Marie Wong

Mapping consumer perceptions of creaminess and liking for liquid dairy products.

Consumer ratings of overall liking and creaminess were compared using internal preference mapping for a range of liquid dairy products. Two dimensions were found to explain ratings of overall liking. The first dimension was related to dairy flavour notes and the texture attributes of mouthcoating, oily/greasy, slipperiness and viscosity and the second dimension was related to the sweet and sour taste of the products plus a number of off-flavours. The same two dimensions were found for creaminess ratings although dimension two had far less significance. A wide variation in consumer liking was found and four segments were identified through cluster analysis. In contrast, there was a consensus in consumer ratings of creaminess, which was related to the fat content of the products tested.

Estimation of Mass Transfer Rates through Hydrophobic Pervaporation Membranes

Abstract In pervaporation of dilute solutions (acids, esters, and ketones) through hydrophobic membranes, mass transfer coefficients increased with temperature in an Arrhenius-like manner. Activation energies and pre-exponential factors were estimated through empirical correlations, allowing estimation of mass transfer coefficients. The activation energy was a function of the heat of sorption and the elastic modulus of the membrane. For low molecular weight compounds, the heat of sorption was the more important of these two factors, whereas the membrane thickness (which influenced the elastic modulus) became more important for larger compounds. The compensation effect allowed pre-exponential factors to be estimated from the activation energies.

Effects of Adding Low Levels of a Disulfide Reducing Agent on the Disulfide Interactions of β-Lactoglobulin and κ-Casein in Skim Milk

Low concentrations of a disulfide reducing agent were added to unheated and heated (80 °C for 30 min) skim milk, with and without added whey protein. The reduction of the β-lactoglobulin and κ-casein disulfide bonds was monitored over time using electrophoresis. The distribution of the proteins between the colloidal and serum phases was also investigated. κ-Casein disulfide bonds were reduced in preference to those of β-lactoglobulin in both unheated and heated skim milk (with or without added whey protein). In addition, in heated skim milk, while the serum κ-casein was reduced more readily than the colloidal κ-casein, the distribution of κ-casein between the two phases was not affected.

Consumption of salmon v. salmon oil capsules: effects on n-3 PUFA and selenium status.

Salmon provides long-chain (LC) n-3 PUFA and Se, which are well recognised for their health benefits. The n-3 and Se status of the New Zealand population is marginal. The objective of the present study was to compare the effects of consuming salmon v. supplementation with salmon oil on LC n-3 and Se status. Healthy volunteers (n 44) were randomly assigned to one of four groups consuming 2 × 120 g servings of salmon/week or 2, 4 or 6 salmon oil capsules/d for 8 weeks. Linear regression analysis predictive models were fitted to the capsule data to predict changes in erythrocyte LC n-3 levels with intakes of LC n-3 from capsules in amounts equivalent to that consumed from salmon. Changes in Se status (plasma Se and whole-blood glutathione peroxidase) were compared between the groups consuming salmon and capsules (three groups combined). Salmon, 2, 4 and 6 capsules provided 0·82, 0·24, 0·47 and 0·69 g/d of LC n-3 fatty acids. Salmon provided 7 μg/d and capsules < 0·02 μg/d of Se. The predictive model (r(2) 0·31, P = 0·001) showed that increases in erythrocyte LC n-3 levels were similar when intakes of 0·82 g/d LC n-3 from salmon or capsules (1·92 (95 % CI 1·35, 2·49) v. 2·32 (95 % 1·76, 2·88) %) were consumed. Plasma Se increased significantly more with salmon than with capsules (12·2 (95 % CI 6·18, 18·12) v. 1·57 (95 % CI - 2·32, 5·45) μg/l, P = 0·01). LC n-3 status was similarly improved with consumption of salmon and capsules, while consuming salmon had the added benefit of increasing Se status. This is of particular relevance to the New Zealand population that has marginal LC n-3 and Se status.

2 – Avocado Oil

Publisher Summary Avocado (Persea americana Mil.) is a subtropical tree that is relatively frost-sensitive and grows to a height of 5–30 m. The fleshy fruit are borne yearly from the current seasons wood and the green fruit ripen only after being harvested. Avocado oil is obtained from the flesh fruit and is a relatively new arrival in culinary circles. The predominant uses of avocado oil are in the cosmetic industry because of its stability and high level of vitamin E (α-tocopherol). The bulk of avocado oil is extracted by relatively harsh methods like high temperature and solvent extraction, typically followed by standard refining steps. The ultimate market of the oil generally dictates the fruit quality required. For the production of good-quality cold-pressed oil, the fruit must be relatively sound with mainly cosmetic-quality issues or too small for sale. Cold-pressed avocado oil is a new product with significant production, commercialization, and marketing only occurring in the 21st century. Avocado oil is a high-value oil with excellent qualities for both culinary and cosmetic uses.

The protein interactions and rheological properties of skim milk heated in the presence of low levels of reducing agent

Skim milk with low levels of added β-mercaptoethanol (SM-ME) and untreated skim milk (SM) were heated and then made into acid gels. Acid gels prepared from heated SM-ME had markedly higher firmness and contained more protein connections than acid gels prepared from heated SM. Electrophoretic analyses of the milks showed that the levels of β-lactoglobulin and α-lactalbumin associated with the casein micelles increased with increasing β-ME concentration. The levels of disulphide-linked whey proteins were higher in SM-ME than in SM. This suggested that there may be higher levels of initiators for thiol-disulphide exchange reactions, resulting in an increase in the rate of the reactions and the formation of greater numbers of small aggregates, in SM-ME than in SM. Consequently, acid gels made from SM-ME may have more bonds and more particles participating in the network, resulting in firmer gels, than acid gels made from SM.

Modern Aqueous Oil Extraction—Centrifugation Systems for Olive and Avocado Oils

Publisher Summary Aqueous oil extraction is a technology with great potential in the oil industry because it offers a number of advantages compared to conventional solvent extraction. This chapter discusses the aqueous extraction process. The aqueous extraction process has already been used successfully and commercially for virgin olive oil and avocado oil production. The aqueous extraction process has made recent advances to become a modern technology with the incorporation of modern efficient separation techniques and the application of processing aids such as exogenous enzymes. Each raw material source requires different handling practices prior to the formation of a pulp-water-oil paste, which is mixed to aid oil release from the oil containing cells. After this point, very similar technologies can be used to separate the oil from the aqueous phase and solids. Aqueous extraction of oils combined with centrifugation can produce high quality oils with unique and desirable organoleptic characteristics without the use of solvents. With good processing management, the production of waste streams can also be reduced.