Heat Treatments Control Extension Growth and Enhance Microbial Disinfection of Minimally Processed Green Onions

Abstract

<jats:p>Extension growth of minimally processed (removal of roots and compressed stem) green onions (<jats:italic>Allium cepa</jats:italic> L. × <jats:italic>A. fistulosum</jats:italic> L.) was greatly reduced by storage in air at 0 °C, while growth of 10-20 mm occurred at 5 °C over 10 days. Heat treatments of 52.5 and 55 -°C water for 4 and 2 min, respectively, were especially effective in reducing growth to less than 5 mm during 12-14 days at 5 °C. Growth was inhibited irrespective of whether the heat treatments were applied before or after cutting. Heat treatments resulted in higher average respiration rates during 12 days at 5 °C, but did not affect the overall visual quality or shelf life. Treatments with 52.5 °C water alone or in combination with different chlorine concentrations (50 to 400 mg·L<jats:sup>-1</jats:sup> NaOCl, pH 7.0) were more effective than use of water or chlorine solutions at 20 °C for initial microbial disinfection.</jats:p>

Low‐Dose Irradiation Improves Microbial Quality and Shelf Life of Fresh Mint (Mentha piperita L.) without Compromising Visual Quality

“…Color values ( a *, b *, and L *) were significantly different on day 9 and 12, though the increase was small (Figure 5). The results showed that discoloration of fresh‐cut green onions resulted in decreased a * and increased b * and chroma color values; but the changes in L * and hue values were not consistent (Cantwell and others 2001). Although the results showed that treated samples were statistically significantly different from controls, the hue angle (°) of all mint samples remained at about 179° regardless of irradiation doses (Table 5).…”

“…Negative a * indicates green and higher positive b * indicates more yellow color. The chroma ( C ) value indicates color intensity or saturation, calculated as C = ( a * 2 + b * 2 ) 1/2 (Cantwell and others 2001). Hue angle was calculated as H°= 180°+ tan −1 ( b */ a *) when a * < 0 and H°= tan −1 ( b */ a *) when a *> 0 and b *≤ 0 (Fukumoto and others 2002).…”

“…Conventional processing procedures such as washing, chemical sanitization, and thermal treatment have limited efficacy against pathogenic bacteria and viruses on food products and fresh produce (Beauchat and Ryu 1997; Prakash and others 2000; Cantwell and others 2001; Foley and others 2004; Dawson and others 2005; Niemira 2007, 2008; Casteel and others 2008). Johnston and others (2005) found that the use of chlorine in wash water did not reduce the microbial load of fresh produce collected from the southern United States; their research showed that total coliform levels on cilantro and parsley increased during the packing process.…”

Effect of Hot Water Treatments on Quality of Highbush Blueberries

“…Many fruits and vegetables tolerate water temperatures of 50 to 60 °C for up to 10 min, but shorter exposure at these temperatures may also control many postharvest plant pathogens (Barkai‐Golan and Phillips 1991). Immersion of fresh fruits and vegetables in hot water has been used to reduce physiological disorders, control surface microorganisms and decay, eradicate insects, or maintain quality in a variety of fresh commodities such as fresh‐cut green onions (Cantwell and others 2001; Kim and others 2005), strawberries (Wszelaki and Mitcham 2003; Karabulut and others 2004), avocados (Woolf and Laing 1996), broccoli (Forney 1995), mango (Sharp and others 1989), and sweet pepper (Fallik and others 1999). Up to now, there was limited knowledge of the effects of applying hot water treatments on decay control, microbial quality, and volatile biosynthesis of blueberries ( Vaccinium corymbosum L.).…”

Application of pulsed light (PL)-surfactant combination on inactivation of Salmonella and apparent quality of green onions

“…Yellowing of the stems (Kasim, 2009) and/or loss of green pigmentation of the leaves (Cantwell, Suslow, & Hong, 2001) after treatment or during shelf-life are considered color defects of green onions. Thus, the b values (yellowness) of green onion stems and a values (greenness) of leaf have been investigated in our study.…”