The influence of temperature on the foaming of milk

The effect of temperature (5–85 °C) on the foaming properties of cows' milk was investigated. The foaming properties of milk as a function of temperature varied considerably depending on fat content and the processing conditions used in manufacture. Skim milk foams were most stable when formed at 45 °C. Milk fat had a detrimental effect on foam formation and stability of whole milk especially in the temperature range 15–45 °C. The detrimental effects of milk fat on foaming properties were reduced by homogenization and ultra-high-temperature (UHT) treatment. No correlation was observed between foam formation and surface tension of whole milk in the temperature range15–45 °C. There was a pronounced difference in the bubble size distributions of whole milk and skim milk especially at half-life of the foams. Bubbles in whole milk foams were smaller and showed a higher degree of rupture as a result of coalescence than those in skim milk foams

Polyphenol metabolites in biological fluids as potential biomarkers to assess their dietary intake

Polyphenols are abundant in many fruits, vegetables and derived beverages and make significant nutritional contributions to the human diet. Epidemiological studies have shown that a polyphenol-rich diet is associated with a decreased risk of developing certain chronic diseases such as diabetes and heart disease. Polyphenol metabolites in body tissues and fluids may provide valuable information regarding the intake of dietary polyphenols (types and amounts) as well as their biological relevance in disease prevention. The usefulness, but also limitations, of polyphenol metabolites as biological biomarkers to assess the intake of dietary polyphenols is presented

Studies on Whey Protein Concentrates. 1. Compositional and Thermal Properties

Cheddar-cheese-type whey protein concentrates were studied for their compositional and thermal attributes. The samples were prepared from three milk systems, namely, skim milk, whole milk, and skim milk enriched with buttermilk. The concentrates from skim milk were lower in all fat components and higher in proteins, except for the membrane-associated protein. The buttermilk-enriched samples had the most membrane-associated components. The concentrates from whole milk and buttermilk-enriched, skim milk were similar in protein composition, except for membrane-associated protein. The whole milk samples had the highest concentrations of total and free fat components. Lactose content and mineral composition were similar for the three types of concentrates. Thermal properties and denaturation kinetics were examined by differential scanning calorimetry. The samples exhibited a single broad endothermic peak with the denaturation temperature near 76°C and the enthalpy ranging from 1.86 to 2.16 cal/g. The concentrates from skim milk had higher denaturation enthalpy, whereas the concentrates from buttermilk-enriched, skim milk had slightly higher thermal stability. The overall denaturation process for whey proteins followed the reaction order n = 1.5 with an activation energy ranging from 217 to 251 kJ/mol. The thermal properties were observed to be related to a number of compositional factors. The denaturation enthalpy was positively correlated with β-lactoglobulin and protein content, and negatively correlated with bound fat, membrane protein, and membrane-associated lipid components. The denaturation temperature correlated positively with phospholipid content, and the onset denaturation temperature correlated positively with iron content

Folate Content of Asian Vegetables

Folates are one of the most nutritionally significant vitamins. Natural sources of folate are reportedly more effective than supplementation or fortification with folic acid. Green leafy vegetables are excellent sources of folates which occur naturally in many forms or vitamers. With an expanding range of Asian vegetables and increasing consumer awareness and acceptance, it is timely to present information on the health attributes of these vegetables

Microbiological assay for folate content: limitations and improvements

The microbiological assay is currently the ‘gold standard’ assay for total folate analysis and is the only method accepted by the AOAC International. It is the accepted standard reference method for Australian and international food composition tables and nutrient databases. Although this assay is widely used, its limitations are wellrecognised. In this study, considerable research effort was dedicated to ensuring that the microbiological assay was optimised and rigorously validated for the analysis of folates in a vegetable matrix to ensure a high level of repeatability, reproducibility and fitness for use as a reference method. As a result, an improved microbiological assay for the analysis of total folates in vegetables was developed. Comparative studies with other laboratories experienced in these assays were undertaken