in accordance with the present invention , the liquid heat - sterilised food may be , for instance , a dairy product such as white coffee , or cocoa or tea . the heat - sterilisation may be carried out in an air - tight vessel , e . g . when the liquid food is canned or bottled . the ingredients of white coffee may be instant coffee powder , coffee extract , coffee concentrate or roast and ground coffee together with water , sucrose and milk , as well as with small amounts of optional ingredients such as dipotassium phosphate and sodium bicarbonate . preferably , the milk ingredient is a mixture of high - fat cream and skim milk powder . the enzymatically - hydrolysed phospholipid is produced by the action of a phospholipase on the phospholipid to give a lysophospholipid . phospholipids , which may advantageously be used in a powdered or paste form , form a class of chemical compounds comprising phosphatidylcholine ( lecithin ) and phosphatidylethanolamine as the main elements . phospholipase a is an enzyme which may be manufactured from porcine pancreatic glands and which hydrolyses phospholipids by specific cleavage of the bond binding a fatty acid ester to the glycerol part of the phospholipid molecule thereby replacing the fatty acid ester by a hydroxyl group . the hydrolysis results in an increase of free fatty acids and a conversion of the phosphatidylcholine ( lecithin ) and phosphatidylethanolamine into several substrates such as lysophosphatidylcholine , lysophosphatidylethanolamine , phosphatidylcholine glycerol and phosphatidylethanolamine glycerol . phospholipase a - 2 ( sold commercially under the trade name lecitase ) is the preferred enzyme and cleaves the bond binding a fatty acid ester to the glycerol part of the phospholipid molecule , mainly at position 2 . the degree of conversion is the proportion of phosphatidylcholine present before hydrolysis that is converted into lyso - phosphatidylcholine , expressed in mol %. in the present invention , the enzymatically - hydrolysed phospholipid preferably has a degree of conversion of at least 90 % and more preferably , of at least 95 %. the enzymatically - hydrolysed phospholipid is conveniently an enzymatically - hydrolysed lecithin which is produced by the action of phospholipase a - 2 on the lecithin to give a lysolecithin . commercial lecithin is predominantly soybean lecithin obtained as a by - product in the manufacture of soybean oil . lecithin can also be isolated from eggs and can be obtained synthetically . it can be used in a powdered or paste form . one method for the enzymatic hydrolysis of phospholipids is claimed in japanese laid - open patent application no . jp - a - 63 44893 in which the phospholipid is hydrolysed with phospholipase a after adding 0 . 1 to 1 part by weight of water to 1 part by weight of phospholipid . the degree of conversion of phospholipid to lysophospholipid in the practical embodiments varies from 80 to 90 %. it is stated that larger amounts of water and / or agitated conditions give lower degrees of conversion . we have found that by using more than 1 part by weight of water to 1 part by weight of phospholipid in the enzymatic hydrolysis of a phospholipid using agitated conditions , we can obtain a degree of conversion greater than 90 % or even 95 %. in carrying out the hydrolysis process of the present invention , the amount of water present in the aqueous medium is preferably from 1 . 5 to 7 . 5 parts , more preferably from 2 to 6 parts , even more preferably from 3 to 5 parts , and most preferably from 3 . 5 to 4 . 5 parts by weight per part by weight of phospholipid . the water of the aqueous medium may be ordinary tap water , distilled water , or ion - exchanged water . the amount of the phospholipid may be from 5 to 40 %, preferably from 10 to 30 % and especially from 15 to 25 % by weight based on the weight of the reaction mixture . the phospholipid may be added in one , two or more stages . the phospholipase may be used in an amount of from 0 . 05 to 0 . 5 %, preferably from 0 . 1 to 0 . 4 % and especially from 0 . 15 to 0 . 3 % by weight based on the weight of the aqueous medium . the enzymatic reaction is preferably carried with slow or gentle agitation . the presence of a water - soluble calcium salt , e . g . 0 . 01 to 0 . 25 % and preferably from 0 . 025 to 0 . 15 % by weight based on the weight of the aqueous medium , is desirable during the reaction . calcium is a co - factor to the phospholipase enzyme . calcium chloride is the preferred salt and is most preferably used in the dihydrate form . the hydrolysis is carried out conveniently in the aqueous medium at a temperature of from 25 ° c . to 70 ° c ., preferably from 30 ° c . to 60 ° c ., more preferably from 40 ° c . to 55 ° c ., and at a ph of from 5 to 9 and preferably of from 6 to 8 . the duration of the hydrolysis reaction may conveniently be from 30 minutes to 5 hours , preferably from 1 to 4 hours , and more preferably from 1 . 5 to 3 hours . although longer times may be used , e . g . up to 50 hours , there is no special advantage obtained in using such longer periods . after the reaction , the mixture is advantageously pasteurised and then dried . after pasteurisation and before drying , antioxidants such as vitamin c , vitamin e , tea extracts , and / or bha / bht may be added to protect the flavour , and a carrier such as maltodextrin , non - fat dried milk , starch , or gum arabic , may be added to the mixture . the enzymatically - hydrolysed phospholipid may be used in a powder or paste form . as stated above , sterilisation has been carried out usually at a temperature of about 121 ° c ., e . g . 1150 ° to 125 ° c ., over a period of from about 20 - 30 minutes , or under uht conditions , e . g . 140 ° to 150 ° c . for from 5 to 20 seconds , and such conditions may be used in the present invention . however , we have found that , by sterilising at 121 ° c . in the presence of an enzymatically - modified phospholipid in accordance with the present invention , the spoilage of liquid heat - sterilised food preparations is significantly less than by sterilising in the presence of ordinary phosphatides even if the period of the sterilisation is much less than 30 minutes . for instance , we have found that periods as low as 5 minutes , preferably from 6 to 15 minutes and more preferably from 7 to 10 minutes , can achieve reduced spoilage . the amount of enzymatically - hydrolysed phospholipid present in the liquid heat - sterilised food may be from 0 . 005 to 2 %, preferably from 0 . 01 to 1 . 25 %, more preferably from 0 . 025 to 1 . 0 % and especially from 0 . 04 to 0 . 75 % by weight based on the weight of the mixture . in the preparation of canned or bottled white coffee , the coffee ingredients and the enzymatically - hydrolysed phospholipid are mixed in the appropriate proportions , homogenised , canned or bottled , and then sterilised or retorted , followed by cooling to ambient or refrigeration temperatures . the amount of the enzymatically - hydrolysed phospholipid may be from 0 . 1 to 15 %, preferably from 0 . 25 to 10 %, more preferably from 0 . 5 to 7 . 5 % and especially from 1 . 0 to 5 . 0 % by weight based on the weight of the coffee solids . the canned or bottled white coffee is transported and normally stored at ambient or refrigeration temperatures . if used in a vending machine , the storage temperature during the winter months may be from about 55 °- 60 ° c ., and we have found that by sterilising the ingredients in the presence of an enzymatically hydrolysed phospholipid in accordance with the present invention , there is significantly less spoilage of the coffee drink than when sterilising the ingredients alone or in the presence of conventional emulsifiers such as a phospholipid which has not been enzymatically hydrolysed . the coffee drink may be stored for several weeks without spoilage . the following examples further illustrate the present invention . parts and percentages are given by weight . the powdered enzymatically hydrolysed lecithin used in the examples according to the invention was prepared as follows : 100 parts of tap water is slowly stirred in a jacketed kettle at 30 ° c . and at ph 8 . 0 . 1 part of calcium chloride dihydrate and 0 . 22 part of phospholipase a - 2 are added and the ph adjusted to 7 , if necessary , by using 10n potassium hydroxide while the temperature is slowly increased to 50 ° c . 10 parts of powdered deoiled soy lecithin ( half the total ) are slowly added to the mixture , whereupon an immediate drop in the ph is observed which indicates that an enzymatic reaction is taking place . the ph is readjusted to 7 by using 10n potassium hydroxide , and the reaction is allowed to proceed for 30 minutes , after which time a further 10 parts ( the second half ) of the lecithin is added and the reaction is allowed to proceed for a further 90 minutes with the necessary ph adjustment to 8 as before . after the reaction , the product is pasteurised by heating to 95 ° c . for 5 minutes to deactivate the enzyme and then cooled to 75 ° c . 10 parts of maltodextrin is added , and the product is mixed into a homogeneous slurry while being cooled to ambient temperature . the slurried product is finally spray - dried at a rate of about 0 . 3 kg per minute where the inlet temperature is 160 ° c . and the outlet temperature is 95 ° c . a white coffee mix is prepared by mixing the following ingredients in the amounts indicated : ______________________________________water 85 . 815cream , 40 % fat 2 . 260skim milk powder 2 . 160sucrose 5 . 500coffee powder , nescafe classic 1 . 100dipotassium phosphate 0 . 080sodium bicarbonate 0 . 060enzyme modified lecithin powder 0 . 025 ( 50 % maltodextrin ) sucrose ester p - 1670 -- water to standarize 3 . 000total 100 . 000 % ______________________________________ after mixing the ingredients , the mix is heated to 76 ° c ., canned , retorted at 121 ° c . for 8 minutes and cooled to ambient temperature . the canned white coffee is incubated at 60 ° c . for 14 days , after which time the spoilage was less than 1 % ( 0 / 100 cans ), and ph drop was zero . a similar procedure to that carried out in example 1 was followed except that , after canning , the mix was held at 76 ° c . for three hours before retorting . the canned white coffee is incubated at 60 ° c . for 14 days , after which time the spoilage was less than 1 % ( 0 / 100 cans ), and ph drop was zero . a similar procedure to that carried out in example 1 was followed but using 0 . 25 %, instead of 0 . 025 %, of ! powdered enzymatically - hydrolysed lecithin based on the total weight of the coffee mix . the canned white coffee is incubated at 60 ° c . for 14 days , after which time the spoilage was less than 1 % ( 0 / 100 cans ), and ph drop was zero . a similar procedure to that carried out in example 1 was followed , but excluding the powdered enzymatically - hydrolysed lecithin . after incubation of the canned white coffee at 60 ° c . for 14 days , the spoilage was 99 % and the ph drop was 90 / 91 . a similar procedure to that carried out in example 1 was followed , but adding 0 . 25 % of powdered lecithin instead of the powdered enzymatically - hydrolysed lecithin there used . after incubation of the canned white coffee at 60 ° c . for 14 days , the spoilage was 7 . 5 % and the ph drop was 6 / 79 . a similar procedure to that carried out in example 1 was followed , but adding 0 . 2 % of powdered lecithin instead of the powdered enzymatically - hydrolysed lecithin there used . after incubation of the canned white coffee at 60 ° c . for 14 days , the spoilage was 48 % and the ph drop was 42 / 87 . a similar procedure to that carried out in example 1 was followed , but adding a mixture of 0 . 09 % durem 207 ( mono and diglycerides ) supplied by van den berg food and 0 . 01 % tween 80 ( polyoxyethylene sorbitan monooleate ) instead of the powdered enzymatically - hydrolyzed lecithin there used . after incubation of the canned white coffee at 60 ° c . for 14 days , the spoilage was 27 % and the ph drop was 24 / 90 . a similar procedure to that carried out in example 1 was followed , but adding a mixture of 0 . 09 % durem 207 and 0 . 01 % panodan pvk ( diacetyl tartaric acid ester of monoglycerides ) supplied by grindsted ingredients , instead of the powdered enzymatically - hydrolysed lecithin there used . after incubation of the canned white coffee at 60 ° c . for 14 days , the spoilage was 20 % and the ph drop was 18 / 90 .
spoilage of heat - sterilized liquid food products is reduced by preparing the liquid food product , prior to sterilization , by mixing an enzymatically - modified phospholipid composition , particularly an enzymatically - modified phospholipid composition having a degree of conversion of greater than 90 %, with the liquid food product . liquid food products which may be so treated include , in particular , coffee , tea , or cocoa beverage - component solids which provide beverage products . additionally , an enzymatically hydrolyzed phospholipid composition having a degree of conversion greater than 90 % may be obtained by hydrolyzing phospholipids in an aqueous medium , wherein the amount of water is greater than one part per part phospholipids , under agitated conditions so that a degree of conversion greater than 90 % is obtained .