Abstract
We developed a novel rapid hygrothermal pasteurization (RHP) method using saturated water vapor with a dew point of 100℃. The aim of this paper is to compare the effect of RHP treatment versus conventional sodium hypochlorite (NaClO) treatments on inactivation of natural mesophilic bacteria and quality attributes on fruits and vegetables. The RHP treatment was performed within a second by free-falling samples (cabbage, cucumber, carrot, bell pepper, pineapple and melon) through cylindrical processing chamber filled with steam. NaClO treatment was performed by washing samples with NaClO solution (100 mg/mL of free chlorine (pH 7), for 1 min). The RHP treatment showed a significantly higher inactivation effect than NaClO treatment on all tested samples. The RHP treatment had a slightly larger influence on color and vitamin C content than NaClO treatment in cabbage. Furthermore, the effects of treatment time and operated temperature were also determined using microbial model system. Elongation of treatment time did not significantly increase the microbial inactivation effect. Lowering of operated temperature by mixing air into steam tended to decrease the inactivation effect. From these results, RHP treatment could be used as an alternative method for decontaminating microorganisms on fruits and vegetables, except on leafy vegetable. In addition, it is suggested that microbial inactivation by RHP treatment was achieved through the initial condensation stage of water vapor on sample surface. By contrast, interfusion of air disturbed the effective condensation of water vapor.
Highlights
In recent years, consumption of fresh-cut fruits and vegetables has continuously increased
We have reported that the rapid hygrothermal pasteurization (RHP) treatment can reduce microorganisms on the surface of fresh fruits and vegetables surfaces with retaining a nutritional component and preserving quality attributes [6]
The novel method, RHP treatment without using chemicals, indicated a similar or higher level of microorganism inactivation effect on many kinds of fresh-cut produces when compared with conventional method, NaClO treatment
Summary
Consumption of fresh-cut fruits and vegetables has continuously increased. Fruits and vegetables are contaminated by microorganisms on their surfaces from many sources, such as soil, water, wild animals, birds, and insects during the growing stage. A large area of cut surfaces can provide ideal conditions for growth of microorganisms, including foodborne pathogens and spoilage microorganisms [1]. Microorganisms impact the economic value of fresh-cut products by decreasing product shelf-life, through spoilage, and by posing a risk to public health by causing foodborne disease [2]. Chlorine solution prepared from sodium hypochlorite (NaClO, 50 - 200 mg/L) is the most used sanitizing agent for washing fresh produce, because it is cheap, applied, chemically stable, readily available, and has been authorized for use with food by FDA and Japanese Ministry of health, Labor and Welfare [3,4,5]. It is known that sodium hypochlorite induces formation of harmful carcinogenic chlorinated by-products such as chloramines and trihalomethanes
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