Food or edible material: processes – compositions – and products – Products per se – or processes of preparing or treating... – Beverage or beverage concentrate
Reexamination Certificate
2000-06-09
2002-08-06
Pratt, Helen (Department: 1761)
Food or edible material: processes, compositions, and products
Products per se, or processes of preparing or treating...
Beverage or beverage concentrate
C426S050000, C426S051000, C426S577000, C426S590000
Reexamination Certificate
active
06428837
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to enzymatically blocked-deesterified pectins that display pseudoplasticity and substantially no phase separation in an aqueous solution comprising at least one polyvalent cation, and processes for producing the same. In particular, the present invention is directed to enzymatically blocked-deesterified pectins prepared by deesterifying isolated high methoxyl pectins with enzymes. The present invention is also directed to processes for suspending particulates using enzymatically blocked-deesterified pectins prepared by deesterifying isolated high methoxyl pectins with enzymes. Furthermore, the present invention relates to stabilized aqueous systems containing enzymatically blocked-deesterified pectins prepared by deesterifying isolated high methoxyl pectins with enzymes.
2. Background of the Invention and Related Art
The problem encountered with drinks containing insoluble components, such as pulps, essential oils, and the like, is the tendency of the insoluble components to separate, e.g., via sedimentation or creaming.
In order to maintain insoluble components in suspension, xanthan has been added to fruity drinks to raise the viscosity or alter the rheology of the drink. Xanthan, when added to aqueous solutions even at low concentrations, exhibits very strong pseudoplasticity and viscoplasticity at low concentration without any evidence of thixotropy. However, xanthan adds negative organoleptic perception (undesirable mouth-feel) in beverages. Thus, there is a need to provide a suspension aid that has the desired properties of xanthan without the undesired mouth-feel.
Alginates and pectins have been used in beverages to raise viscosity since they do not add negative mouth feel. Alginates and pectins useful for this application, however, tend to undergo syneresis during long term storage. Attempts have been made to use pectins as suspension aids with reduced syneresis properties, but without success.
Pectin is a structural polysaccharide commonly found in the form of protopectin in plant cells. The backbone of pectin comprises ∝-1-4 linked galacturonic acid residues which are interrupted with a small number of 1,2 linked∝-L-rhamnose units. Some of the carboxyl groups of the galacturonic residues are esterified, typically by methyl groups. The remaining residues are present as free carboxyl groups. Esterification of the carboxyl groups occurs in the plant tissue after polymerization of the galacturonic acid residues. However, it is extremely rare for all of the carboxyl groups to be esterified. Usually, the degree of esterification varies from 0 to 90% of the available carboxylic groups.
The term “degree of esterification” is intended to mean the extent to which free carboxylic acid groups contained in the polygalacturonic acid chain of the pectin have been esterified (e.g., by methylation) or in other ways rendered non-acidic (e.g., by amidation).
Pectin is available as either low methoxyl pectin (LMP) or high methoxyl pectin (HMP). Low methoxyl pectin as defined here has a degree of esterification (DE) of less than about 45% and is highly reactive with cations such as calcium. High methoxyl pectin as defined here has a DE of greater than about 45% and typically is less reactive with polyvalent cations such as calcium.
The structure of the pectin, in particular the degree of esterification, dictates many of its physical and/or chemical properties. For example, pectin gelation caused by the presence of calcium cations depends especially on the degree of esterification. Gelation is believed to result from the calcium ions forming cross-linked complexes with free carboxyl groups of a number of pectin chains causing the formation of a continuous three-dimensional gelled matrix.
Pectin, as first extracted, has a relatively high degree of esterification of about 70-75%. Such pectin is ideal for use in jam and jellies. However, other uses require the preparation of pectins with different setting characteristics. This can be accomplished by modifying pectin to reduce the degree of esterification. One common process for achieving this is an acid hydrolysis. Alternative processes are directed to the use of alkali at low temperatures, ammonia, or to use a pectin methyl esterase.
During deesterification, the ester groups on the pectin can be removed in a random or blockwise manner. When the ester groups are removed from any galacturonic acid residues on more than one of the pectin chains non-sequentially, they are referred to as being deesterified in a “random manner.” When the ester groups are removed either at non-reducing ends or next to free carboxyl groups by a single-chain mechanism in a sequential manner, they are referred to as being deesterified in a “blockwise manner,” as blocks of unesterified galacturonic acid units are created. The sequential or blockwise removal esters are typically mediated by pectin methyl esterases. The unesterified galacturonic acid units formed by blockwise deesterification are highly reactive to polyvalent cations such as calcium. Pectins having such blocks of unesterified galacturonic acid are said to be “calcium sensitive.”
It is well known that the methyl content of pectin is modified in nature by plant pectin esterases that are present in the plant tissue. Many of these plant esterases, usually called pectin methyl esterases (PMEs), demethylate esterified carboxylic groups that are next to at least two contiguous free carboxylic acid groups. The demethylation proceeds in this way forming blocks. For example, the unpurified proteases papain and bromelain from plant tissue are also known to contain pectin methyl esterases as contaminants that demethylate pectins in a blockwise manner.
To a small extent these blocks of unesterified galacturonic acid units occur naturally in commercial high DE pectins when first isolated. In a commercial, pectin having a typical degree of esterification of approximately 68-74%, the length of the free carboxylic blocks may vary from molecule to molecule, and each pectin molecule typically includes several blocks of different lengths. For example, it is known that the distribution of the free carboxyl groups along the polymer chain is important for determining whether the pectin is suitable for use as a stabilizer for acidified milk drinks. It has been proposed that pectin can stabilize a suspension of casein particles by adsorbing onto the surface of the casein particles at specific points of the pectin molecule where the block-deesterified regions occur. To obtain complete stability a significant proportion of the surface of a casein particle should be covered by the pectin. Nevertheless, aside from stabilizing casein these pectins have found limited utility for stabilization of pulp or other materials in typical beverage applications.
Pectins that have been randomly deesterified have also been tested for use in stabilization of particles in liquid foods and beverages. Commercial pectins that have been reduced randomly to low-methoxyl pectins can also be reactive with polyvalent cations such as calcium. Calcium is the most common source of polyvalent cations for food gel applications involving these types of pectins. Gelation is due to the formations of intermolecular junction zones between homogalacturonic acid units. Because of the electrostatic nature of the bonds, pectin gels are very sensitive to conditions that can modify the environment of the carboxyl groups through which the calcium ion is linked to a neighboring pectin molecule. The gel forming ability of pectin increases with decreasing DE, and low methoxyl pectins with a large number of free carboxyl groups are very sensitive to low calcium levels. As the number of free carboxyl groups along the pectin backbone the increasing sensitivity of low DE pectin to calcium is an increased tendency for the pectin to gel and to display syneresis. The properties of gel contraction and syneresis in these types of randomly deesterified pectins are unsuitable for stabiliz
Forman Susan C.
Gerrish Timothy C.
Luzio Gary
CP KELCO APS
Greenblum & Bernstein P.L.C.
Pratt Helen
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