Food selection by calanoid copepods in response to between-lake variation in food abundance

1. Food selection experiments were conducted by acclimating calanoid copepods (Eudiaptomus spp.) in suspensions of natural seston and then adding pairs of dual-labelled (¹⁴C/³²P) algae. Each feeding trial measured selectivity between a small, high-quality reference alga, Chlamydomonas reinhardii, and a test alga that differed in size and/or food quality. The influence of food concentration on food selection was tested by using seston from two lakes with contrasting food abundance and by including treatments with filtered lake water ('starved’) and seston diluted with filtered water or enriched with cultured algae. 2. Copepods that had been starved or acclimated to natural seston with low food abundance preferred the larger of two labelled algae, regardless of the nutritional quality of the algae. In agreement with the predictions of an optimal diet model, however, copepods that were acclimated to high food conditions discriminated against low-quality foods, including digestion-resistant algae and dead algae. 3. Selectivity coefficients showed excellent agreement with a previous study involving the same taxa of copepods and labelled algae but in which the copepods had been acclimated to pairs of cultured algae rather than natural seston. Thus, these comparisons emphasize the importance of food availability in modulating copepod selectivity for foods that differ in nutritional quality and suggest that such behaviour occurs in nature.     

Paddlefish Polyodon spathula juveniles food searching behaviour evoked by natural food odour

Using the behavioural bioassay, food search behaviour was investigated in paddlefish Polyodon spathula juveniles (2.3, 3.0, 5.0, 15.0 and 35.0 cm TL; and 16, 23, 35, 50 and 130 days post‐hatch respectively) evoked by Daphnia water extracts. Main characteristics of this behaviour were increased swimming speed, sinking to the lower water layer, short and straight trajectories in the odour cloud and opening of the mouth. These responses were seldom clearly pronounced and had a fairly short time‐pattern. Biting and snapping, common in food search by many other species, were never observed. Ability to respond to food odour developed at the beginning of exogenous feeding. Olfactory sensitivity of P. spathula to natural food extract was relatively low, 10⁻¹–10⁻² g L⁻¹, 2–3 orders of magnitude lower than in some sturgeons. It was concluded that olfaction plays a minor role in the food search behaviour of paddlefish.     

Position of horseshoe crabs in estuarine food webs: N and C stable isotopic study of foraging ranges and diet composition

To discern the position of horseshoe crabs as a potentially important predator in estuarine food webs, we determined where they foraged and what they ate. We used N and C stable isotopes to link adult horseshoe crabs to their oraging locations and potential food sources in Pleasant Bay, Cape Cod. The δ¹⁵N in tissues of horseshoe crabs and their potential foods suggest crabs were loyal to local foraging sites and did not forage substantially in subestuaries receiving >110 kg N ha⁻¹ year⁻¹. Among locations where crabs foraged, δ¹³C values in potential foods showed that food webs in subestuaries subject to higher N loads were supported by algal producers, while food webs in subestuaries with lower N loads were also supported by Spartina. δ¹³C values in horseshoe crab tissue did not change with load, suggesting they ate a mixed diet, regardless of N load. N and C isotopes in horseshoe crab feces were similar to signatures of estimated diet, suggesting low assimilation efficiency, perhaps due to ingestion of low quality organic matter. Although horseshoe crabs were relatively opportunistic in foraging habits, conservation or culture of horseshoe crabs may require habitats with higher water quality, ample particulate organic matter, and supporting a variety of prey.     

Contamination of Foods by Food Handlers: Experiments on Hepatitis A Virus Transfer to Food and Its Interruption

Hepatitis A virus (HAV) is an important pathogen which has been responsible for many food-borne outbreaks. HAV-excreting food handlers, especially those with poor hygienic practices, can contaminate the foods which they handle. Consumption of such foods without further processing has been known to result in cases of infectious hepatitis. Since quantitative data on virus transfer during contact of hands with foods is not available, we investigated the transfer of HAV from artificially contaminated fingerpads of adult volunteers to pieces of fresh lettuce. Touching the lettuce with artificially contaminated fingerpads for 10 s at a pressure of 0.2 to 0.4 kg/cm² resulted in transfer of 9.2% ± 0.9% of the infectious virus. The pretreatments tested to interrupt virus transfer from contaminated fingerpads included (i) hard-water rinsing and towel drying, (ii) application of a domestic or commercial topical agent followed by water rinsing and towel drying, and (iii) exposure to a hand gel containing 62% ethanol or 75% liquid ethanol without water rinsing or towel drying. When the fingerpads were treated with the topical agents or alcohol before the lettuce was touched, the amount of infectious virus transferred to lettuce was reduced from 9.2% to between 0.3 and 0.6% (depending on the topical agent used), which was a reduction in virus transfer of up to 30-fold. Surprisingly, no virus transfer to lettuce was detected when the fingerpads were rinsed with water alone before the lettuce was touched. However, additional experiments with water rinsing in which smaller volumes of water were used (1 ml instead of 15 ml) showed that the rate of virus transfer to lettuce was 0.3% ± 0.1%. The variability in virus transfer rates following water rinsing may indicate that the volume of water at least in part influences virus removal from the fingerpads differently, a possibility which should be investigated further. This study provided novel information concerning the rate of virus transfer to foods and a model for investigating the transfer of viral and other food-borne pathogens from contaminated hands to foods, as well as techniques for interrupting such transfer to improve food safety.     

Delivery of Functionality in Complex Food Systems: Physically Inspired Approaches from Nanoscale to Microscale

The purpose of this Delivery of Functionality in Complex Food Systems symposium was to develop a fundamental understanding of the rational design principles required to create high-quality and healthy foods. The symposium highlighted the need for a multidisciplinary and integrated approach to rational food design, involving physicists, chemists, biologists, food technologists, physiologists, sensory scientists, psychologists, chefs, and social scientists. The conference moved from a consideration of the characteristics and interactions of basic food components to the nanoscopic and microscopic structures created by assembly of these basic components, to the bulk physicochemical and sensory properties of foods, to the interaction of foods with the mouth and gastrointestinal tract, and finally, to the scientific basis of fine cuisine (molecular gastronomy).     

Determining the limits and confounders for the 2-pentyl furan breath test by gas chromatography/mass spectrometry

Aspergillus fumigatus produces 2-pentyl furan (2-PF), a volatile compound not produced by many other pathogens or normal human metabolism. 2-Pentyl furan has been detected in the breath of patients with invasive aspergillosis (IA) by SPME pre-concentration coupled with CG/MS providing the possibility of an attractive diagnostic test. The limit of detection (LOD) and quantification (LOQ) for peak integration were assessed both statistically and empirically respectively. 2-Pentyl furan was detected from 10 of 45 food stuffs tested. Levels were highest from soymilk (3 of 3 brands), lower from pumpkin, peanuts, rolled oats 2, Ensure Plus, tinned asparagus, tinned beans and a vegetable exact (Marmite). No 2-PF was detectable in anti-fungal medications used to treat IA or commonly used cosmetics tested. There was no difference in 2-PF breath levels between morning and afternoon or fasting and non fasting samples taken from healthy subjects eating a diet without 2-PF rich foods. 2-Pentyl furan levels were present in breath samples immediately after a mouth rinse with soy milk (P<0.001), and in some subjects after ingesting soy milk and rinsing their mouth with water. The breath test for 2-PF can be conducted without an overnight fast or at a specified time provided the mouth has been rinsed 30 min or more from when 2-PF containing products have been ingested.     

Food processing by high hydrostatic pressure

High hydrostatic pressure (HHP) process, as a nonthermal process, can be used to inactivate microbes while minimizing chemical reactions in food. In this regard, a HHP level of 100 MPa (986.9 atm/1019.7 kgf/cm²) and more is applied to food. Conventional thermal process damages food components relating color, flavor, and nutrition via enhanced chemical reactions. However, HHP process minimizes the damages and inactivates microbes toward processing high quality safe foods. The first commercial HHP-processed foods were launched in 1990 as fruit products such as jams, and then some other products have been commercialized: retort rice products (enhanced water impregnation), cooked hams and sausages (shelf life extension), soy sauce with minimized salt (short-time fermentation owing to enhanced enzymatic reactions), and beverages (shelf life extension). The characteristics of HHP food processing are reviewed from viewpoints of nonthermal process, history, research and development, physical and biochemical changes, and processing equipment.     

Phagostimulation of Lytechinus variegatus (Lamarck) (Echinodermata: Echinoidea)

Artificial agarose foods containing either starch, glycogen, carragheenan, alginate, casein, gelatin, albumin, or peptones at a concentration of 1% dry weight were not phagostimulatory. Artificial foods containing sugars, especially galactose, at a concentration of 0.005 M were phagostimulatory. Of the common amino acids, only L‐phenylalanine was phagostimulatory at this concentration. The initiation of feeding postures (movement of the spines, tube feet, peristome, and Aristotle's lantern) of Lytechinus variegatus was little affected by the concentration of plant extracts. Many aspects of this behavior were attributable to physical rather than chemical stimulation. Feeding rates of L. variegatus upon artificial agarose foods containing either Thalassia testudinum or Gracilaria verrucosa were directly dependent upon plant tissue concentration. All artificial agarose food‐items were initially moved to the mouth and fed upon, however the time spent feeding was directly dependent upon plant type and tissue concentration. Retention of the artificial food‐items upon the test after feeding was not influenced by plant type or tissue concentration. Differences in consumption of foods by L. variegatus are determined by the degree of persistence in feeding upon encountered items and not be selection before initiating feeding or by retention of food‐items for subsequent feedings.     

Measuring the Toughness of Primate Foods and its Ecological Value

The mechanical properties of plant foods play an important role in the feeding process, being one of many criteria for food acceptance or rejection by primates. One of the simplest justifications for this statement is the general finding that primates tend to avoid foods with high fiber. Although fiber is largely tasteless, odorless, and colorless, it imparts texture, a sensation in the mouth related to the physical properties of foods. All primates encounter such mechanical resistance when they bite into plant food, and studies on humans show that an incisal bite facilitates quick oral assessment of a property called toughness. Thus, it is feasible that primates make similar assessments of quality in this manner. Here, we review methods of measuring the toughness of primate foods, which can be used either for making general surveys of the properties of foods available to primates or for establishing the mechanisms that protect these foods from the evolved form of the dentition.     

ASSESSMENT OF IMPEDANCE MICROBIOLOGICAL METHOD FOR THE DETECTION OF ESCHERICHIA COLI IN FOODS

This study was conducted to determine the sensitivity and specificity of the impedance-based microbiological method for the detection of Escherichia coli in foods within 24 h of testing. A Malthus Microbiological Analyzer system (Malthus System V, Malthus Instruments Ltd., Bury, United Kingdom), and a modified Malthus Coliform Broth Medium (MCBM), and an incubation temperature of 44C were used. The sensitivity of the impedance method was determined by testing E. coli-negative food samples spiked with different concentrations of E. coli. The specificity of the method was determined by testing E. coli -negative food samples spiked with Klebsiella pneumoniae, Enterobacter cloacae and Pseudomonas aeruginosa. The test results were compared with those obtained by the Most Probable Number (MPN) method. Milk, milk products, raw and ready-to-eat meats, and vegetables were tested for the presence of E. coli by both methods. The sensitivity of the impedance method and the MPN method for the detection of foods containing 10¹ CFU/g was 100% and 84.4%, respectively. Both methods had a specificity of 100% for food samples spiked with 10¹ CFU/g E. coli. The specificity of the impedance and the MPN methods for the detection of E. coli in naturally contaminated milk and meat samples was 100% and 95.7% respectively. E. coli was detected in foods by the impedance method within 4–24 h of testing at a detection limit of 1 CFU/mL. These results demonstrate that the impedance method can be used as a rapid and sensitive method for the detection of E. coli in foods.     

Food and water resources used by the Madagascan hissing-cockroach mite,Gromphadorholaelaps schaeferi

We determined the food source and water balance properties of the hissing-cockroach mite, Gromphadorholaelaps schaeferi. The food source for mites was identified using Evans blue dye by direct injection into a fasting host cockroach, Gromphadorhina portentosa, or by incorporation into cockroach food. No coloration was observed in mites on dye-injected cockroaches, but coloration was present in mites when only the food for the cockroaches had been stained. Thus, the mites are scavengers of cockroach food, and are not parasitic as previously thought. Our results demonstrate that the mites can absorb water from the air anywhere between 0.84 and 0.93 a _v (%RH/100), and wax-block experiments revealed that the mouth is the site of uptake. The mites are normally clumped together on the host, typically in between the cockroach's legs and around the spiracles. Water loss rates for mites in groups (0.16% h^-1) were far lower than for isolated mites (0.30% h^-1), suggesting a group effect with regard to water balance. Above the transition temperature of 30°C rate of water loss was rapid. The sites occupied by mites on the cockroach's body seem to be highly specific for feeding and absorption of water vapour.     

Determination of selenium in canadian food items by cyclic instrumental neutron activation analysis

Instrumental neutron activation analysis (INAA) and pseudocyclic INAA (PCINAA) have been used to determine the selenium content of a variety of Canadian food items. Use of the 162-keV gamma ray of short-lived^77mSe in INAA allowed relatively simple and rapid determinations and was suitable for many of the foods. PCINAA was found to give lower detection limits and was used for the low-selenium food samples. Both internal and external quality assessments were used to evaluate and assure the accuracy and precision of the methods developed.     

Experience influences diet mixing by herbivores: implications for plant biochemical diversity

We often assume the intrinsic value of a food or habitat is similar for individuals of a species and above a certain threshold density more profitable foods should always be preferred over less profitable foods. Nevertheless, individual herbivores differ in their preferences for foods due in part to experience, and experience in variable environments is variable. In this report, we show that how sheep learned about their foraging environment was crucial to the development of their dietary habits, and that experience with foods that contained plant secondary metabolites (PSM) markedly enhanced their use of PSM-containing foods, even when familiar, nutritious alternatives were available ad libitum. Lambs who learned to eat foods that contained either tannins, terpenes, or oxalates ate more when they could select two of the foods offered simultaneously (tannins-terpenes, tannins-oxalates, or terpenes-oxalates) than when they were offered only one food. Lambs offered foods containing all three toxins ate more than lambs offered two of the toxins, and their intake was comparable to lambs offered the food that contained no toxins. Experience and the availability of nutritious alternatives both influenced food choice when the preferences of lambs with 3 months’ experience mixing tannin, terpenes, and oxalates were compared with lambs naive to the toxin-containing foods. During these studies, all lambs were offered five foods, two of them familiar to all of the lambs (ground alfalfa and a 50:50 mix of ground alfalfa:ground barley) and three of them familiar only to experienced lambs (a ground ration containing either tannins, terpenes, or oxalates). Half of the lambs were offered the familiar foods ad libitum, while half of the lambs were offered only 200 g of each familiar food daily. Throughout the study, naive lambs ate much less of the foods with toxins if they had ad libitum as opposed to restricted access to the nutritious alternatives (66 vs 549 g d⁻¹). Experienced lambs also ate less of the foods with toxins if they had ad libitum, as opposed to restricted, access to the nutritious alternatives (809 vs 1497 g d⁻¹). In both cases, however, lambs with experience ate remarkably more than naive lambs of the foods containing the toxins, whether access to the alfalfa-barley alternatives was ad libitum (811 vs 71 g d⁻¹) or restricted (1509 vs 607 g d⁻¹). These differences in food preferences and intake persisted during trials 8 months later. Plant communities offer a diverse matrix of biochemicals to herbivores, which may produce an array of interactions not accounted for by the traditional approach of studying nutrients and plant secondary metabolites (PSM) in isolation. How herbivores experience nutrient-PSM interactions may influence defoliation patterns and the potential for plant survival within plant communities. Thus, learning to mix foods that differ in kinds and concentrations of nutrients and PSM can enhance diet breadth and promote more uniform use of all plants in a community, which can influence the structure and function of ecosystems. Conversely, lack of experience learning to eat a variety of foods can diminish diet breadth and result in less uniform use of plants in a community.     

The flow of food in colonies of the fire ant, Solenopsis invicta: a multifactorial study

ABSTRACT. A study was conducted to determine the interaction of several factors in the trophallactic distribution of food in colonies of Solenopsis invicta Buren. Radioactive iodine (¹²⁵I) was used to quantify both the ingestion of test foods by foragers and the distribution of this food to nestmates. A multifactorial design tested the simultaneous effects of: (1) food-type (sugar water, casein hydrolysate, or oil), (2) temperature during foraging and food-sharing (25, 30 or 35°C), and (3) starvation period (colonies deprived for 0, 3, 7 or 14 days). The amount of food consumed by foragers was influenced by the interaction of food-type and starvation. Foragers from severely starved colonies ingested more aqueous foods than did those from slightly starved colonies, but oil was always taken in smaller quantities and its ingestion was least affected by starvation. Ingestion was generally lowest at 35°C, probably because of mutual interference of workers while feeding. Within the colony, food sharing varied with food type and increased with starvation. The sugar solution was utilized primarily by workers. Amino acids were shared throughout the colony, but were directed preferentially to the growing larvae. Soy oil was equally shared among workers and larvae and reached more colony members per initial unit volume than did the other foods. The test factors also interacted in their influence on trophallaxis. Starvation stimulated the dispersal of labelled foods, but at different intensities for different foods. The probability of the queen's receiving food increased when the labelled food was widely exchanged among her nestmates. Casein hydrolysate reached the queen in more cases than did the other tested foods.     

Estimation of Excess Cancer Risk on Time-Weighted Lifetime Average Daily Intake of PAHs from Food Ingestion

The purposes of this study were to quantify the time-weighted, lifetime average, daily intake (LADI) of polycyclic aromatic hydrocarbons (PAHs) through food ingestion and to estimate the excess cancer risk based on lifetime dietary PAH intake. Twenty-seven different food commodities were selected from the 2001 Korean National Health and Nutrition survey based on their frequent consumption and high PAH level. The foods were analyzed for the profile of 14 PAH congeners using high performance liquid chromatography (HPLC) and fluorescence detector. Considering the toxic equivalent (TEQ) level converted with the toxic equivalent factors (TEFs), the highest total TEQ level of PAHs in foods was detected from roasted laver at 1.2 ug TEQ/kg. For the PAH exposure assessment according to ingested foods, the average body weight was separated according to the following age groups, 1–6, 7–19, 20–64 and over 64 years, and the daily food ingestion rates from the National Health and Nutrition survey were used. The estimated Lifetime Average Daily Intake (LADI) of PAHs was 3.22 × 10^–3 ug/kg/day for carcinogenic effects and was higher in the younger age groups under 20 years old than in the older groups. The dietary excess cancer risk estimated using the cancer potency of benzo(a)pyrene (7.3(mg/kg/day)^?1) was 2.3 × 10^?5, which is equivalent to a probability of tumor eruption in the upper gastrointestinal tract of two per hundred thousand persons.     

Slow Food: Sustained Impact of Harder Foods on the Reduction in Energy Intake over the Course of the Day

Background

Previous research has shown that oral processing characteristics like bite size and oral residence duration are related to the satiating efficiency of foods. Oral processing characteristics are influenced by food texture. Very little research has been done on the effect of food texture within solid foods on energy intake.

Objectives

The first objective was to investigate the effect of hardness of food on energy intake at lunch, and to link this effect to differences in food oral processing characteristics. The second objective was to investigate whether the reduction in energy intake at lunch will be compensated for in the subsequent dinner.

Design

Fifty subjects (11 male, BMI: 21±2 kg/m², age: 24±2 y) participated in a cross-over study in which they consumed ad libitum from a lunch with soft foods or hard foods on two separate days. Oral processing characteristics at lunch were assessed by coding video records. Later on the same days, subjects consumed dinner ad libitum.

Results

Hard foods led to a ∼13% lower energy intake at lunch compared to soft foods (P<0.001). Hard foods were consumed with smaller bites, longer oral duration per gram food, and more chewing per gram food compared to the soft foods (P<0.05). Energy intake at dinner did not differ after both lunches (P = 0.16).

Conclusions

Hard foods led to reduced energy intake compared to soft foods, and this reduction in energy intake was sustained over the next meal. We argue that the differences in oral processing characteristics produced by the hardness of the foods explain the effect on intake. The sustained reduction in energy intake suggests that changes in food texture can be a helpful tool in reducing the overall daily energy intake.