Chill Period Research Articles

Off-Season Spawning of Yellow Perch

Abstract The thermal and light conditions for 2-year-old broodstock of yellow perch Perca flavescens were shifted by 6 months in an effort to change spawning from spring to autumn and fall. The natural photothermal conditions consisted of a chill period of 10°C and 10 h of light during January–March followed by increases in temperature to 20–22°C and photoperiod to 15 h light during July–September. The natural spawning of yellow perch occurs in April–May at 12–14°C and 12 h light. In the present study, the broodstock were maintained at a higher temperature and a longer period of light during September–February (18°C and 13 h light). The photothermal conditions were decreased gradually until June. The chill period (10°C and 11 h light) was 60 d in duration (June–July) and was followed by gradually increased water temperature and longer daylight (12°C and 19 h). Following this period, 50% of the females were fully ovulated, and they were stripped or spawned naturally. The males spermiated during the entire ...

Improved method for measuring hydrolyzable tannins using potassium iodate

Until now, the recommended procedure for measuring hydrolyzable tannins has been to mix the reagent and sample, subject the mixture to a certain amount of chill, allow the reaction to continue for some time at a higher temperature and then measure the absorbance of the colored solution. The effect of different chill conditions has been studied by many workers but the effect of conditions after the chill period has not been studied. In this work, the effects of changing certain reaction variables during the increased temperature time period were examined and it was found that small changes in the reaction conditions resulted in large changes in the reaction process. Additionally, the behavior of the reaction depended on the variety of plant from which the hydrolyzable tannins were extracted and the time of the season when the leaves were collected. It is recommended that no chill be used in the colorimetric procedure but, instead, the following procedure should be used: extract the plant material with 70% acetone and take 1 ml of the extract plus 5 ml of 2.5% potassium iodate and place in a test-tube. Vortex mix the mixture and immediately place the test-tube in a 25 °C water bath. When the optimum length of time has passed (which should be determined for each type of plant material and must be precisely measured), remove the sample from the water-bath and measure the absorbance at 550 nm.

Discovery of Multiyear Diapause in Illinois and South Dakota Northern Corn Rootworm (Coleoptera: Chrysomelidae) Eggs and Incidence of the Prolonged Diapause Trait in Illinois

Northern corn rootworm, Diabrotica barberi Smith & Lawrence, eggs were obtained from female beetles collected in August 1985 from cornfields in Champaign, Ill., and Madison, S. Dak. Eggs were buried in soil or placed in environmental chambers that closely simulated natural soil temperature conditions and were observed for hatch during 4-5 yr. Egg diapause ranged from 1 to 4 yr for both populations. Northern Corn rootworm eggs were also obtained in August 1986 from female beetles collected from four Illinois cornfields that experienced greater rootworm damage than was expected for cornfields rotated annually with a soybean crop, and from females collected from the previously sampled Champaign field. The percentage of eggs that hatched after prolonged diapause (>1 chill period) ranged from 13.9% for eggs from northwest Illinois to 51.3% for eggs from east central Illinois. When the percentage of northern Corn rootworms with prolonged diapause in a given county was regressed on the percentage of rotational corn grown in that county, a significant positive correlation was obtained (r = 0.89, df = 3, P = 0.04).

The roles of low temperature and light in accumulation of a 31‐kDa polypeptide in the light‐harvesting apparatus of maize leaves

Abstract Previously, accumulation of a 31‐kDa polypeptide had been observed in the light‐harvesting apparatus of thylakoids of maize leaves exposed to 5°C and high light (Hayden et al., 1986). The accumulation and disappearance of this 31‐kDa polypeptide in thylakoids of maize leaves are examined as a function of photon flux density and temperature. The accumulation of large amounts of the polypeptide at 5°C was light‐dependent during a 6‐h chill period, with 50% of maximal accumulation occurring at a photon flux density of 60 μmol m−2 s−1.Some polypeptide accumulation did occur in leaves kept in the dark at 5°C for 6 h, i.e. ca. 18% of that accumulating at a photon flux density of 1500 μmol m−2 s−1. The temperature optimum for polypeptide accumulation was ca. 9°C with greater than 50% of maximal accumulation being achieved between 5 and 11°C. The breakdown of maximally accumulated polypeptide on returning leaves to 25°C was complete after 1 h, had a half‐time of ca. 20 min and was independent of light. Breakdown of the polypeptide was also observed when thylakoids isolated from chilled leaves were incubated at 25°C. Reductions of thylakoid incubation temperature between 13 and 5°C markedly reduced the rate of polypeptide disappearance. The accumulation of the polypeptide is discussed in relation to temperature and light effects on the rate of the polypeptide synthesis and of peptidase activities. The results are also discussed in the context of accumulation of the polypeptide in maize leaves in the field and consideration is given to the possible physiological significance.

Effects of Rapid Processing on the Chemical and Sensory Properties of Restructured Steak Made From Bull and Steer Meat

ABSTRACTSouth Devon cattle (10 bulls, 10 steers) were slaughtered to determine effects of sex condition and postmortem temperature conditioning on the chemical and sensory properties of restructured beefsteak. Chucks from each left side were boned following a 4 hr delayed chill (DC, 13°C) period, while chucks from right sides were boned following a 48 hr conventional chill (CC. 2°C). Chucks were mechanically tenderized and formulated into restructured steaks. Bulls produced restructured steaks less prone to oxidative rancidity. Restructured steaks from bulls exhibited higher (P<0.01) cooking losses and Kramer Shear values. There were no differences between treatments in tenderness, juiciness, flavor, and connective tissue residue ratings; however, DC restructured steaks had lower (P<0.05) bind values than CC restructured steaks.

Color formation and retention in fresh beef (1987)

We conducted two studies in response to a severe problem with ground beef color encountered by beef fabricators and retailers. We concluded that: (1) Loss of muscle chemical-reducing capability upon grinding, with subsequent color deterioration, results from both the mechanical effect of grinding and incorporation of oxygen into the beef. (2) Flat, thin, surface muscles from beef carcasses retain more ability to bloom (turn bright red) if they are removed by hot boning or after a relatively short chill period.

Diapause in the Nearctic Species of the virgifera Group of Diabrotica1: Evidence for Tropical Origin and Temperate Adaptations

Voltinism and diapause were studied in the species of the virgifera group of Diabrotica (Coleoptera: Chrysomelidae) that occur in the United States. The well-known univoltinism and egg diapause of the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, and the northern corn rootworm (NCR), D. longicornis barberi Smith and Lawrence, was the basis for comparisons. Examination of museum collection records support univoltinism for D. cristata (Harris) (CRI), D. longicornis longicornis (Say) (LON), D. lemniscata LeConte (LEM), and the Mexican corn rootworm (MCR), D. virgifera zeae Krysan and Smith. Laboratory studies demonstrated an egg diapause in CRI, LEM, and LON. Eggs of MCR and WCR from 15 sites from throughout the geographic distribution diapause in the same embryonic stage, i.e., an early, undifferentiated germ band. Eggs of CRI and LEM diapause in that same stage; by contrast, LON diapauses as a segmented embryo with clearly defined cephalic lobes. The enhancement of diapause termination by a chill period (7°C) was demonstrated in CRI and LON and confirmed for the NCR. A cline in diapause duration was detected in eggs of the WCR; the more northerly populations had shorter diapause. The relationship prevailed at three temperatures: 15, 18, and 25°C. The results favor a hypothesis that these taxa, which now occupy the temperate climate, share, via common evolutionary origin, a diapause mechanism which originally evolved in the tropics. Adaptations that have evolved in the temperate climate incude low thermal optima for diapause development in the NCR, LON, and CRI and brief diapause in the WCR.

Processing-induced changes in frozen storage life of lamb

Quality deterioration of lamb under frozen storage was assessed in terms of rancid flavour development. Twenty-five lamb carcasses were each given one of eight processing treatments and the fifty loins from these lambs were each assigned to one of three storage periods (10, 15, 20 weeks) at −5°C. Minced lamb samples from a separate carcass were also stored at −5°C. Rancid flavour was assessed by a fiften member trained taste panel. Pre-storage freezing to a high nadir (−5°C) or electrical stimulation both appear to prolong the subsequent storage life at −5°C. Mincing, freezing to a low nadir (−35°C), or a 24 h pre-freezing chill (6°C) period appear to significantly reduce subsequent storage life.

Effects of Chill Temperatures on Developing Western Corn Rootworm1 Eggs2

Eggs of western corn rootworm, Diabrotica virgifera LeConte, in different embryonic stages separated according to their sp. gr. were exposed to 4 temperatures and their viability was determined. Results indicated that, in developing eggs, survival was adversely affected by a chill period of 12 wk. The effect was more pronounced at more advanced stages of development and at lower chill temperatures. Overall % hatch means for 20°, 10°, 5°, and 0°C were 81.7, 63.3, 45.7, and 31.0, respectively. Results also showed that time to hatch was delayed and the duration of hatching was shortened following chill. Thus, if eggs developed in the field during the fall they would not survive and hatch in the spring, and the species would not adapt to produce 2 generations per season.

Eeffects of die casting conditions on the mechanical properties of ADC 12

The object of this study was to know the effects of various die casting conditions such as injection pressure, locking force, injection speed, sleeve temperature, chill period, molten metal temperature, automatically controlled mold temperature, and injection speed ratio on the mechanical properties of ADC12 alloy products (ASTM E8 test bar). The die casting machine used in our laboratory was of DC 250 type, which can record the measuring results of the above casting conditions and also can control the mold temperature. The results obtained were as follows:1. Injection pressure and locking force gave almost no effects on the mechanical properties of ASTM test bar.2. Mechanical properties decayed at extremely high or low injection speed, but they were improved with the increase of injection speed, because the pressure increased immediately after filling molten metal into the cavity, whereby beneficial effects were given on the strength of the products.3. Higher casting temperature (680°C) was recommended for better mechanical properties from the viewpoints of fluidity and castability of molten metal.4. Mechanical properties decayed with the elevation of mold temperature.5. They were the best at the injection speed ratio of 1 to 1.6. Mechanical properties of ASTM test bar, were independent of the chill period of 5-10 seconds.

Water Absorption in Broilers as Influenced by Carcass to Coolant Ratio

PROCESSED poultry are generally chilled in a combination of crushed ice and water. During the chill period, processed poultry may show either a decrease or increase in carcass weights (Tarver et al., 1956; Thomson et al., 1960; and Mickelberry et al., 1962). Several factors, including prechill weight and class of processed poultry, type and circulation of coolant, will influence the degree of water absorption (Connally et al., 1954; Orr, 1953; and Roberts and Robertson, 1941). May et al. (1963), reported low levels of phosphate (4 ounces per gallon of ice slush solution) significantly increased broiler carcass weights during chilling.The present study was undertaken to determine the effect of reducing volumes of coolant per pound of carcass on cooled broiler carcass weights. EXPERIMENTALIn a series of 6 trials, 895 uncooled commercially eviscerated broilers were delivered to the Poultry Science Department processing laboratory. Immediately, each carcass was randomly identified, weighed…