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PubMed2001

New analytical techniques in food science.

In this review, some of the latest analytical techniques that are being used for the study and characterization of food are examined. This work intends to provide an updated overview (including works published up to June 1999) on the principal applications of such techniques together with their main advantages and drawbacks in food analysis. Some future developments of these systems and their foreseeable application in food characterization are also discussed. The reviewed techniques are those based on spectroscopic, biological, separation, and electrochemical procedures. Moreover, some relevant facts on new systems for sample preparation and on-line couplings are also given.

Chemistry Techniques, Analytical↗
PubMed2003

Stable isotope food web analysis of a large subtropical lake: alternative explanations for 15N enrichment of pelagic vs. littoral fisheries.

The food webs of littoral, pelagic, and littoral-pelagic ecotone (interface) regions of a large subtropical lake were investigated using stable isotope ratio methods, expanding the focus of a previous fish-only study to include other food web components such as primary producers and invertebrates. In these food webs, delta13C increased approximately 4 per thousand and delta15N increased approximately 10 per thousand from primary producers to fish. The delta15N of fish was approximately 9 per thousand in the littoral zone, approximately 10 per thousand in the ecotone, and approximately 12 per thousand in the pelagic zone. The cross-habitat enrichment in fish 15N corresponded with both an increase in the size of fish and an increase in the d15N of primary consumers (mollusks). Despite larger body size in the pelagic zone, fish in all three habitats appear to occur at the same average trophic level (TL = 4), assuming an enrichment factor of 3.4 per thousand per trophic level, and normalizing to the delta15N of primary consumers.

Animals↗
PubMed1987

Twenty four hour oesophageal acidity in achalasia before and after pneumatic dilatation.

Radiotelemetric ambulatory 24 hour oesophageal pH measurement was carried out in 17 patients with symptomatic manometrically proven achalasia before and after pneumatic dilatation. Before dilatation an abnormally high percentage acid exposure time was present but typical episodes of gastro-oesophageal reflux occurred in only one patient. In nine patients who had a oesophageal food residue these values were significantly greater than those found in the remaining patients without retained food. Analysis of oesophageal food residues revealed that the low pH was predominantly caused by lactic acid. These findings indicate that preoperative oesophageal pH studies do not offer a valid means of selection of patients in whom an antireflux procedure should be combined with cardiomyotomy. Repeat studies one week after pneumatic dilatation showed a fall in the acid exposure time in patients with initial food residue presumably resulting from improved oesophageal emptying after treatment. A significant rise in acid exposure time after dilatation was seen in those patients without initial food residue presumably resulting from gastro-oesophageal reflux after therapeutic disruption of the lower oesophageal sphincter. Troublesome symptoms of gastro-oesophageal reflux were, however, uncommon after bag dilatation.

Adolescent↗
PubMed1985

Cluster analysis to improve food classification within commodity groups.

Mathematical clustering algorithms were used to classify foods within dairy, grain, and fat commodity groups on the basis of nutrients with limited availability in the food supply as well as those posing a possible health risk due to excess consumption. The procedure overcomes the problem that has made objective and accurate grouping, i.e., dealing simultaneously with 10 or more nutrients, difficult. The clustering routine classifies foods on the basis of similar nutrient content for any number of food attributes and assigns a degree of association to each food to indicate its compositional similarity to a prototype food for the cluster group. Foods within dairy, grain, and fat commodity groups were clustered on the basis of similar content of vitamin B-6, calcium, iron, magnesium, folacin, zinc, and added sugar, fat, cholesterol, and sodium. Whole milk and natural cheese clustered together on the basis of their moderate nutrient and relatively high fat and sodium content. Whole wheat breads, pumpernickel bread, and pancakes from mix constituted a grain subgroup with highest nutrient content, lowest cholesterol and sugar, lower fat, and higher sodium. Other subgroups based upon similarities in attributes were identified within food commodity categories. The result is an expansion of some food groups to incorporate concepts of both nutritional adequacy and moderation of food components of current nutritional concern.

Dairy Products↗
PubMed1997

Analysis of foods for heterocyclic aromatic amine carcinogens by solid-phase extraction and high-performance liquid chromatography.

Carcinogenic and mutagenic heterocyclic aromatic amines (HAA) are natural products often present at ng/g levels in muscle meats when they are cooked at temperatures over 150 degrees C. Using solid-phase extraction and high performance liquid chromatography (HPLC) with photodiode array UV detection, samples were analyzed for the following heterocyclic amines: DiMeIQx (2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline); IQ (2-amino-3-methylimidazo[4,5-f]quinoline); MelQx (2- amino-3,8-dimethylimidazo[4,5-f]quinoxaline); and PhIP (2-amino-1-methyl- 6-phenylimidazo[4,5-b]pyridine). Quality control samples, analyzed periodically over two years in a blind study, show relative standard deviations ranging from 22 to 38% for the compounds found, variations typical for analysis at ng/g levels. Amounts range from undetectable levels (less than 0.1 ng/g) to hundreds of ng/g of PhIP for frying or grilling at high meat surface temperatures. Beef, chicken, pork and lamb can all have greater than 10 ng/g of PhIP. Ground chicken breast meat has lower amounts of heterocyclic amines than intact muscle pieces of the same size cooked identically. Restaurant prepared samples that we analyzed contained undetectable levels up to 14 ng/g total heterocyclic amines for a beef steak sample. Not extracted with the above method are related mutagenic heterocyclic amines, which have been reported in cooked foods in our laboratory and others. Method development using ion exchange on an SCX solid-phase extraction cartridge shows promise in providing a method for the quantitation of these mutagenic dimethyl-, trimethyl- and furo-imidazopyridines where a practical analysis method is needed.

Amines↗
PubMed1986

Comparison of calculated estimates and laboratory analysis of food offered to hospitalized eating disorder patients.

Estimation of caloric intake is an integral part of a comprehensive research/treatment program for patients with eating disorders at the National Institute of Mental Health. Caloric intakes are estimated by recording daily food intake and calculating calories using food exchange lists and food composition tables. To evaluate the validity of that method, caloric intake estimates were compared with laboratory analysis data over a 15-day period. The estimations for daily caloric intake in comparison with the laboratory analysis data were underestimated by a mean percent difference of 2.4%. The estimated carbohydrate and fat intakes were overestimated by 4.5% and 5.4%, respectively. The estimated protein intake was underestimated by 1.1%. The data suggest that estimates of caloric intake based on food exchange lists and food composition tables are within an acceptable range of error and, therefore, represent a practical approach to estimating caloric intake for patients hospitalized with an eating disorder.

Anorexia Nervosa↗
PubMed1994

Statistical analysis of food webs.

The numbers of species in different trophic levels of a food web are modeled as a trinomial random vector, with cell probabilities potentially depending on the total number of species in the web. A maximum likelihood method is developed to test the hypothesis that the fractions of species in different levels are independent of the total number of species. The method is applied to a data set whose properties have been debated in the literature, and it is shown to be a powerful alternative to the simple linear regression approach used in previous analyses.

Animals↗
PubMed2005

RAPD & FINS (mitochondrial 16s rRNA gene sequence) in analysis of food contamination: detection of food poisoning by Lizard.

In poisoning, detection of the nature of causative agent is important for management of trauma and forensic investigation. Most of the methods in clinical toxicology are developed for detection of toxins and poisons. A random amplified polymorphic DNA (RAPD)-based method has been described for detection of species of animal from its morphologically unrecognizable fragments, recovered from food substances, consumption of which caused even death. Pre-mixed RAPD reaction beads and six RAPD primers were used in polymerase chain reaction analysis. Among six RAPD primers used, any one of them was sufficient in resolving this practical forensic situation. To enhance the probability values for matching in the present study of fixing identity of an animal, six set of market available RAPD primers were used. This is the first report of a forensic application of RAPD DNA typing in identification of charred skeleton remnants of Lizard species in food material. Furthermore unique amplicons were generated for different reptilian species, which can be used as species specific markers for species identification in forensic situation, however, no variations among individuals of same species were observed.

Animals↗
PubMed1987

A nutritional analysis of food provided to Royal Naval personnel at sea.

The aim of this study was to determine the nutritional content of the foods provided to, and the confectionary purchased by, personnel serving at sea in British warships. Data were collected from the stores accounts of six ships over a period of 32,354 man-victualling-days. Analysis was carried out at the Nuffield Laboratories of Comparative Medicine. The food from the ships' gallies provided mean daily intakes of 3750 kcal, of which 42 per cent were derived from fats (17 per cent from saturated fats) and 9 per cent from added sugars. In taking account of confectionary purchased from NAAFI sources the total energy intake was raised to 4200 kcal of which 40 per cent were derived from fats (15 per cent saturated fats) and 12 per cent from added sugars. The results do not compare favourably with the recommendations of the reports of expert committees.

Adult↗
PubMed1985

Mood and food: an analysis of bulimic episodes.

The present study examined those factors which differentially lead to normal eating and binge eating. Twenty-one bulimic subjects and comparison subjects monitored their mood, hunger, and food intake hourly over a number of days. The bulimic sample ate fewer meals and had lower overall mood. Positive mood, food abstinence combined with intensified hunger, and being in the company of another person preceded normal eating (i.e. retained meal). Negative mood, recent consumption of food, and being alone preceded bulimic episodes.

Adult↗