Raw material selection -fruits and vegetables 23 many varieties have quite similar flavour. A consumer would be unlikely to be able to tell the difference between many varieties of, say, iceberg lettuce On the other hand, flavour has been a particular issue with Brussels sprouts Varieties differ in flavour, particularly in levels of bitterness and excess bitterness has caused some varieties to be unacceptable. The flavour and aroma characteristics of varieties are governed by their chemical constituents. Breeders may be able to manipulate these, in order to improve varietal quality. The chemicals responsible for bitterness in Brussels sprouts have been identified as the glucosinolates, sinigrin and progoitrin. In the 1970s and 80s deep green coloured varieties appeared on the market, which had been selected for resistance to insect pests. However, taste panel assessments showed these varieties to be bitter and chemical analysis confirmed that they were high in glucosinolates Some varieties, such as Topline, Rasalon and Lunet had consistently good quality over several years. Van Doorn et al. conducted consumer studies with a ange of different Brussels sprout varieties and suggested that at a level of glucosinolates(sinigrin plus progoitrin) of above 2.2g per kg negative consumer reaction was registered. Breeders can now select for lower levels of these chemicals either by analysis or by tasting Flavour can vary even within the portion of the crop that is consumed. Both leeks and celery have white tissue at the base of their stems and greener tissue and leaves higher up. There are differences in flavour between white and green portions. EU regulations' dictate the proportions of white and green in celery for sale and varieties vary in their ability to satisfy this requirement The texture of a product also contributes to eating quality. This is often related to maturity, with an over-mature product becoming tough. However, there may be variety differences. Potatoes have obvious texture differences being either waxy or floury. Waxy varieties are firm and will retain their shape after cooking. They are preferred for salad use or for products such as potato scallops. Floury varieties, which soften on cooking, are used for mashed Chilled food manufacturers use large volumes of sliced and diced onions to add flavour to their products. Onion varieties differ in pungency. In the UK the majority of main crop onions are of the rijnsburger type which are relatively high in pungency. Some of the varieties grown in Spain are less pungent and hence"Spanish'onions are used if the onion is to be eaten raw. The American Vidalia type is noted for its sweetness Sweetness is an important flavour attribute of most crops but sugar levels can also be important for other reasons. Amounts of reducing sugars in potatoes influence colour after frying and there is a strong variety-related component to this effect. Maris Piper is a preferred variety for the chipping trade because it is lower in reducing sugars. Flavour ariations in tomatoes are related to differences in the amounts of sugars and acids in the fruit. If both are at low levels the flavour will be bland. Commercial varieties with high levels of both acid and sugar are preferred
many varieties have quite similar flavour. A consumer would be unlikely to be able to tell the difference between many varieties of, say, iceberg lettuce. On the other hand, flavour has been a particular issue with Brussels sprouts. Varieties differ in flavour, particularly in levels of bitterness and excess bitterness has caused some varieties to be unacceptable. The flavour and aroma characteristics of varieties are governed by their chemical constituents. Breeders may be able to manipulate these, in order to improve varietal quality. The chemicals responsible for bitterness in Brussels sprouts have been identified as the glucosinolates, sinigrin and progoitrin.3 In the 1970s and 80s deep green coloured varieties appeared on the market, which had been selected for resistance to insect pests. However, taste panel assessments showed these varieties to be bitter and chemical analysis confirmed that they were high in glucosinolates. Some varieties, such as Topline, Rasalon and Lunet had consistently good quality over several years.4 Van Doorn et al.5 conducted consumer studies with a range of different Brussels sprout varieties and suggested that at a level of glucosinolates (sinigrin plus progoitrin) of above 2.2g per kg negative consumer reaction was registered. Breeders can now select for lower levels of these chemicals either by analysis or by tasting. Flavour can vary even within the portion of the crop that is consumed. Both leeks and celery have white tissue at the base of their stems and greener tissue and leaves higher up. There are differences in flavour between white and green portions.6 EU regulations7 dictate the proportions of white and green in celery for sale and varieties vary in their ability to satisfy this requirement. The texture of a product also contributes to eating quality. This is often related to maturity, with an over-mature product becoming tough. However, there may be variety differences. Potatoes have obvious texture differences being either waxy or floury. Waxy varieties are firm and will retain their shape after cooking. They are preferred for salad use or for products such as potato scallops. Floury varieties, which soften on cooking, are used for mashed potatoes. Chilled food manufacturers use large volumes of sliced and diced onions to add flavour to their products. Onion varieties differ in pungency. In the UK the majority of main crop onions are of the Rijnsburger type which are relatively high in pungency.8 Some of the varieties grown in Spain are less pungent and hence ‘Spanish’ onions are used if the onion is to be eaten raw. The American Vidalia type is noted for its sweetness. Sweetness is an important flavour attribute of most crops but sugar levels can also be important for other reasons. Amounts of reducing sugars in potatoes influence colour after frying and there is a strong variety-related component to this effect.9 Maris Piper is a preferred variety for the chipping trade because it is lower in reducing sugars. Flavour variations in tomatoes are related to differences in the amounts of sugars and acids in the fruit. If both are at low levels, the flavour will be bland. Commercial varieties with high levels of both acid and sugar are preferred. Raw material selection – fruits and vegetables 23
24 Chilled foods Recently there has been interest in the health-promoting effects of some of the mponent substances found in fruit and vegetables. Varieties may differ in amounts of these so called bioactive substances. Schonhof et al. working on calabrese determined concentrations of carotenoids, chlorophylls and glucosino- lates in three different varieties. They reported that although there were seasonal influences on the concentrations of these, the genetic differences were constant 1. 2. 2 Crop maturity Another major consideration in raw material production and selection is arvesting of crops at the optimal stage of maturity. Visual indications often reflect the stage of development of the plant and aid the grower in timely harvesting. When bulb onions are mature the leaves begin to wilt and bend over Growers refer to the 'fall-over' date. assessment criteria are different for vegetables and fruits and assessment of the correct stage depends on the part of the plant that is consumed eafy crops are harvested according to size and firmness. Most types of cabbage and lettuce are allowed to produce a heart and the heads should be firm and of the size required by the particular outlet. Cabbage greens are harvested before the hearts have had time to form Lettuce and spinach for leafy salads are harvested only a few weeks after drilling, when leaf size is very small. In crops such as cauliflower and calabrese, where the flowering heads are consumed assessment is also by eye and development is monitored until firm heads have formed. Once this stage is passed the heads will open out as flower development proceeds. In over-mature calabrese, the yellow flower petals may be seen Harvest time is less critical with root crops such as carrots, swedes, turnips,or parsnips. They may be harvested when they reach the size required by a particular outlet but are often stored in the field for several months. Carrots may be considered to have reached maturity when there is no white coloration at the tip of the root but will continue to grow after this. Bunching carrots may be harvested immature, with some white roots. Other types are harvested at a later stage when roots have achieved a sufficient size to meet specific market equirements. Similarly early potatoes are harvested immature, but other maincrop'orware' potatoes are harvested after the leaves have died down, this being a sign that the crop has completed bulking up In some crops the immature pods or immature seeds are consumed(e.g. runner beans, dwarf French beans, peas, sweetcorn). As the seeds develop and swell they accumulate carbohydrates, first of all in the form of sugars and these are then converted to starch as the seed dries out. At the same time the pods are drying out and the texture becomes tough or mealy. Maturity assessment particularly critical for these crops as they rapidly become tough if left in the field after optimum maturity In beans the seed development is monitored and aturity is related to pod and bean size for specific varieties Fruits are divided into two ripening types. Climacteric fruits such as 'pe fruits(apples and pears)apricots, peaches, plums and kiwifruit continue to
Recently there has been interest in the health-promoting effects of some of the component substances found in fruit and vegetables. Varieties may differ in amounts of these so called bioactive substances. Schonhof et al.10 working on calabrese determined concentrations of carotenoids, chlorophylls and glucosinolates in three different varieties. They reported that although there were seasonal influences on the concentrations of these, the genetic differences were constant. 1.2.2 Crop maturity Another major consideration in raw material production and selection is harvesting of crops at the optimal stage of maturity. Visual indications often reflect the stage of development of the plant and aid the grower in timely harvesting. When bulb onions are mature the leaves begin to wilt and bend over. Growers refer to the ‘fall-over’ date. Assessment criteria are different for vegetables and fruits and assessment of the correct stage depends on the part of the plant that is consumed. Leafy crops are harvested according to size and firmness. Most types of cabbage and lettuce are allowed to produce a heart and the heads should be firm and of the size required by the particular outlet. Cabbage greens are harvested before the hearts have had time to form. Lettuce and spinach for leafy salads are harvested only a few weeks after drilling, when leaf size is very small. In crops such as cauliflower and calabrese, where the flowering heads are consumed, assessment is also by eye and development is monitored until firm heads have formed. Once this stage is passed the heads will open out as flower development proceeds. In over-mature calabrese, the yellow flower petals may be seen. Harvest time is less critical with root crops such as carrots, swedes, turnips, or parsnips. They may be harvested when they reach the size required by a particular outlet but are often stored in the field for several months. Carrots may be considered to have reached maturity when there is no white coloration at the tip of the root but will continue to grow after this. Bunching carrots may be harvested immature, with some white roots. Other types are harvested at a later stage when roots have achieved a sufficient size to meet specific market requirements. Similarly early potatoes are harvested immature, but other ‘maincrop’ or ‘ware’ potatoes are harvested after the leaves have died down, this being a sign that the crop has completed bulking up. In some crops the immature pods or immature seeds are consumed (e.g. runner beans, dwarf French beans, peas, sweetcorn). As the seeds develop and swell they accumulate carbohydrates, first of all in the form of sugars and these are then converted to starch as the seed dries out. At the same time the pods are drying out and the texture becomes tough or mealy. Maturity assessment is particularly critical for these crops as they rapidly become tough if left in the field after optimum maturity. In beans the seed development is monitored and maturity is related to pod and bean size for specific varieties. Fruits are divided into two ripening types. Climacteric fruits such as ‘pome’ fruits (apples and pears) apricots, peaches, plums and kiwifruit continue to ripen 24 Chilled foods