Effect of triple-layer hermetic bagging on mould infection and aflatoxin contamination of maize during multi-month on-farm storage in Kenya

Field trials were conducted in small-scale farmers' grain stores in an aflatoxin endemic region to assess the effect of storing maize in triple layer hermetic (PICS™) bags on aflatoxin contamination. Shelled maize grain was purchased from farmers, and filled into PICS bags, woven polypropylene (PP) and jute bags and kept in the farmers' own stores for 35 weeks. Grain moisture content, total mould count and mould incidence levels were examined at onset and after every 7 weeks during the 35 weeks of storage. Aflatoxin contamination was examined at onset, and after 14, 28 and 35 weeks. Ambient temperature and r.h. in the trial site and in all the bags, as well as oxygen and carbon dioxide levels in the PICS bags were also monitored. Initial moisture content (m.c.) of maize varied from farmer to farmer and ranged between 12.4 and 15.0%. The m.c. of maize stored in PICS bags remained significantly higher (P < 0.05) than in PP and jute bags in the last 14 weeks of storage. Total mould count and aflatoxin contamination of maize stored at an initial m.c. < 13% and 13% ≤ m.c. ≤ 14% increased significantly in PP and jute bags but not in PICS bags. After 35 weeks, total aflatoxin of maize stored in the PICS bags at an initial m.c. < 13% and 13% ≤ m.c. ≤ 14% did not change where as it increased 5–8 folds in the PP and jute bags. Total mould count and aflatoxin contamination of maize stored at an initial m.c. > 14% increased profusely in the three types of bags. Our findings demonstrate that storing maize in PICS bags can prevent accumulation of aflatoxin in rural farmers' stores if grain moisture is <14%.     

A time-saving method for sealing Purdue Improved Crop Storage (PICS) bags

Purdue Improved Crop Storage (PICS) bags were designed to reduce grain storage losses on smallholder farms. The bag consists of three layers: two high-density polyethylene liners fitted inside a woven polypropylene bag. Recently, farmer groups, development relief programs, and government food security agencies have shown interest in PICS bags for large-scale use. PICS bags are conventionally closed by a twist-tie (TT) method, which involves twisting, folding, and tying the lip of each layer individually with a cord. This is not only time and labor intensive, but also may affect the integrity of the liners. We evaluated three new bag closure methods: i) inner liner rolled onto itself and middle liner fold-tied (IR), ii) both liners folded together and tied (FT), and iii) both liners folded and tied separately (FS), along with the conventional twist tie (TT) method. The time to close partially or fully filled 50 kg-capacity PICS bags filled with maize grain was assessed. Results showed that FT was the most time-saving method, reducing bag sealing time by >34% versus the usual TT method. The average internal oxygen levels reached <2% within a week in bags containing grain highly infested with Sitophilus zeamais, while it remained >5% levels for less-infested bags. In both cases, insect population growth was suppressed. Oxygen depletion rates among tying methods remained the same regardless of the closure method used. When large numbers of bags need to be closed, the time-saving FT method is a good alternative PICS sealing method over the conventional twist-tie approach.     

Assessing Purdue Improved Crop Storage (PICS) bags to mitigate fungal growth and aflatoxin contamination

Storing maize in regions of the world without sufficient drying and storage capacity is challenging due to the potential risk of aflatoxin contamination produced by Aspergillus flavus. This study sought to determine if storage of maize in Purdue Improved Crop Storage (PICS) bags prevents mold growth and aflatoxin accumulation. PICS bags are a three-layer, hermitic bag-system that forms a barrier against the influx of oxygen and the escape of carbon dioxide. Maize conditioned at 12, 15, 18, and 21% grain moisture was inoculated with 50 g of maize kernels infected with fluorescent-marked strain of A. flavus. The grain was stored in either PICS or woven bags at 26 °C, and percent oxygen/carbon dioxide levels, fungal growth, aflatoxin, moisture content, and kernel germination were assessed after 1 and 2 months incubation. Maize stored in woven bags was found to equilibrate with the ambient moisture environment over both storage periods, while PICS bags retained their original moisture levels. Aspergillus flavus growth and aflatoxin accumulation were not observed in maize stored in any PICS bags. No aflatoxin B1 was detected in woven bags containing low-moisture maize (12 and 15%), but detectable levels of aflatoxin were observed in high moisture maize (18 and 21%). The percentage of oxygen and carbon dioxide within PICS bags were dependent on initial grain moisture. Higher carbon dioxide levels were observed in the bags stored for 1 month than for 2 months. High initial moisture and carbon dioxide levels correlated with low kernel germination, with the 18 and 21% treatment groups having no seeds germinate. The results of the study demonstrate that storage of maize in PICS bags is a viable management tool for preventing aflatoxin accumulation in storage.     

Effects of PICS bags on insect pests of sorghum during long-term storage in Burkina Faso

The PICS bags, originally developed for cowpea storage, were evaluated for sorghum (Sorghum bicolor) preservation. Batches of 25 kg of sorghum grain were stored in 50 kg PICS or polypropylene (PP) bags under ambient conditions for 12 months and assessed for the presence of insect pests and their damage, seed viability and, oxygen and carbon dioxide variations. The grain was incubated for 35 days to assess whether any insects would emerge. After six months of storage, oxygen levels decreased in the PICS bags compared to polypropylene bags. After 12 months of storage, only two pests, Rhyzopertha dominica and Sitophilus zeamais were found in the PICS bags. However, in PP bags there were additional pests including Tribolium castaneum and Oryzeaphilus mercator and Xylocoris flavipes. Grain weight loss and damage caused by these insects in the PP bags were significantly higher compared to those stored in PICS bags. Germination rates of sorghum grains stored in PP bags decreased significantly while no changes were observed in grains stored in PICS bags when compared to the initial germination. After the incubation post storage period, there was a resurgence of R. dominica in sorghum grains from PICS bags but the population levels were significantly lower compared to polypropylene bags. PICS bags preserved the quality and viability of stored sorghum grains and protected it from key insect pests. The PICS technology is effective for long-term sorghum storage but the potential resurgence of insects in low-oxygen environment calls for further research.     

Purdue Improved Crop Storage (PICS) bags for safe storage of groundnuts

Groundnut seeds are prone to quality deterioration and damage due to improper storage. Hermetic storage of pods offers a novel, sustainable and ecologically safe alternative over traditional methods. In this paper, we demonstrate the efficacy of triple-layer “Purdue Improved Crop Storage (PICS)” bags, (that comprises of two inner high density polyethylene bags and one outer woven polypropylene bag), for protecting pods from quality deterioration, damage by bruchids (Caryedon serratus) and aflatoxin contamination (Aspergillus flavus). Custom made triple-layer bags were used and pods (of cv ICGV 91114) were placed @ 2 kg/bag. Over four months of storage under ambient conditions, triple-layer bags supported retention of seed weight, germinability and oil content significantly better than cloth bags. Further, under both natural and artificial infestations with A. flavus, seed aflatoxins levels were lower in PICS bags compared to cloth bags. Toxin accumulation in PICS bags deliberately infested with bruchids and A. flavus was less compared to cloth bags under similar conditions. Bruchid damage to pods was less in PICS bags versus cloth bags in all cases. Our results suggest the superiority of triple-layer PICS bags over cloth bags in protecting seed viability, seed weight and oil content while safeguarding the groundnuts from bruchids and retarding toxin accumulation.     

Safe storage of maize in alternative hermetic containers

Purdue Improved Crop Storage (PICS) bags have been developed and extended as a way to address grain storage issues faced by smallholder farmers in developing nations. A hermetic technology, PICS bags reduce insect damage to grain significantly while maintaining its quality for many months or longer. Farmers with varying and often small volumes of grain at harvest, may still benefit from alternatives to PICS bags for storing their grain. We evaluated plastic bottles, which may be hermetically sealed, for storing maize grain. Clean maize grain was stored for eight months in sealed and unsealed plastic bottles with half of these bottles being infested by maize weevil (Sitophilus zemais, Motschulsky). Oxygen levels in the bottles were monitored throughout the trial and grain was assessed for moisture content, insect damage, germination rate and insect population size when the study was terminated. Sealed bottles preserved grain quality significantly better than unsealed, infested bottles and as well as non-infested unsealed containers. Plastic soda bottles can be used as hermetic containers for safely storing grain.     

Maintaining dryness during storage contributes to higher maize seed quality

Smallholder farmers in Pakistan store their seeds and grains in porous polypropylene (woven) and jute bags or in bulk. Seed stored in these containers is susceptible to fluctuating seasonal relative humidity and temperature, which promote mold and insect growth. The present study assessed the performance of Purdue Improved Crop Storage (PICS) bags for maize seed storage during a two-month period. Seed moisture content increased in polypropylene bags while it remained constant in PICS bags. No change in germination was observed in maize seeds stored in PICS bags while in polypropylene bags it was reduced in half when compared to the initial germination. Seed stored in polypropylene bags had higher insect damage with a weight loss of 35% while in PICS bags the infestation was minimal with a weight loss of about 3%. Higher aflatoxin contamination levels were observed in seeds stored in polypropylene than PICS bags. PICS bags are effective at preserving the dryness of maize seed in storage during high relative humidity conditions, which leads to maintenance of seed quality.     

PICS bags safely store unshelled and shelled groundnuts in Niger

We conducted an experiment in Niger to evaluate the performance of hermetic triple layer (Purdue Improved Crop Storage- PICS) bags for the preservation of shelled and unshelled groundnut Arachis hypogaea L. Naturally-infested groundnut was stored in PICS bags and woven bags for 6.7 months. After storage, the average oxygen level in the PICS bags fell from 21% to 18% (v/v) and 21%–15% (v/v) for unshelled and shelled groundnut, respectively. Identified pests present in the stored groundnuts were Tribolium castaneum (Herbst), Corcyra cephalonica (Stainton) and Cryptolestes ferrugineus (Stephens). After 6.7 months of storage, in the woven bag, there was a large increase in the pest population accompanied by a weight loss of 8.2% for unshelled groundnuts and 28.7% for shelled groundnut. In PICS bags for both shelled and unshelled groundnuts, by contrast, the density of insect pests did not increase, there was no weight loss, and the germination rate was the same compared to that recorded at the beginning of the experiment. Storing shelled groundnuts in PICS bags is the most cost-effective way as it increases the quantity of grain stored.     

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.     

Performance of hermetic storage bags for maize grains under farmer-managed conditions: Good practice versus local reality

There are various types of grain storage bags available to farmers in tropical countries. However, these bags differ in price, quality, and reduced post-harvest losses due to insect pests and mould infestation. This study aimed to compare the effectiveness of three types of storage bags of Purdue Improved Crop Storage (PICS), Grain pro-super (GPS) and woven (WN) bags under assumed small farmer’s storage practices in the sub-tropical climatic conditions. The practice of weekly routine opening of the bags was compared with the recommended practice of keeping the bags closed for at least 3 months. Under laboratory experiment, insect population, moisture content, grain humidity, and temperature were measured at the weekly intervals while under farmer’s setting, moisture content (%) of maize and percentage of insect damage were measured after 3 and 6 months of storage at the farmer’s homestead. Considering the routine weekly opening effect, the PICS bag kept a low grain humidity average (56.6%) compared to the Grain pro-super bag (64.2%) and Woven bag (71.5%). The PICS bag reduced the insect population to an average of zero (0.4) compared to GPS (6.5) and the WN (14.8). Under farmer’s conditions, the mean difference in the percentage of insect damage between the PICS and GPS were insignificant (P > 0.05) at both 3 and 6 months of storage, and the insect damage throughout decreased with time. The results of this study indicate that PICS bag may support positively the practice of routine weekly opening compared to the GPS and WN in the sub-tropical climatic conditions.     

Evaluating of hermetic bags for long-term storage of turmeric (Curcuma longa L.) rhizomes

Hermetical and traditional storage bags were evaluated for their effect on the postharvest storage of turmeric at laboratory conditions. The traditional Polypropylene (PP) woven bags and the jute bags were compared with Purdue Improved Crop Storage (PICS), Super Grainpro, Savegrain bags, and Ecotect bags. Every month, for eleven months, the levels of oxygen and carbon dioxide, moisture, insect damage, live insect count, weight loss of turmeric rhizomes were monitored. A slight change in moisture was observed for turmeric stored in PICS, Grainpro, Savegrain, and Ecotect bags. But, a significant decrease in moisture was observed for turmeric stored in jute bags. The levels of oxygen in PICS and Ecotect bags decreased from 20% to 8% while carbon dioxide content increased in PICS bags from 0.2% to 12% during the period of storage. In jute bags, the level of oxygen was approximately 19.3% but the level of carbon dioxide increased from 0.05% to 0.43% due to insect activity. In all hermetic bags, the risk of insects has decreased over time, and weight loss has also decreased as compared with jute bags. In Polypropylene woven and jute bags, damage by insects and weight loss increased during storage while the curcumin content reduced. Our study showed the effectiveness of PICS, Grainpro, Savegrain, and Ecotec bags in controlling insects and weightloss in turmeric rhizomes over the traditional bags. All the four hermetic bags performed well in long-term storage of turmeric rhizome and can be recommended.     

Exploring the profitability of improved storage technologies and their potential impacts on food security and income of smallholder farm households in Tanzania

This study assesses the profitability of selected improved grain storage technologies and the potential impact of their adoption on food security and income of smallholder maize producers in Tanzania. We used on-farm experiment data, time series maize price data, and household survey data to address the objectives. For the improved technologies, we considered Purdue Improved Crop Storage (PICS) bags, metallic silos of different sizes, and polypropylene (PP) bags treated with Actellic Super®. We compared them with PP bags without insecticide treatment as the control. Results show that PICS bags and PP bags plus Actellic Super are profitable in all locations and not significantly different. While the feasible period varies by location, profit is most likely negative if farmers sell their maize in the first two months after harvest and in the last two months before the next harvest. There are mixed results with regards to the profitability of metallic silos; bigger silos are profitable for farmers who have economies of scale to use them while smaller ones are profitable only within the context of higher grain price and bigger seasonal price gap. The results also show that PICS bags (or PP bags plus Actellic Super) are useful to address food security and income objectives among poor rural households whereas metallic silos with bigger storage capacity can increase the income of those farmers who have bigger surplus grain to sale.     

密封小包装内气体环境对大米贮藏效果的影响

研究了在密封小包装内填充N2、CO2、空气以及真空包装对大米储藏效果的影响,研究结果表明:包装内填充不同的气体以及真空包装对大米含水量变化没有影响;在高温条件下填充N2、CO2以及真空包装较填充空气有更好的品质保持效果,尤其是CO2作用显著,在高水分条件下效果更加明显。     

Sorghum seed storage in Purdue Improved Crop Storage (PICS) bags and improvised containers

Seed storage is a major challenge for smallholder farmers in developing nations. Purdue Improved Crop Storage (PICS) bags effectively control the postharvest insect pests of cowpea and other crops. Farmers, encouraged by this success, have begun to expand the use of PICS bags for storing other crops. Little is known about how sorghum seed, one of these important crops, fares when stored under hermetic conditions. Accordingly, we stored sorghum seed for six months in either airtight containers (PICS bags or sealed plastic bottles) or open ones (woven polypropylene bags and open plastic bottles). Overall, sorghum seed stored in PICS bags and in sealed plastic bottles maintained its initial moisture level, germination rate and seed weight. Porous polypropylene bags and open plastic bottles lost moisture over six months. We conclude that sorghum seed can be safely stored in hermetic containers without any loss of quality for extended periods of time.     

Impact of opening hermetic storage bags on grain quality,fungal growth and aflatoxin accumulation

Purdue Improved Crop Storage (PICS) bags are used by farmers in Sub-Saharan Africa for pest management of stored grains and products, including maize. These bags hermetically seal the products, preventing exchange with external moisture and gases. Biological respiration within the bags create an environment that is unsuitable for insect development and fungal growth. This study was conducted to determine the impact of routine opening of the storage bags for maize consumption on fungal growth and aflatoxin contamination. Maize with moisture contents (MC) high enough to support fungal growth (15%, 16%, 18% and 20%) was stored in PICS bags, which were opened weekly and exposed to humid conditions (85% RH) for 30 min over a period of 8 weeks and 24 weeks. Monitors indicated that oxygen defused into the open bags but did not reach equilibrium with the bottom layers of grain during the 30-min exposure period. Fungal colony forming units obtained from the grain surface increased 3-fold (at 15% MC) to 10,000-fold (at 20% MC) after 8 weeks. At both 8 weeks and 24 weeks, aflatoxin was detected in at least one bag at each grain moisture, suggesting that aflatoxin contamination spread from a planted source of A. flavus-colonized grain to non-inoculated grain. The results indicate that repeatedly breaking the hermetic seal of the PICS bags will increase fungal growth and the risk of aflatoxin contamination, especially in maize stored at high moisture content. This work also further demonstrates that maize should be properly dried prior to storage in PICS bags.     

不同保鲜包装对天麻贮藏生理和效果的影响

为探究天麻的保鲜技术,以汉中天麻(Gastrodia elata Bl)为试材,选取PE20、PE30、PE40和抗菌四种保鲜袋包装天麻,常温贮藏。每8 d测试比较天麻失重率、腐烂指数、呼吸强度、蛋白质、总糖和天麻素含量指标的变化,结果表明,PE20保鲜袋对天麻的保鲜效果最佳,在贮藏过程中有效地防止了天麻的失水萎蔫和腐烂,抑制了天麻呼吸强度的上升,较好地控制了天麻蛋白、总糖和天麻素含量的损失,延长天麻贮藏期至65 d,保鲜效果较好。该研究结果可为天麻低温贮运保鲜提供参考。      

Quality of maize grains treated with allyl isothiocyanate stored in hermetic bags

This purpose of this study was to evaluate the quality of maize grain treated with allyl isothiocyanate (AITC) and stored under hermetic conditions. Maize grains with moisture contents of 14.8 or 17.9% wet basis (w.b.) initial moisture content were packaged in high density polyethylene bags and submitted to treatment with AITC at a concentration of 300 μL kg⁻¹. The bags were stored in controlled temperature chambers at 15, 25 or 35 °C. At 30-day intervals, for a period of 150 days, three bags were removed from the chambers and the grains were submitted to commercial classification, moisture content, bulk density, germination potential and electrical conductivity analyses. It was verified that AITC at 300 μL kg⁻¹ has no significant effect on the physiological quality of maize grains stored in hermetic bags. The microbiological analyses indicate the control of fungi and yeasts on the grains stored with 17.9% w.b. and treated with AITC. The maize grains stored with 14.8% w.b. moisture content in hermetic systems suffered no deterioration and retained their quality for a longer period than grains stored with 17.9% w.b. moisture content, independent of AITC treatment.     

The effect of multiwall Kraft paper or plastic bags on physico-chemical changes in milk powder during storage at high temperature and humidity

Plastic bags have recently been introduced as an alternative to multiwall Kraft paper bags in packaging milk powder in 25-kg sizes as it is thought that plastic bags are more durable and would preserve the quality of milk powders during storage better than paper bags. However, there is little scientific information available on the performance of plastic bags for milk powder storage. The aim of this study was to compare the properties of skimmed milk powder (SMP) packaged in plastic or paper bags. Commercially produced and packaged SMP in 25-kg plastic or paper bags was stored at 37°C and 90% relative humidity. Samples were analysed at intervals (0, 45, 90 and 135 days) for moisture, water activity, lactic acid content, pH, insolubility index, bulk density, flowability, dispersibility and particle size. The magnitude of change in the majority of SMP properties measured during storage suggests that plastic bags are similar to paper bags in maintaining milk powder quality 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.     

Triple bagging hermetic technology for post-harvest preservation of paddy rice Oryza sativa L. in the Sahel of West Africa

Trials of the Purdue Improved Crop Storage (PICS) bag technology for the storage of paddy rice, Oryza sativa L., were conducted in Burkina Faso, Ghana and Niger. Paddy rice naturally infested with insects, the most abundant species being Tribolium spp. and Rhizopertha dominica, was sealed in triple layer PICS bags, or in conventional woven polypropylene sacks. At the end of 7–18 months of storage in PICS bags the number of insects did not increase, the weight of 100 seeds did not change, and the proportion of damaged seeds was not different from that present when the paddy was first put into the bags. By contrast, paddy stored in the conventional way in woven polypropylene bags exhibited weight losses ranging from 3 to 8.7%. In Bolgatanga, Ghana, where paddy was stored for 18 months, germination of paddy kept in the PICS bags was comparable to that present at the beginning of the experiment. PICS bags can be used for the safe, low-cost, insecticide free storage of paddy rice.