摘要:

A total of 459 specimens covering 51 species in 9 families was collected from October 1992 to May 1996 in Taiwan. All specimens were assayed for the presence of tetrodotoxin (TTX) and paralytic shellfish poison (PSP). The specimens of five xanthid crabsZosimus aeneus, Lophozozymus pictor, Ategatopsis germaini, Atergatis floridus, andDe‐mania reynaudiwere found to contain potent toxins. Among them,A. germainishowed the highest toxicity. The toxin profile of each toxic crab species was as follows: 82% TTX and 18% PSP in Z.aeneus, 89% TTX and 11% PSP inL.pictor, 3% TTX and 97% PSP inAgermaini, 85% TTX and 15% inA. floridus, and 88% TTX and 12% PSP inD. reynaudi. PSP was mainly composed of gonyautoxins (GTXs) 1–4 in Z.aeneus, L. pictor, andA. floridus, but GTX 3 and hydroxysaxitoxin inA. germaini, and neosaxitoxin inD. reynaudi. The PSP‐producing dinoflagellate planktonAlexandrium minutumand TTX‐producing bacteria includingVibrio alginolyticusandVibrio parahaemolyticuswere isolated and considered as the sources of the toxins.

ISSN:8755-9129    

DOI:10.1080/87559129909541184

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

High voltage (10–50 kV·cm−1) and very short (< 10μs)electric pulses can be used to pasteurize fluid foods at low or moderate temperatures apparently without significant sensorial quality changes. The main components of a pulsed electric field system are the high voltage‐high current switches, and the static or continuous treatment chambers with plate or coaxial parallel electrodes. The respective energy and other characteristics of pulses with constant polarity (exponential decay or square wave) or pulses with reversing polarity are discussed. The few existing industrial or research systems which are commercially available are indicated. The main independent process parameters are: voltage across the capacitors; number of capacitors; in‐terelectrode gap; number and frequency of pulses; food resistivity; food flow rate in the treatment chamber. Variations of these parameters influence the electric field, the width, and the energy of each pulse and the rate of ohmic heating of the food. The usual range of food resistivity is 0.4–100 O·m and depends on temperature and on the heterogeneous/homogeneous structure of the food. The electric field behavior of a food or a biological cell can be modeled by a resistance (conduction of charge carrying molecules) and a capacitor (polarization of dipoles) placed in parallel. Exposed to an intense electric field, foods can undergo dielectric breakdown, in which neutral dielectric constituents or molecules become suddenly conductive. When this phenomenon takes place within a biological membrane, the latter becomes permeable to ions and to current. This may cause cell rupture. Dielectric breakdown may also occur within gases. Air ionization takes place when the electric field exceeds 10 kV·cm−1(moist air) or 30 kV·cm−1(dry air) and usually produces ozone and hydrogen peroxide. These oxidants, together with localized heating arising from electrical arcing, can cause food damage. Electrochemical reactions at the chamber electrodes may also be detrimental, but are minimal with very short duration or alternating field pulses, and with the use of an appropriate electrode material.

ISSN:8755-9129    

DOI:10.1080/87559129909541185

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Investigations on the biological effects of high voltage electric pulses primarily concern membrane permeabilization and microbial inacti‐vation. Electroporation resulting from increased transmembrane potential is probably the main cause for membrane permeabilization. Equations are presented for this phenomenon. Results from several studies on the inactivation of microorganisms by pulsed electric fields are summarized in tables that relate the rate of inactivation to process conditions. The influence of three sets of parameters is discussed: 1) type and physiological state of the microorganism; 2) chemical composition and electrical resistivity of the microorganism‐containing food or medium; 3) process conditions such as field intensity, duration and number of pulses, dissipated energy, final temperature, type of pulse and of treatment chamber. Data can be used to select conditions which produce a 5–6 log cycle inactivation for many yeasts or vegetative bacteria. Bacterial spores generally resist inactivation. Pulsed electric fields of relatively low intensity may be used to permeabilize larger cells from plant or animal tissues in order to facilitate theextraction of specific constituents or to increase the drying rate. Little is known concerning the possible chemical or physico‐chemical modifications of food constituents by high voltage electric pulses. Some enzymes appear to be inactivated, even at low temperatures, while others are more resistant. The sensorial characteristics of a number of foods subjected to electric fields do not appear to be significantly altered. Potential food applications are numerous and mainly related to liquid foods (fruit juices, milk, sauces, liquid egg) or to pumpable food pastes (fruit or vegetable purées, minced meat, etc.). Both neutral and acidic foods are likely candidates. The main objectives of microbial inactivation by electric pulses are food sanitation and/or extension of chilled storage. The process should be nonthermal (maximum ?T of ∼30°C) to preserve food freshness and quality. A low operating cost, estimated at 0.4–0.8 US cents per liter of food (capital investment not included) and continuous operation at high flow rate (>1000 L/h) represent significant industrial advantages for this new technology.

ISSN:8755-9129    

DOI:10.1080/87559129909541186

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In times of low wheat reserves, newly harvested wheat is processed almost immediately after harvest, which presents a series of problems to the millers and bakers. Newly harvested wheat generally has poor milling and baking quality. However, after wheat is aged, the bran is easier to separate from the endosperm, flour extraction increases, and ash content drops. These improvements have been related to posthar‐vest maturation and physical changes in the wheat kernel. On the other side of the milling process, freshly milled flour does not perform as well as flour that has been kept in storage. To address this issue, extra flour storage capacity is needed, or millers and bakers must add chemicals to their flours. Flour components change during aging. Aged soft wheat flour behaves similarly to chlorinated flour. Flour hydration rate and batter viscosity increase, and cakes have greater volumes without collapse. Aged hard wheat flour has higher water absorption, better mixing tolerance, and greater gas retention capability and produces bread with greater loaf volume. This review compiles the published studies related to wheat and flour aging.

ISSN:8755-9129    

DOI:10.1080/87559129909541187

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Lactose maldigestion (i.e., lactase non‐persistence, lactase restriction) is a very common condition worldwide. It is more common in Asian and African populations than in Caucasians, but its prevalence in America and in some European populations is also fairly high. The causes of both primary and secondary lactose maldigestion have been well established since its discovery in the 1960s. Until now, research has focused on lactose maldigestion, but symptoms have received relatively little attention. Because the presence or absence of symptoms and their severity guide the food choices of an individual and his/her need to consult health professionals, knowledge of the symptoms of lactose intolerance should be of concern to the health authorities and to the food industry. Despite the vast amount of research carried out on lactose intolerance, many questions still remain open. In this review, both recent works and early literature on lactose intolerance with regard to milk composition, gastric emptying, and functional bowel disorders are presented.

ISSN:8755-9129    

DOI:10.1080/87559129909541188

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

More than 170 million Americans consume low‐calorie foods and beverages. The interest of the consumer in low‐calorie foods that contain alternative sweeteners has grown. Currently, non‐nutritive high‐intensity sweeteners, aspartame and sucralose have been approved for use in the United States. Another sweetener, alitame, used in other countries such as Australia and China has not been granted approval for use in the States.

ISSN:8755-9129    

DOI:10.1080/87559129909541189

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:8755-9129    

DOI:10.1080/87559129909541190

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:8755-9129    

DOI:10.1080/87559129909541183

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor