Changes in Volatile Components of Stored Tangerines and Other Specialty Citrus Fruits with Different Coatings

ABSTRACT: Shellac and wax-based citrus coatings were applied to Fallglo, Robinson, Sunburst, Dancy and Murcott tangerines, Nova and Orlando tangelos, and Temple oranges. Flavor volatiles were measured before and after storage. Concentrations of ethyl acetate, ethyl butyrate, isopentanol and 2-methyl-3-buten-2-ol increased markedly for fruit with shellac-based coatings, and were highly correlated with ethanol content, but at different ratios for the different varieties. The concentration increases were relatively less for fruit coated with the wax-based coatings, and suggest that high-gloss shellac and resin-based coatings are not appropriate for tangerines.     

Volatile Compounds of Raw Beef from 5 Local Spanish Cattle Breeds Stored Under Modified Atmosphere

Volatile compounds of raw beef from Asturiana de los Valles, Morucha, Parda Alpina, Pirenaica, and Retinta cattle breeds were studied. Steaks were packaged under 60% O₂, 30% CO₂, and 10% N₂, and 53 volatile compounds were tentatively identified by purge‐and‐trap extraction and gas chromatography with mass spectrometry after 0, 5, 10, and 15 d of chill storage. The degradation of beef quality with increasing storage time was evidenced by the increase in 2,3,3‐trimethylpentane, 2,2,5‐trimethylhexane, 3‐octene, 3‐methyl‐2‐heptene, 2‐octene, and 2‐propanone and by the decrease in dimethyl sulfide. Consequently, some of the volatile compounds, which are believed to be formed by thermal degradation of meat, might be formed during chill storage, and the rate of formation of some was dependent on the specific compound.     

Electronic Sensing of Aromatic Volatiles for Quality Sorting of Blueberries

An electronic sniffer using semi-conductor gas sensors that nondestructively measured aromatic volatile gas emissions from fruit was developed to assess blueberry quality. The sniffer detected soft and damaged fruit in packaged containers at a 5% level of damage and distinguished four of five fruit ripeness classes: (1) mature-green and green-pink; (2) blue-pink; (3) blue; and (4) ripe fruit. Sniffer response increased as fruit ripened, as did total concentration of aromatic volatiles. Sniffer response correlated with berry firmness, pH, titratable acidity, and color, and detected differences among 10 cultivars, as did impact response analysis. The electronic sniffer is rapid, nondestructive and may be used to sort and quality check for presence of unripe or damaged fruit in closed packs of fresh berries.     

Effect of maillard reaction volatile products on lipid oxidation

Maillard reaction volatile compounds (MRV), prepared by heating a glucose-glycine solution, were tested as antioxidants in soybean oil (SBO) thermoxidation. The volatiles were transferred into the oil by stripping with a stream of Nitrogen and substituting the atmosphere above the oil with air containing MRV. Standard accelerated oxidation was performed by heating the SBO. Peroxide value measurement and headspace gas Chromatographic analysis were carried out on all the samples. The MRV antioxidant activity was evaluated by determining the effect of the induction period and the kinetic rate constant of peroxide and oxidation volatiles formation. The MRV showed a significant antioxidant activity. The effectiveness was variable depending on MRV transfer method to the oil, and the Maillard reaction extent was related to the browning level of glucose/glycine solution. It was found that the maximum effect of MRV prolonged about three times the induction period and reduced the kinetic rate constant by half in relation to the control sample. MRV affects oxidative stability of soybean oil by lengthening the induction period as well as by decreasing the rate of oxidation at the propagation state and reducing the formation of hexanal.     

Olfactory recognition of nonhosts aspen and birch by conifer bark beetlesTomicus piniperda andHylurgops palliatus

The field response ofTomicus piniperda (L.) andHylurgops palliatus (Gyll.) (Coleoptera: Scolytidae) to the attractant ethanol in combination with volatile wood constituents released from the nonhost tree speciesPopulus tremula L. (Salicaceae) andBetula pendula Roth (Betulaceae) was studied using flight barrier traps. The attraction of both species decreased when aspen or birch wood was added to the ethanol bait. The same was true forRhizophagus depressus (F.) (Coleoptera: Rhizophagidae), a predatory species associated with conifer bark beetles.Glischrochilus quadripunctatus (L-),Epuraea bickhardti St.-Claire Deville,E. unicolor (Oliv.) (Coleoptera: Nitidulidae), andRhizophagus parvutus (Payk.) (Coleoptera: Rhizophagidae) were caught in higher numbers in traps baited with both ethanol and wood of aspen or birch than in traps baited with ethanol alone. In a separate experiment, landings ofT. piniperda andH. palliatus on nonhosts (black plastic tubes) were demonstrated with sticky traps.     

Volatile constituents of palm wine and palm sap

Palm wine and pasteurised palm sap volatiles were collected, concentrated on a Tenax GC and analysed by gas chromatography and gas chromatography-mass spectrometry. Eighty-two components were identified: 47 esters, 9 alcohols, 5 acids, 6 carbonyls, 2 acetals, 4 terpenes and 9 hydrocarbons. These had all been found previously in conventional wines. Odour evaluation of the separated palm wine components as they eluted suggested that no one compound is responsible for the characteristic palm wine odour. The acetates of higher alcohols and the ethyl esters of straight-chain aliphatic C₆-C₁₀ acids seemed to be important and may play a big role in imparting the fruity nuances of characteristic palm wine odour. Their association with alcohols seemed also to be necessary for the expression of typical palm wine odour. The qualitative difference between palm sap aroma and palm wine aroma appeared to be due mainly to the presence of these esters and alcohols in palm wine and their apparent absence from palm sap, as well as to the presence of some low-boiling esters and alcohols in palm sap and their apparent absence from palm wine.     

The effects of harvest maturity,ripeness and storage on kiwifruit aroma

Quantitative gas chromatographic analysis of the volatile aroma components has been used as an objective measure of the effects of maturity at harvest, ripeness and storage on the aroma volatiles of kiwifruit. Increasing ripeness is associated with a rapid increase in the levels of aroma volatiles, especially esters, while increasing storage time prior to ripening is accompanied by a decrease in the amount of aroma volatiles.     

Effect of volatiles collected above fecal pellets on behavior of the rabbit,Oryctolagus cuniculus,tested in an experimental chamber

Gas chromatographic techniques were used to trap and fractionate the volatile substances emanating from the fecal pellets of wild rabbits,Oryctolagus cuniculus, which incorporate the odor of the anal gland secretion. The volatiles were bubbled through water, trapped on Chromosorb 105, transferred to Silicone SF96 traps, passed through a GC capillary column, and retrapped on SF96. The behavioral effect of trapped and fractionated volatiles was determined in four series of bioassays involving 51 adult, male, wild-type rabbits in 112, ten-minute tests. The bioassay was based on the demonstration of territorial confidence by the rabbits under the influence of their own odor. In the bioassays of the unfractionated volatiles eluted from Chromosorb 105 and SF96 traps the animals were significantly more confident in the presence of the volatiles from their own fecal pellets. One of the two fractions of the total volatiles was ineffective while the effect of the other was less than that of the unfractionated odor. The results demonstrate that the gas chromatographic techniques can be used to manipulate complex mammalian odors with precision. Combined with a discriminative bioassay, this opens up the possibility of identifying the specific combinations of volatile substances involved in the formation of olfactory signals.     

Host odor and visual stimulus interaction during intratree host finding behavior ofRhagoletis pomonella flies

Responses ofRhagoletis pomonella (Walsh) (Diptera: Tephritidae) flies to host fruit visual stimuli (apples or models of apples) and chemical stimuli (synthetic apple volatile blend) were studied in semidwarf field-caged apple trees. Three different fruit or model densities (1, 4, or 16 fruit or models/ tree) and two odor release rates [ca. 0.7g/hr (close to the natural release rate of a ripe apple) and ca. 500g/hr (amount of odor released by commercially sold apple maggot traps)] were tested. Individually released flies were followed as they moved within a tree for a maximum of 20 min. We recorded three-dimensional search paths followed by foraging flies and computed such variables as total relative distance traveled before alighting on a fruit or model, track length between individual alightment sites, and directness of flight to fruits or models. Effect of odor on propensity to alight on fruit or models and host-searching behavior prior to alighting on fruit or on models varied according to fruit or model color and density. If the fruit visual stimulus was strong (e.g., red color), odor did not increase the probability of finding fruit or fruit models. As the visual stimulus became progressively weaker (red to green to clear), odor (irrespective of concentration) appeared to aid flies during the fruit-finding process. As density of fruit or models increased, the probability of flies finding a fruit or model also increased (e.g., 50% of flies found a red fruit model at 1 model/tree while 90% found a red model at 16 models/tree; 4% of flies found a clear model with odor at 1 model/tree while 35% found a clear model with odor at 16 models/tree). Findings reported elsewhere indicate thatR. pomonella flies are able to discover a point source of odor (an odor-bearing tree in a patch of trees) by flying upwind (in the tree patch) in response to intermittent exposure to odor. Findings here indicate that after arrival on a host tree (point source), flies discover individual apparent and abundant host fruit on the basis of vision. If fruit are less apparent or scarce, odor appears to interact with vision during the fruit-finding process.     

Olfactory Responses of Banana Weevil Predators to Volatiles from Banana Pseudostem Tissue and Synthetic Pheromone

As a response to attack by herbivores, plants can emit a variety of volatile substances that attract natural enemies of these insect pests. Predators of the banana weevil, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae) such as Dactylosternum abdominale (Coleoptera: Hydrophilidae) and Pheidole megacephala (Hymenoptera: Formicidae), are normally found in association with weevil-infested rotten pseudostems and harvested stumps. We investigated whether these predators are attracted to such environments in response to volatiles produced by the host plant, by the weevil, or by the weevil–plant complex. We evaluated predator responses towards volatiles from banana pseudostem tissue (synomones) and the synthetic banana weevil aggregation pheromone Cosmolure+ in a two-choice olfactometer. The beetle D. abdominale was attracted to fermenting banana pseudostem tissue and Cosmolure+, whereas the ant P. megacephala was attracted only to fermented pseudostem tissue. Both predators were attracted to banana pseudostem tissue that had been damaged by weevil larvae irrespective of weevil presence. Adding pheromone did not enhance predator response to volatiles from pseudostem tissue fed on by weevils. The numbers of both predators recovered with pseudostem traps in the field from banana mats with a pheromone trap were similar to those in pseudostem traps at different distance ranges from the pheromone. Our study shows that the generalist predators D. abdominale and P. megacephala use volatiles from fermented banana pseudostem tissue as the major chemical cue when searching for prey.