Continuous Chilling Research Articles

Effect of Warm Temperature Interruption on the Accumulation of Winter Chilling in Kiwifruit (Actinidia chinensis Planch. and A. deliciosa A. Chev.)

Warm temperature exposure during winter has reportedly resulted in the apparent negation of chilling in several fruit species. This study was conducted to investigate the floral and vegetative response of two pistillate kiwifruit cultivars to intermittent warm temperature interruption during chilling accumulation. Dormant 1-year-old canes of Actinidia chinensis ‘AU Golden Dragon’ and Actinidia deliciosa ‘AU Fitzgerald’ were collected in December 2018 and 2019 (334 and 360 chilling units, respectively), shortly after leaf abscission. Canes were cut to 10 nodes after removing the first six basal nodes, placed in jars filled with distilled water, and transferred to respective chilling treatments. Treatments included continuous chilling (CC) (in addition to base chilling) at 1-week (168 chilling units) increments (0–5 weeks) and chilling exposure at the same increments with intermittent warm temperature (WT). For the WT treatments, each week of chilling was followed by 3 days of exposure to warm conditions. Chilling and warm temperature exposure were simulated by 7/4 °C and 25/17.2 °C (day/night) air temperatures, respectively, using separate climate-controlled growth chambers. After treatments, canes were forced in a third chamber at 21.1 to 25.0 °C with light-emitting diode lighting. Vegetative budbreak, floral bud number (from here on defined as floral response), and floral development stage were recorded for each cane at 2-day intervals. For ‘AU Golden Dragon’, WT did not result in any reduced floral response at any of the observed chilling levels. However, lower mean floral response was observed with WT, as compared with CC for ‘AU Fitzgerald’ at 5 weeks of chilling over the 2 years (P = 0.05). WT also lessened the effect of apical dominance with respect to vegetative/floral response to node position for both cultivars. Chilling type had no significant effect on vegetative response in either cultivar. Estimated chilling requirements (CC) in this experiment were similar to those reported previously for these cultivars. Results suggest that A. chinensis cultivars may respond more favorably than A. deliciosa to the erratic winter temperature patterns experienced in the southeastern United States.

Alleviation of Seed Dormancy in Kala Zeera (Bunium Persicum) Through Chilling and Phytohormones

Kala zeera (Bunium persicum) is a high-value medicinal spice plant. The seeds and extracts are used for culinary, perfumery, flavouring food and medicinal purposes. The commercial cultivation of kala zeera is hampered due to poor seed germination and deep physiological dormancy. To break the dormancy of kala zeera, three phytohormones, gibberellic acid (100 μmol L-1), 6-benzylaminopurine (10 μmol L-1) and thidiazuron (6.3 μmol L-1) were tested individually and in combination, under two temperature levels: continuous chilling at 4°C and one week chilling at 4°C followed by incubation at room temperature. The combined application of the three phytohormones under continuous chilling (4°C) improved the germination from 11.25 to 93.25% and reduced the mean germination time 60 to 50 days. The lowest mean germination time (34.78 days) and high mean daily germination (1.57 seeds day-1) with a high coefficient of germination velocity (2.88), were found under combined application of phytohormones as compared to their individual application. The findings have implications in successful propagation and systematic cultivation of this high-value medicinal spice plant.

An experimental study on the effects of intermittent chilling at different growth stages on rice yield in Northeast China

AbstractIn Northeast China, the frequency and intensity of chilling events has been increasing continuously, which places regional rice production at an increasing risk for yield loss. Previous studies have shown that continuous chilling at the tillering, booting and flowering stages could reduce rice grain yield. However, the effects of intermittent chilling at different growth stages on rice yield have rarely been reported. In this study, we conducted a temperature‐controlled experiment on rice plants at the tillering, booting and flowering stages, with both continuous and intermittent chilling treatments at two chilling temperatures and four chilling durations. The results showed that rice grain yield was most affected by chilling at the booting stage, followed by chilling at the flowering stage and least affected by chilling at the tillering stage. For per 1 day increase in chilling duration, the continuous (intermittent) chilling treatment at T1 (11°C/12°C/12°C) at the tillering, booting and flowering stages decreased the grain yield per plant by 1.0%, 6.0% and 2.9% (0.9%, 2.7% and 1.6%), respectively. For per 10°C·day increase in cooling degree days, the continuous (intermittent) chilling treatment at the booting stage decreased the grain yield per plant, spikelet fertility, grain number per spike and thousand grain weight by 10.7%, 7.9%, 5.4% and 1.6% (5.6%, 1.5%, 4.4% and 1.2%), respectively. While the continuous (intermittent) chilling treatment at the flowering stage decreased the grain yield per plant and spikelet fertility by 4.9% and 3.9% (2.8% and 3.2%), respectively. Our study is complementary to the current knowledge gap concerning the mechanism of chilling‐induced yield losses for rice. In particular, the results of this study could be used to (a) modify the chilling effects algorithms in rice models to improve the simulation accuracy in rice yields and (b) target the genetic features to breed new rice varieties with greater cold tolerance.

Effects of Chilling Duration on Marbling Score of Beef Carcasses

Two hundred and nine beef carcasses (body weight of 361±53 kg) from crossbred, grain-finished cattle were harvested in a commercial abattoir and subjected to continuous chilling for 96 h at 0°C to 3°C in a commercial hot box with a wind speed of 3.1 m/s and 153 lux of fluorescent light. At 24, 48, 72, and 96 h, the carcasses were analyzed for fatty acid composition,marbling score, pH, shrinkage, color, and aerobic plate count (n = 50). Carcasses reached 3°C after 12 to 16 h of chilling. There were minimal changes in shrinkage among time point (−0.4% to 1.2%; P ≤ 0.002), pH (5.56 to 5.69; P ≤ 0.001), and aerobic plate count (0.1 to 0.7 log; P < 0.001). Initial 24-h grading by a USDA grader revealed a grade composition of 21.1% Slight (n = 44), 34.0% Small (n = 71), 17.2% Modest (n = 37), 17.7% Moderate (n = 36), and 10.1% Slightly Abundant (n = 21). With a marbling score in numeric values between 200 (Practically Devoid00) and 1100 (Abundant00), carcasses that had Small or greater marbling score at 24 h experienced a decrease of 34 to 60 points after 96 h of chilling (P ≤ 0.042). Comparatively, the marbling scores of the Slight carcasses increased from 442 points at 24 h to 469 points at 96 h. Moreover, Slight carcasses had a greater percentage of polyunsaturated fatty acids (P < 0.001). Results indicate that chilling for 96 h increases the marbling score of USDA Select but has minimal impacts on the marbling score of greater USDA quality grades.

Plant growth and fruit enlargement among different watermelon (<i>Citrullus lanatus</i>) cultivars in continuous chilling night temperature conditions

Plant growth and fruit enlargement among different watermelon (<i>Citrullus lanatus</i>) cultivars in continuous chilling night temperature conditions

Individual based modeling and analysis of pathogen levels in poultry chilling process

Pathogen control during poultry processing critically depends on more enhanced insight into contamination dynamics. In this study we build an individual based model (IBM) of the chilling process. Quantifying the relationships between typical Canadian processing specifications, water chemistry dynamics and pathogen levels both in the chiller water and on individual carcasses, the IBM is shown to provide a useful tool for risk management as it can inform risk assessment models. We apply the IBM to Campylobacter spp. contamination on broiler carcasses, illustrating how free chlorine (FC) sanitization, organic load in the water, and pre-chill carcass pathogen levels affect pathogen levels of post-chill broilers. In particular, given a uniform distribution of Campylobacter levels on incoming poultry we quantify the efficacy of FC control in not only reducing pathogen levels on average, but also the variation of pathogen levels on poultry exiting the chill tank. Furthermore, we demonstrate that the absence/presence of FC input dramatically influences when, during a continuous chilling operation, cross-contamination will be more likely.

Different chilling stresses stimulated the accumulation of different types of ginsenosides in Panax ginseng cells

Ginseng (Panax ginseng) is one of the most medically important plants in the world. Dammarane-type ginsenosides, which mainly include protopanaxatriol-type (PPT-type) and protopanaxadiol-type (PPD-type) ginsenosides, are the major pharmacologically relevant compounds that are produced by ginseng. Dammarenediol-II synthase (DDS) is the first committed enzyme in the ginsenoside biosynthetic pathway for dammarane-type ginsenosides, and PPD-type and PPT-type ginsenosides are catalyzed by protopanaxadiol synthase (PPDS) and protopanaxatriol synthase (PPTS), respectively. Ginseng cells are often used in stress studies. During their growth and development, ginseng plants are often exposed to cold stress. This study evaluated the effects of different chilling stresses on the accumulation of ginsenosides and the expressions of the DDS, PPDS and PPTS genes in ginseng cells. The results showed that continuous chilling (5 °C for 12 h) induced the PPT-type ginsenosides; whereas intermittent chilling (25 °C for 12 h and 5 °C for 12 h) stimulated the accumulation of PPD-type ginsenosides. The expression levels of DDS, PPDS and PPTS were clearly consistent with the accumulation pattern for PPT-type ginsenosides under continuous chilling stress or PPD-type ginsenosides under intermittent chilling stress, as was their order of involvement in the PPT-type or PPD-type biosynthetic pathway. These results indicate that different chilling treatments stimulated the accumulation of different types of ginsenosides, suggesting that cold stress may be one of the reasons for ginsenoside accumulation in ginseng cells.

Effect of extending processing plant operating time on the microbiological quality and safety of broiler carcasses

In Australia, increased consumer demand for chicken meat and socioeconomic pressures have forced poultry operations to extend plant operating time with delayed spin-chiller emptying and cleaning to maximise water use efficiency. There are concerns that these measures may compromise the microbiological quality and safety of the product. Therefore, the objective of this trial was to determine the microbiological status of broiler carcasses collected hourly during 24 h and 48 h continuous chiller operation within a three week period (total n = 196). Carcass rinses were analysed for total viable count, Escherichia coli and Campylobacter spp. counts, and Salmonella prevalence. Corresponding spin-chiller parameters (pH, oxidation-reduction potential [ORP], core temperature and HOCl concentration) were recorded. There was no statistically significant difference (P > 0.05) in bacterial populations and spin-chiller parameters when various sized chickens were processed. Therefore, the microbiological data and consequent quality were shown to be statistically equivalent between carcasses sampled from 24 h to 48 h continuous processing using a fully automated (water temperature, pH and chlorine control) spin-chiller. However, improvements to processing, including rehang and scald hygiene, and weight-specific hypochlorous acid concentrations, should be researched in order to further reduce bacterial contamination.

Proteomic changes in the roots of germinating Phaseolus vulgaris seeds in response to chilling stress and post-stress recovery

Plants respond to different environmental cues in a complex way, entailing changes at the cellular and physiological levels. An important step to understand the molecular foundation of stress response in plants is the analysis of stress-responsive proteins. In this work we attempted to investigate and compare changes in the abundance of proteins in the roots of bean (Phaseolus vulgaris L.) germinating under long continuous chilling conditions (10°C, 16 days), exposed to short rapid chilling during germination (10°C, 24h), as well as subjected to recovery from stress (25°C, 24h). The results we obtained indicate that germination under continuous chilling causes alterations in the accumulation of the proteins involved in stress response, energy production, translation, vesicle transport, secondary metabolism and protein degradation. The subsequent recovery influences the accumulation of the proteins implicated in calcium-dependent signal transduction pathways, secondary metabolism and those promoting cell division and expansion. Subjecting the germinating bean seeds to short rapid chilling stress resulted in a transient changes in the relative content of the proteins taking part in energy production, DNA repair, RNA processing and translation. Short stress triggers also the mechanisms of protection against oxidative stress and promotes expression of anti-stress proteins. Subjecting bean seeds to the subsequent recovery influences the abundance of the proteins involved in energy metabolism, protection against stress and production of phytohormones. The exposure to long and short chilling did not result in the alterations of any proteins common to both treatments. The same situation was observed with respect to the recovery after stresses. Bean response to chilling is therefore strongly correlated with the manner and length of exposure to low temperature, which causes divergent proteomic alterations in the roots.

Changes in the protein patterns in pea (Pisum sativum L.) roots under the influence of long- and short-term chilling stress and post-stress recovery.

Amongst many factors restricting geographical distribution of plants and crop productivity, low temperature is one of the most important. To gain better understanding of the molecular response of germinating pea (Pisum sativum L.) to low temperature, we investigated the influence of long and short chilling stress as well as post-stress recovery on the alterations in the root proteomes. The impact of long stress was examined on the pea seeds germinating in the continuous chilling conditions of 10 °C for 8 days (LS). To examine the impact of short stress, pea seeds germinating for 72 h in the optimal temperature of 20 °C were subjected to 24-h chilling (SS). Additionally, both stress treatments were followed by 24 h of recovery in the optimal conditions (accordingly LSR and SR). Using the 2D gel electrophoresis and MALDI-TOF MS protein identification, it was revealed, that most of the proteins undergoing regulation under the applied conditions were implicated in metabolism, protection against stress, cell cycle regulation, cell structure maintenance and hormone synthesis, which altogether may influence root growth and development in the early stages of plant life. The obtained results have shown that most of detected alterations in the proteome patterns of pea roots are dependent on stress duration. However, there are some analogical response pathways which are triggered regardless of stress length. The functions of proteins which accumulation has been changed by chilling stress and post-stress recovery are discussed here in relation to their impact on pea roots development.

Role of phytochrome B in the development of cold tolerance in cucumber plants under light and in darkness

Cold tolerance of cucumber (Cucumis sativus L.) seedlings was investigated using wild-type plants and the phytochrome B-deficient mutant (lh-mutant). Plants were subjected for 6 days to intermittent short-term cooling (12°C for 2 h per day) and to continuous chilling under conditions of 16-h photoperiod (day/night = 16/8 h) and permanent illumination. “Dehardening” process was initiated by the transfer of plants to either light or dark conditions at 23°C. It was concluded that phytochrome B participates in the development of cold tolerance in cucumber plants under stress conditions, i.e., under short-term intermittent chilling at nights and during dehardening in continuous darkness.

Stomatal conductance in Cucumis sativus upon short-term and long-term exposures to low temperatures

We studied stomatal conductance (gs) in leaves of cucumber plants (Cucumis sativus L., cv. Zozulya) subjected at early developmental stages to either short-term daily cooling (2 h at the end of night periods) or continuous chilling (12°C throughout the day and night). Irrespective of the irradiance during measurements, continuous chilling either lowered gs or had no effect, as compared to gs of control plants (23°C). In plants subjected to periodic short-term cooling, the gs was found to increase at low temperatures both at moderate and high irradiance; it also increased at high temperature (33°C) but only at photosynthetically active irradiance of 800 μmol/(m2 s). It is supposed that heat-loving plants, subjected to different types of low-temperature treatment, mobilize different mechanisms of stomatal regulation and employ different strategies of adaptation in response to low- and high-temperature treatments. The unusual behavior of stomata, manifested in stomatal opening at both low and high temperatures, extends the adaptive potential of plants subjected daily to short-term low-temperature treatments. This leads to a high level of photosynthesis, biomass accumulation, and supports high physiological activity in plants.

Bud burst timing in Picea abies seedlings as affected by temperature during dormancy induction and mild spells during chilling

In trees adapted to cold climates, conditions during autumn and winter may influence the subsequent timing of bud burst and hence tree survival during early spring frosts. We tested the effects of two temperatures during dormancy induction and mild spells (MS) during chilling on the timing of bud burst in three Picea abies (L.) Karst. provenances (58-66 degrees N). One-year-old seedlings were induced to become dormant at temperatures of 12 or 21 degrees C applied during 9 weeks of short days (12-h photoperiod). The seedlings were then moved to cold storage and given either continuous chilling at 0.7 degrees C (control), or chilling interrupted by one 14-day MS at either 8 or 12 degrees C. Interruptions with MS were staggered throughout the 175-day chilling period, resulting in 10 MS differing in date of onset. Subsets of seedlings were moved to forcing conditions (12-h photoperiod, 12 degrees C) throughout the chilling period, to assess dormancy status at different timings of the MS treatment. Finally, after 175 days of chilling, timing of bud burst was assessed in a 24-h photoperiod at 12 degrees C (control and MS-treated seedlings). The MS treatment did not significantly affect days to bud burst when given early (after 7-35 chilling days). When MS was given after 49 chilling days or later, the seedlings burst bud earlier than the controls, and the difference increased with increasing length of the chilling period given before the MS. The 12 degrees C MS treatment was more effective than the 8 degrees C MS treatment, and the difference remained constant after the seedlings had received 66 or more chilling days before the MS treatment was applied. In all provenances, a constant temperature of 21 degrees C during dormancy induction resulted in more dormant seedlings (delayed bud burst) than a constant temperature of 12 degrees C, but this did not delay the response to the MS treatment.

CONTROL OF CLOSTRIDIUM PERFRINGENS IN A MODEL ROAST BEEF BY SALTS OF ORGANIC ACIDS DURING CHILLING1

ABSTRACTControl of Clostridium perfringens germination and outgrowth by the following salts of organic acids, sodium lactate [Purasal™S/SP (Purasal); 1.50, 3.00 and 4.80%], sodium lactate supplemented with sodium diacetate [Purasal™ Opti.form™ (Optiform), 1.50, 3.00 and 4.80%], buffered sodium citrate [Ional™ (Ional), 0.75, 1.00 and 1.30]) and buffered sodium citrate supplemented with sodium diacetate [Ional Plus™ (Ional Plus), 0.75, 1.00 and 1.30%] was evaluated during continuous chilling of a model roast beef product. Beef rounds were ground through an 1/8′’ plate and NaCl, potato starch and potassium tetra pyrophosphate were added to final concentrations of 0.85, 0.25 and 0.20%, respectively, and mixed. Portions (250 g) of the meat were mixed with either Purasal (1.5, 3.0 or 4.8%), Optiform (1.5, 3.0 or 4.8%), Ional (0.75, 1.0 or 1.3%) or Ional Plus (0.75, 1.0 or 1.3%) along with a control that did not have any added antimicrobials. Each product (10 g) inoculated with C. perfringens spores (ca. 2.2 log10 spores/g) was packaged into vacuum bags (2 in. × 3 in.), vacuum sealed, heated to 60C within 1 h, and subsequently chilled from 54.4C to 7.2C in 18 or 21 h following exponential chilling rates. Products were sampled immediately after cooking to enumerate the C. perfringens populations (spores surviving heat treatment) and subsequent to chilling (total C. perfringens populations, including spores and vegetative cells resulting from germination and outgrowth of the spores). Chilling of cooked, model ground roast beef resulted in germination and outgrowth of C. perfringens spores; the population densities increased by 4.13 and 4.40 log10 CFU/g, following 18 and 21 h chill rates, respectively. Incorporation of Purasal (1.5–4.8%), Optiform (1.5–4.8%), Ional and Ional Plus (0.75–1.3%) substantially (P ± 0.05) inhibited germination and outgrowth of C. perfringens spores. Incorporation of antimicrobial ingredients resulted in ± 1.0 log10 CFU/g increase of the pathogen, except for model roast beef with Ional Plus at 0.75% concentration, following 18 h chilling rate. Similar results were obtained when 21 h chilling rate was followed, with roast beef containing ingredients (at all the concentrations) resulting in either reductions or ± 1.0 log10 CFU/g growth in total C. perfringens populations, except for Purasal and Ional Plus at 1.5 and 0.75% concentrations, respectively. Use of sodium salts of organic acids in formulation of model roast beef can reduce the risk of C. perfringens spore germination and outgrowth during extended chilling rates.

Inhibitory effects of organic acid salts on growth of Clostridium perfringens from spore inocula during chilling of marinated ground turkey breast

Inhibition of Clostridium perfringens germination and outgrowth by salts of organic acids such as sodium lactate, sodium acetate, buffered sodium citrate and buffered sodium citrate supplemented with sodium diacetate was evaluated during continuous chilling of ground turkey. Turkey breast meat was injected with a brine-containing NaCl, potato starch and potassium tetra pyrophosphate to yield final in-product concentrations of 0.85%, 0.25% and 0.20%, respectively. The meat was ground, mixed with either sodium lactate (1%, 2%, 3% or 4%), sodium acetate (1% or 2%), buffered sodium citrate (Ional™, 1%) or buffered sodium citrate supplemented with sodium diacetate (Ional Plus™, 1%), in addition to a control that did not contain added antimicrobials. Each product was mixed with a three-strain C. perfringens spore cocktail to obtain final spore concentrations of ca. 2.8 log 10 spores/g. Inoculated products (10 g) were packaged into cook-in-bags (2×3 in.), vacuum sealed, cooked at 60 °C for 1 h, and subsequently chilled from 54.4 to 7.2 °C in 15, 18 and 21 h following exponential chilling rates. Products were sampled immediately after cooking and then after chilling. Chilling of cooked turkey following 15, 18 and 21 h chill rates resulted in germination and outgrowth of C. perfringens spores to 6.6, 7.58 and 7.95 log 10 CFU/g populations, respectively, from initial spore populations of ca. 2.80 log 10 CFU/g. Incorporation of sodium lactate (1%), sodium acetate (1%), Ional or Ional Plus (1%) substantially inhibited germination and outgrowth of C. perfringens spores compared to controls. Final C. perfringens total populations of 3.12, 3.10, 2.38 and 2.92 log 10 CFU/g, respectively, were observed following a 15-h exponential chill rate. Similar inhibitory effects were observed for 18 and 21 chill rates with the antimicrobials at 1% concentrations. While sodium lactate and sodium acetate concentrations of 1% were sufficient to control C. perfringens germination and outgrowth (<1.0 log 10 CFU/g growth) following 15 h chill rates, higher concentrations were required for 18 and 21 h chill rates. Ional at 1% concentration was effective in inhibiting germination and outgrowth to <1.0 log 10 CFU/g of C. perfringens for all three chill rates (15, 18 and 21 h) tested. Use of sodium salts of organic acids in formulation of ready-to-eat meat products can reduce the risk of C. perfringens spore germination and outgrowth during chilling.

アルストロメリアの気温および地温に対する開花反応

アルストロメリアの地中冷却による切り花生産を行うに当たって,気温および地温に対する開花反応を'レジナ','カルメン'('カナ'),'ウイルヘルミナ'を用いて調べた.1.開花シュートの発生に必要な低温要求量は,'ウイルヘルミナ'では2℃,3～6週間,'カルメン'では6週間であったが,'レジナ'では10週間以上であった.2.'レジナ'では,25℃,18℃いずれの温度下でも開花シュートがやがて発生しなくなったが,地温を14℃に冷却すると気温に関係なく開花が継続した.3.'レジナ'の地下茎では,地温の1日当たりの15℃以下経過時間数が6時間であっても開花シュートの発生が継続した.しかし,発生した栄養シュート数は連続して低温を与えた地下茎に比べて増加した.4.低温に遭遇している殊に28/22℃(昼温12時間/夜温12時間)の高温を与えた場合,'レジナ'では4週間,'カルメン'では10週間の高温処理により開花が中断された.

Hydrogen Cyanamide Stimulates Early Foliation of `Misty' Southern Highbush Blueberry

Two-year-old, container-grown `Misty' southern highbush blueberry plants were sprayed to drip with two concentrations of hydrogen cyanamide (HCN) (20.4 g·L–1 and 10.2 g·L–1) after exposure to 0, 150, or 300 hr of continuous chilling at 5.6°C. All plants were sprayed immediately after chilling and placed in a greenhouse for several weeks. The plants were moved outdoors during flowering to increase cross-pollination from nearby `Sharpblue' blueberry plants. HCN sprays killed some of the more advanced flower buds on shoot terminals and on small-diameter wood from the previous spring growth flush. Significantly greater flower bud mortality occurred for the 20.4 g·L–1 HCN sprays than for the 10.2 g·L–1 sprays. Flower buds subjected to 0 hr of chilling were more susceptible to spray burn than flower buds receiving 150 or 300 hr of chilling. Very little flower bud death occurred with the 10.2 g·L–1 HCN rate on plants receiving 300 hr of chilling. Vegetative budbreak was advanced for both HCN treatments compared to controls, regardless of chilling treatment. HCN-treated plants were heavily foliated at full bloom, while non-treated plants had very few to no leaves during bloom. HCN may be useful for stimulating vegetative growth in some southern highbush blueberry cultivars that suffer from poor foliation during flowering and fruit set.

Chilling Stress Protection in Cucumber: A Role for Antioxidants?

To examine the role of endogenous antioxidants in providing chilling stress protection, field-grown cucumber (Cucumis sativus L. cv. Eureka) fruit were stored in the dark and evaluated throughout storage. Storage treatments included continuous chilling (C) (5°C), continuous tempering (T) (12°C), intermittent warming (IW) (1 day at 12°C every 4 days) for 1, 2, 3, or 4 cycles, and preconditioning (PC) (12°C for 4 or 8 days) before chilling. Fruit exposed to in-field chilling (FC) were also stored under continuous chilling at 5°C. Samples were evaluated visually for tissue damage (lack of exudate, water-soaked appearance), and ascorbic acid (Asc) and reduced (GSH) and oxidized (GSSG) glutathione levels and glutathione reductase (GtR) and ascorbate free radical reductase (AFRR) activities were determined. Each 4 days of PC extended storage life by 7 days relative to C. FC or 1–2 IW cycles also extended storage life relative to C. With all treatments, Asc depletion preceded visual tissue damage, whereas GSH, GtR, and AFRR were not depleted before such damage. GSSG levels remained low throughout storage. GtR activity was elevated by FC and IW. AFRR activity was elevated by all treatments. Asc levels were elevated initially by all treatments, with this elevation lasting longer with PC and T. These results suggest that Asc levels decline during stress in the absence of an obvious lesion in the Asc regeneration scheme.

Effects of Chilling of Bemisia argentifolii (Homoptera: Aleyrodidae) Infesting Cabbage

Cold temperatures affected the biology of Bemisia argentifolii Bellows and Perring on cabbage both directly and indirectly. Continuous chilling of 0°C and 4°C significantly increased mortality of adults and eggs. Variable daily chilling of 0°C for 6 h and then greenhouse conditions for the remainder of the day increased adult mortality but did not affect egg mortality for the 10 days of exposure. Prior plant exposure to 0°C resulted in reduced adult B. argentifolii preference and increased adult mortality. Previous 0°C and 4°C plant exposure also had an impact on within plant distribution of adults and eggs. On nonchilled and recently chilled plants, adults and eggs were found on the youngest (highest) leaves. On plants chilled at 0°C and 4°C three and five days before infestation, adults and eggs were found on lower leaves. Lower immature mortality was recorded on the nonchilled plants than on the chilled plants.

Application of a Temperature Function Integration Technique to Assess the Hygienic Adequacy of a Process for Spray Chilling Beef Carcasses

The hygienic performance of a commercial beef carcass cooling process was assessed by a temperature function integration technique. The process involves the automatic loading of beef sides into two continuous chillers, where the sides are periodically sprayed with water during the early part of the process, and subsequently are exposed to subzero air temperatures. The times required for the beef sides to cool to a deep temperature of 7°C indicated that the process was in accord with currently accepted views of Good Manufacturing Practice. The potential proliferations of Escherichia coli were calculated from 48 temperature histories obtained from the site-on-side surfaces that have been shown to remain at the highest temperatures for the longest periods. The extent of calculated E. coli proliferation did not correlate significantly with the time for deep tissue to cool to a chilled temperature. The range of proliferation values was comparable with the ranges obtained for other, dissimilar meat cooling processes. The spray-chilling process therefore met with a temperature function integration criterion for the hygienic adequacy of meat cooling processes that had been proposed on the basis of the finding from other meat cooling procedures.