Measuring the crispness of fried vegetable products

Cooking in oil is widely used in the production of snack foods of various kinds, and results in drastic changes to the structure of the food.

Penetration of oil is particularly important for structure development in products such as potato chips, tortilla chips and potato crisps. In products which become totally hard and crisp, the oil first coats the surface and begins to move into the chip. As the heat builds up inside, moisture turns to steam and exits the chip, leaving a sponge-like network of tunnels which fill with oil.

This process occurs within the first 20 seconds of frying. Starch granules gelatinise inside the chip, but not at the surface. The interior becomes smooth and plastic as protein, starch and lipids interact to form a continuous phase which hardens upon dehydration.

Tofu texture

In the Far East, tofu is the most popular soybean food whilst in the West, tofu is gaining in popularity.

Tofu is very similar to cheese in appearance, texture, and chemical composition. By controlling the amount of coagulants and pressure applied during moulding, the texture of the tofu may be varied from extra firm, firm, soft, to silken.

Measuring the consistency of vegetable purées

Purées are very thick and viscous slurries made from processed vegetables that are often concentrated and include fibrous material or fruit pieces that adds structure. 

They are commonly used in fillings for pies, ketchup or baby food. Additional ingredients are usually added to manipulate consistency and processing properties.

For the measurement of consistency, a Back Extrusion test can be carried out by fixing a suitable diameter disc to the TA.XTplus texture analyser: the disc moves down into the vessel with good clearance between the vessel and disc so as not to produce erroneous increase force readings due to ‘side effects’.

Testing the overall firmness of a weight or quantity of cooked vegetables

Processed root and tuber products

Thermal treatment is one of the most important processes in the manufacture of storable and ready-to-serve food products of agricultural origin.

During thermal treatment, many desirable and undesirable reactions take place; components such as vitamins and colour components, for example, and also physical properties, such as texture, may be changed.

Cooking just to the point of softness produces vegetables with optimal texture which is where texture analysis plays a major role in determining processing times.

Testing cooked individual vegetable texture

Most vegetables are cooked before consumption, a process that softens their texture (unless there is a lot of lignification) and gelatinises the starch deposited as food for the plant. 

 

Starch and protein deposits are particularly abundant in beans, peas, and corn picked at maturity. A sugar to starch equilibrium reaction occurs during the storage of some vegetables, and this can affect their texture.

Sweetcorn and sweet peas when picked immature have much sugar and a succulent texture. Within hours the texture of sweetcorn can become tougher and drier due to sugar conversion to starch.

Testing fresh individual vegetable texture

As opposed to fruits, which are generally picked when mature but unripe, many vegetables (apart from legume seeds, tubers, bulbs and roots) are picked and consumed when still immature, tender and succulent.

 

This is largely due to the fact that while fruits generally soften on maturation and storage, young vegetables become tougher when they age. This toughening is due to the lignification of the primary cell wall and formation of the secondary cell wall. When cucumbers are stored below 7°C, their texture breaks down due to excessive softening and exudation of liquid as tissue undergoes a structural collapse. Tomatoes are also susceptible to low-temperature injury.

Many of the form, structure and physiological considerations discussed in connection with fruit texture also apply to vegetable texture. The main difference is that, while on maturation the fruit tissue stops growing and suffers enzymatic degradation, the vegetable tissue proceeds to differentiate and cell growth and enlargement continue. The amount of fibrous tissue increases. Toughening may reach the point where the vegetable is no longer suitable for human consumption.

Measuring Vegetable Texture and Vegetable Product Quality

From the point of view of texture, vegetables represent a very diverse group of products. They can be consumed in many different textural forms.

For instance, cooked asparagus is soft, fibrous and pulpy, cucumber is crisp, firm and juicy, raw carrots are hard and crisp, and cooked peas are soft and mealy. The tissue structure in each case determines the texture as received by the consumer.

For many types of vegetables, consumer acceptance of the product is decisively influenced by the vegetable’s texture, along with other qualities such as colour, smell and taste. Texture is a critical quality attribute to all vegetables, whether it is to assess ripeness or functional performance in their processed forms.

Latest Texture Analysis in Research: Vegetables

Is there a best technique to cook vegetables? A study carried out at the University of Brazil about physical and sensory aspects to stimulate their consumption has attempted to answer this. 

Consumers are becoming more health-conscious and have less time to prepare meals. They are often confused about which time and cooking method are adequate to preserve nutrients in vegetables. All cooking techniques cause changes in the nutrient content and the taste of a vegetable. 

The objective of this study was to determine the best cooking method for different vegetables using sensory evaluation and instrumental analysis of texture and colour. The chosen vegetables for this study were broccoli, carrot and Brazilian zucchini because they are among the most consumed vegetables in Brazil. The cooking methods were boiling, steaming, cooking in the combined oven, microwave, and steaming in the microwave.

Effect of storage on Texture: Vegetables

From the point of view of texture, vegetables represent a very diverse group of products.

 

They can be consumed in many different textural forms. For instance, cooked asparagus is soft, fibrous and pulpy, cucumber is crisp, firm and juicy, raw carrots are hard and crisp, and cooked peas are soft and mealy. The tissue structure in each case determines the texture as received by the consumer.

Fresh vegetables

As opposed to fruits, which are generally picked when mature but unripe, many vegetables (apart from legume seeds, tubers, bulbs and roots) are picked and consumed when still immature, tender and succulent. This is largely due to the fact that while fruits generally soften on maturation and storage, young vegetables become tougher when they age. This toughening is due to the lignification of the primary cell wall and formation of the secondary cell wall.

The Textural Challenges of a Vegan Diet

Veganism is growing in popularity due to increased education about its environmental, health and ethical benefits. 

An Alpro report from 2018 (‘Plant-Based Profits with Alpro and BB Food Service’) stated that the UK plant based market at the time was worth £443m, having grown by £129m in three years. Due to this growth, vegan alternatives to products traditionally made with animal produce have swarmed the food market, and most use the new term ‘plant-based’ to describe a vegan product. It is now possible to buy a vegan version of almost every animal based product from chocolate fudge cake to crispy duck, and new companies are popping up that are dedicated solely to plant alternatives.

Chips, Crisps & Mash – Getting the Texture Right!

Potatoes are a common, even basic, vegetable in Western diets, in some cases assuming the status of a staple.

Potato snack foods include French Fries and dried miniature versions of them (chips in the US sense, or crisps in UK) in many flavours. They appear as mashed potato in many convenience meals such as TV dinners, and as potato salads in take-away meals.

Fruit and Vegetable Texture Measurement and Analysis

The market for fruit and vegetables, especially in many industrial countries, is constantly changing and evolving.

Every year new crops are being offered for sale in markets and this stimulates innovation in handling methods and studies of quality factors. 

Texture is one of the most important quality attributes affecting the acceptability of both fresh and processed foods. Fruit and vegetable quality is a concept based on several criteria which depend on the objective. 

Texture Analysis in action: the Miniature Kramer/Ottawa Cell

The MINIATURE KRAMER SHEAR/OTTAWA CELL (HDP/MK05* or HDP/MKS*) is particularly suited to reduce the force of bulk shearing/compression of multi particle products or non-uniform products.

It attaches to the HDP/90 Heavy Duty Platform. A 5-bladed head or compression platen can be attached to the arm of the texture analyser depending upon whether a shearing or bulk compression/extrusion test is required.