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MICROFLORA CHANGES REFRIGERATED STORAGE TEMPERATURES MICROFLORA CHANGES REFRIGERATED STORAGE TEMPERATURES

MICROFLORA CHANGES REFRIGERATED STORAGE TEMPERATURES - PDF document

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MICROFLORA CHANGES REFRIGERATED STORAGE TEMPERATURES - PPT Presentation

vitamins in the especially vitamin C The quality of vegetables are affected field and harvested conditions Microorganisms are the vegetables machinery and humans involved in the harvesting operation ID: 379975

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MICROFLORA CHANGES REFRIGERATED STORAGE TEMPERATURES vitamins in the especially vitamin C. The quality of vegetables are affected field and harvested conditions. Microorganisms are the vegetables machinery and humans involved in the harvesting operation. The common vegetable due to is caused the saprophytic bacteria. Microorganisms, from the sources listed above, enter the plant tissue through the stomata due to the plant, such as cuts and Temperature, relative humidity, the atmosphere influence the postharvest quality vegetables. These factors also influence the growth microorganisms present the fruits When conditions are favorable, will grow cause spoilage it is very important to control the microbial population in fresh storage. Refrigeration, atmosphere storage irradiation have control microbial populations fresh produce during storage (Cooper Salunkhe 1963; Kader 1988; James and no microbial study has the use fresh produce. studies washing was but not washing agents used were water (Anderson 1977), organic acids Woolthuis 1985) chlorinated water. some methods, recycled. The use of water a washing agent microbial contamination practiced extensively for 1987; Crouse Carpenter 1974), poultry (Lillard also for example, Crouse reported that automated water sprayed surfaces reduced aerobic plate log,, cfu/200cmz coliform counts log,, cfu/200cm2. the washing effects, water function as a humidifying thus help maintain initial moisture content the product. Automatic misting a type of humidification technology developed to prevent dehydration, extend shelf-life promote better appearance retail display cases. During misting, in the form the produce a constant time interval. Misting considered a humidification treatment even though occur during misting. addition, depending the source the misting water, endogenous water treatment chemicals also affect the quality attributes 1992) found that misting was significantly effective in retaining content of broccoli. The effect of microflora changes fresh produce, however have thus far not MICROFLORA CHANGES DURING MISTING The objective this work to determine the effect microflora changes broccoli stored for five days. In addition, data were collected to determine the effect the initial microbial load the broccoli. Relative humidity in the cold rooms moisture content broccoli were also determined. obtained approximately three days postharvest from a local wholesale distributor in Urbana, The broccoli harvested in Salinas, CA, hydrocooled and packed for transportation. delivery, the broccoli were sorted integrity, compact- ness, color, freedom from defects. Minor defects were corrected trimming the bunches with a sharp knife. The broccoli was under cold distributed into three groups: nonmisted stored in the cold room stored in a different cold room (DNM). Cold rooms were used evaporative cooling effects misting observed in a previous study using retail Two nonmisted control treatments were to help humidity versus washing affects on the growth the broccoli samples. treatment, the broccoli bunches were a 45-degree slope wire frame. The wire covered with rubber netting (Sure Grip Liner, Hubert Company, Harrison, a 4500 surface area. tray was placed underneath the frame to collect the misting water. The cold rooms equipment were sanitized use with a concentrated water-Lysol Products, Montvale, XY-12 Liquid sanitizer (Klenzade, Paul, MN) with sodium hypochlorite the active ingredient. PVC misting system with a snap-fit design manufactured the Corrigan Corporation (Northbrook, IL) an ordinary cold storage room which equipped with temperature humidity control cool-white lights (average level). Fluorescent lights were used because they are commonly in retail stores. Lights were kept during the entire experimental period, in both cold source of the misting water was tap water, standard end point residual chlorine (Northern Illinois Water Company, Misting intervals were min, providing a total water each interval. Temperature the cold rooms the misting The water drained from the system (referred collected for microbial analysis discarded. A prefilter the water supply system to trap large particles a microfilter (Versaflow capsule, pm pore size, Gelman Sciences was placed the misting line to filter particles. A piece hung to separate the (M) from nonmisted (SNM) treatments. The plastic sheath cut into strips to provide air prevent condensa- The misting experiment Procedure and Microbiological Analysis each time interval, 5 days, duplicate samples broccoli were taken from the stored in the the misted (SNM), nonmisted stored a different cold room experimental conditions. sample, 25 g broccoli were placed a sterile stomacher bag. The stomacher were put into a container containing crushed ice held for h until microbiological the time analysis, approximately the volume peptone water was added the sterile bag, after which the contents were homogenized for min with a (Dynatech Laboratories, Alexandria, VA). The remainder the peptone water homogenate and shaking the bag. The homogenate placed in a container of crushed ice for allow the settle. Serial dilutions were from the homogenate. From three appropriate dilutions pour-plated according the International Commission logical Specification Plate Count agar (PCA), Violet Bile agar acidified Potato Dextrose agar (PDA) (Difco Laboratories, Detroit, MI) were used respectively for enumeration aerobic plate count, and yeast and mold. Plates were incubated room temperature (about 25C) for two days for and VRBA three days for PDA. Viable counts were determined counting the number of colony forming units per gram Each microbial analysis duplicate at Since the initial viable counts of the broccoli experimental trials were different, viable count values were normalized CHANGES DURING initial viable count for microorganism group (aerobic plate count, mold) and experimental trial: count at Initial Microbial Load fresh broccoli under running cold tap water were weighed, homogenized, pour-plated using Plate Count Agar the growth media. Plate counts were conducted previously described. Quality and Rinsate Microbial Load the start of the experiment, duplicate samples of water from the nozzles were taken microbiological analysis. Each day the experiment, duplicate rinsate samples were microbiological analysis. the original, without dilution, 1/100 diluted) were pour-plated using Plate Count Agar the growth media. Plate counts were conducted described previously. Determination of Relative Humidity The percent relative humidity (RH) of each cold room for the five storage period. dry bulb values both cold rooms were recorded using a psychrometer (Psychrodyne, Industrial Instruments Suppliers, Southampton, PA) RH values were obtained using a psychrometric chart. florets with approximately 1 cm stems were cut from the spears, wiped with adsorbent paper towel and then ground into small pieces. The ground broccoli triplicate moisture contents were determined nonmisted SNM DNM broccoli samples (AOAC 1980). a drying oven overnight then transferred to a vacuum oven (Equatherm, Curtin Matheson Scientific less than until constant weights were attained. Samples were cooled in a desiccator for before weighing. Percent moisture content determined on a wet weight basis (g water/100 g Statistical significance three different viable counts (aerobic plate and yeast using a confidence level. The sources variations were time treatment condition confidence interval for the difference between means was each microbiological analysis to determine the location significance differences obtained. Statistical significance confidence level microbial load, relative humidity difference in cold rooms the broccoli under the three treatment conditions. ensure the free from microbial contamination, microflora counts (APC) from the misting nozzles viable counts were detected. Count (APC) The initial values for the two trials were Over the five APC values values were found to be lowest in the M samples highest in the SNM samples all time periods studied. ANOVA indicated significant difference APC values M, SNM, confidence interval for the difference between means, calculated for the normalized differences were found days four SNM treatments. CHANGES DURING FOR BROCCOLI STORED FIVE EXPERIMENTAL TREATMENT CONDITIONS, MISTED STORED IN ROOM AS AND NONMISTED STORED DIFFERENT COLD The initial coliforms counts from the trials were specific growth trends were exhibited the coliforms in treatments, although in cases, coliforms counts were highest in in the indicated significant difference the three treatments. The confidence interval for the difference means, calculated for the normalized coliform values, Significant differences were found days two, three five between days four Yeast and Mold yeast and mold counts from the two trials were The counts in the were highest days one three but 1 2 3 NORMALIZED COLIFORM VALUES FOR STORED FIVE 1C UNDER THREE EXPERIMENTAL TREATMENT CONDITIONS, MISTED NONMISTED STORED SAME COLD MISTED (SNM), AND NONMISTED STORED A DIFFERENT COLD NORMALIZED YEAST AND MOLD VALUES BROCCOLI STORED FIVE DAYS UNDER THREE EXPERIMENTAL TREATMENT CONDITIONS, MISTED NONMISTED STORED SAME COLD MISTED (SNM), NONMISTED STORED A DIFFERENT COLD MICROFLORA CHANGES DURING MISTING the counts were nearly the same as other days. Yeast and counts were consistently lowest in the M In the case misting, on zero counts. Two-way ANOVA a significant difference (p the three treatments. The confidence interval for the difference between the means, calculated the normalized yeast and mold M vs. two, three, four, differences were treatments from one through five. Prewashing on Initial Microbial were found be reduced one log the fresh broccoli with water (Table significant differences (p broccoli before after washing. wash water was tap water which contained approximately the reduction in counts due to the the chlorine. FRESH BROCCOLI Before washing deviation. Different lower case within a row indicate a significant Prewashing is very important in removing the produce during harvesting removed, the will not also be more spoilage problems during storage. MARTIN and After three hours zero), the microbial count the rinsate This value dropped after the first day remained relatively constant for the remainder of the an average The presence microorganisms in the rinsate suggests washing occurred during misting, where the water from the misting system microorganisms on the broccoli into the rinse water. Anderson reported that washing reduced the bacterial counts surfaces. However, significant difference were only found largest volume per min). The rate of microor- ganisms being off from found to be affected the nature the ionic environment (Appl observed to removed the highest average number surfaces compared Compared to water, three times as bacteria from the surface the inoculated mentioned previously, the reduction counts observed for the misting also be due to the effect the residual chlorine in the IN MICROBIAL IN RINSATE DURING MISTING FIVE DAYS Misting Period Aerobic Plate Count (log,, Relative Humidity Despite using an identical relative humidity set point of the relative humidity (RH) significantly higher in the cold room which housed the misting system than in the cold room CHANGES DURING the misting system throughout the storage period (Table for the cold room with misting over the five storage period due to the effects Whereas, the cold room without misting continuously over the period due to condensation on the cooling system heat exchanger. The atmosphere outside the cold room on the HUMIDITY IN COLD Cold Room Cold Room without misting represent mean deviation. Different lower case letter superscripts within a a significant difference at the have reported that high moisture and/or growth rate thus increase the the particular organism studied (Scott 1978; Troller 1980). In this study, growth rates under the three conditions (M, SNM, the microorganism APC, the were larger the higher resulted in APC values but that misting, through a resulted in the lowest APC the case and yeast treatments were both greater time periods cause a large difference in the through a microbial activity. MOHD-SOM, L.A. SPOMER, The low microbial count in fresh produce stored in a high explained by a few workers. some microbes, especially fungus with thick walls, are generally resistant to desiccation. Lewis the treatment of carrot roots at a humidity approaching saturation accelerated wound repair thus diminished subsequent infection observation was found who noted that wounds in potato tubers at lower the rate the surface cells great enough inhibit suberization periderm formation, which are wound healing. stored carrots several temperatures, air-flows, humidities, time periods only took place when the carrots lost greater than a critical percentage their weight the production extracellular pectolytic enzyme was studied Berg and Yang the fungi produced significantly extracellular pectolytic enzyme when the carrots were exposed when exposed MOISTURE CONTENT MISTED AND NONMISTED BROCCOLI STORED AT Storage (Day) *Values represent standard deviation. Different lower case letter superscripts between columns within a row indicate a significant difference confidence level. **Zero day moisture content value was the same for three treatment conditions. initial moisture content the fresh broccoli Throughout the storage period, the moisture content of the remained close the initial value, only decreasing (wb). The CHANGES DURING a slight decrease in moisture content while the nonmisted DNM showed a pronounced decrease in moisture content value (Table significant difference (p between all three treatment conditions Moisture content in the DNM samples due to caused by the low the cold room without misting. hand, the nonmisted SNM had a higher moisture content than the DNM because the SNM sample located in the cold room with the misting However, the SNM a lower moisture content than misted M because the SNM did not receive the direct misting treatment. This work showed that broccoli stored refrigerated tempera- aerobic plate counts coliform counts yeast and controls. Prewashing important to reduce the initial microbial before storage. A washing take place during misting. This washing effect been enhanced the use chlorine containing tap water the misting water source. Misting found to the cold room relatively constant moisture content in the broccoli. study the effects the misting water the microflora changes in important to identify the microbes present on the produce being compared with nonmisted produce. Another area which needs studied is the significance water purification treatments ionization/distillation, ozonation chlorination treatment) microflora changes. GOLL, S.J. spray chilling carcass spacing carcass cooler grade factors. Anim. Sci. M.E, HUFF, lamb carcasses dipped with acetic vacuum packaged at ANDERSON, M MARSHALL, R.T., STRINGER, 1977. Combined individual effects bacterial counts of P26 from AOAC. 1980. the Association Chem., Washington, B.P. 1990. Misting effects retention in broccoli during cabinet Food Sci. 1187-1188, 1191. SCHMIDT, S.J. Misting affects broccoli during retail Food Sci. 1984a. Inoculation of potato tubers with during simulated practices. Am. Potato KELMAN, A. 1984b. soft-rot potential in potato tubers relation to temperatures water during simulated commercial handling practices. 1980. Water relations in the life-cycles of soil-borne plant pathogen. Potential Relations in Soil pp. 119-139, Soil Sci. SOC. 1978. Role of water potential in microbial development of plant disease with special reference post-harvest pathology. SALUNKHE, D.K. 1963. of gamma-radiation, and packaging sweet cherries. Food Technol. 1988. Microbial and weight affected by automated washing pressure time spray. HUNG, Y.C. Extending the shelf-life shrink-wrapping, refrigera- Food Sci. Their Significance and Methods Ed. The International Commission Foods ICMSF, Toronto Press, Toronto, Canada. JAMES, S.J. and BAILEY, C. 1990. Chilling (Gormley, ed.) pp. 1-35, Elsevier Applied CHANGES DURING and KERBEL, Modified atmosphere packaging of Sci. Nutr. and GARROD, Wound-healing in carrot roots in relation Appl. Biol. HAMM, D. Effect of spray- washing uneviscerated carcasses microbiological quality of hot-boned harvested after reduced processing. 1974. Bactericidal properties of propionic acids pork carcasses. Anim. Sci. 1957. Water relations of food spoilage microorganisms. Food Res. and WOOLTHUIS, Immediate and delayed microbiological effects of lactic decontamination of calf carcasses-in- conventionally boned versus hot-boned behavior of stored with respect their invasion Rhizopus stolonifer Food Technol. 1980. Influence water activity microorganisms in foods. Food Technol. relative humidity production of extracellular pectolytic enzymes Botrytis cinerea temperature, oxygen tension and relative the wound-healing process Potato Res. and KADER, 1988. Modified atmosphere packaging of fresh produce. Food Technol.