metal hemostatic clips. An intraperitoneal injection of [3H]thymidine was given 3 weeks later. Three or 48 h after the injection a 10 cm segment of small intestine was exteriorized through a midline abdominal incision and heated at 38.0 degrees C, 42.5 degrees C, or 43.5 degrees C for 45 min. Intestinal damage was assessed 24 h after hyperthermia. The following four endpoints were used: histopathological injury score, the number of villi per intestinal circumference, the number of labelled epithelial cells in fixed areas of autoradiographic specimens, and incorporation of [3H]thymidine as determined by liquid scintillation counting. The correlation of results among the four methods of assessment was highly significant. The autoradiography data showed better correlation with both morphological parameters than the results of liquid scintillation counting. There was significantly less damage in heated segments from pancreatic duct-occluded animals than in segments from sham-operated controls. When hyperthermic injury was assessed morphologically the protection conferred by pancreatic duct occlusion was equivalent to lowering the temperature of heating by 1 degree C. It is concluded that morphological criteria may be superior to endpoints based on [3H]thymidine incorporation for assessment of hyperthermic injury in rat small intestine. Reducing the intraluminal pancreatic secretions appears to confer significant protection from small bowel injury after localized hyperthermia.