摘要:

Despite differences in the structures of aldoses and ascorbic acid, ASA, the non‐enzymic browning of the latter involves intermediates similar to those found in Maillard browning. The kinetics of the sulphite‐inhibited browning of ASA suggest that, under anaerobic conditions, the rate of reaction of sulphite species, S(IV), is of first order with respect to S(IV). The possibility that S(IV) could catalyse the hydrolysis of the lactone ring of ASA is considered by reference to D‐glucono‐δ‐lactone. Evidence is presented to suggest that, under aerobic conditions, autoxidation of ASA leads to the oxidation of S(IV). The composition of melanoidins from ASA—glycine mixtures is compared with that from arabinose—glycine; the former contain 2.5 times more ASA‐derived residues per glycine molecule than arabinose‐derived residues per glycine molecule in the latter. The implications of these findings to the mechanism of ASA browning are discussed.

ISSN:0265-203X    

DOI:10.1080/02652039209374099

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Sulphite species, S(IV), inhibit the non‐enzymic browning of fructose—amino acid mixtures. Inhibition of browning is accompanied by a loss of S(IV). The kinetics of the reaction of S(IV) in the system: fructose—glycine‐S(IV) are described in detail; two distinct mechanisms have been identified. One involves only fructose in the rate determining step. The other requires fructose and both the glycine and S(IV). Some amines (e.g. taurine and ethanolamine) can markedly increase the rate of the S(IV)‐independent step. Arginine and lysine are particularly effective for increasing the rate of reaction of S(IV) in the S(IV)‐dependent reaction.

ISSN:0265-203X    

DOI:10.1080/02652039209374100

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Under aerobic conditions, the reaction of sorbic acid with sulphite species, S(IV), involves a pH‐dependent oxidative mechanism with the loss of S(IV). Sorbic acid is essential to the process. In the absence of air, a much slower nucleophilic addition of sulphite ion to undissociated sorbic acid takes place.

ISSN:0265-203X    

DOI:10.1080/02652039209374101

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The general characteristics of the reaction between sorbic acid and thiols are reviewed. Cysteine adds to the conjugated diene in position 5 to form the substituted 3‐hexenoic acid. This is labile in acid solution, yielding a quantitative amount of sorbic acid. When wheat flour doughs are treated with sorbic acid and heated, a significant amount of the sorbic acid is not recovered on extraction with methanol. The use of acidified methanol leads to a quantitative recovery of the preservative and evidence is presented to suggest that sorbic acid—thiol adducts are formed. This is the first report of ‘reversibly bound’ sorbic acid in a food.

ISSN:0265-203X    

DOI:10.1080/02652039209374102

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

N‐Acetyl‐l‐cysteine and reduced glutathione were excellent inhibitors of browning of potatoes. In most cases, these two SH‐containing compounds were more efficient inhibitors than l‐cysteine and approached the effectiveness of sodium sulphite. These considerations suggest thatN‐acetyl‐l‐cysteine and reduced glutathione merit extensive evaluation as potentially useful inhibitors for food products.

ISSN:0265-203X    

DOI:10.1080/02652039209374103

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Rapid methods of analysis for the simultaneous determination of acids and sugars in fruits and vegetables using trimethylsilylation and gas chromatography are reported. The methods have been shown to be generally applicable, rapid, simple and cheap. Typical applications are shown involving the determination of a range of organic acids and sugars in carrot, potato, cucumber, tomato, apple, pear, grape, strawberry and citrus fruits.

ISSN:0265-203X    

DOI:10.1080/02652039209374104

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Despite the benefits attributed to food preservatives, some concern still remains regarding their safety and possible influence on nutrients. Surprisingly, there is quite a lack of scientific knowledge in this field. In order to describe a few examples, the effects of the extensively used sulphite on thiamine, folates, pyridoxal and other nutrients have been reported. Among its antibrowning effects, inhibition of ascorbic acid browning is also considered. As far as sorbic acid is concerned, notwithstanding its easy reaction with protein, probably the acid environment of the stomach determines the breakdown of the sorbic—protein adducts. Detoxication of nitrite by tocopherol and ascorbic acid leads, in the last case, to dehydroascorbic acid and its oxidative products with loss of vitamin activity. Any oxidizing substance destroys ascorbic acid, vitamin E and free vitamin A. Phosphates are largely used with different aims, including preservation, in food processing. Their antimicrobial activity is due to both a direct effect and an interaction with other antimicrobials. Sequestering capacity of phosphates and its nutritional implications are discussed. Also mechanisms of action of organic acids are reported, focusing on sorbic acid effects on single amino acids and proteins. Finally, the little information available about the potential impact of food preservatives on nutritional functions is presented.

ISSN:0265-203X    

DOI:10.1080/02652039209374105

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The methods which may be applied to estimating population intakes of food additives are outlined. The applications in studies of the intakes of some preservatives and food colours in Italy are reported. It was concluded that there is a need to investigate comparability between the various methods used. The surveys carried out indicated that, in general, the levels of consumption of the additives studied did not present a health risk.

ISSN:0265-203X    

DOI:10.1080/02652039209374106

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The role of intake studies in the safety assurance process is discussed with reference to food preservatives and related to the variations in the authorizations for use.

ISSN:0265-203X    

DOI:10.1080/02652039209374107

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Estimates have been made of the consumption levels of sulphites in foods in France using two methods, a global and a segmented protocol. The global method gave an estimated average intake of 20 mg SO2/day/capita;the segmented method gave estimates of 1.96 mg/day/capitafor non‐consumers of alcoholic beverages and 31.5 mg/day/capitafor average consumers of cider, beer and wine. The risk of exceeding the Acceptable Daily Intake concerns only regular consumers (40–75 years old) of alcoholic beverages, particularly wine, the main vector. The global approach appears to be a simple and useful method for estimating intakes.

ISSN:0265-203X    

DOI:10.1080/02652039209374108

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor