Development and evaluation of a photographic atlas as a tool for dietary assessment studies in Middle East cultures.

OBJECTIVE: To assess the errors between estimates of amounts based on photographs and actual quantities of food presented to adults or eaten on the previous day. DESIGN: A photographic atlas was constructed by taking digital photographs of three pre-weighed portion sizes of 212 traditional Lebanese dishes. In a first approach, ten portions of real pre-weighed foods were assessed using the photographic atlas. In a second approach, the participants weighed all foods consumed at one meal and recalled the amount of food that was eaten the previous day using the photographic atlas. Differences between actual quantities and estimation were assessed using a signed rank test (P < 0·05). Spearman's correlation coefficients and bias (Bland-Altman plot) between the methods were calculated. SETTING: Lebanese university canteen and Lebanese homes. SUBJECTS: Forty adults (twenty males, twenty females) completed the first protocol and fifty adults (twenty-five males, twenty-five females) completed the second protocol; all were volunteers aged 21 to 62 years. RESULTS: Mean differences between actual and estimated portion sizes by photographs were between -13·1 % and +24·5 % when pre-weighed foods were presented, and between -10·4 % and +3·8 % when foods were consumed the day before. No significant differences were found between actual and estimated portion sizes except for three dishes (loubieh bil zeit, tabbouleh and yachnet bazella). Bland-Altman plots showed good agreement for all dishes with a negligible bias of -0·2 g between estimated and presented portions, and -6·3 g between estimated and eaten portions. CONCLUSIONS: In the Lebanese diet, food photographs seem a reliable tool for quantification of food portion sizes.

Assessment of heat treatment of dairy products by MALDI-TOF-MS.

The formation of the Amadori product from lactose (protein lactosylation) is a major parameter to evaluate the quality of processed milk. Here, MALDI-TOF-MS was used for the relative quantification of lactose-adducts in heated milk. Milk was heated at a temperature of 70, 80, and 100 degrees C between 0 and 300 min, diluted, and subjected directly to MALDI-TOF-MS. The lactosylation rate of alpha-lactalbumin increased with increasing reaction temperature and time. The results correlated well with established markers for heat treatment of milk (concentration of total soluble protein, soluble alpha-lactalbumin and beta-lactoglobulin at pH 4.6, and fluorescence of advanced Maillard products and soluble tryptophan index; r=0.969-0.997). The method was also applied to examine commercially available dairy products. In severely heated products, protein pre-purification by immobilized metal affinity chromatography improved spectra quality. Relative quantification of protein lactosylation by MALDI-TOF-MS proved to be a very fast and reliable method to monitor early Maillard reaction during milk processing.