Food or edible material: processes – compositions – and products – Products per se – or processes of preparing or treating... – Foam or foamable type
Reexamination Certificate
1998-03-13
2001-03-13
Nessler, Cynthia L. (Department: 1761)
Food or edible material: processes, compositions, and products
Products per se, or processes of preparing or treating...
Foam or foamable type
C426S524000, C426S656000, C426S660000, C426S101000, C530S350000
Reexamination Certificate
active
06200622
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention relates to a process for the preparation of a food product containing AFPs and to food products containing AFPs.
BACKGROUND TO THE INVENTION
Anti-freeze peptides (AFPs) have been suggested for improving the freezing tolerance of foodstuffs. For the purpose of this invention the term AFP has the meaning such as well-known in the art, see for example “Antifreeze proteins and their potential use in frozen food products”, Marilyn Griffiths et al. Biotechnology Advances, Vol.13, pp.375-402, 1995
WO 90/13571 discloses antifreeze peptides produced chemically or by recombinant DNA techniques from plants. The AFPs can suitably be used in food-products such as ice-cream.
WO 92/22581 discloses AFPs from plants which can be used for controlling ice crystal growth in ice-cream. This document also describes a process for extracting a polypeptide composition from intercellular spaces of plants by infiltrating leaves with an extraction medium without rupturing the plant cells.
WO 94/03617 discloses the production of AFPs from yeast and their possible use in ice-cream. WO 96/11586 describes fish AFPs produced by microbes.
Up till now, however the use of AFPs has not been applied to commercially available food products. One reason for this is that up till now it has proved difficult to reproducibly produce a frozen food product having the desired texture and eating characteristics.
The present invention aims at providing solutions to these problems. In particular the invention aims at providing frozen food products containing AFPs and having a non-brittle texture, said texture being maintained upon prolonged storage at low temperatures.
PCT/EP97/03635 (non-pre-published) relates to the production of frozen food products containing AFPs and having a relatively hard and brittle texture by adapting the aspect ratio of the ice-crystals in the product.
PCT/EP97/03636 (non-pre-published) relates to the production of frozen food products containing AFPs and having a relatively soft although brittle texture by adapting the aspect ratio of the ice-crystals in the product.
Surprisingly it has been found that it is possible to obtain frozen food products containing AFPs which are non-brittle, provided the process of producing the AFP containing product is carefully selected.
Accordingly in a first aspect, the invention relates to a process for the production of a frozen food product comprising AFP, wherein the product is at least partially pre-frozen in the substantial absence of free AFP, followed by including the free AFP therein.
Without being bound by any theory applicants believe that the favourable textural properties of the product can be explained as follows: If food products are pre-frozen, ice-crystals are formed throughout the product. If free AFPs become thereafter available in the pre-frozen products this generally leads to a maintenance of the shape and size of the initially formed crystals even if the product is subjected to temperature changes during storage. However the presence of the free AFPs only at a late stage of the freezing process, i.e. after at least part of the ice-crystals have been formed, seems to lead to a reduction of aggregation between the ice-crystals of the final product, therewith resulting in a less brittle product.
For the purpose of the invention the term free AFP encompasses all forms of AFP which can interact with the ice-crystals. The absence of free AFP means that either no AFP is present in the system or AFP is present in a form such that it cannot interact with the ice-crystals. The presence of free AFP can be shown by using the recrystallisation inhibition test such as illustrated in the examples.
Many consumers are in favour of less brittle frozen food products or ingredients such as ice-cream or water-ice.
Surprisingly we have found that AFPs offer the opportunity to formulate frozen food products which on the one hand are less brittle and on the other hand retain improved ice-recrystallisation and temperature tolerance properties upon storage abuse.
Products according to the invention are characterised by a significantly lower Brinell hardness, than products with the same composition, wherein free AFP is present before freezing. Preferably at −18° C. the force (in N) at a displacement of 2 mm measured as in the examples for products where the free AFP is present prior to (partial) freezing is at least 1.5 times the force (in N) for the same composition wherein free AFP is present only after (partial) prefreezing. More preferably the force is from 2.0 to 4.0 times the force of products of the invention. The force for products of the invention and measured as indicated above is preferably from 5 to 100 N, more general from 7 to 40 N, more specifically from 10 to 30 N.
The aspect ratio of ice-crystals in compositions produced according to the process of the invention is preferably less than 2.0, e.g. from 1.0 to 1.9. The aspect ratio of ice-crystals is defined as the average ratio of the length and the breadth of the ice-crystals. An aspect ratio of less than 2.0 corresponds to roundish ice-crystals, which are not elongated in shape. The aspect ratio of crystals can be determined by any suitable method. A preferred method is illustrated in the examples.
Preferably the frozen product of the invention are non-brittle. Preferably the minimum layer thickness at which fracture behaviour can be observed is more than 10 mm, more preferred more than 50 mm. Fracture behaviour can either be measured by preparing layers of varying thickness and determining at which minimum thickness fracture behaviour occurs or calculated from the Young Modulus as described in the examples.
During the formulation and subsequent freezing of food products several parameters can influence the aspect ratio of the ice-crystals to be formed. Examples of factors influencing the aspect ratio are given below. Applicants believe that it is well-within the ability of the skilled person to choose those conditions such that the aspect ratio of the ice-crystals falls within the desired range.
One factor influencing the aspect ratio of ice-crystals is the rate of freezing the product. Generally speaking an increase of the rate of freezing may lead to a decrease in the aspect ratio for the ice-crystals.
Another factor influencing the aspect ratio of ice-crystals is the mobility of the product during freezing. For example if a liquid water-ice or ice-cream mix is to be frozen, quiescently freezing will lead to a fairly high aspect ratio for the ice-crystals, while stirring leads to a lower aspect ratio. High shear mixing will lead to even lower aspect ratios.
Another factor to influence the aspect ratio of the ice crystals is the presence and amounts of ingredients. For example the presence of ingredients which tend to form a network structure in the product (e.g. gums or fats) may lead to a lower aspect ratio than in products without these ingredients. Also other ingredients may lead to lower aspect ratios, for example high solids levels e.g. high sugar levels may lead to low aspect ratios. Also high phase volumes for the ice may lead to higher aspect ratios.
Finally the nature and amount of the AFPs present may lead to a change in aspect ratios. Some AFPs seem to favour the formation of low aspect ratios, while other AFPs seem to induce higher aspect ratios. Variation in the amount of AFPs may lead to a change in aspect ratios.
The process of the invention involves at least the partial pre-freezing of the product prior to the presence of free AFP. This partial prefreezing preferably freezes at least 20 wt % of the water present in the pre-mix, e.g. from 30-100 wt %, preferably 40-80 wt %. This pre-freezing can be done by any suitable method. Particularly preferred however is the partial pre-freezing in a device wherein freezing and aeration (if desired) takes place at the same time. Suitable devices for this are for example scraped surface heat exchangers, wherein the food product is pre-frozen e.g. to a temperature of between −2 and −
Darling Donald Frank
Hoddle Andrew
Farrell James J.
Good Humor - Breyers Ice Cream, division of Conopco
Nessler Cynthia L.
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