illustrative and alternative embodiments and operational details of the firming process to enhance texture of thermally processed iqf fruits and vegetables will be discussed in detail as follows with reference to fig1 . fresh fruits and vegetables are individually quick frozen — a widely used commercial process — to preserve flavor , texture , and nutritional value . individually quick frozen or “ iqf ” is used in its ordinary meaning to refer generally to frozen fresh fruits or vegetables that may or may not have been blanched prior to freezing , may be preservative free , and are maintained at a freezing temperature . thermal processing — after fruits and vegetables are subjected to iqf processing — may substantially degrade texture and firmness . a purpose of the disclosed embodiments is to produce a consumable fruit or vegetable product having an improved or enhanced texture after exposure to texture damaging heat during sterilization . enhancing texture is achieved as the calcium of the soak solution interacts with naturally occurring elements of the fruit or vegetable . for example , the calcium ions in the soak solution cross - link with pectin to enhance firmness in fruits . another purpose of the disclosed embodiments is to allow for continuous year - round production with iqf fruits and vegetables to provide high quality shelf ready and shelf stable food products . the process of the invention may preferably take place in a large scale commercial operation whereby each step may be automated with commercial machinery , carried out manually , or some combination of both . for this disclosure , the term “ fruit ” is used in its ordinary meaning to refer generally to any edible reproductive body of a seed plant or succulent plant part . illustrative examples of fruits include , but are not limited to , blueberries , strawberries , blackberries , peaches , pears , grapes , and the like . also , the term “ vegetables ” is used in its ordinary meaning to refer generally to the edible part of an herbaceous plant . illustrative examples of vegetables include , but are not limited to , peas , carrots , green beans , corn , potatoes , and the like . fruits and vegetables may be whole , sliced , diced , cubed , cored , pared , shaved , etc . in an illustrative embodiment of the invention shown in fig1 , iqf fruits or vegetables 100 — previously sorted for size with blemished and damaged ones removed 102 — are immersed and soaked 104 in a soak solution to enhance the texture and firmness of the fruit or vegetable . the iqf fruits or vegetables are kept in a frozen or near frozen state at a temperature between about − 5 ° f . to about 30 ° f . up to the point of immersion in the soak solution contained in a vessel . the vessel may be any food - grade container that can withstand cold temperatures including , but not limited to , buckets , drums , kettles , etc . in an embodiment , the vessel is covered during the soak to avoid microbial contamination or any debris . the iqf fruits or vegetables may be batched in any commercially practical weight and immersed in any commercially practical volume of soak solution . the ratio of iqf fruit or vegetable to soak solution may be about 1 : 1 by weight during the soak 104 for full immersion . but the ratio may be adjusted for various fruits and vegetables so that they are fully immersed in the soak solution . the soak solution may be isotonic and may also be referred to as an isotonic solution or an isotonic sucrose solution in different embodiments . the soak solution may comprise about 80 - 90 % water by weight , about 10 - 20 % sucrose by weight , and about 0 . 5 - 1 . 5 % calcium lactate ( puracal pp / usp ) by weight . in an embodiment , the soak solution comprises about 86 . 4 % water by weight , about 12 . 5 % sucrose by weight , and about 1 . 089 % calcium lactate by weight . in another embodiment , the soak solution comprises about 87 . 2 % water by weight , about 12 % sucrose by weight , and about 0 . 8 % calcium lactate by weight . a food enzyme , such as pectinmethylesterase ( novozyme novoshape pme ), may be added as an optional soak solution ingredient . in yet another embodiment , the soak solution comprises about 85 . 9 % water by weight , about 12 . 5 % sucrose by weight , 0 . 5 % food enzyme ( novozyme novoshape ) by weight , and about 1 . 089 % calcium lactate by weight . the brix of the sucrose in the soak solution may be adjusted to match the brix of the iqf fruit or vegetable to be immersed in the soak solution or the desired brix of the finished fruit or vegetable product . in alternative embodiments , the sucrose ingredient of the soak solution may be replaced with other forms of sugar or other forms of salt . for example , the soak solution may comprise an isotonic solution of salt , sugar , or combination of both . in an embodiment , the soak solution comprises about 90 - 95 % water by weight , about 3 - 9 % sugar by weight , about 0 . 1 - 1 % sodium salt by weight , and about 0 . 5 - 1 . 5 % calcium lactate by weight . in another embodiment , the soak solution comprises about 92 . 9 % water by weight , about 6 % sugar by weight , about 0 . 3 % sodium salt by weight , and about 0 . 8 % calcium lactate by weight . the starting temperature of the soak solution should be kept at a degree that prevents iqf fruits or vegetables from refreezing during the soak . in an embodiment , the starting temperature of the soak solution may be in a range of about 50 ° f . to about 150 ° f . prior to immersion of the iqf fruits or vegetables . iqf fruits or vegetables are immersed in the soak solution 118 to soak 104 for a time period in a range of about 18 hours to about 72 hours . in another embodiment , the time period ranges from about 24 hours to about 48 hours . the soak solution and iqf fruits or vegetables should be maintained throughout the soaking immersion at a temperature ranging from about 32 ° f . to about 52 ° f . or more . in yet another embodiment , the temperature of the soak may be 37 ° f . during the soak 104 , the temperature of the soak solution may be maintained by any commercial means including , but not limited to , ambient air , cold or hot water baths , refrigeration , etc . after soaking the iqf fruits or vegetables , the soak solution is drained from the vessel 106 . draining can occur by way of a sieve , strainer , or commercial machinery including , but not limited to , a dewater belt or the like . draining can take place immediately before iqf fruits or vegetables are weighed into serving quantities , but no more than about 2 hours before weighing servings into containers . drained iqf fruits or vegetables may be optionally maintained at a temperature ranging from 32 ° f . to about 52 ° f . throughout the weighing process . soaked iqf fruit or vegetable quantities are weighed at specified weights , or measured volumetrically to desired volumes , and filled into containers with an opening 108 . containers may comprise any food - grade plastic or other acceptable food - grade material in the form of cans , jars , cups , bowls , bags , pouches , or the like . serving quantities can be weighed or measured into any desired size . the quantity size depends on the size and nature of the container and the finished product . in an embodiment , the fruit or vegetable serving quantities may fill about 50 % to about 60 % of the container that they are placed in and fit loosely within the container . servings may be kept at a temperature ranging from about 32 ° f . to about 52 ° f . a topping 116 is then placed into the container to fill the remaining space within the container and to generally cover the fruit or vegetable 110 . the topping may be water or a syrup or juice or brine solution . in an illustrative example , the syrup may comprise water , sugar , and acids , and flavoring may also be added as an optional ingredient 120 . in an embodiment , the syrup comprises about 78 % water by weight , about 20 % sucrose by weight , about 0 . 3 % flavoring by weight , about 0 . 2 % ascorbic acid by weight , and about 0 . 2 % citric acid by weight . in another embodiment , the syrup comprises about 78 . 75 % water by weight , about 20 . 5 % sucrose by weight , about 0 . 3 % flavoring by weight , about 0 . 228 % ascorbic acid by weight , and about 0 . 225 % citric acid by weight . the topping may also comprise a brine solution which may or may not be isotonic . in an embodiment , the brine solution topping may comprise water and a form of salt , such as , for example , sodium or the like . the topping may be batched and kept at ambient temperature . in an embodiment , the topping is batched and then heated to about 190 ° f . before filling containers with specified quantities of an iqf fruit or vegetable 116 , 120 . the brix of the sucrose or other sugar in the topping may be adjusted to meet the brix of the finished product . the topping may be placed in the container within minutes and no later than about 2 hours after soaked fruits or vegetables are placed in the container . container openings are then hermetically sealed with or without a film — depending on the nature of the container — using commercial techniques 112 . in an embodiment , a film is heat sealed to the container to close the opening . the film may be any food - grade plastic or other acceptable food - grade material . in an alternative embodiment , the container , such as a bag or pouch , is sealed to itself without using a film . sealed containers are heated to commercially sterilize iqf fruit or vegetable and topping contents 114 . commercial sterilization may occur in a hot water bath at atmospheric pressure , using a retort to cook at a higher temperature , or any other commercial means suitable for cooking the contents of the container . the container contents should be cooked to commercial sterility in a range of about 180 ° f . to about 260 ° f . or higher . and then , the containers are immediately cooled to less than about 100 ° f . in an illustrative example , whole iqf berries were fully immersed at about a 1 : 1 ratio in an isotonic sucrose solution consisting of about 84 % water by weight , about 15 % sucrose by weight , and about 0 . 8 % calcium lactate ( puracal pp / usp ) by weight in a covered food - grade vessel for about 24 hours at about 35 ° f . the isotonic sucrose solution was about 70 ° f . prior to the immersion of iqf berries . after immersion , the isotonic sucrose solution was drained from the vessel for about 5 minutes with a strainer . specified weights of iqf berries were immediately weighed into serving size quantities , and the servings were placed into 4 ounce plastic food - grade cups to fit loosely within , but filling about 50 % of , the cups . the iqf berries were maintained at a temperature of about 40 ° f . during weighing . about 100 ounces of syrup heated to about 190 ° f . was added to fill each cup immediately after the cups were filled with iqf berries . the syrup consisted of about 81 . 7 % water by weight , about 17 . 5 % sucrose by weight , about 0 . 3 % flavoring by weight , about 0 . 228 % ascorbic acid by weight , and about 0 . 225 % citric acid by weight . the brix of the sucrose in the syrup was adjusted to meet the brix of the finished iqf berries . each cup was hermetically heat sealed with a film . the sealed cups were cooked in a water spray retort to about 222 ° f . to commercially sterilize the iqf berry contents . once the cook was completed , the cups were immediately cooled to less than about 100 ° f . comparative experiments illustrate various berry textures after processing with prior art practices and after processing with the practices of the invention . iqf blueberries ( duke variety ) were treated in eight different combinations of defrosting , soak , and calcium treatments to determine the affect of calcium soak on finished product texture . the eight treatments consisted of : ( 1 ) a control of iqf berries — no soak , no calcium salt added , ( 2 ) iqf berries soaked in an isotonic sucrose solution ( 11 . 3 % sucrose ), no calcium salts added during the soak or in the topping syrup of the finished product ( a in fig2 ), ( 3 ) iqf berries , unsoaked , with 0 . 2 % calcium chloride solution added in the topping syrup of the finished product ( b in fig2 ), ( 4 ) iqf berries , unsoaked , with 0 . 18 % calcium lactate added in the topping syrup of the finished product ( c in fig2 ), ( 5 ) iqf berries , soaked in an isotonic sucrose solution ( 11 . 3 % sucrose ) no calcium salt for 24 hours , 0 . 18 % calcium lactate added to the topping syrup of the finished product ( d in fig2 ), ( 6 ) iqf berries , soaked in an isotonic sucrose solution ( 11 . 3 % sucrose ) with no calcium salt for 24 hours , 0 . 2 % calcium chloride added in the topping syrup of the finished product ( e in fig2 ), ( 7 ) iqf berries , soaked in an isotonic sucrose solution ( 11 . 3 % sucrose ) with 0 . 8 % calcium lactate solution for 24 hours , no calcium salts added in the topping syrup of the finished product ( f in fig2 ), and ( 8 ) iqf berries , soaked in an isotonic sucrose solution ( 11 . 3 % sucrose ) with 1 . 1 % calcium chloride for 24 hours , no calcium salts added in the topping syrup of the finished product ( g in fig2 ). all samples were packed into four ounce fruit cups and topped with a light syrup comprised of 77 . 8 % water , 21 . 7 % sugar , and organic acids ( 0 . 225 % citric acid and 0 . 228 % ascorbic acid ) and calcium salts where indicated . the topping syrup and fill weights were consistent throughout all variables . the cups were hermetically sealed and cooked to commercial sterility . for each reading , three cups of blueberries were drained to collect a 150 gram sample of blueberries . texture was tested using a taxt 21 texturometer with a 29 pronged probe . as shown in table a and summarized in fig2 , texture results indicate that the highest texture reading was achieved when the berries were treated with calcium salts . this result also suggests that , on a relative basis , firming improves more with exposure to calcium than it does with sucrose , during the soak . fig2 also shows that the soaking method with calcium yields better texture compared to adding calcium salts into the pack media or topping which is widely practiced in the industry . iqf blueberries ( duke variety ) were treated with three different calcium treatments to compare the results of dosing topping syrup with calcium lactate to calcium lactate / isotonic sucrose soak method with and without pme enzyme . serving as a control , commercially available canned blueberries ( oregon brand ) were evaluated for texture . a can of oregon brand blueberries in light syrup was drained to collect 100 g of blueberries for the control . the three treatment groups were ( a ) iqf berries , unsoaked , dosed with 0 . 08 % calcium lactate in the topping syrup of the finished product , ( b ) iqf berries , soaked in an isotonic sucrose solution ( 15 % sucrose ) with 0 . 8 % calcium lactate for 24 hours , no calcium salts added to the topping syrup of the finished product , and ( c ) iqf berries , soaked in an isotonic sucrose solution ( 15 % sucrose ) with 0 . 8 % calcium lactate and 0 . 5 % pme ( novoshapes ) for 24 hours , no calcium salts were added to the topping syrup of the finished product . all samples were packed into four ounce fruit cups and topped with a light syrup comprised of 81 . 7 % water , 17 . 5 % sugar , organic acids ( 0 . 225 % citric acid and 0 . 228 % ascorbic acid ), and flavoring ( 0 . 3 % natural blueberry flavor ). the topping syrup and fill weights were consistent throughout all variables . the cups were hermetically sealed and cooked to commercial sterility . samples were evaluated organoleptically after production and over time to monitor the affect of storage . samples were stored six months before texture testing . one set of samples was stored at 65 ° f . to mimic ambient storage and one set of samples was stored at 85 ° f . to mimic accelerated storage conditions . for each texture reading , two cups of blueberries for each experiment group were drained to collect a 100 gram sample of blueberries . texture was tested using the taxt 21 texturometer with a 29 pronged probe . as shown in table b and summarized in fig3 , texture results indicate that the conventional berry products on the market with calcium in syrup topping are significantly softer than the berries treated with the calcium salt soak . fig3 also illustrates texture results showing that the berries soaked in calcium prior to thermal processing had better texture after six months of storage . in some cases , the soaking method using calcium and pme had higher texture readings . however , in sensory tests throughout the six month storage , the texture of the enzyme soaked berries was perceived to be too tough and less appealing . two fruits , iqf blueberries ( duke variety ) and iqf diced peaches , were treated with two different treatments to compare the results of soaking fruits in an isotonic sucrose calcium solution with a water and calcium soak solution . the two treatment groups were ( a ) iqf fruit , soaked in an isotonic sucrose solution ( 15 % sucrose ) with 0 . 8 % calcium lactate for 24 hours , no calcium salts added to the topping syrup of the finished products , and ( b ) iqf fruit , soaked in water with 0 . 8 % calcium lactate for 24 hours , no calcium salts added to the topping syrup of the finished product . serving as a control , unsoaked iqf fruit was also evaluated for texture . the blueberry samples were packed into four ounce fruit cups and topped with a light syrup comprised of approximately 80 % water , 20 % sugar , organic acids ( 0 . 225 % citric acid and 0 . 228 % ascorbic acid ), and flavoring ( 0 . 3 % natural blueberry flavor ). the peach samples were packed into four ounce fruit cups and topped with light syrup comprised of approximately 75 % water . the topping syrup and fill weights were adjusted for each variable to meet a target sugar level in the finished product . the cups were hermetically sealed and cooked to commercial sterility . for each texture reading , three cups of blueberries for each experiment group were drained to collect a 150 gram sample of fruit . texture was tested using the taxt 21 texturometer with a 29 pronged probe . as shown in table c and summarized in fig4 , texture results indicate that the unsoaked iqf blueberry sample is softer than the samples soaked in isotonic and water calcium solutions . two fruits — iqf blueberries ( duke variety ) and iqf diced peaches — were treated with two different treatments to compare the results of soaking fruits in a 0 . 1 % calcium lactate solution with a 0 . 8 % calcium soak solution . the two treatment groups were ( a ) iqf fruit , soaked in an isotonic sucrose solution ( 15 % sucrose ) with 0 . 1 % calcium lactate for 24 hours , no calcium salts added to the topping syrup of the finished product , and ( b ) iqf fruit , soaked in water with 0 . 8 % calcium lactate for 24 hours , no calcium salts added to the topping syrup of the finished product . serving as a control , unsoaked iqf fruit was also evaluated for texture . the blueberry samples were packed into four ounce fruit cups and topped with a light syrup comprised of approximately 80 % water , 20 % sugar , organic acids ( 0 . 225 % citric acid and 0 . 228 % ascorbic acid ), and flavoring ( 0 . 3 % natural blueberry flavor ). the peach samples were packed into four ounce fruit cups and topped with light syrup comprised of approximately 75 % water , the topping syrup and fill weights were adjusted for each variable to meet a target sugar level in the finished product . the cups were hermetically sealed and cooked to commercial sterility . for each texture reading , three cups of blueberries for each experiment group were drained to collect a 150 gram sample of fruit . texture was tested using the taxt 21 texturometer with a 29 pronged probe . table d texture data texture calcium g / mm relative ppm 150 g texture blueberries iqf , no soak , no calcium 54 242 , 321 100 % iqf , isotonic sucrose soak - 83 389 , 611 161 % with 0 . 1 % calcium lactate iqf , isotonic sucrose soak - 234 733 , 457 303 % with 0 . 8 % calcium lactate peaches iqf , no soak , no calcium 36 20 , 061 100 % iqf , isotonic sucrose soak - 71 44 , 279 221 % with 0 . 1 % calcium lactate iqf , isotonic sucrose soak - 269 59 , 305 296 % with 0 . 8 % calcium lactate as shown in table d and summarized in fig5 , texture results indicate that the unsoaked iqf blueberry sample is softer than the samples soaked in isotonic solutions with 0 . 1 % and 0 . 8 % calcium lactate . firming occurred with both levels of calcium addition . while the invention has been described in conjunction with specific embodiments , it is evident that many alternatives , modifications , permutations , and variations will become apparent to those skilled in the art in light of the foregoing description . accordingly , it is intended that the invention embraces all such alternatives , modifications and variations as fall within the scope of the claims below .
thermally processed fruits and vegetables are softer in texture than fresh . it is challenging to obtain acceptable texture from thermally processed iqf fruits and vegetables . the soaking method of the invention enhances the texture of high quality iqf fruits and vegetables before thermal processing resulting in a processed , shelf - stable fruit or vegetable product with significantly improved texture . when compared to other traditional firming methods using calcium salts added directly to the pack medium or finished product , or using a food enzyme , such as pectinmethylesterase , the soaking method yields fruit and vegetable products with significantly better post - cook textures . using this method will also enable manufacturers of shelf - stable fruit and vegetable products to use iqf ingredients in continuous year - round production .