Life history studies of the yam moth, Dasyses rugosella Stainton (Lepidoptera: Tineidae)

A life history study of the yam moth, Dasyses rugosella Stainton, was carried out in the laboratory at an ambient temperature of 28±2 °C and 75±5% relative humidity. Freshly emerged male and female adults were paired in glass vials and average fecundity determined. Eggs were incubated in Petri dishes lined with filter paper underneath which was moistened cotton wool. Hatchability and incubation period were noted. Freshly emerged first instar larvae were then reared on small Dioscorea alata L. tubers in plastic containers until adult emergence.The average fecundity per female D. rugosella was 107.4±9.9 eggs at an average oviposition period of 3.8±0.2 days. Most of the eggs were laid on the second day of oviposition. The eggs, which were laid singly, in groups and in chains, were elliptical in shape and measured 0.80±0.01 mm long and 0.42±0.01 mm wide. Hatchability was 66.7%. The mean incubation period was 5.1±0.2 days. Dasyses rugosella passed through six larval instars. The mature larva was eruciform with a large uniformly sclerotised head. The pupa was obtect, adecticous and highly sclerotised with a stout profile. The mean larval and pupal developmental periods were 44.5±1.8 and 11.9±0.2 days, respectively. The mean total developmental time from egg to adult was 61.6±3.7 days (range 53-75 days). The females were always bigger than the males. The wing span measurement of the female ranged from 18.0-18.5 mm, while that of the male ranged from 13.0-14.0 mm. The body length of the female ranged from 7.8-8.5 mm while that of the male ranged from 5.3-6.8 mm. The unmated males lived longer (8.5 days) than unmated females (7.1 days), mated males (3.8 days) and mated females (4.1 days).The maximum daily mean progeny production was 25.7 on the 63rd day of pivotal age. The innate capacity for increased r_c was 0.06 per female per day. The cohort generation time T_c was 63.0 days and the finite rate of increase h_c was 1.06. The net reproductive rate R_o was 52.9.     

Effect of rearing temperature on the fecundity and development of Euzopherodes vapidella Mann (Lepidoptera: Pyralidae), a pest of stored yam

The fecundity and development of the yam moth, Euzopherodes vapidella Mann on Dioscorea alata L. was investigated in the laboratory at four different temperatures, 20, 24, 29 and 33 degrees C. The mean fecundity per female at 20, 24, 29 and 33 degrees C was 51.8+/-3.5, 102.4+/-3.8, 123.3+/-4.4 and 124.4 +/-4.4 eggs, respectively. Hatchability of eggs was highest at 29 degrees C and lowest at 20 degrees C. The mean developmental time at 20, 24, 29 and 33 degrees C was 12.1+/-0.6, 6.2+/-0.3, 3.0+/-0.0 and 2.7+/-0.1 days for the egg, 23.6+/-1.1, 20.0+/-0.9, 15.4+/-0.7 and 12.9+/-0.4 days for the larval stages, 13.0+/-0.03, 8.9+/-0.02, 7.9+/-0.02, and 6.4+/-0.03 days for the pupa and 48.7+/-3.5, 35.1+/-2.3, 26.3+/-1.2 and 22.0+/-1.0 days for the period from egg to adult emergence, respectively. The developmental threshold for the egg stage was estimated as 16.8 degrees C with thresholds of 8.0, 6.2 and 11.4 degrees C for larvae, pupae, and egg to adult emergence, respectively. Storage of yam tubers at low temperatures (but higher than 12 degrees C to avoid damage to tubers) will significantly retard the development of E. vapidella and therefore help in their control. Adult males ranged from 0.50 to 0.65cm in length and females from 0.70 to 0.90cm.     

Development, reproduction, and control of the Indian meal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), in stored seed garlic in Mexico

Developmental time, fecundity, and egg hatch rate were determined for the Indian meal moth, Plodia interpunctella (Hübner), reared on fresh garlic seed at room temperature in Mexico. Duration of the egg stage averaged 4.7±0.8 days with an egg hatch rate ranging from 82% to 95%. Five larval instars were determined based on head-capsule width. Total larval developmental time from egg hatch to adult emergence ranged from 42 to 47 days. Adult females began to oviposit within 12-48 h after mating with the maximum oviposition rate occurring during the first 24 h after mating. The mean (±SE) number of eggs laid by females was 212±34 with a range of 117-303. Application of pirimiphos-methyl, malathion, and permethrin to 30 kg lots of garlic seed failed to prevent infestation and bulb damage by the larvae. However, compared with controls, the percentage of damaged bulbs and the number of larvae detected during 12 weeks of storage was smaller on garlic treated with four doses of pirimiphos-methyl.     

Growth and survival of Salmonella in ground black pepper (Piper nigrum)

A four serovar cocktail of Salmonella was inoculated into ground black pepper (Piper nigrum) at different water activity (a_w) levels at a starting level of 4–5 log cfu/g and incubated at 25 and at 35 °C. At 35 °C and a_w of 0.9886 ± 0.0006, the generation time in ground black pepper was 31 ± 3 min with a lag time of 4 ± 1 h. Growth at 25 °C had a longer lag, but generation time was not statistically different from growth at 35 °C. The a_w threshold for growth was determined to be 0.9793 ± 0.0027 at 35 °C. To determine survival during storage conditions, ground black pepper was inoculated at approximately 8 log cfu/g and stored at 25 and 35 °C at high (97% RH) and ambient (≤40% RH) humidity. At high relative humidity, a_w increased to approximately 0.8–0.9 after approximately 20 days at both temperatures and no Salmonella was detected after 100 and 45 days at 25 and 35 °C, respectively. Under ambient humidity, populations showed an initial decrease of 3–4 log cfu/g, then remained stable for over 8 months at 25 and 35 °C. Results of this study indicate Salmonella can readily grow at permissive a_w in ground black pepper and may persist for an extended period of time under typical storage conditions.     

Lethal effects of sulfuryl fluoride on eggs of different ages and other life stages of the warehouse moth Ephestia elutella (Hübner)

Sulfuryl fluoride (SF) is a fumigant used for the control of stored-product pest insects and is a feasible alternative to some uses of methyl bromide. SF was first registered in Germany in 2004 for disinfestation of emptied flourmills, emptied food storages and dried fruit. One- to 4-day-old eggs, larvae and pupae of the warehouse moth, Ephestia elutella (Hübner) (Lepidoptera) were investigated for their susceptibility to SF under different conditions. Each life stage was exposed for 18 h, 24 h or 48 h, to 11.6 g/m³ or 21.3 g/m³ at 15 °C, 20 °C or 25 °C and 65% relative humidity. A Fourier transform infrared (FTIR) spectrometer was used to determine the concentrations of SF. Within 18 h of exposure, all larvae and pupae of E. elutella died at 11.6 g/m³ at all three temperatures. The 1 and 2- day-old eggs were generally more susceptible, whereas the 3 and 4-day-old eggs were more tolerant to the SF treatment. All eggs of all ages were controlled within 48 h of exposure to the concentration of 21.3 ± 1.3 g/m³ at temperatures of 20 °C and 25 °C.     

Persistence and activity towards Sitophilus zeamais (Coleoptera: Curculionidae) of pirimiphos-methyl sprayed at different temperatures on maize

The air temperature in storage units in tropical areas frequently exceeds 50°C during the warmest periods of the day. Since protectant insecticides are sprayed on grains under these conditions, such high temperatures may interfere with the insecticidal activity. To assess this possibility we sprayed maize grains with pirimiphos-methyl 500 EC (0.8 ml c.p./l and 1.5 l/t) at different temperatures (25°C, 30°C, 35°C, 40°C, 45°C, and 50°C) and 55% r.h. The grains were then maintained at 27±1°C and 55±5% r.h. throughout the experiment which lasted 90 days. Residues of pirimiphos-methyl on the sprayed grains were analyzed every 30 days. Grain samples were assessed every 15 days after the insecticide spraying for their effect on the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae). Insect mortality was evaluated after 24 and 48 h of exposure to the treated grain. The level of pirimiphos-methyl residue on maize grains decreased with an increase in storage period and air temperature during the insecticide spraying (varying from 11.0±0.1 to 1.1±0.1 ppm, corresponding to the residue levels at 25°C on the day of the spraying and after spraying at 50°C and 90 days of storage). The same trend was observed for mortality of the maize weevil, which dropped from 95.4±13.3% to 2.5±2.5% after 90 days storage after insecticide spraying at 50°C. These results indicate that temperature at spraying can affect insecticide persistence and activity during storage.     

Composition and availability of soluble and insoluble oxalates in raw and cooked taro (Colocasia esculenta var. Schott) leaves

Taro (Colocasia esculenta var. Schott) is a major staple food crop in parts of Asia and the Pacific Islands and is grown as a minor crop in New Zealand. Soluble, insoluble and total oxalate content of young and older leaves were determined by HPLC following hot water (80 °C) and hot (80 °C) acid (0.2 mol/L HCL) extractions. Young taro leaves contained 589 ± 35.8 mg total oxalates/100 g fresh weight (FW) while older taro leaves contained (443 ± 15.0 mg total oxalates/100 g FW). Soluble oxalates were 74% of the total oxalate content of the young and old leaves.     

Effects of storage temperatures on the antioxidative activity and composition of yam

The effects of storage temperatures on the composition and antioxidative activities of one kind of Taiwanese yam tubers, Tainung No. 1 (TNG1) (Dioscorea alata), were investigated at room temperature (20 ± 8 °C), 17 ± 2 and 10 ± 1.5 °C. Measurements of the antioxidative activities included reducing power and α,α-diphenyl-β-pricryl-hydrazyl radical-scavenging activity. The crude lipid and fibre contents decreased with storage time at all three temperatures, but the reducing sugar contents increased during storage. Both the reducing power and DPPH radical-scavenging activity of TNG1 decreased after 3 and 11 weeks at room temperature and 17 °C, respectively. At 10 °C, significant decline in the reducing power was found after 14 weeks, while the DPPH radical-scavenging activity tended to increase after 7 weeks due to the microbes causing rottenness.     

Life history parameters of Lasioderma serricorne (F.) as influenced by food sources

Fecundity, egg to adult survival rate, developmental time, and adult body weight of the cigarette beetle, Lasioderma serricorne (Coleoptera: Anobiidae) were evaluated on seven food sources at 28 °C. Ground chili, paprika, cayenne pepper, chewing leaf tobacco, cigar tobacco, a commercial insect bait referred to as NOW bait, and wheat flour were used to evaluate mean lifetime fecundity. The highest fecundity (52.4±4.8 eggs/female) was observed in wheat flour, whereas the lowest fecundity (5.8±0.8 eggs/female) was observed in cigar tobacco. Among the seven food sources, beetles reared in wheat flour showed the highest survival rate of 91.0±2.7%. Only 15% of the eggs laid in NOW bait developed to the adult stage. In the three food sources containing Capsicum spp. the survival rate ranged from 30% to 40%. The egg, larval, and pupal development times varied from 3 to 5, 38 to 92 and 4 to 18 d, respectively, among food sources. Body weight and adult longevity studies showed that the heavier adults also had the longest life span. Ovipositing female L. serricorne appear to discriminate among different food sources. Although L. serricorne laid eggs in all food sources evaluated, larval and pupal survival were lowest in NOW bait. Information on the biology and host use pattern of L. serricorne may help to explain how various stored commodities are affected by this species and may lead to develop appropriate pest management strategies for this insect pest.     

Effects of different freezing treatments on physicochemical responses and microbial characteristics of Japanese sea bass (Lateolabrax japonicas) fillets during refrigerated storage

In order to establish an effective freezing method for quality control, the present research evaluated the effects of the different freezing treatments on the quality of Japanese sea bass (Lateolabrax japonicas) over a period of 20 days storage at 0 ± 1 °C. Fish pH value, total volatile basic nitrogen (TVB-N), K-value, trimethylamine nitrogen (TMA-N), drip loss, hardness, color, biogenic amines, microbiological characteristics were measured. Sea bass fillets were stored at −18 °C (T1), −55 °C for 24 h and then −18 °C (T2), −55 °C (T3) for 3 months prior to refrigerated storage. T2 showed lower TVB-N, pH value, biogenic amines and drip loss than T3 and T1 did. Significant lower value of bacterial loads, b* value and hardness were observed in T1, T2 and T3 than those of control group. No significant differences were observed among T1, T2 and T3 for TMA-N and a* value. The study demonstrated that Japanese sea bass fillets treated with −55 °C for 24 h and then −18 °C up to 3 months maintain better quality during refrigerated storage.     

Fate of Staphylococcus aureus in cheese treated by ultrahigh pressure homogenization and high hydrostatic pressure

We evaluated the influence of ultrahigh pressure homogenization (UHPH) treatment applied to milk containing Staphylococcus aureus CECT 976 before cheese making, and the benefit of applying a further high hydrostatic pressure (HHP) treatment to cheese. The evolution of Staph. aureus counts during 30 d of storage at 8°C and the formation of staphylococcal enterotoxins were also assessed. Milk containing approximately 7.3 log₁₀ cfu/mL of Staph. aureus was pressurized using a 2-valve UHPH machine, applying 330 and 30 MPa at the primary and the secondary homogenizing valves, respectively. Milk inlet temperatures (T_in) of 6 and 20°C were assayed. Milk was used to elaborate soft-curd cheeses (UHPH cheese), some of which were additionally submitted to 10-min HHP treatments of 400 MPa at 20°C (UHPH+HHP cheese). Counts of Staph. aureus were measured on d 1 (24 h after manufacture or immediately after HHP treatment) and after 2, 15, and 30 d of ripening at 8°C. Counts of control cheeses not pressure-treated were approximately 8.5 log₁₀ cfu/g showing no significant decreases during storage. In cheeses made from UHPH treated milk at T_in of 6°C, counts of Staph. aureus were 5.0 ± 0.3 log₁₀ cfu/g at d 1; they decreased significantly to 2.8 ± 0.2 log₁₀ cfu/g on d 15, and were below the detection limit (1 log₁₀ cfu/g) after 30 d of storage. The use of an additional HHP treatment had a synergistic effect, increasing reductions up to 7.0 ± 0.3 log₁₀ cfu/g from d 1. However, for both UHPH and UHPH+HHP cheeses in the 6°C T_in samples, viable Staph. aureus cells were still recovered. For samples of the 20°C T_in group, complete inactivation of Staph. aureus was reached after 15 d of storage for both UHPH and UHPH+HHP cheese. Staphylococcal enterotoxins were found in controls but not in UHPH or UHPH+HHP treated samples. This study shows a new approach for significantly improving cheese safety by means of using UHPH or its combination with HHP.     

Movement and distribution of adult Cryptolestes ferrugineus (Coleoptera: Laemophloeidae) in stored wheat in response to temperature gradients, dockage, and moisture differences

The movement and distribution of adult Cryptolestes ferrugineus were determined in 100×100×1000 mm wheat columns with or without 5 °C/m temperature gradients (from 27.5±0.2 to 32.5±0.2 °C or at 27.5±0.2 °C) under: (1) 5% and 10% uniform dockage (14.5±0.2% moisture content (m.c.), wet basis); (2) half of the columns with 5% or 10% dockage and the other half without dockage; (3) 12.5%, 14.5% or 16.5% m.c. wheat without dockage; and (4) half of the columns with 12.5% or 14.5% m.c. wheat and the other half with 16.5% m.c. wheat.Adults introduced in the middle of the horizontal wheat columns with or without uniform dockage showed no bias in the direction of net displacement, with the distribution pattern gradually becoming more uniform when time increased from 1 to 144 h. In vertical columns with 0%, 5% and 10% uniform dockage, the adults preferred to move down in the first 24 h; however, they moved up after 24 h. Grain with a high percentage of dockage (10%) decreased beetle movement speed. A low percentage of dockage (5%) did not influence insect movement and distribution. Positive geotaxis was more important than the attraction of dockage.Adults responded to both temperature gradients and moisture differences in columns of wheat with temperature gradients and moisture content differences. The response was different at different moisture conditions. Adults were more sensitive to moisture differences and moved faster in 12.5% m.c. wheat than in 14.5% m.c. wheat. Adults stayed in warmer sections in both high and low moisture grain. At different moisture conditions, adults changed their preference (e.g., preferred high moisture grain in dry grain, and preferred warmer temperature in damp grain).     

Temperature-mediated functional response of Theocolax elegans (Hymenoptera: Pteromalidae) parasitizing Rhyzopertha dominica (Coleoptera: Bostrichidae) in stored wheat

The functional response of Theocolax elegans (Westwood) parasitizing the lesser grain borer, Rhyzopertha dominica (F.) was examined over a range of temperatures. A type II functional response equation was fitted to each temperature regime. The parasitization rate was highest at 30°C (20 hosts per day) and was lowest at 20°C (2 hosts per day). Handling time was inversely proportional to temperature, and ranged from 1.6 days at 20°C to 0.05 days at 30°C. Instantaneous search rate also changed with temperature. It was lowest at 20°C and highest at 30°C. A temperature-mediated functional response equation was fitted to the data, in which handling time was a quadratic function of temperature. The equation explained 74% of the variance in parasitization rate. Theocolax elegans has a narrower optimal temperature range than other parasitic stored-product Hymenoptera. Temperatures greater than 32.5°C caused high parasitoid mortality.     

Effect of high-temperature pre-irradiation on reproduction and mating competitiveness of male Sitotroga cerealella (Olivier) and their F1 progeny

Pupae of the Angoumois grain moth, Sitotroga cerealella (Olivier) were irradiated with substerilizing doses of 150, 180 and 210 Gy of gamma radiation. Inherited deleterious effects due to irradiation of P males irradiated as pupae were recorded for F₁ progeny. The radiation damage increased when pupae were kept at high temperature (32.5 °C) for 24 h before irradiation, where a marked reduction in fecundity and egg hatch was obtained among P males and their F₁ progeny. This reduction was significantly increased by increasing the dosage. F₁ progeny were more sterile than the irradiated parent generation, though F₁ males were more sterile than F₁ females. Also, the combination of high temperature and irradiation applied to parental male pupae decreased larval survival and percentage of F₁ female progeny, whereas it did not affect the mating frequency among P males and F₁ progeny at the tested doses. Laboratory mating competitiveness indicated that parental males heat-treated with 32.5 °C and irradiated with 150, 180 and 210 Gy and their F₁ progeny were fully competitive with their untreated siblings.     

Efficacy of powder and essential oil from Chenopodium ambrosioides leaves as post-harvest grain protectants against six-stored product beetles

Powder and essential oil obtained from dry ground leaves of Chenopodium ambrosioides were tested under laboratory conditions (25±1°C, 70-75% r.h.) for their ability to protect grains from damage by six insect pests, Callosobruchus chinensis, C. maculatus, Acanthoscelides obtectus, Sitophilus granarius, S. zeamais and Prostephanus truncatus. The insects were reared and tested on whole maize grain for S. zeamais and P. truncatus, whole wheat for S. granarius, green peas for C. chinensis, mung bean for C. maculatus and white bean for A. obtectus. The powder prepared from dry leaves of C. ambrosioides was mixed with grains at different dosages ranging from 0.05-0.80% (wt/wt) for C. chinensis, C. maculatus and A. obtectus and from 0.8-6.4% (wt/wt) for S. granarius, S. zeamais and P. truncatus. The dosage of 0.4% killed more than 60% of all the bruchids 2 days after treatment, while a dosage of 6.4% induced total mortality of S. granarius and S. zeamais within the same exposure time. All levels of the dry ground leaf concentrations inhibited F1 progeny production and adult emergence of the tested insects. The dosage of 0.2 μl/cm² of the essential oil killed 80-100% of the beetles within 24 h except C. maculatus and S. zeamais, where this dosage induced only 20% and 5% mortality, respectively. These results indicate a scientific rationale for the use of this plant in grain protection by local communities in the western highlands of Cameroon.     

Sugar metabolism and involvement of enzymes in sugarcane (Saccharum officinarum L.) stems during storage

Sugarcane (Saccharum officinarum L. cv. Badila) was harvested at the mature stage and stored at 2, 10, and 20 °C for 30, 90, and 120 days, respectively. Metabolic changes in the contents of sucrose and reducing sugar in relation to the activities of soluble acid invertase (SAI), neutral invertase (NI) and sucrose-phosphate synthase (SPS), in sugarcane juice, were studied. Extractable juice, sucrose and vitamin C declined significantly with increasing storage temperatures, while respiration rate increased. There was a rapid increase in titratable acidity during storage, with a more rapid rate at higher temperatures. A sharp increase in reducing sugar was observed within 20 days at 20 °C and 70 days at 10 °C, followed by a rapid decrease. Both SAI and NI activities showed a sharp increase within 15 days at 20 °C, followed by a rapid decrease, while a moderate increase occurred within 40–60 days at 10 °C. Slight increases were observed in SPS activity within 20 days at 20 °C and 50 days at 10 °C. Enzyme activities remained steady or underwent a small change in canes stored at 2 °C. Enzyme activities were significantly correlated with reducing sugar content.     

Optimization of gelatine gel preparation from New Zealand hoki (Macruronus novaezelandiae) skins and the effect of transglutaminase enzyme on the gel properties

Response Surface Methodology (RSM) was adopted to optimize the preparation of NZ hoki (Macruronus novaezelandiae) gelatine gels treated with Transglutaminase (TGase) and some of the rheological properties were characterized. The optimum concentration of the enzyme [X₁] was 3.33 mg/g, incubation time, [X₂] was 30 min, and incubation temperature, [X₃] was 37 ^°C. The calculated gel strength achieved by RSM was in very good agreement with the experimental value. The addition of TGase to hoki gelatine at the optimum concentration of increased the gel strength from 197 ± 5 g to 278.2 ± 0.19 g and the melting point from 21.4 ± 0.8 ^°C to 25.9 ± 0.1 ^°C. The increase in the G' values with the addition of TGase indicated the formation of firmer gels and the changes in G' and G" values with increase in temperature showed increase in melting point.     

Effects of cold storage, rearing temperature, parasitoid age and irradiation on the performance of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae)

In this study, the effects of cold storage, rearing temperature, parasitoid age, and irradiation on the performance of the egg parasitoid Trichogramma evanescens were investigated. Pupae of T. evanescens can be stored at 4 °C for up to 3 weeks without much loss of performance. The longevity and walking speed of adults emerging from chilled pupae significantly decreased after longer storage periods. The F₁ generation of adults which emerged from pupae stored up to 3 weeks was able to parasitize as well as the control. The parasitization rate was similar at 24, 27, and 30 °C, but significantly decreased at 33 and 36 °C. Although T. evanescens developed to the pupal stage at 36 °C, no adult emergence was observed at this temperature. Developmental periods were longer at 24 °C than at higher temperatures. The optimum age for T. evanescens to successfully parasitize host eggs ranged from 24 to 90 h. The parasitization frequency of the 56-78 h aged females was higher than for the other age groups. The daily egg laying pattern of female T. evanescens adults was similar when they were reared on Ephestia kuehniella or Plodia interpunctella eggs. Gamma- or ultraviolet-irradiated and unirradiated host eggs were equally preferred by adult females.     

Studies on insect infestation in chocolates

The ability of stored-product pests including the cigarette beetle, Lasioderma serricorne, the sawtoothed grain beetle, Oryzaephilus surinamensis, the rust-red flour beetle, Tribolium castaneum, and the almond moth, Ephestia cautella, to infest chocolates under packaged and unpackaged conditions was investigated in the laboratory at 25±1 °C and 65±5% r.h. Four types of chocolates were investigated: milk, nut, dried fruit and nut, and wafer chocolates. Adults (beetles only, 20 per replicate) or eggs (30 per replicate) were released on unpackaged and packaged chocolates and infestation levels (number of living adults and larvae) were determined 45 days later. When adult beetles were released on unpackaged chocolates, the degree of infestation varied depending on the species and the type of chocolate. The highest infestation observed in unpackaged chocolate was that of O. surinamensis in wafer chocolate (mean 138.4). When eggs were released on unpackaged chocolates, the most numerous species was E. cautella in dried fruit and nut chocolate (mean population=180.8). With packaged chocolates exposed to adults or eggs, insect infestation was nil or negligible (mean population <6.0). Although infestation levels were low, infestations were found in 50% of treatments over all. Damage to the packaging material along the folds or edges was observed in infested chocolates. The study has shown that milk, nut, dried fruit and nut, and wafer chocolates can support insect infestation and therefore, insect-proof packing of the chocolates and storage under hygienic conditions are important to avoid customers’ complaints.     

Quantitative analysis of allantoin and allantoic acid in yam tuber,mucilage, skin and bulbil of the Dioscorea species

Allantoin and allantoic acid in yam tubers of the D. batatas (Hualien no. 3) and D. pseudojaponica Yamamoto (Keelung) were quantitatively analyzed because the compounds were thought to prevent inflammation and ulcers in humans as well as playing an important role in the storage and translocation of nitrogen in higher plants. To expand yam tuber use, yam tuber mucilage can be used as an ingredient in functional foods and as a skin protectant. The objectives of this research are to analyze the contents of allantoin and allantoic acid in D. batatas and D. pseudojaponica Yamamoto and to compare bubble separation and centrifugation for recovering allantoin and allantoic acid from the mucilage. The total amount of allantoin and allantoic acid of the following Dioscorea (yam) in both the pulp and skin, respectively, were (mean ± RSD, mmoles/g solid): tuber of Keelung yam (D. pseudojaponica Y.) 0.370 ± 6.8%, 1.130 ± 3.4%; tuber of Hualien no. 3 yam (D. batata) 0.278 ± 7.8%, 0.714 ± 9.1%; bulbil of Hualien no. 3 yam (D. batata) 0.179 ± 7.9%, 0.297 ± 3.4%. The Keelung yam was much higher in allantoin and allantoic acid content than the Hualien no. 3. The skin of yam tuber is rich in allantoin and allantoic acid. The allantoin and allantoic acid content is 305% (in Keelung yam) and 257% (in Hualien no. 3) higher than that of the pulp. Bubble separation is an appropriate procedure in the practice for maximum recovery of allantoin and allantoic acid in yams. It was found that 80% of allantoin and allantoic acid yield can be recovered from the low starch contents of mucilage of the Keelung yam using bubble separation.