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1.
Maize grains are used as raw material in various food products. In countries where the production is seasonal, the grains must be stored throughout the year in order to provide sufficient maize supply for the food industries and consumers. During storage, the environmental temperature is considered as one of the most critical variables that affects grain quality. This study aimed to evaluate the effects of various storage temperatures (5, 15, 25 and 35 °C) on the proximate composition, pH, fat acidity, percentage of grains infected by molds, grain color, protein solubility and pasting properties of maize stored for 12 months. Grains stored at 35 °C during the 12 months period showed the greatest decrease in grain yellowness, pH, protein solubility and breakdown viscosity. An increase in disulfide bonds within the protein structure and interaction between starch and non-starch components seems to be responsible for the changes in protein solubility and pasting properties determined in maize during the storage period. Fat acidity and the percentage of grains infected by visible molds were concluded to be very dependent of moisture content. The result of this study demonstrated that the minimum temperature of 5 °C was able to maintain the quality of maize stored for up 12 months.  相似文献   

2.
Investigations were carried to study the effect of heart incorporation (0%, 15% and 20%) and increasing levels of fat (20% and 25%) on physicochemical (pH, moisture content and thiobarbituric acid, TBA number) and microbiological (total plate count and yeast and mold count) quality and shelf life of semi dry sausages of buffalo meat during refrigerated storage (4 °C). Different levels of fat significantly (p < 0.05) increased the pH of the sausage samples. However different levels of heart incorporation did not significantly (p < 0.05) affect pH, moisture content and TBA number of sausage samples. Fresh samples had pH, moisture content and TBA number in the range of 5.15–5.28, 42.4–47.4% and 0.073–0.134 respectively. Refrigerated storage significantly (p < 0.05) increased TBA number of control samples while storage did not significantly (p < 0.05) increase the TBA number of sodium ascorbate (SA) treated samples. Total plate counts of twelve sausage samples were f under the TFTC (too few to count) limit at the initial stage. Incorporation of different levels of heart and also increasing levels of fat did not significantly (p < 0.05) increase the log TPC/g values. Yeast and molds were not detected in twelve samples of semi dry fermented sausages in their fresh condition. Storage revealed that there was a consistent decrease in pH, and moisture content. Refrigerated storage significantly (p < 0.05) reduced both pH and moisture contents. TBA number and total plate counts and yeast and mold counts of controls were found to increase significantly (p < 0.05) during refrigerated storage. However, in SA treated sausage, only TPC and yeast and mold count significantly (p < 0.05) increased during refrigerated storage. Shelf life of the sausages was found to be 60 days under refrigerated storage (4 °C).  相似文献   

3.
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.  相似文献   

4.
Maize grain (corn) from three harvest years (1986, 1991, and 1992) was harvested, dried, and stored in small bins. Samples taken at harvest and samples taken after various periods of bin storage (up to 77 months) were subjected to accelerated storage tests for measurement of carbon dioxide (CO2) evolution. The initial (t < 72 h) slopes (SLOPE72) of CO2 evolution rate curves were related to storability (r = 0.82), as measured by cumulative CO2 evolution at 200 h. SLOPE72 (a faster test method than cumulative evolution) was subsequently used to evaluate the effects of the following factors on storability: (1) hybrid, (2) drying method, and (3) previous storage history. Differences in storability, attributable to hybrid, were significant both at harvest and after periods of bin storage. One extremely unusual growing year (severe drought stress) affected the otherwise consistent storability ranking among hybrids. Maize grain dried by high-temperature (95 °C) batch crossflow drying had significantly lower storability (i.e. greater SLOPE72) than did the same hybrids dried by low-temperature (ambient air) drying. Previous storage history (moisture content and duration) affected subsequent storability. Storage for longer periods, given the same moisture content, resulted in lower subsequent storability, and storage at higher moisture content, given the same time period, also resulted in lower subsequent storability.  相似文献   

5.
The effect of airtight storage of pearl millet, Pennisetum americanum (L.) Leeke, on intergranular atmosphere, insects, mold infection, grain viability and moisture content (m.c.) was investigated in the laboratory. Six hermetically sealed 19-1 cans were used to store millet of three moisture contents (9.9, 12.8 and 15.6%) for 76 days at 27 ± 1°C. One can of grain of each m.c. was infested with 150 adult Sitophilus oryzae L./kg; the others remained uninfested. Carbon dioxide concentrations increased and oxygen concentrations decreased in all cans infested with insects, and in uninfested grain of 15.6% m.c. The changes in atmospheric concentrations were slower in the uninfested grain than in the infested 15.6% m.c. grain. No live insects were found in any treatment, percentages of mold-infested kernels were not significantly different among treatments, and m.c. did not change due to treatment or time. Kernel viability decreased significantly only in the 15.6% m.c. gram. All grain appeared normal; but the 15.6% m.c. grain had a slightly sour odor.  相似文献   

6.
Fungal colonization of shelled maize (Pioneer 3320) harvested from a field near Furman, South Carolina, in 1992 was determined after 348 and 751 days of continuous storage at each of seven temperatures (10, 15, 20, 25, 30, 35, or 40°C) and four constant relative humidities, giving equilibrium grain moisture contents ranging from 9.4% to 17.5% m.c. in 28 grain conditioning environments. Twenty fungal species infected surface sterilized seeds and were recorded from these conditioned grain treatments, including species commonly found in preharvest maize [e.g. Acremonium zeae, Aspergillus flavus, Fusarium moniliforme (syn. F. verticillioides), Penicillium pinophilum (syn. P. funiculosum), etc.]. Eupenicillium cinnamopurpureum and Monascus ruber were recorded only from conditioned grain treatments. Eurotium chevalieri colonized 50–96% of the kernels from grain conditioning treatments with the highest moisture content for each incubation temperature. Grain samples with>33% E. chevalieri infection had a decreased occurrence of F. moniliforme and A. zeae, and no kernels from these samples germinated. No fungi colonized more than 50% of the kernels conditioned at 30–40°C and 9.4–14.2% m.c. The results of this study indicate that individual patterns of fungal colonization during grain conditioning were a function of the survival rates for preharvest fungal colonists and their potential replacement by E. chevalieri.  相似文献   

7.
Maize is a major staple crop and calorie source for many people living in Sub-Saharan Africa. In this region, Aspergillus flavus causes ear rot in maize, contributing to food insecurity due to aflatoxin contamination. The biological control principle of competitive exclusion has been applied in both the United States and Africa to reduce aflatoxin levels in maize grain at harvest by introducing atoxigenic strains that out-compete toxigenic strains. The goal of this study was to determine if the efficacy of preharvest biocontrol treatments carry over into the postharvest drying period, the time between harvest and the point when grain moisture is safe for storage. In Sub-Sahara Africa, this period often is extended by weather and the complexities of postharvest drying practices. Maize grain was collected from fields in Texas and North Carolina that were treated with commercial biocontrol products and untreated control fields. To simulate moisture conditions similar to those experienced by farmers during drying in Sub-Sahara Africa, we adjusted the grain to 20% moisture content and incubated it at 28 °C for 6 days. Although the initial number of kernels infected by fungal species was high in most samples, less than 24% of kernels were infected with Aspergillus flavus and aflatoxin levels were low (<4 ppb). Both toxigenic and atoxigenic strains grew and spread through the grain over the incubation period, and aflatoxin levels increased, even in samples from biocontrol-treated fields. Our molecular analysis suggests that applied biocontrol strains from treated fields may have migrated to untreated fields. These results also indicate that the population of toxigenic A. flavus in the harvested grain will increase and produce aflatoxin during the drying period when moisture is high. Therefore, we conclude that preharvest biocontrol applications will not replace the need for better postharvest practices that reduce the drying time between harvest and storage.  相似文献   

8.
Experimental lines of hybrid grain sorghums were produced with thousand‐kernel‐weights (TKW) varying between 23.1–44.9 g. The proportion of germ in the normal‐seeded hybrids with TKW 23–27 g was ∼ 9.9–10.2% of dry kernel weight, whereas that in the large‐seeded hybrids with TKW 37–45 g was ∼ 10.8–11.2%. Starch in grain decreased ∼ 4% as kernel weight increased which was offset by an increase in protein level. Wet‐milling of the grain was done without steeping after an initial coarse‐grinding step in two parts of water with 0.3% sodium bisulfite. Three of four samples of large‐seeded and soft‐textured grain sorghums gave 77–82% recovery of starch with 0.5–0.7% protein, while one gave 59% recovery and 0.6% protein. The starches had < 0.5% damaged starch, gave no rancid off‐odor after storing 26 months at 25°C in a sealed glass container, and had lightness (L*) values of 93.1–93.7 vs. 95.2 for a commercial corn starch. Their pasting curves were similar to that of commercial corn starch. The bran/germ/endosperm fraction obtained by limited wet‐milling of one large‐seeded hybrid was separated by flotation to recover one‐half the germ in 98% purity as estimated by fat content.  相似文献   

9.
To predict the storability of grain, detailed information is required on the moisture distribution within the grain bulk since a significant variance can be expected in the moisture content between individual grain kernels during storage. Therefore, it is important to consider and determine the single kernel moisture content distribution. The aim of this work was to investigate mass transfer processes that occur during long-term and intermediate storage of grain. For it, the method of particle moisture distribution analysis by means of the Time Domain Nuclear Magnetic Resonance spectroscopy was used. For this purpose, fundamental laboratory-scale experiments were conducted in small storage containers. As these storage experiments revealed, the width of the particle moisture distribution decreased noticeably when there was enough air available in the container for moisture exchange. Thereafter, the storage experiments were extended to pilot-scale using barrels to store grain for months in the scope of about 90 kg per batch. These experiments were performed without ventilation so as to simulate dead zones of airflow that often occur under industrial-scale flat storage conditions. In the closed barrels, no equalization of the particle moisture content was observed even after eleven months of storage. The knowledge gained from the experiments conducted at the micro and meso levels facilitates the understanding of the mass transfer processes that occur during macro scale storage, which are difficult to examine as an entity.  相似文献   

10.
Quality aspects of sliced dry-cured beef “Cecina de León” preserved in vacuum and gas mixtures (20%/80% CO2/N2 and 80%/20% CO2/N2) were studied. The evolution of microbiological, physicochemical and sensory parameters were analysed during storage (210 days) at 6 °C. Although microbial counts at 60 days of the gas-packaged samples were lower than the vacuum-packed ones, they were never higher than the spoilage limit (7 log ufc/g). A slight increase (p < 0.05) in pH was observed throughout storage of “Cecina de León” packaged under vacuum and in gas mixtures. However, a decrease (p < 0.05) in aw was observed during storage of “Cecina de León” packaged under vacuum but aw did not vary (p > 0.05) during storage in the gas-packaged samples. No changes were observed (p > 0.05) in lightness (L*), redness (a*) and yellowness (b*) in vacuum and gas packaged samples during storage. However, sensorially evaluated colour showed lower values in gas packaged samples during 30 days storage. This difference was decisive in establishing the shelf-life of “Cecina de León” slices preserved in gas mixtures (20%/80% CO2/N2 and 80%/20% CO2/N2). Therefore, from a microbiological point of view, gas mixtures are more effective in extending the shelf-life of “Cecina de León” slices. It is concluded that vacuum packaging allows longer storage than gas-packaging as it maintains a good visual appearance of “Cecina de León”, the main parameter in consumers’ perception of meat quality.  相似文献   

11.
Under humid and warm conditions harvested grains are susceptible to molding and rapid deterioration. Therefore, they should be dried to safe moisture levels that inhibit the activity of microorganisms. Drying to these moisture levels is not economical for farmers in developing countries. Preservation of grains at intermediate moisture levels under hermetic storage conditions could be feasible and economical in warm and moist climates.

The purpose of the current study was to examine the effect of various moisture contents (m.c.) on the quality of maize grains in self-regulated modified atmospheres during hermetic storage.

Maize at 14, 16, 18, 20 and 22% m.c. was initially conditioned for 28 days in tightly wrapped plastic bags and then stored in sealed containers at 30 °C for up to 75 days. Carbon dioxide produced within the containers replaced the oxygen. As the m.c. increased the time for O2 depletion shortened, from 600 h at 14% m.c. to 12 h at 22%. The maize at 20 and 22% m.c. exhibited the highest dry matter (DM) losses, the lowest germination rates and the highest yeast and bacteria counts. The major fermentation product in the hermetically sealed maize was ethanol (0–5 g kg−1 DM), along with lower concentrations of acetic acid (0–1 g kg−1 DM).

The results obtained from the in vitro experiments indicate that maize at the tested moisture levels can be stored satisfactorily under sealed conditions in which self-regulated atmospheres provide protection against microflora damage. Further large-scale trials will be needed to evaluate the economic feasibility of storing high-moisture maize.  相似文献   


12.
Piles M  Blasco A  Pla M 《Meat science》2000,54(4):347-355
The effect of selection for growth rate on carcass composition and meat quality was assessed by comparing two groups of rabbits belonging to different generations of a selection experiment. A Bayesian approach was used. Embryos belonging to generations 3 and 4 of selection were frozen and thawed to be contemporary of animals from generation 10. A control group (C), formed from offspring of these embryos, was contemporary to offspring of generations 10 and 11 of selection, chosen at random, which constituted the selected group (S). One hundred and thirty-one contemporary rabbits were slaughtered at approximately the Spanish commercial live weight of 2 kg. Carcasses were dissected and measured according to the norms of the World Rabbit Scientific Association. An animal model including effects of genetic group (C, S) and sex, and slaughter weight as a covariate was used. S animals had a higher development of liver, kidneys and of a set of organs consisting of the thymus, trachea, oesophagus, lung and heart, relative to C. For dissectible fat, S animals had less than C: −0.31 g for scapular fat, −1.62 g for perirenal fat and −2.03 g for inguinal fat. S had a lower content (−0.39%) of dissectible fat percentage in the “Reference” carcass, indicating a lower degree of maturity at slaughter. The meat to bone ratio was not affected by selection, but the meat and bone contents of the hind leg were 3.25 and 0.71 g higher, respectively, in the C group. Selected animals had a lower water holding capacity in the raw meat (−2.10%), a higher water holding capacity in the cooked meat (2.17%), a higher cooking loss (3.31%) and a lower fat percentage in the meat of a hind leg (−0.37%). Females had more fat than males: 0.26 g for scapular fat, 1.02 g for perirenal fat, 1.10 g for inguinal fat, and 0.24% for total dissectible fat percentage of the “Reference” carcass.  相似文献   

13.
目的:明确酶辅助碱法提取的龙眼核淀粉的结构及理化性质。方法:以龙眼核为原料,碱性蛋白酶为酶解剂提取龙眼核淀粉,研究了其化学组成、粒径、微观形貌、晶体结构、透明度、溶解度及膨润力、热力学特性及糊化特性等。结果:100 g龙眼核淀粉中含有82.64 g淀粉、0.68 g粗脂肪、0.46 g粗蛋白和1.06 g灰分,其直链淀粉含量为36.37%;其颗粒多呈椭圆形或不规则多边形,平均粒径为11.21 μm,结晶结构为A型,近程有序程度较高;1%(w/v)龙眼核淀粉糊的透光率为4%;溶解度和膨润力均随温度上升而增大,90 ℃时分别为11.26%和15.93%;龙眼核淀粉具有较高的糊化起始温度(70.4 ℃)、峰值温度(75.9 ℃)、结束温度(82.1 ℃)和糊化焓(13.7 J/g),其热糊稳定性较差,冷糊稳定性较好。结论:酶辅助碱法提取的龙眼核淀粉直链淀粉含量高,蛋白质含量下降明显,颗粒小,不易糊化。  相似文献   

14.
The limiting conditions of grain moisture content (m.c.) and storage temperature for growth of Fusarium and production of the mycotoxin, zearalenone, were defined in maize, wheat, barley and oat culture. Grain moisture content was the major influence on establishment of the fungus, but storage temperature directly affected the rate of zearalenone synthesis. All the grains tested were susceptible to invasion by Fusarium above 18% m.c. (calculated on a wet-weight basis), even when stored at 7 ºC. In the range 15 to 18% m.c. the grain was increasingly at risk as the storage temperature was raised. Maximum zearalenone yields (500 to 2000 μg/g grain) were obtained in cultures stored at 12 and 18 ºC, even though mycelial growth had been reduced. At 25 ºC, where there was rapid mycelial growth and almost total utilisation of grain after two months' storage, toxin yields were seldom higher than 100 μg/g grain.  相似文献   

15.
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.  相似文献   

16.
研究了高水分稻谷中分离纯化的优势霉菌,以及探讨了微波工艺对染单一优势霉菌稻谷的菌落活性及后期储藏期间菌落数的影响。研究发现,从高水分稻谷中分离纯化分析得出优势霉菌是:链格孢霉、雪腐镰刀菌、白曲霉、灰绿曲霉、产黄青霉。然后在微波功率485、927和1349 W对染单一优势菌稻谷进行灭菌处理,发现稻谷表面霉菌降低约3 lg CFU/g,内部霉菌致死率约95%,同时随着微波时间的延长,受优势菌侵染的稻谷表面及内部霉菌数量均降低,致死率上升。此外通过微波工艺对杀菌后的稻谷侵染单一优势菌,以常规热风处理为对照组进行储藏,发现微波处理后稻谷霉菌生长量明显低于常规热风储藏的稻谷,有益于粮食长时间储藏。因此本文研究了微波工艺对高水分稻谷优势霉菌致死率及后期储藏的影响,为高水分粮食安全储藏提供一定的理论基础。  相似文献   

17.
INFRARED HEATING of HULLESS and PEARLED BARLEY   总被引:1,自引:0,他引:1  
Whole hulless and pearled barley were subjected to infrared heating (micronization) at moisture contents between 12.2% and 26.5% and surface temperatures of 105C to 150C. Infrared heat processing markedly affected the functional, structural and physical properties of the grains. Both micronizing temperature and initial grain moisture content had pronounced effects on these characteristics. the characteristics evaluated are bulk and particle densities, water absorption of whole kernel when soaked for 4 h and 24 h, flour water hydration capacity, protein solubility at pH of 2.0 to 12.0 and flour thermal properties using differential scanning calorimetry. Infrared heating did not change the chemical constituents (starch, protein, total dietary fiber, ash and fat) of hulless and pearled barley.  相似文献   

18.
It has been well documented that the general public holds many mistaken beliefs about foods and their roles in weight gain and health/disease. For example, foods that are perceived as bad for health (e.g., 3 slices of bacon; 109 calories) are typically judged to promote significantly more weight gain than more reputable foods (e.g., a large raisin bran muffin; 460 calories), even if the “bad” food contains far fewer calories than the “good” food. The current study was unique in that participants were provided not only names of snacks but also their caloric amounts and then asked to judge each snack’s capacity to promote weight gain. Results indicated that, despite the caloric information presented, respondents rated “bad” foods as weight promoters (compared to “good” foods) and only fat content (not energy density or fiber and sugar content) primarily predicted which foods would be judged to promote weight gain. It appears that “high fat” may be a synonymous with “bad” for many people or that dietary fat is perceived to have a far greater impact on body weight than is justified by the nutrient’s caloric content. In either case, it appears that a potentially harmful message has been assimilated by the general public.  相似文献   

19.
Sorghum (cv. Maldandi M35-1) was modified to 12, 14 and 16% moisture content (m.c.) and heat-treated with microwave energy at 3 levels, for 30 sec (=4.5, 9 and 18 kJ), and 60 sec (=9, 18 and 36 kJ). The effect of microwave heating on rise and subsequent fall in grain temperature, reduction in m.c. and quality characteristics including germination, seedling dry matter, free fatty acids (FFA) and contaminant fungi was determined. The temperature attained and the moisture loss in the sorghum grain was affected by grain m.c. and the time of exposure. At the lowest and highest microwave treatment level grain temperatures reached 30–40°C and 90–101°C, respectively. However, a 60-sec treatment at the highest energy level was lethal for the grain, particularly at 14 and 16% m.c. The FFA values were unaffected by microwave treatment. Statistical analyses showed that the microwave power level and time individually, and power level × time interactions were significant for most quality characteristics. The fungi present most abundantly on the sorghum grain were Eurotium spp., Aspergillus candidus, A. niger and Penicillium spp. Increasing m.c. and microwave heating resulted in elimination of most fungi after a 30-sec exposure time. With a 60-sec exposure period, practically all fungi were eliminated from the grain.  相似文献   

20.
The effects of processing hot versus chilled goat meat, as such and after freezing in chunk or mince forms, were studied in relation to physico-chemical and organoleptic properties of patties. The differences in the pH of the meat samples were non-significant (P < 0·05) at 3–4 h post mortem (PM) at room temperature (30°C) and after 24 h at 4°C. The yield of the broiled patties, prepared from hot meat at 3–4 h PM, was significantly lower (P<0·05) as compared to those from chilled meat. However, this trend was reversed, if processing of hot meat into patties was done within 1–2 h PM. Freezing of chilled meat in chunk or mince forms gave significantly higher (P < 0·05) cooking yields than freezing of hot meat in similar forms.

The organoleptic scores of the raw-cooked patties were similar for all treatments. Freezing of precooked patties at −10°C for 10 days, thawing and reheating did not reduce most of the sensory scores significantly (P<0·05). Moisture, protein and fat contents of the broiled patties were not significantly (P<0·05) affected by the treatments. Standard plate count of hot versus chilled meat, for all levels of processing and storage, were within acceptable limits.  相似文献   


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