The microbial spoilage of ‘soft’ melon ball snack under tropical conditions

19 microorganisms, mostly hazardous and spoilage species were isolated from ‘soft’ melon ball snack samples in the humid Western Nigeria. Physical biodeterioration was recorded from the 6th day of storage with the early occurring rope (slime) of Bacillus sp. found to be a faster visible objectionable indicator than the commonly used fungal growth. All the 14 isolated fungi grew though, to varying extents on the snack agar and in the melon seeds infusion medium in which they also induced significant changes in the oil (decrease) and free fatty acids (increase) contents after 10 days of incubation at 30 °C. The results implicated Rhizopus arrhizus, R. nigricans, Aspergillus flavus, A. ochraceus, A. tamarii, A. niger, Mucor fragilis and Penicillium citrinum as the major fungal deteriogens. Isolation of the coliform bacterium (Escherichia coli) suggested the need for a more hygienic handling of the snack. Addition of varying amounts of breadfruit nuts mash as adjunct to melon seeds mash in order to enhance mastication of snacks with lower moisture content was investigated. Samples prepared with 20% adjunct recorded mean acceptability rating of 178 and keepability period of 10 days while 200 and 5 days were obtained respectively for the control.     

Spoilage moulds and deterioration of the Nigerian groundnut cake snacks under three storage methods

Twelve species of toxigenic and zoopathogenic fungi were isolated from three major types of the Nigerian groundnut cake snacks. All the isolates grew well on groundnut cake infusion medium and induced changes in the oil (decrease) and free fatty acid (increase) contents of groundnut seed medium with time. The largest changes were induced by Aspergillus flavus, A. niger and A. fumigatus. Mould deterioration of groundnut cake snack samples kept under traditional, “industrial” and retailer's storage methods was studied. Mouldiness was first recorded on the 5th day for samples stored under the retailer's method and on the 10th day for samples from other storage methods. The odour and taste acceptability values, although partly affected by the different storage techniques decreased rapidly with storage period. The overall results suggest the need for research into the processing and packaging to extend the shelf life of the snacks.     

Enzyme activities during post-harvest storage of kolanut (Cola nitida, Schoot and Endlicher)

The activities of polyphenol oxidase, peroxidase and catalase were determined in extracts of kolanut,Cola nitida stored for 3 months. Enzyme activities measured in nut extracts at the early stages of storage (0–30 days of storage) were not significantly lower than those present in extracts of the fresh unstored nuts. The activities of polyphenol oxidase, peroxidase and catalase measured in the stored kolanut extract were decreased at the intermediate (30–60 days of storage) and mature (60–90 days of storage) periods. Weight changes due to moisture loss during the storage period were also observed. Weight and moisture losses were high during the early storage period and weight loss was steady during the mature storage period. These changes in activities play a significant role in the deterioration of kolanut in storage.     

Effect of time,temperature and humidity on biodeterioration of corn cake snack

Food spoilage microorganisms representing 5, 6 and 10 genera of moulds, yeasts and bacteria, respectively were isolated from corn cake snack. Each of the samples analysed had initial pH value favourable to microbial growth and activities while only 28% had spoilage-enhancing moisture contents (> 13%). The effect of temperature and relative humidity (RH) on biodeterioration during a 24-day storage period was determined by monitoring changes in the pH and total microbial colony counts. Whereas very little or no deterioration was recorded for samples contained in 51% and 71% RH chambers at 30 and 45 °C, substantial deterioration was obtained at the same temperatures under 89.5% and 100% RH. At 15 °C, very little or no deterioration was detected except under 79.5%, 89.5% and 100% RH when slight spoilage changes were recorded as from the 12th or 18th day. The overall results show that the obtained colony counts and pH values monitor spoilage equally.     

Enzyme activities during post-harvest storage of kolanut (Cola nitida,Schoot and Endlicher)

The activities of polyphenol oxidase, peroxidase and catalase were determined in extracts of kolanut,Cola nitida stored for 3 months. Enzyme activities measured in nut extracts at the early stages of storage (0–30 days of storage) were not significantly lower than those present in extracts of the fresh unstored nuts. The activities of polyphenol oxidase, peroxidase and catalase measured in the stored kolanut extract were decreased at the intermediate (30–60 days of storage) and mature (60–90 days of storage) periods. Weight changes due to moisture loss during the storage period were also observed. Weight and moisture losses were high during the early storage period and weight loss was steady during the mature storage period. These changes in activities play a significant role in the deterioration of kolanut in storage.     

Use of lambda DNA as a marker to assess DNA stability in olive oil during storage

Filtered olive oil samples spiked with three different concentrations of λDNA were stored at 25 °C under a 12 h photoperiod for up to a year. These samples were used for DNA extraction and PCR amplification of λDNA amplicons of 107, 415 and 691 bp length. The amplification signal was gradually decreased with longer storage periods, while the strength of the signal was related to the initial concentration of spiking λDNA particularly during longer storage periods. The 107 bp amplicon was the only one successfully amplified from all the samples, regardless of both concentration of spiking λDNA and storage period. The amplification of 415 and 691 bp amplicons was not successful for samples stored longer than a threshold period of 20 and 10 days, respectively. These results suggest that detection of polymorphic markers requiring DNA templates shorter than 100 bp might have a wider range of applications in DNA fingerprinting of olive oil. In addition, the DNA extracts were tested for the presence of inhibitors in PCR amplification reactions of yeast DNA amplicons. The inhibitory effect of olive DNA extracts was partial and gradually increased with the storage period of the olive oil samples used for the DNA extraction.     

Microbiological,chemical and sensory changes of whole and filleted Mediterranean aquacultured sea bass (Dicentrarchus labrax) stored in ice

The effect of filleting on the microbiological, chemical and sensory properties of aquacultured sea bass (Dicentrarchus labrax) stored in ice was studied. Pseudomonads, H₂S‐producing bacteria (including Shewanella putrefaciens) and Brochothrix thermosphacta were the dominant bacteria at the end of the 16 day storage period in ice for both whole ungutted and filleted sea bass. Enterobacteriaceae were also found in the spoilage microflora of whole ungutted and filleted sea bass, but their counts were always lower than those of pseudomonads, H₂S‐producing bacteria (including S putrefaciens) and B thermosphacta. Total viable counts for whole ungutted sea bass were always lower than those for filleted sea bass samples. Of the chemical indicators of spoilage, TMA (trimethylamine) values of whole ungutted sea bass increased very slowly, whereas significantly higher values were obtained for filleted samples, with respective values of 0.253 and 1.515 mg N per 100 g muscle being reached at the end of their shelf‐life (days 13 and 9 respectively). TVB‐N (total volatile basic nitrogen) values showed a slight increase for whole ungutted sea bass during storage, reaching a value of 26.77 mg N per 100 g muscle (day 13), whereas for filleted fish a corresponding value of 26.88 mg N per 100 g muscle was recorded (day 9). TBA (thiobarbituric acid) values increased slowly for whole ungutted and filleted sea bass samples throughout the entire storage period, reaching final values of 4.48 (day 13) and 13.84 (day 9) mg malonaldehyde kg^?1 respectively. Sensory assessment of raw fish using the EC freshness scale gave a grade E for up to 5 days for whole ungutted sea bass, a grade A for a further 4 days and a grade B for an additional 4 days, after which sea bass was graded as C (unfit). Overall acceptability scores for odour, taste and texture of cooked whole ungutted and filleted sea bass decreased with increasing time of storage. The results of this study indicate that the shelf‐life of sea bass stored in ice, as determined by overall acceptability sensory scores and microbiological data, is 8–9 days for filleted and 12–13 days for whole ungutted fish. Copyright © 2003 Society of Chemical Industry     

FACTORS INFLUENCING FUNGAL QUALITY OF PECANS STORED AT REFRIGERATION TEMPERATURES

TWO factors greatly affecting the growth of fungi on stored pecan nuts (Curya illioensis) are moisture content and temperature. Experiments designed to simulate conditions of commercial practice were carried out to determine the effects of sap (naturally occurring) moisture and superficial or imbibed moisture, i.e., moisture originating from sources other than the tree, on survival of fungi on stored pecans. A second objective was to determine the effect of temperature of storage on the rate of equilibration of moisture in pecans. Of particular interest was the effect of this rate of change on populations of naturally occurring fungal contaminants. In-shell pecans were stored in Kraft paper and plastic bags at ?18, ?6.5, and 0°C for periods of 6, 12, and 24 wk. Results indicate that pecan kernels with low sap and low superficial moisture at the time of harvest are less likely to support fungal growth than are kernels with high sap moisture, or low sap moisture but high superficial moisture. Fungi are capable of growing on pecans at 0°C and to a less extent at ?6.5°C after prolonged storage. Rapid reduction of moisture content accompanied by ventilation in chambers with air having relative humidities in the range 60–68% is most desirable for preserving pecans against fungal deterioration.     

Characterisation of Brown and Milled Yellow Rice and Development of an Expanded Snack

Brown rice and yellow milled rice were characterised in relation to milling properties, cooking, processing quality and microbial testing, and utilised to develop an expanded snack. The extrusion process was done in a Mapimpianti single screw cooker-extruder. A flour sample feed rate of 70 g (dry matter) min⁻¹ was maintained by varying the force-feeder speed. A screw speed of 150 rev min⁻¹ and a die with 20 die-nozzle orifices (2 mm in dia) were used. The die zone was heated at 110°C by electrical resistance. Compressed air was circulate around the barrel to maintain precise control of the temperature. The moisture content of the samples was 120, 150 and 180 g kg⁻¹. The grains were classified as long-thin with an average size of 2·13 mm×6·79 mm. The milling yields obtained in the laboratory with paddy rice were 700 g kg⁻¹ brown rice and 600 g kg⁻¹ milled rice. Brown rice and yellow milled rice had similar amylose contents, 225 and 256 g kg⁻¹, respectively. Gel consistency was soft with low gelatinisation temperature (63–68°C) for both samples. Field fungi such as Helminthosporium oryzae and storage fungi as Aspergillus spp were present in paddy, yellow milled and commercial rice. Helminthosporium oryzae was not present in extruded products. The extruded products showed low density and a high degree of expansion, with the optimum degree of expansion obtained in flours processed with moisture at 150 g kg⁻¹ in both milled and brown rice. The highest values for water solubility index were obtained with flours from milled yellow rice and none of the extruded products showed significant differences on water absorption index. Sensory analyses carried out on the snack products showed them to be acceptable, with the bent acceptance for products made from milled yellow rice processed with 150 g kg⁻¹ moisture.     

小麦储藏水分、温度和真菌生长危害进程预测的研究

对小麦储藏水分、温度、真菌最初生长时间和危害进程进行了初步探索性研究。采用喷雾着水方法将样品水分调至13.2%、13.6%、14.0%、14.5%、15.1%、15.5%、16.9%,分别于10、15、20、25、30、35℃恒温箱模拟储藏,定期检测各样品真菌生长变化情况,周期为120 d。结果表明,小麦在不同温度储藏,随着温度增加,真菌生长速度加快,30℃时达到最高,35℃时生长速度降低。在6个试验温度中,从安全和经济角度评价,最佳储藏温度为20℃;16.9%水分的小麦,由于出现一些青霉生长,即使低温储藏,这个水分仍存在着较大风险;根据上述研究结果,研究首次提出了小麦储藏水分、温度和真菌最初生长关系曲线,小麦在不同温度下储藏,真菌危害进程所需的时间。由于储粮真菌生长影响因素的复杂性,本试验数据仅供参考。     

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.     

The impacts of water and ethanolic extracts of propolis on vacuum packaged sardine fillets inoculated with Morganella psychrotolerans during chilly storage

The impacts of water and ethanolic extracts of propolis at a dose of 0.4 or 0.8% on vacuum packaged sardine fillets inoculated with Morganella psychrotolerans DSM 17886 during storage at 3 ± 1°C for 15 days were investigated. All fish groups were inoculated with M. psychrotolerans (10⁸ cfu/ml) at a rate of 1%. Sensory, colorimetric, chemical analysis (total volatile basic nitrogen, thiobarbituric acid, peroxide values, and free fatty acids), pH value, and microbiological analysis (viable mesophilic and psychrophilic bacteria, coliform, and lactic acid bacteria count) were carried out. An enhance in L* values was found in the group treated with 0.8% ethanolic extracts of propolis on the seventh day of the storage. Application of propolis extract on fish fillets significantly inhibited bacterial growth during storage and extended shelf life of sardine for 4 and 6 days by the use of water extract and for 8 days by the use of ethanolic extract at doses of 0.4 and 0.8%, respectively. The result of the study revealed that application of propolis extracts, mainly ethanolic propolis extracts on sardine fillets resulted in lower lipid oxidation and bacterial growth, therefore, could be natural food additive for preservation of fish fillets.     

Effect of Ganghwayakssuk (Artemisia princeps Pamp.) on oxidative stability of deep fried chicken nuggets

This study was conducted to examine the antioxidant effects of various levels of added ganghwayakssuk (Artemisia princeps Pamp.) extract on deep fried chicken nuggets. The frying loss, pH, and yellowness values of all treatments were higher than those of the control (p<0.05). Additionally, the lightness and redness values of all treatments were lower than those of the control and as the amount of ganghwayakssuk ethanolic extracts (GEE) increased. At the end of the storage period (day 10), the peroxide values (POV), conjugated dienes (CD), and thiobarbituric acid reactive substances (TBARS) values were lower than those of the control. The sensory evaluation of all samples was not different significantly at the early days of storage (p<0.05). With increases in the storage period, deep fried chicken nuggets containing various levels of GEE had higher overall acceptability than those of the control. The results demonstrate that ganghwayakssuk has strong lipid antioxidation activity added to deep fried chicken nuggets.     

Effect of Storage on the Physico‐Chemical and Antioxidant Properties of Strawberry and Kiwi Leathers

Strawberry and kiwi leathers were used to develop a new healthy and preservative‐free fruit snack for new markets. Fruit puree was dehydrated at 60 °C for 20 h and subjected to accelerated storage. Soluble solids, titratable acidity, pH, water activity (a_w), total phenolic (TP), antioxidant activity (AOA) and capacity (ORAC), and color change (browning index) were measured in leathers, cooked, and fresh purees. An untrained panel was used to evaluate consumer acceptability. Soluble solids of fresh purees were 11.24 to 13.04 °Brix, whereas pH was 3.46 to 3.39. Leathers presented an a_w of 0.59 to 0.67, and a moisture content of 21 kg water/100 kg. BI decreased in both leathers over accelerated storage period. TP and AOA were higher (P ≤ 0.05) in strawberry formulations. ORAC decreased 57% in strawberry and 65% in kiwi leathers when compared to fruit puree. TP and AOA increased in strawberries during storage. Strawberry and Kiwi leathers may be a feasible new, natural, high antioxidant, and healthy snack for the Chilean and other world markets, such as Europe, particularly the strawberry leather, which was preferred by untrained panelists.     

MODEL TO PREDICT THE COOL-DOWN CHARACTERISTICS OF VARIABLE AIR TEMPERATURE POTATO COLD STORAGE USING COMPUTATIONAL FLUID DYNAMICS

In Indian commercial potato cold storage facilities, the air temperature does not remain constant during the loading period. Also, because of stepwise loading pattern, the product loaded on different days would undergo different time‐temperature histories. Under this transient condition, the product takes longer to reach the steady state and loses more moisture of about 1.7% during 1 month of storage period. In addition, the sensible product‐cooling load is different for the product loaded on different days. In the present study, therefore, the product temperature, moisture loss and sensible product‐cooling load were predicted for the product loaded on different days under the condition of variable storage air temperature in the range of 3.5–10C and constant relative humidity of 90% using the computational fluid dynamics technique. It was found that the product loaded during the middle of loading period incurred more moisture loss than that loaded during early and latter stages of loading. However, the former case imposed more sensible product‐cooling load. The trends of temporal variation of average product temperature, moisture loss and sensible product‐cooling load depended on the day of loading of the product in the cold storage facility.     

Spoilage moulds and aflatoxins from poultry feeds

Aflatoxin producing strains of Aspergillus flayus Link (IMI 280819) and A. oryzae (Ahlb.) Cohn (IMI 280831) were among the eleven spoilage moulds isolated from five types of poultry feeds. The recorded pH and moisture content values of the various feeds are conducive to mould deterioration. All the four principal aflatoxins (B₁, B₂, G₁, G₂) were detected in the analysed feeds though at toxicologically ‘safe’ levels for most farm animals. Significant quantities of aflatoxin B₁ were produced by the two fungal isolates in all the five classes of poultry feeds with A. flavus yielding the larger amounts. Optimum aflatoxin B₁ production and mycelial growth in chick mash infusion medium were recorded for both species at 30 and 35 °C, respectively and similarly on the 8th and 6th day respectively when cultures were incubated at 30 °C.     

Effect of storage temperatures and time on shelf‐life of sliced and modified atmosphere packaged Pastırma,a dried meat product,produced from beef

The effects of modified atmosphere on some physical, chemical and microbiological properties of sliced past?rma made from beef Longissimus dorsi muscle were investigated. Sliced‐past?rma samples (moisture 43.65 ± 0.15%, pH 5.71 ± 0.02) were stored in modified atmosphere packages (50% N₂ + 50% CO₂) at 4 and 10 °C for 150 days. The storage period had a significant effect (p < 0.01) on moisture, pH, thiobarbituric acid reactive substances, free fatty acid, non‐protein nitrogen, water‐soluble nitrogen, colour values and total aerobic bacteria, lactic acid bacteria and Micrococcus/Staphylococcus counts. The storage temperatures (4 and 10 °C) also had a significant effect (p < 0.01) on moisture, pH, thiobarbituric acid reactive subctances, free fatty acid, water soluble nitrogen, a* values, total aerobic bacteria lactic acid bacteria, and Micrococcus/Staphylococcus counts. It was determined that the storage period × the storage temperature interactions had a significant (p < 0.01) effect on the values of pH, a* and the counts of total aerobic bacteria, lactic acid bacteria, Micrococcus/Staphylococcus. It was also observed that the yeast and mold count was the highest in the first storage period and decreased throughout storage. Enterobacteriaceae count was also below the detectable level (<2.00 cfu g^?1) throughout the storage period. Copyright © 2005 Society of Chemical Industry     

Shelf Life of Pretreated Dried Tomato

Determining the shelf life has become a factor of major importance in the development of foods designed to meet consumer demands in terms of quality and safety. The goal of the present study was to investigate the shelf life of vacuum-packed dried tomatoes, stored at both room and refrigeration temperature (4 °C) for a period of 180 days. The following determinations were performed during the storage period studied: microbiological analysis, instrumental color, lycopene, and ascorbic acid. Sorption isotherms were determined at both temperatures (room temperature and 4 °C). The microbiological quality of vacuum-packed dried tomatoes remained unchanged during 180 days for the refrigerated samples and 90 days for the samples stored at room temperature. The rate constant (k) of lycopene degradation of the refrigerated samples and the samples stored at room temperature was 3.209 × 10⁻⁵ and 12.994 × 10⁻⁵/day, respectively. The rate constant (k) of ascorbic acid degradation was 3.339 × 10⁻⁴/day for cold storage and 76.655 × 10⁻⁴/day for storage at room temperature. The tomatoes stored at room temperature were subjected to analysis over 90 days of storage, period after which both the appearance and sensory characteristics of the product fell below the levels of consumer acceptability. As for the tomatoes stored at refrigeration temperature, the original sensory characteristics were maintained throughout the entire storage period of 180 days.     

Effects of sodium chloride and relative humidity on growth and sporulation of moulds isolated from cured fish

A total of 14 moulds were isolated from 84 samples of cured fish obtained from several processing centres and retail shops in Lagos, Ogun and Oyo States, Nigeria. Aspergillus niger, A.flavus and A. chevalieri were the most prevalent. With the exception of Basipetospora sp., slight inhibition of mycelial growth and/or sporulation was recorded when isolates were cultured in basal medium containing 5% sodium chloride. The extent of inhibition increased with increasing salt concentrations, and at 25% level all the species had their growth completely inhibited. When fish substrates inoculated with test fungi were kept inside 65% relative humidity (RH) chambers for 21 days, no detectable utilization of the substrates was recorded for any of the fungal species. Whereas only A. chevalieri and A. restrictus utilized the substrates when placed inside 70% RH chambers, all the test moulds recorded detectable utilization (though at varying extents) of same at 80% and 90% RH levels. The latter RH was the most conductive and under it A. niger, Penicillium sp. and the two isolated Scopulariopsis sp. brought about the greatest loss in weight of the substrates.     

Shelf-life extension and quality attributes of the whey cheese “Myzithra Kalathaki” using modified atmosphere packaging

The present work evaluated the effect of modified atmosphere packaging (MAP) on quality characteristics and shelf-life extension of the whey cheese “Myzithra Kalathaki” using microbiological, chemical and sensory analyses. Myzithra cheese was packaged in four different atmospheres: vacuum, 20% CO₂/80% N₂ (M₁), 40% CO₂/60% N₂ (M₂) and 60% CO₂/40% N₂ (M₃); identical cheese samples were packaged in air, taken as controls. All cheese samples were kept under refrigeration (4±0.5 °C) for 45 days. Of the four atmospheres, the M₂ and M₃ gas mixtures were the most effective for inhibiting growth of aerobic microflora and psychrotrophs in cheese samples until days 40 and 33 of refrigerated storage, respectively. Lactic acid bacteria (LAB) were part of the cheese microflora becoming dominant toward the end of the storage period regardless of packaging conditions. Enterobacteriaeceae were also part of the cheese microflora being effectively inhibited after day 35 of storage. Molds and yeasts were also totally inhibited by MAP (M₂ and M₃) gas mixtures throughout the entire storage period. Of the chemical quality indices determined, lipid oxidation varied below 0.005 absorbance at 532 nm for all treatments, except control samples for which absorbance values of 0.02 were recorded after 35 days of storage. Lipolysis did not vary significantly with type of packaging treatment while proteolysis values showed and increasing trend up to day 25 of storage and then decreased toward the end of the storage period. Sensory evaluation (odour and taste) showed that Myzithra cheese packaged under MAP (M₂ and M₃) retained good sensory characteristics for 30 days of storage while control samples were sensorily unacceptable after 10-12 days of storage.