The first half of this chapter conc

The first half of this chapter concluded with an account (loi ich) of the taste of meat and it seems reasonable to emphasise the dependence of flavour on both taste and odour by immediately returning to the same foods. There are three major groups of compounds that contribute to the flavour of meat and one of these, the umami substances and dipeptides, was covered in the previous section.
The other two groups are:
1 Heterocyclic compounds derived from amino acids, nucleotides, sugars and thiamine via the Maillard reaction (see Chapter 2) during cooking.
2 Unsaturated fatty acid breakdown products (see Chapter 4) formed during cooking.
The Maillard reaction can yield a great diversity of carbonyl compounds from the residual sugars (from glycogen and nucleotides) in meat, including 2-oxopropanal (2.36), 2,3-butanedione (2.43), hydroxypropan-2- one (2.44), hydroxymethylfurfural (Figure 2.9). The Strecker degradation (Figure 2.12) of these with most amino acids yields the corresponding aldehydes but, as shown in Figure 7.8, cysteine gives rise to both hydrogen sulfide, and ammonia, which can contribute to the formation of a variety of heterocyclic compounds. Thiazoles and oxazoles are considered important in roasted meat flavour. Reactions of hydrogen sulfide with aldehydes can lead to ring compounds with multiple sulfur atoms that are thought to be particularly important in the flavour of boiled (as oppose to roasted) meat. Several other sulfur compounds that contribute to cooked

Figure 7.8 The formation of heterocyclic meat flavour compounds following the Strecker degradation o f cysteine. For simplicily the complex sequence of condensation reactions postulated to lead to the ring compounds has not been shown. R represents any of the terminal fragments of sugar molecules that can arise in the Maillard reaction. It is likely that aldehydes and dicarbonyls from the degradation of other amino acids will join in the sequence and provide even greater diversity of end products. The boxed reactions show the formation, from acetaldehyde and hydrogen sulfide, o f the cyclic sulJides that have been identified in boiled rneatJavouE
meat flavour have been traced back to the thermal decomposition of the vitamin thiamin. Thermal decomposition of ribonucleotides (e.g. IMP, 7.39) has been shown to lead to compounds, such as methylfuranolone (7.45), that not only have a pronounced meaty odour themselves but can also be precursors of sulfur-containing compounds (the sulfur is derived from the breakdown of cysteine and methionine), such as methylthiophenone (7.46), that also have a strong meaty odour.

Fatty-acid breakdown, along the lines of the autoxidation reactions described in Chapter 4, is also an important source of the characteristic odours of meat products. The low content of polyunsaturated fatty acids in the depot fat and intra-muscular fat of beef, lamb and pork points to the polar membrane lipids of muscle cells as the most likely source of flavour significant autoxidation products. The arachidonic acid has been shown to break down on heating to give four aldehydes which together have a distinctive cooked-chicken odour:

Aldehyde fatty acid fragments such as these can react with hydrogen sulfide or ammonia to provide yet another source of odorous heterocyclic compounds, as illustrated here (7.47).

This is an appropriate point at which to mention boar taint. Male animals tend to be more lean than females and in theory this should make them preferred for meat production. Unfortunately this presents a difficulty for pig rearers. The uncastrated male pig, as it reaches about 200 lb (90 kg) live weight,” accumulates 5-androst- 16-ene-3-one (7.48) in its body fat. This by-product of normal steroid metabolism is the causative substance of boar taint. Being volatile, this steroid is driven off when the meat is cooked, and its odour may give offence - not everyone can smell it! Over 90% of women but only about 55% of men can detect it at typical cooking concentrations, and of those that can smell it far more women than men find it unpleasant. One can only speculate as to the implications for human behaviour or physiology of this evidence of gender differences between olfactory organs. The odour is described as having much in common with both urine and sweat, and it is therefore hardly surprising that the meat industry would like to find a method of dissuading boars from synthesising it.

Kết quả (Anh) 1:

The first half of this chapter concluded with an account (loi ich) of the taste of meat and it seems reasonable to emphasise the dependence of flavour on both taste and odour by immediately returning to the same foods. There are three major groups of compounds that contribute to the flavour of meat and one of these, the work umami and dipeptides, was covered in the previous section.The other two groups are:1 Heterocyclic compounds derived from amino acids, nucleotides, sugars and thiamine via the Maillard reaction (see Chapter 2) during cooking. 2 Unsaturated fatty acid breakdown products (see Chapter 4) well-formed during cooking.The Maillard reaction can yield a great diversity of carbonyl compounds from the residual sugars (from glycogen and nucleotides) in meat, including 2-oxopropanal (2.36), 2,3-butanedione (2.43), 2-hydroxypropan-one (2.44), hydroxymethylfurfural (Figure 2.9). The Strecker degradation (Figure 2.12) with most of these amino acids yields the corresponding aldehydes but, as shown in Figure 7.8, cysteine gives rise to both hydrogen sulfide and ammonia, which can contribute to the formation of a variety of heterocyclic compounds. Thiazoles and oxazoles are considered important in roasted meat flavour. Reactions of aldehydes with hydrogen sulfide can lead to ring compounds with multiple sulfur atoms that are thought to be particularly important in the flavour of boiled (as oppose to roasted) meat. Several other sulfur compounds that contribute to cooked Figure 7.8 The formation of heterocyclic meat flavour compounds following the Strecker degradation o f cysteine. For simplicily the complex sequence of condensation reactions postulated to lead to the ring compounds has not been shown. R represents any of the terminal fragments of sugar molecules that can arise in the Maillard reaction. It is likely that aldehydes and dicarbonyls from the degradation of other amino acids will join in the sequence and provide even greater diversity of end products. The boxed reactions show the formation, from acetaldehyde and hydrogen sulfide, o f the cyclic sulJides that have been identified in boiled rneatJavouE meat flavour have been traced back to the thermal decomposition of the vitamin thiamin. Thermal decomposition of ribonucleotides (e.g. IMP, 7.39) has been shown to lead to compounds, such as methylfuranolone (7.45), that not only have a pronounced meaty odour themselves but can also be precursors of sulfur-containing compounds (the sulfur is derived from the breakdown of cysteine and methionine), such as methylthiophenone (7.46), that also have a strong meaty odour. Fatty-acid breakdown, along the lines of the autoxidation reactions described in Chapter 4, is also an important source of the characteristic odours of meat products. The low content of polyunsaturated fatty acids in the fat depot and intra-muscular fat of beef, lamb and pork points to the polar membrane lipids of muscle cells as the most likely source of flavour significant autoxidation products. The arachidonic acid has been shown to break down on heating to give four aldehydes which together have a distinctive odour-chicken cooked: Fatty acid aldehyde fragments such as these can react with hydrogen sulfide or ammonia to provide yet another source of odorous heterocyclic compounds, as illustrated here (7.47). This is an appropriate point at which to mention boar taint. Male animals tend to be more lean than females and in theory this should make them preferred for meat production. Unfortunately this presents a difficulty for pig rearers. The uncastrated male pig, as it reaches about 200 lb (90 kg) live weight, "accumulates 5-androst-16-ene-3-one (7.48) in its body fat. This by-product of normal steroid metabolism is the causative substance of boar taint. Being volatile, this steroid is driven off when the meat is cooked, and its odour may give Monster offence-not everyone can smell it! Over 90% of women but only about 55% of men can detect it at typical cooking concentrations, and of those that can smell it far more women than men find it unpleasant. One can only speculate as to the implications for human behaviour or physiology of this evidence of gender differences between olfactory organs. The odour is described as having much in common with both urine and sweat, and it is therefore hardly surprising that the meat industry would like to find a method of dissuading boars from synthesising it.

Kết quả (Anh) 2:

The first half of this chapter concluded with an account (benefit) of the taste of meat and it Seems reasonable to emphasise the dependence of taste and flavor on cả Odour ngay by returning to the same foods. There are three major groups of compounds That Contribute to the flavor of meat and one of những, the umami substances and dipeptides, was covered in the previous section.
The other two groups are:
1 heterocyclic compounds derived from amino acids, nucleotides, sugars and thiamine via the Maillard reaction (see Chapter 2) the during cooking.
2 Unsaturated fatty acid breakdown products (see Chapter 4) formed the during cooking.
The Maillard reaction can yield a great diversity of carbonyl compounds from the residual sugars (from glycogen and nucleotides) in meat, Including 2-oxopropanal (2:36), 2,3-butanedione (2:43), hydroxypropan-2- one (2:44), hydroxymethylfurfural (Figure 2.9). The Strecker degradation (Figure 2:12) Most of These amino acids with aldehydes yields tương ứng but, as shown in Figure 7.8, cysteine ​​cả Gives rise to hydrogen sulfide, and ammonia, mà can Contribute to the formation of a variety of heterocyclic compounds. Thiazoles and oxazoles are Considered Important in roasted meat flavor. Reactions of aldehydes with hydrogen sulfide can lead to multiple ring compounds with sulfur atoms được Particularly Important Thought to be in the flavor of boiled (as oppose to roasted) meat. Vài other sulfur compounds That Contribute to cooked Figure 7.8 The formation of heterocyclic compounds meat flavor the Strecker degradation of cysteine ​​sau. For simplicily the complex sequence of condensation Reactions postulated to lead to the ring compounds được hasnt shown. R là any of the terminal fragments of sugar molecules That Arise in the Maillard reaction can. It Is Likely That aldehydes and dicarbonyls from the degradation of other amino acids in the sequence and join sẽ cung chẵn greater diversity of end products. The boxed Reactions show the formation, from acetaldehyde and hydrogen sulfide, of the cyclic sulJides mà Identified in boiled rneatJavouE past tense past tense meat flavor traced back to the thermal decomposition of the vitamin thiamine. Thermal decomposition of ribonucleotides (eg IMP, 7:39) Đã shown to lead to compounds, như methylfuranolone (7:45), That not only have a pronounced meaty Odour Themselves but am also can be precursors of sulfur-containing compounds (sulfur is derived from the the breakdown of cysteine ​​and methionine), như methylthiophenone (7.46), mà am also have a strong meaty Odour. Fatty-acid breakdown, along the lines of the autoxidation Reactions tả in Chapter 4, is am also an Important source of the characteristic odours of meat products. The low content of polyunsaturated fatty acids in the depot fat and intra-muscular fat of beef, lamb and pork points to the polar membrane lipids of muscle cells as the Most Likely source of the significant flavor autoxidation products. The arachidonic acid to break down Đã shown on heating to give aldehydes mà four together have a cooked-chicken Distinctive Odour: Aldehyde fatty acid fragments can như những React with hydrogen sulfide or ammonia to cung yet another source of odorous heterocyclic compounds, as Illustrated here (7:47). This is an mà at the appropriate point to mention boar taint. Male animals Tend to be more lean coal females and in theory make this shouldnt add preferred for meat production. Unfortunately this presents a difficulty for pig rearers. The uncastrated male pig, as it Reaches about 200 lb (90 kg) live weight, "androst- accumulates 5-ene-3-16-one (7:48) in the its body fat. This by-product of normal metabolism of steroids is the causative substance of boar taint. Being volatile, this steroid is driven off the meat is cooked khi, và Odour give offence unfortunately - not everyone can smell it! Over 90% of women but only about 55% of men can detect it at concentrations typical cooking, and of Those That can smell it far more women find it unpleasant charcoal yeast. One can only speculate as to the implications for human behavior or Physiology of this Evidence of gender Differences Between olfactory Organs. The Odour is tả as having much in common with urine and sweat cả, and it is therefore hardly surprising rằng meat industry would like to find a method of synthesising dissuading it from boars.