The effectiveness of ozone and acidulant treatments in extending the refrigerated shelf life of fresh-cut potatoes

Abstract: The objective of the study was to determine the effectiveness of acidulant dip treatments (with or without aqueous ozone) to reduce enzymatic browning and to extend the shelf life of fresh‐cut potato slices during refrigerated storage (4 °C) for 28 d. Potato slices subjected to aqueous ozone (2 ppm) had significantly (P≤ 0.05) higher L‐values and lower a‐values, but ozone did not appear to have any effect on aerobic plate counts (APCs) or polyphenol oxidase (PPO) activity. NatureSeal (NS) and sodium acid sulfate (SAS) were the most effective acidulant treatments in reducing browning (significantly [P≤ 0.05] higher L‐values, lower a‐values, and browning index values) regardless of ozone treatment. NS and SAS also had lower PPO activity compared to other treatments on days 0 and 28, and significantly (P≤ 0.05) lower APCs (≤2.00 log CFU/g) over refrigerated storage. Therefore, the SAS treatment was comparable to NS, a commercially available product, and showed promise as an effective antibrowning dip to reduce browning and spoilage in fresh‐cut potato products. Practical Application: A 1% SAS dip treatment which included 1% citric and 1% ascorbic acid was found to be an effective antibrowning dip for fresh‐cut potatoes along with NatureSeal®'s PS‐10, compared to other treatments. They were both effective in maintaining low microbial counts over refrigerated storage. Additionally, aqueous ozone washes (2 ppm) showed significant benefits to reduce browning; however, ozone did not affect microbial counts or PPO enzyme activity. Therefore, the SAS treatment could have potential use in the fruit and vegetable industry to reduce browning and spoilage in fresh‐cut potato products.     

杨木胶合板动态杨氏模量的检测与分析

基于LabVIEW软件采用共振法和敲击法测定杨木胶合板的动态杨氏模量,并与其静态力学性能对比。结果表明:敲击法和共振法得到的动态杨氏模量值较为接近;共振法得到的动态杨氏模量与胶合板的静曲强度、弹性模量呈显著线性回归;杨木胶合板的动态杨氏模量与取样方向有关,沿表板纹理纵向测定值大于横向测定值,且纵向动态杨氏模量与密度呈显著线性相关。     

Fat deposition, fatty acid composition and meat quality: A review

This paper reviews the factors affecting the fatty acid composition of adipose tissue and muscle in pigs, sheep and cattle and shows that a major factor is the total amount of fat. The effects of fatty acid composition on meat quality are also reviewed. Pigs have high levels of polyunsaturated fatty acids (PUFA), including the long chain (C20-22) PUFA in adipose tissue and muscle. The full range of PUFA are also found in sheep adipose tissue and muscle whereas cattle ‘conserve’ long chain PUFA in muscle phospholipid. Linoleic acid (18:2n − 6) is a major ingredient of feeds for all species. Its incorporation into adipose tissue and muscle in relation to the amount in the diet is greater than for other fatty acids. It is deposited in muscle phospholipid at a high level where it and its long chain products eg aracidonic acid (20:4n − 6) compete well for insertion into phospholipid molecules. Its proportion in pig adipose tissue declines as fat deposition proceeds and is an index of fatness. The same inverse relationships are not seen in ruminant adipose tissue but in all species the proportion of 18:2n − 6 declines in muscle as fat deposition increases. The main reason is that phospholipid, where 18:2n − 6 is located, declines as a proportion of muscle lipid and the proportion of neutral lipid, with its higher content of saturated and monounsaturated fatty acids, increases. Oleic acid (18:1cis − 9), formed from stearic acid (18:0) by the enzyme stearoyl Co-A desaturase, is a major component of neutral lipid and in ruminants the same enzyme forms conjugated linoleic acid (CLA), an important nutrient in human nutrition. Like 18:2n − 6, -linolenic acid (18:3n − 3) is an essential fatty acid and is important to ruminants since it is the major fatty acid in grass. However it does not compete well for insertion into phospholipid compared with 18:2n − 6 and its incorporation into adipose tissue and muscle is less efficient. Greater biohydrogenation of 18:3n − 3 and a long rumen transit time for forage diets also limits the amount available for tissue uptake compared with 18:2n − 6 from concentrate diets. A positive feature of grass feeding is that levels of the nutritionally important long chain n − 3 PUFA are increased ie EPA (20:5n − 3) and DHA (22:6n − 3). Future research should focus on increasing n − 3 PUFA proportions in lean carcasses and the use of biodiverse pastures and conservation processes which retain the benefits of fresh leafy grass offer opportunities to achieve this. The varying fatty acid compositions of adipose tissue and muscle have profound effects on meat quality. Fatty acid composition determines the firmness/oiliness of adipose tissue and the oxidative stability of muscle, which in turn affects flavour and muscle colour. Vitamin E is an essential nutrient, which stabilises PUFA and has a central role in meat quality, particularly in ruminants.     

Increased susceptibility to intramammary infection following removal of teat canal keratin.

Influence of teat canal keratin on susceptibility to intramammary infection was investigated in lactating Jersey cows. In each of two replicate trials, keratin was removed from the left teats of 20 cows immediately before milking. Immediately after milking, all teats were exposed to bacterial challenge by immersion in a suspension of Streptococcus agalactiae (5 x 10(7) cfu/ml). Bacterial challenge was repeated after the next four milkings. Foremilk samples were obtained for 8 d after keratin removal to determine infection status. A mammary quarter was classified as infected based solely upon the bacteriological criteria outlined by the National Mastitis Council. The rate of infection in quarters from which keratin was removed was greater than that in control quarters. Infection rates were 26.3% for keratin-removed quarters and 8.3% for control quarters in trial 1 and 13.5 and 0%, respectively, in trial 2. When more stringent criteria (recovery of greater than 100 cfu of S. agalactiae/ml in three or more successive milk samples and a SCC of greater than 10(6)) were used to identify a subset of infections that were clearly intramammary, infection rates were 9.3% for keratin-removed quarters and 1.4% for control quarters. Thus, partial removal of keratin from the teat canal compromised the ability of the teat to prevent passage of bacterial pathogens from the external environment into the mammary gland.     

Physical and chemical properties of polypyrrole–carbon fiber interphases formed by aqueous electrosynthesis

The properties of carbon fibers modified by aqueous electrochemical synthesis of pyrrole has been determined by using the dynamic contact angle analyzer (DCA), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Electrochemical process parameters such as the initial pyrrole concentration, electrolyte concentration, applied voltage, electrolyte type, and reaction time were systematically varied, and their impact on the polypyrrole–carbon fiber interphases surface free energy and morphology was ascertained. The surface free energies of the polypyrrole–carbon fiber interphases were obtained by using single fiber filaments. SEM analysis of the interphases revealed several distinct surface structures, including smooth, porous, granular, microspheroidal, and leafoidal morphologies. The noncoated but commercially surface oxidized carbon fibers have smooth surface morphology with occasional longitudinal striations. FTIR analysis of the polypyrrole interphases confirmed that the counterions derived from the electrolytes were incorporated into the film. The surface free energies of the electrochemically formed polypyrrole–carbon fiber interphases equivalent to 60–75 dynes/cm, was determined to be up to 40% higher than that for the surface oxidized but unsized carbon fibers equivalent to 50 dynes/cm. This improvement in the surface free energies of the polypyrrole–carbon fiber interphases suggests easy wettability by polymer matrices such as epoxy resin, γ ˜ 47 dynes/cm and, polyimide matrix, γ ˜ 45 dynes/cm. © 1996 John Wiley & Sons, Inc.     

Global synchronisation in Linda

The paper examines the ‘Distributed Summation’ problem, and its solution in Linda. A number of problems with the current set of primitives are examined, and a new primitive, collect, is proposed.     

U.S. Food safety and Inspection Service testing for Salmonella in selected raw meat and poultry products in the United States, 1998 through 2003: an establishment-level analysis

The U.S. Food Safety and Inspection Service (FSIS) pathogen reduction-hazard analysis critical control point systems final rule, published in 1996, established Salmonella performance standards for broiler chicken, cow and bull, market hog, and steer and heifer carcasses and for ground beef, chicken, and turkey meat. In 1998, the FSIS began testing to verify that establishments are meeting performance standards. Samples are collected in sets in which the number of samples is defined but varies according to product class. A sample set fails when the number of positive Salmonella samples exceeds the maximum number of positive samples allowed under the performance standard. Salmonella sample sets collected at 1,584 establishments from 1998 through 2003 were examined to identify factors associated with failure of one or more sets. Overall, 1,282 (80.9%) of establishments never had failed sets. In establishments that did experience set failure(s), generally the failed sets were collected early in the establishment testing history, with the exception of broiler establishments where failure(s) occurred both early and late in the course of testing. Small establishments were more likely to have experienced a set failure than were large or very small establishments, and broiler establishments were more likely to have failed than were ground beef, market hog, or steer-heifer establishments. Agency response to failed Salmonella sample sets in the form of in-depth verification reviews and related establishment-initiated corrective actions have likely contributed to declines in the number of establishments that failed sets. A focus on food safety measures in small establishments and broiler processing establishments should further reduce the number of sample sets that fail to meet the Salmonella performance standard.     

Extraction of phenolic compounds from fresh leaves: A comparison of methods

The conventional sonicator/shaker bath method for phenolic extraction was compared with a less traditional one using a homogenizer. The homogenizer proved to be both more efficient and consistent in extracting phenolics from tender, as well as tough, leaves. We propose that adoption of the homogenizer technique will increase phenolic yield and efficiency.     

Glyceryl ethers in insects: identification of alkyl and alk-1-enyl glyceryl ether phospholipids

Alkyl and alk-1-enyl glyceryl ethers have been identified in the phospholipids of three insect species, the American cockroach (Periplaneta americana), the tobacco budworm (Heliothis virescens), and the boll weevil (Anthonomus grandis). Glyceryl ethers were not detected in the neutral lipids. The ethers were found in the phospholipid fraction of whole insects and in isolated fat body tissue. The ether content varied among the three insect species, and fluctuated during various developmental stages. Gas liquid chromatographic analysis of the alkyl glyceryl ethers and aldehydes derived from the alk-1-enyl glyceryl ethers of the cockroach and budworm whowed striking differences in chain length. However, the hydrocarbon side-chain of the two ether fractions were similar in length for each species. Preliminary evidence indicates that 1-¹⁴C-acetate can be incorporated into alkyl ethers but not into alk-1-enyl ethers ofHeliothis pupae. Presented at the AOCS-AACC joint meeting, Washington, D.C., 1968. Under contract with the U.S. Atomic Energy Commission.