Impact of moisture content and maize weevils on maize quality during hermetic and non-hermetic storage

The objective of this study was to determine the impact of moisture content and Sitophilus zeamais Motschulsky on maize quality during hermetic and non-hermetic storage conditions. Commercial Channel 211-97 hybrid maize kernels were conditioned to 14, 16, 18, and 20% moisture content (wet basis), and then three replications of 300 g of maize grain were stored in glass jars or triple Ziploc^® slider 66-μm(2.6-mil) polyethylene bags at four conditions: hermetic with weevils, hermetic no-weevils, non-hermetic with weevils, non-hermetic no-weevils. All jars and bags were stored in an environmental chamber at 27 °C and 70% relative humidity for either 30 or 60 d. At the end of each storage period, jars and bags were assessed for visual mold growth, mycotoxin levels, gas concentrations, pH level, the numbers of live and dead S. zeamais, and maize moisture content. The maize stored in non-hermetic conditions with weevils at 18 and 20% exhibited high levels of mold growth and aflatoxin contamination (>150 ppb). Conversely, very little mold growth was observed in maize stored in hermetic, and no aflatoxins were detected in any moisture level. CO₂ increased and O₂ gradually decreased as storage time increased for maize stored in hermetic conditions (with or without weevils) in all moisture level. No significant difference in pH was observed in any storage conditions (P < 0.05). Total mortality (100%) of S. zeamais was observed in all hermetically stored samples at the end of 60 days storage. Moisture content for hermetically stored maize was relatively constant. A positive correlation between moisture content and storage time was observed for maize stored in non-hermetic with weevils (r = 0.96, P < 0.05). The results indicate that moisture content and the number of S. zeamais weevils plays a significant role in maize storage, both under hermetic and non-hermetic conditions.     

Paddy rice stored under hermetic conditions: The effect of relative humidity,temperature and storage time in suppressing Sitophilus zeamais and impact on rice quality

The aim of this study was to analyse the effect of relative humidity in suppressing Sitophilus zeamais, in paddy rice stored under hermetic conditions, during four and seven months, at different average temperatures, as well as the impact on rice quality.Hermetic bags, GrainPro^® SuperGrainbag^® Farm™, were used to store two rice varieties under three different relative humidities: 67%, 75% and 85% RH, and average temperatures of 14 °C, 17 °C and 24 °C, both monitored by Hobo^® Data loggers, with the probe placed inside the bags. CheckpointII Portable O₂ and CO₂ Gas Analyzer was used to assess gas contents on the top and bottom of each bag. At the end of the trials, paddy samples were collected to estimate water activity (a_w). The rheology behaviour of rice pastes prepared with race flour obtained from the different treatments was also evaluated, using a controlled stress rheometer.The results showed that the response of the stored-product insects changes with environmental conditions, O₂ and CO₂ contents. Other parameters were considered; a_w increased with relative humidity and temperature, but decreased with storage time. The relative humidity played an important role, together with the increase of temperature, in suppressing insect populations. A modified atmosphere was naturally produced inside the hermetic bag, under 85% RH, with low O₂ and high CO₂ contents, at different average temperatures, 14 °C and 17 °C. These results demonstrated that S. zeamais can survive, but has no progeny. Under the same conditions, but at the higher average temperature of 24 °C, S. zeamais attained 100% mortality before producing progeny.The increase on respiration rate, registered by CO₂ increase and O₂ decrease, for higher RH values, reduced the viscoelastic functions and changed the starch gelatinization point of Indica and Japonica rice.The results obtained showed that storing paddy hermetically, at low relative humidity, did not change atmospheric content and maintained the viscoelastic functions of the rice pastes.     

Grain size and grain depth restrict oxygen movement in leaky hermetic containers and contribute to protective effect

Postharvest insect pests threaten the nutritional and financial security of smallholder farmers in the developing world. Hermetic storage, a technology that protects grain against insects by blocking their supply of oxygen, alleviates the problem of insect-caused losses. PICS (Purdue Improved Crop Storage) bags represent one hermetic technology that improves food availability and incomes of farmers. The polyethylene liners of PICS bags are sometime damaged during use, acquiring small holes or tears. Observations in the laboratory and field suggest that insect development remains localized around the point where the bag is damaged. We hypothesized that the grain within a hermetic container that has minimal localized damage (such as an insect hole), helps retard leakage of oxygen into the bag and contributes to limiting insect damage and to the overall protective effect. To test this hypothesis, we filled 4 cm dia. by 10 cm long PVC pipes with Callosobruchus maculatus (F.) infested cowpeas and sealed them with caps having a single, insect-sized hole in its center. A vertical tube positioned above the cowpea-filled PVC pipe was filled with one of three different grains (sesame, sorghum, and maize) to different depths (0, 5, 15, 30, 50 cm). Seed size and grain barrier depth significantly reduced the level of bruchid damage to the stored cowpea in the PVC container. Smaller sized grains used for the barriers retarded insect development more effectively than larger sized grains, while deeper grain depth was more effective than shallower barriers. The grain held in a hermetic container contributes in a small, but significant, way to the effectiveness of the containers.     

Desiccant drying prior to hermetic storage extends viability and reduces bruchid (Callosobruchus chinensis L.) infestation of mung bean (Vigna radiata (L.) R. Wilczek) seeds

Seeds of mung bean (Vigna radiata (L.) R. Wilczek) are subject to loss of viability due to aging and damage from pulse beetles (or bruchids; Callosobruchus spp.) infestation during storage. We investigated whether seed drying using desiccants and hermetic packaging would prevent or ameliorate these consequences of storage. Sun-dried mung bean seeds at a moisture content of 10% were subjected to further drying for 72 h using five different desiccants: Drying Beads® (a zeolite-based desiccant), silica gel, sodium aluminum silicate, activated alumina, and cow-dung ash (a traditional desiccant). Seeds were subsequently stored in hermetic plastic containers in the presence of these desiccants under ambient conditions along with sun-dried seeds stored in cloth bags or in hermetic containers. In addition, parallel samples of each treatment were inoculated with one pair of bruchid beetles (C. chinensis L.) and stored under the same conditions. The seed drying treatments did not affect initial seed quality (germination percentage and seedling vigor) significantly. After storage for 9 months at ambient temperatures, seeds dried using Drying Beads, silica gel, sodium aluminum silicate and activated alumina had higher germination percentages, seedling vigor indices and soil emergence, and lower electrical conductivity (leakage upon imbibition) and fungal infestation compared to other conditions. In addition, the mung bean seeds inoculated with bruchids and stored with these effective desiccants had less damage, oviposition, and insect respiratory activity in the hermetic containers and maintained higher seed germination and seedling vigor after six months of storage compared to other treatments and controls. The results demonstrate the superior ability of desiccants to quickly and safely dry seeds prior to and during storage and the benefits of such drying and hermetic storage conditions for preventing seed deterioration and insect damage during storage.     

Comparative effects of hermetic and traditional storage devices on maize grain: Mycotoxin development,insect infestation and grain quality

A large-scale study was conducted to assess which of the five most accessible hermetic storage devices on the Kenyan market fulfill the needs of smallholder farmers by positively impacting three major areas of concern: insect infestation, grain quality, and mycotoxin (aflatoxin and fumonisin) contamination. Efficacy of two hermetic silos (plastic and metal) and three hermetic bags (PICS, GrainPro's GrainSafe™, and Super Grain) was directly compared to current maize storage in polypropylene (PP) bags under local environmental conditions using representative storage volumes during a 6-month storage period. Impact of maize grain stored at typical (∼15%) and recommended (<13.5%) moisture levels and potential efficacy losses through frequent interruption of the underlying hermetic principals was assessed. Hermetic storage significantly reduced the increase in aflatoxin compared to PP bags regardless of the moisture level of the grain. An <5% per month aflatoxin increase was achieved by three of the five devices tested: Metal silo, PICS and GrainSafe™ bag. A strong correlation between grain moisture, storage time and aflatoxin development was found in PP bags, but not in any of the hermetic devices. The same result was not obtained for fumonisin development in stored maize. The rate of Fumonisin increase was similar in all tested devices, including the polypropylene bags, and conditions. The periodic opening of the hermetic devices had no significant effect on the efficacy of the hermetic devices but the repeated disturbance of the PP bags led to a significant increase in aflatoxin levels. The maize weevil Sitophilus spp. was most commonly found with a total incidence of 72%. Grain storage under hermetic conditions reduced insect infestation, grain weight loss and discoloration. However, maize storage above recommended moisture levels led to a distinct odor development in all hermetic devices but not the PP bags. Hence, proper grain drying is a prerequisite for maize storage in airtight conditions.     

Field effectiveness of improved hermetic storage technologies on maize grain quality in Central Mexico

Maize is the main crop cultivated by small scale farmers (SSF) in Mexico, and its production represents an important goal for local food security. However, SSF very often face severe post-harvest losses in maize, mainly because of insect pests and the lack of suitable storage technology. This study was conducted to compare the field effectiveness in terms of maize quality under on-field conditions of SSF of two improved hermetic storage technologies with the traditional storage. The field experiment was performed on-farm in the highlands of Central Mexico. Maize grains were stored in three storage devices: hermetic plastic bag (sBag), hermetic plastic silo (Bioxilo), or traditional polypropylene sacks. The study considered the quantitative evaluation of storage, physical, nutritional, and industrial qualities of maize after 4, 8 and 12 months of storage. Environmental conditions of storage such as oxygen levels, temperature and humidity were monitored. After 1 year of field storage, compared with traditional sacks, sBag and Bioxilo showed a significant lower losses in storage due to insects. When controlled infested maize by artificial insect infestation methods was used, the improved technologies were also effective in reducing grain losses. Furthermore, both sBag and Bioxilo prevented grain quality detriment in terms of physical, nutritional and industrial (for tortilla and seed) properties (p < 0.01). Additionally, compared with traditional storage, sBag and Bioxilo showed efficient control of the hermetic conditions in terms of oxygen, temperature and humidity, but no significant differences were detected between the two improved technologies. In summary, under on-farm conditions, the successful preservation of maize grain quality was achieved by the improved sBag and Bioxilo in the highlands of Mexico. In the future, positive effects of this storage system will need to be validated under tropical conditions.     

Effects of storage methods, storage time and different agro-ecological zones on chemical components of stored sorghum grain in Hararghe, Ethiopia

Sorghum grain stored in traditional underground pits was sampled from seven districts of Hararghe, eastern Ethiopia, representing lowland, intermediate and highland zones, from February to August 2001, and was analysed at the International Livestock Research Institute (ILRI) for changes in chemical composition over time. Samples were also taken from a replicated aboveground bin and pit storage experiment at Alemaya University campus at 2-month intervals from March 2000 to August 2001 and analysed in a similar manner. The effect of geographic location on chemical composition was significant, but there were differences in the sorghum varieties grown. The organic matter (OM) content of grain samples from pits in the lowlands was lower than those from the highlands. The crude protein (CP) and OM contents of samples from the seven districts did not change in 7–9 storage months. The OM content decreased and the CP slightly increased over time in samples from soil pits without any lining material on Alemaya University campus. The OM content decreased from 97.8 to 91.6%; and CP increased from 10.1 to 11.2% in these samples over a 17-month period. Soluble carbohydrate (SCHO) content significantly decreased over time in samples from the districts (from 2.4 to 1.2% by 7 months) and in samples from soil pits on campus (from 2.4 to 1.9% after 7 months and to 0.97% after 17 months). There was no significant change in the organic matter, CP and SCHO contents in samples taken from the cemented aboveground bin, cement- and dung-lined pits at the Alemaya campus, all of which were lined with polythene sheeting. From these data, we conclude that the combination of storage methods, storage period, geographic location and/or sorghum variety affected grain quality. Grain storage in traditional underground pits for long periods does lead to grain deterioration. The use of improved grain storage structures maintains the grain quality and nutritional value of sorghum for a reasonably long period.     

Impact of pre-treatment (soaking or germination) on nutrient and anti-nutrient contents,cooking time and acceptability of cooked red dry bean (Phaseolus vulgaris L.) and chickpea (Cicer arietinum L.) grown in Ethiopia

Pulses are processed in diverse ways prior to consumption. Soaking and germination are among the most common traditional, household-level food processing strategies. This study was carried out to determine the effects of soaking, germination, cooking and their combinations on the contents of selected nutrients and anti-nutrients of red dry bean and chickpea. In addition, the effects of pre-treatment on cooking time and the acceptability of dishes prepared from red dry bean and chickpea were determined. The nutrient compositions (zinc, iron and calcium) of most soaked-cooked and germinated-cooked red dry bean and chickpea samples were not significantly different than those of respective controls. However, soaking and germination pre-treatments significantly lowered the phytate and tannin contents of the red dry bean and chickpea samples, with a few exceptions, and overall, polyphenol contents were lower after soaking-cooking than after germination-cooking. Most scores for sensory attributes of bean-based and chickpea-based dishes prepared from soaked or germinated samples were not significantly different than those of the controls. For most red dry bean and chickpea samples, longer germination times yielded superior results in terms of reductions in cooking time, tannin content, and phytate:zinc and phytate:iron molar ratio.     

Response of storage molds to different initial moisture contents of maize (corn) stored at 25 °C, and effect on respiration rate and nutrient composition

Maize was stored for 2 months in chambers maintained at 25 °C to simulate conditions observed in the central part of the “Corn Belt” of the United States when the grain warms because of high summertime temperatures after a period of winter storage. Maize was brought to three moisture contents (m.c.) within the range typically observed in farm and commercial storage, and was inoculated to simulate the amount of storage mold contamination typical of this situation. Certain of the experimental units were packed in insulation so that heat could accumulate within the grain masses to simulate hot spots. The wettest grain heated rapidly and became semi-anaerobic. The hot grain then dried rapidly, with the amount of moisture loss influenced by the ratio of water vapor pressures inside and outside the grain. The hot grain cooled and became more aerobic over time. New infections by storage molds, disappearance of viable field molds, development of kernel damage, and changes in atmospheric gases within the grain masses were correlated with the grain moisture or temperature and the rate at which the moisture and temperature changed. The rate of increase in new kernel damage was as high as 3.3% per week. Both the rate of respiration and the estimated ratio of starch to fat consumed were associated with the mean grain m.c. during the trial, and the estimated ratio of starch to fat consumed was in the range of 2.2/1–2.6/1 in the grain containing 16.6–18.2% m.c. That both fat and starch were consumed calls into question loss estimates based on starch metabolism alone. The fat content of the grain decreased more than 10% in some experimental units, but increased less than 5% in others. The protein content generally increased as other grain constituents were consumed.     

Relationships between volatile production,fruit quality and sensory evaluation of Fuji apples stored in different atmospheres by means of multivariate analysis

Aroma compounds, quality parameters and sensory characteristics of Fuji apples were analysed after 3, 5 and 7 months of storage at 1 °C in normal air (AIR; 210 l m^?3 O₂/0.3 l m^?3 CO₂) and in controlled atmospheres with O₂/CO₂ ratios of 10 l m^?3/10 l m^?3 (ULO1), 10 l m^?3/20 l m^?3 (ULO2) and 30 l m^?3/20 l m^?3 (SCA). After storage the apples were kept at 20 °C for 1, 5 and 10 days. The components that contributed most to the characteristic aroma of Fuji apples were ethyl 2‐methylbutanoate, 2‐methylbutyl acetate and hexyl acetate. The highest aroma compound production was found in ULO1 fruits after 5 months of cold storage and 1 day of shelf‐life. After 3 and 5 months of storage, ULO1 fruits showed the highest firmness after both 1 day and 10 days at 20 °C. After 7 months of storage plus 1 day at 20 °C, ULO2 fruits showed higher titratable acidity and soluble solid content; fruit firmness was also maintained throughout the shelf‐life period. Generally, background and superficial colour were not influenced by storage conditions. A statistically significant correlation was found between aroma compounds, quality parameters and sensory evaluation. Copyright © 2003 Society of Chemical Industry     

Changes in biogenic amines of silver carp (Hypophthalmichthys molitrix) fillets stored at different temperatures and their relation to total volatile base nitrogen,microbiological and sensory score

BACKGROUND: Biogenic amines have received considerable attention owing to their undesirable effects in humans. There are few studies of changes in biogenic amine contents related to freshwater fish. Silver carp is an important freshwater fish species in China. This study aimed to investigate the changes in biogenic amines and their relation to total volatile base nitrogen (TVB‐N), microbiological and sensory score of silver carp fillets stored at 0, 3 and 15 °C. RESULTS: The total biogenic amine contents of all silver carp fillets (regardless of storage time and temperature) ranged from 13.05 to 318.10 mg kg^?1. Putrescine and histamine were the main biogenic amines in silver carp fillets during storage. Cadaverine was only detected after 12 days at 3 °C and after 2 days at 15 °C. Spermidine and spermine contents increased during the early storage period and then slightly decreased. CONCLUSION: Low temperature could control the quality of silver carp fillets by inhibiting the contents of biogenic amines. Putrescine showed significant correlation with TVB‐N, total aerobic content, sensory score, tryptamine and phenylethylamine. Putrescine was a good quality marker of silver carp fillets in the cold chain. Copyright © 2012 Society of Chemical Industry     

Monitoring colour,volatiles in the headspace and enzyme activity to assess the quality of broccoli florets (Brassica oleracea L. italica cv. Bellstar and Legacy) during postharvest storage

The research objective was to study whether volatile organic compounds released in the headspace could be used to assess the broccoli quality (Brassica oleracea L. italica cv. Bellstar and Legacy) during postharvest storage (23 °C for 7 days) and correlated with colour change and the activity of peroxidase/POD, ascorbic acid oxidase/AAO and lipoxygenase/LOX. Volatile organic compounds were monitored using PTR‐MS. Methanol had the highest concentration compared with other volatiles released in the headspace that significantly increased during senescence. The methanol concentration was approximately 500 ppbv before the broccoli colour began to change from green to yellow. The concentration of methanol in the headspace increased to 1000–1100 ppbv for Bellstar and Legacy when the colour became yellowish. LOX had high correlation (0.91 and 0.83 for Bellstar and Legacy, respectively) with volatiles for both cultivars, but not for POD. Methanol production is proposed as the best volatile marker to assess the broccoli quality.     

Cold storage,reconditioning potential and chip processing quality of spring potato (Solanum tuberosum L. cv. Hermes) tubers in response to differential nitrogen fertilisation

BACKGROUND: Crop management has been implicated in tuber sugar accumulation and potato processing quality. However, reports on potato postharvest behaviour, tuber composition and processing quality in response to crop nitrogen (N) fertilisation have been sparse and inconclusive. In this study, chipping potato cv. Hermes was treated with four preplanting N rates (0, 100, 200 and 300 kg ha^?1) to evaluate the effect of N fertilisation on sugar accumulation profiles and processing quality at harvest, after cold storage at 4.5 °C for up to 200 days and after reconditioning at 16 °C for 10–30 days. RESULTS: Preharvest leaf petiole analysis and tuber nitrate analysis at harvest confirmed crop response to N rates. At harvest, tuber specific gravity decreased marginally beyond 200 kg N ha^?1. Chip colour as well as tuber sucrose and reducing sugar (RS) content was unaffected by N fertilisation rate. During cold storage and reconditioning, tuber fresh weight loss and sprout growth were unaffected by N rate, while its effect on tuber sugar levels was either statistically or practically insignificant. Tuber sucrose and RS contents correlated highly with chip colour (r = ? 0.729, P <0.001 and r = ?0.791, P <0.001 respectively). Importantly, postharvest chip colour was also unaffected by N rate, though it declined markedly with the onset of cold storage and improved significantly throughout reconditioning. Differences in chip colour between years were limited but potentially critical in meeting the commercial standard. CONCLUSION: Completion of physiological crop senescence of the spring potato crop under Mediterranean climatic conditions seems to mitigate the potential interference of preplanting N fertilisation with tuber maturation and subsequently cold storage performance, reconditioning potential and processing quality. Copyright © 2009 Society of Chemical Industry