Characterization of native microbial populations on Swiss chard (Beta vulgaris,type cicla) cultivated by organic methods

The native microflora of fresh Swiss chard (Beta vulgaris, type cicla) cultivated by organic methods was quantified and characterised. The concentration of the different microorganism groups presented less variability among different lots than results found on chard leaves produced by conventional methods. These results would indicate a greater degree of homogeneity among the different samples of chard produced by organic procedures.The microbial populations on Swiss chard leaves produced by organic methods were 6.8×10⁵ CFU/g for mesophilic microorganisms, 3.9×10³ CFU/g for psycrotrophic microorganisms, 1.4×10⁴ CFU/g for lactic acid microorganisms, 5.1×10³ CFU/g for total coliforms and 1.66×10³ CFU/g for Staphylococcus spp. Neither fecal coliforms nor human pathogens were identified. Immersion of organic Swiss chard leaves in tap water at 18°C for 4 min reduced microbial populations but did not accomplish more than 70% removal in any of the populations under study.     

The effects of temperature and relative humidity on ochratoxin A formation in fresh liquorice root

In this study, the effects of temperature and relative humidity (RH) on ochratoxin A (OTA) formation during liquorice root storage were investigated. For this purpose, a real storage procedure in which fresh root was dried in the open air was simulated. Four RH-temperature combinations corresponding to average climate conditions (RH-temperature) of each season in an important liquorice growing and processing region were simulated as follows: A, autumn (T?=?15°C, RH?=?49%); B, winter (T?=?9°C, RH?=?51%); C, spring (T?=?22°C, RH?=?35%); and D, summer (T?=?29°C, RH?=?27%). The crushed fresh roots were incubated for 60 days, and the OTA content of the roots was determined at 20-day intervals by using inverse ion mobility spectrometry. The results showed that the maximum levels of OTA occurred after 40 days and were 4.3?±?1.1, 0.9?±?0.2, 7.3?±?0.0 and 24.2?±?2.5?ngg^?1 in roots stored under simulated conditions A, B, C and D, respectively. After 40 days, the amount of OTA started to decline in all samples but at different rates. The results seem to indicate that temperature plays a more significant role than RH in producing OTA by moulds in liquorice root. It appears that 22°C could be considered as the critical temperature for OTA formation in liquorice root stored under experimental conditions. It could be concluded that liquorice-processing plants should obtain, dry and store fresh moist root when the temperature is below the critical point. Moreover, the roots stored in the open shade condition should not be covered by plastic films even when it is raining as this increases the root temperature.     

Shelf Life of Leafy Vegetables Treated with Natural Essential Oils

ABSTRACT: Essential oils as natural sanitizing agents were sprayed on Swiss chard leaves produced by organic methods. Samples were stored at 0 and 5°C and 97% to 98% relative humidity. Microbial populations, peroxidase activity, and sensory attributes were monitored during storage. No significant differences were observed between treated and control samples stored at 0°C. However, samples treated with the essential oils of eucalyptus, tea tree, and clove and stored at 5°C presented microbial counts significantly lower than those of control samples. The essential oils of eucalyptus, tea tree, lemon, rosemary, and clove presented peroxidase activity inhibition that, in the case of eucalyptus, increased to 65% during storage. Although some of the essential oils did appear to reduce microbial counts and peroxidase activity compared with controls, they were not effective in extending the shelflife of the Swiss chard leaves from a sensory point of view.     

Improved keeping quality of minimally fresh processed celery sticks by modified atmosphere packaging

Recommended storage conditions of green celery sticks are 4 °C for 10 days, but there are no reports about optimal modified atmosphere packaging (MAP) conditions to preserve them longer. The objective of this research was to describe the gas composition of MAP generated by two polymeric films and its effects on chemical, sensorial and microbial quality, and physiological disorders of celery sticks stored at 4 °C for 15 days. Green sticks of 15-cm length of ‘Trinova’ cv. were placed in hermetically sealed plastic bags: low-density polyethylene, oriented polypropylene (OPP) and polyethylene-perforated bags as control (air). The O₂ and CO₂ concentrations, soluble solid content, pH, titratable acidity, colour, sensorial quality and sugar and organic acids contents were monitored. Compared to the control, both MAP treatments improved the sensory quality, avoided the loss of green colour, decreased the development of pithiness and retarded the growth of microorganisms. In any treatment neither off-odours nor off-flavours were detected. After 15 days at 4 °C within the OPP bags a steady-state atmosphere of 6 kPa O₂+7 kPa CO₂ was reached and celery sticks stored under these bags showed the best quality.     

Storage conditions affect quality of noodles with added soy flour and sweet potato

Summary Noodles were prepared from a formulation in which a portion of the flour was replaced with 10% defatted soy flour and sweet potato as 10% flour or 15% puree. Dried noodles were packaged in plastic bags under partial vacuum or air and stored at 4.4 °C or 22–30 °C for 6 months. Colour, β-carotene and sensory characteristics were analyzed at 2-month intervals. Packaging atmosphere had minor effects on colour. Stored noodles became lighter and yellower, and β-carotene decreased, with all changes being greater at 22–30 °C. Storage conditions influenced acceptability scores minimally. Noodles were stored successfully under air with greater quality retention with 4.4 °C storage.     

Effect of Packaging Material on Nitrate Nitrogen Content of Irradiated Potatoes

The effect of packaging materials on nitrate nitrogen content of irradiated potatoes was investigated. Tubers were irradiated at 10, 30 and 100 Krads and stored for 12 wk at 5°C in paper or plastic bags. Nitrate nitrogen content was significantly (p < 0.01) higher in tubers packaged in plastic as compared to those in paper bags. Irradiation significantly (p < 0.01) increased nitrate nitrogen content between the lowest and highest levels of treatment in tubers stored in both paper and plastic bags.     

Listeria monocytogenes Inactivation in Turkey Rolls and Battered Chicken Nuggets Subjected to Simulated Commercial Cooking

Cured and uncured turkey rolls inoculted with 10⁷Listeria monocytogenes CFU/g were vacuum packaged and cooked to internal temperatures of 68°C and 74°C, respectively, in a steam-injected chamber. Samples were stored up to 15 wk at 4°C. Battered chicken nuggets were also inoculated internally with about 10⁷L. monocytogenes CFU/ g. Nuggets enclosed in bags were cooked under moist heating conditions in a convection oven to an internal temperature of 71°C. Nuggets were flushed with 30% CO₂, 70% N₂ atmosphere and sealed. Chicken nuggets were stored at 4°C up to 30 days. No Listeria monocytogenes were recovered from the cooked products suggesting that similar commercial processes are adequate to reduce populations of L. monocytogenes below detection limits.     

Staphylococcus aureus Growth and Enterotoxin Production in Mushrooms

An enterotoxin A (SEA) producing strain of Staphylococcus aureus was inoculated onto mushrooms and incubated under simulated pre-and post-canning conditions. S. aureus grew and produced SEA in mushrooms incubated at 25°C in 10% to 20% NaCl. Growth and SEA production occurred when mushrooms were stored in plastic bags at 37°C, but not at 25°C. Mushrooms heat-processed at 121.1°C supported S. aureus growth and SEA production. No SEA was recovered from mushrooms inoculated with 1 or 10 ng SEA/g and heated at 121.1°C for 4.5 min. At higher inoculated SEA levels (100 and 1,000 ng/g), SEA was detectable after 10 min of heating. Staphylococcal enterotoxin could be present in canned mushrooms as a result of pre-, but more likely post-processing contamination.     

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.     

Effects of storage condition and domestic cooking on the quality and nutrient content of African leafy vegetables (Cassia tora and Corchorus tridens)

BACKGROUND: The main objective of this research was to determine changes in nutrient content of two African leafy vegetables, Cassia tora and Corchorus tridens, on cooking and storage under different temperature conditions, i.e. room storage (20 °C), refrigerated storage (4 °C) and frozen storage (?18 °C). RESULTS: The leafy vegetables were analysed for moisture, colour (Hunter L, a, b), texture, total chlorophyll, ascorbic acid, dehydroascorbic acid and total phenolics. Results indicated that the degradation of ascorbic acid was highest as a result of frozen storage, followed by room temperature storage. The dehydroascorbic acid content was correspondingly high in frozen stored leafy vegetables, whereas it was undetectable in the room temperature and refrigerated stored materials. The total phenolic content of the leaves increased with storage time while the total chlorophyll content decreased under all storage conditions. Domestic cooking resulted in significant additional losses of ascorbic acid following storage under all temperature conditions, with only 1–10% retention in the leaves and 50–60% retention in the cooking water. The green colour of the leafy vegetables was retained best under refrigerated and frozen storage, while the peak force and toughness of the leaves increased upon storage under all conditions. The moisture content of the leafy vegetables did not show any significant difference on storage. CONCLUSION: This study is one of few to report nutrient content changes on the same raw material stored under various temperature conditions and cooked domestically. Refrigerated storage resulted in the highest retention of ascorbic acid and green colour in the leafy vegetables. Copyright © 2009 Society of Chemical Industry     

Color Changes of Chicken Leg Patties Due to End-point Temperature, Packaging and Refrigerated Storage

Patties of broiler leg muscle were heated to end-point temperatures (EPT) of 60, 65, 70, 75, 80 or 85°C, packaged in polyethylene bags or vacuum skin packs and stored at 4°C for up to 14 days. As EPT increased, lightness (“L”) and yellowness (“b”) increased whereas redness (“a”) decreased. Patty top surface center color “L” and “a” values correlated highly with the interior cut surface values. Patties stored in plastic zipper bags tended to show a lower “b” (P<0.05) reading than patties stored in vacuum skin packs and plastic film. Storage for 2 wk at 4°C increased “L”, and decreased “a” and “b” for all patties. As EPT increased, the color difference (AE) at the interior cut surface of patties heated to lower EPT and those heated to 85°C were reduced.     

Astaxanthin Extraction from Shrimp Wastes and its Stability in 2 Model Systems

Abstract: The objective of this work was to study the stability of astaxanthin, obtained from shrimp wastes, and incorporated to 2 model systems: egg albumin protein solution and sunflower oil. Shrimp wastes were ensiled by a treatment with formic/acetic acids (4%–4% v/w wastes) and stored at 4 °C for 24 h. The pigment was extracted with organic solvents (petroleum ether:acetone:water, 15 : 75 : 10) and concentrated. The storage parameters studied were: illumination (light/dark), temperature (4/20 °C), atmosphere (air/air-free), and storage time (0, 1, 2, 3, 4, 5 wk). Results showed that total xantophylls and astaxanthin were more stable in sunflower oil than in the protein system. Total xantophylls showed more stability than astaxanthin, possibly due to the presence of other, more stable carotenoids quantified together with xantophylls. Astaxanthin concentration was significantly affected by storage time; its degradation followed a first-order reaction rate under all the studied conditions. This pigment was stable only for 17 d, even when stored in air-free flasks, under refrigeration, and in the dark. Practical Application: Shrimp catching and farming generate large amounts of polluting wastes; they can be an important source of added-value red-orange pigments. However, these pigments are highly unstable to various transformation processes and to storage conditions. This research studied the effect of storage on 2 model systems (protein and lipid) on pigment degradation.     

Hygroscopic Coatings Control Surface White Discoloration of Peeled (Minimally Processed) Carrots During Storage

White discoloration on peeled carrots is partially due to surface dehydration which can be controlled with hygroscopic coatings: e.g., polyhydric alcohols and salt solutions. This study was performed at 2.5, 7.5, 10, and 15°C, using a model system controlling relative humidity at 33, 75 or 98% or a commercial system with low-density polyethylene (LDPE) plastic film bags. The moisture sorption properties of propylene glycol, sorbitol, glycerol and calcium chloride enabled them to keep the carrot surface moist and maintain a transparent surface layer through which the underlying orange color was visible. This effect was only observed at high relative humidities (e.g., 98% RH). Similar effects were observed on treated peeled carrots stored in LDPE bags. The moisturized appearance provided by the hygroscopic coatings during storage was effective at several different temperatures.     

Minimal Processing and Modified Atmosphere Packaging Effects on Pigmentation of Pomegranate Seeds

The influence of different washings, temperatures, and packagings on anthocyanins of minimally processed pomegranate seeds was evaluated. No differences were found in anthocyanin composition after washing with different solutions, although a slight decrease in pigments occurred. Storage in perforated polypropylene bags preserved pigments and a slight increase in most anthocyanins occurred. During storage in modified atmospheres, anthocyanins increased at 1°C, but decreased at 8 and 4°C. The delphinidin derivatives were the most sensitive while cyanidin and pelargonidin derivatives were stable and increased slightly. The 3,5-diglucosides were more stable than 3-glucosides. Compared with storage at 1°C for 7 days in perforated OPP bags, unperforated OPP bags maintained the pigments better. However, stored an additional 4 days at 4°C to simulate domestic storage, they were better preserved in perforated films.     

Chemical changes in almonds throughout storage: modeling the effects of common industry practices

Further investigations of almond degradation under typical industrial storage conditions from a quantitative perspective are warranted. This study modeled effects of packaging, temperature (TEMP), relative humidity (RH) and roasting on chemical attributes of almonds stored according to common industry practices throughout 16 months. Roasted samples were stored in high-barrier bags (HBB) or polypropylene bags (PPB) at multiple combinations of TEMP and RH. Raw samples were held in unlined cardboard cartons (UC) or PPB under the same conditions. Almonds were assessed bimonthly for oxidation products, free fatty acids, moisture content and water activity. Results indicated roasting almonds improved quality preservation. Models showed HBB (rather than PPB) to provide benefits to stability comparable to reductions in storage TEMP of ~15 to 30 °C. PPB (rather than UC) showed benefits to peroxide formation of similar magnitude. Our data shows HBB to be a superior packaging choice, and UC to associate with the greatest rates of degradation.     

Shelf Life of Sunflower Kernels

One raw and two oil roasted samples of sunflower kernels packaged in paper bags and in two types of low oxygen atmosphere pouches were stored at 5, 21 and 38°C. Quality of the stored samples was monitored by an expert sensory panel, peroxide, hexanal, free fatty acids and moisture determinations. Liking ratings, obtained with 99 consumers after 24 wk storage, were used to select end points for expert sensory ratings. The shelf life for roasted sunflower kernels was greater than 12 month when stored in nitrogen flushed pouches and as low as 8 wks when exposed to air at 38°C. Hexanal was a better index for shelf life of roasted sunflower kernels than was peroxide. The shelf life of raw sunflower kernels was > 12 month in packages providing some moisture but no oxygen protection.     

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.     

Effect of modified atmosphere packaging on oxidative changes in frozen stored cold water shrimp (Pandalus borealis)

Shrimps caught at sea were boiled in seawater, air blast or nitrogen frozen, glazed and then packed in plastic bags with a low oxygen transmission rate. The bags were either flushed with nitrogen (modified atmosphere packaging) or with atmospheric air before sealing. The shrimps were then stored for up to 12 months in a freezer cabinet at −17°C with fluctuating temperatures. During storage they were either exposed to fluorescent light or kept in darkness. To investigate the effect of fluctuating temperatures some of the modified atmosphere-packed shrimps were stored in darkness in a cold store at a constant temperature of −18°C. Quality changes were determined by sensory evaluation combined with chemical/physical analyses, including determination of the pigment astaxanthin and measurement of the oxidative stability by determination of thiobarbituric acid-reactive substances (TBARS). Packaging in modified atmosphere resulted in overall better quality in relation to colour fading, development of rancid flavour and toughening of the meat. Light exposure influenced both colour fading and lipid oxidation negatively. Temperature fluctuations resulted in very pronounced formation of frost in the packages. After 6 to 9 months of frozen storage, the amount of frost corresponded to the weight of the glazing layer applied before storage.     

Extending the shelf life of kohlrabi stems by modified atmosphere packaging

ABSTRACT:  Kohlrabi stems (without leaves) were stored under modified atmosphere packaging (MAP) for 60 d at 0 °C. An additional retail sale period of 3 d at 12 °C after each cold storage evaluation (30 and 60 d) was applied. Under high relative humidity (RH) and 0 °C, the stems showed low metabolic activity, as no changes in sugars and organic acids were found. From day 21 at 0 °C, air-stored stems showed a yellowing of stalks and later they fell down. This disorder severely affected the appearance of stems. A gas composition of 4.5 to 5.5 kPa O₂ plus 11 to 12 kPa CO₂ was reached using antimist oriented polypropylene plastic bags of 20-μm thicknesses. The stems in MAP conditions kept a high sensorial quality. It was enough for commercial purpose of 2 mo. The storage of kohlrabi stems in plastic bags, either MA or in perforated (control) packages, provided an additional protection reducing physical damage. The MAP conditions delayed the weight loss and development of bacterial soft and black rot, extending the shelf life of kohlrabi stems to 60 d at 0 °C plus 3 d at 12 °C. Stems are not chilling injury sensitive.     

Chlorophyll degradation and resulting catabolite formation in stored Japanese bunching onion (Allium fistulosum L.)

BACKGROUND: Loss of green colour is the main factor in quality deterioration of stored Japanese bunching onion (JBO, Allium fistulosum L.) leaves. Elucidation of chlorophyll (Chl) degradation has not been performed to date. In the present study, Chl catabolism and Chl‐degrading enzyme activities in stored JBO leaves were investigated. RESULTS: Green leaves of JBO stored at 25 °C turned yellow within 3 days, whereas no changes occurred at 4 °C. Pheophytin (Phy) a, chlorophyllide (Chlide) a, pheophorbide (Pheide) a and C13²‐hydroxychlorophyll (OHChl) a were the main catabolites of Chl a and diminished at 25 °C concomitant with leaf yellowing, whereas no significant reductions were observed at 4 °C. The activities of Chl‐degrading peroxidase and Mg‐dechelation increased significantly at 25 °C but not at 4 °C. CONCLUSION: Chl degradation was accelerated and catabolite levels (mainly Phy a, Chlide a, Pheide a and OHChl a) were diminished in JBO leaves stored at 25 °C, suggesting that the catabolites are rapidly converted into their following forms. Activities of Mg‐dechelation and Chl‐degrading peroxidase were significantly enhanced during storage at 25 °C, indicating that these two enzymes have major roles in Chl degradation in stored JBO leaves. Copyright © 2008 Society of Chemical Industry