BOHDAN M. SLABYJ, GORDON E. RAMSDELL, and RUTH H. TRUE

Quality of Squid, II/ex illecebrosus,Mantles Canned in Oil

Introduction

Squid meat is equal to fish meatin protein content (16-20 percent)and amino acid composition andcan be considered as an excellentsource of protein (Takahashi, 1965).Compared with other marine ani­mals eaten by man, squid provide arelatively higher yield of edibleparts. With vertebrate fishes, therecoverable edible portion rangesfrom 20 to 50 percent; and in thecommonly eaten shellfish, the edibleparts are from 20 to 40 percent. Insquid, the edible portion, whichconsists of the mantle, fins, and ten­tacles, is from 60 to 80 percent ofthe weight of the animal, dependingon the species and its size (Ampola,1974). In this period when moreabundant food resources are urgent­ly needed, it is time for concertedaction for the utilization of squid inthe United States.

The utilization of squid from theNew England squid fishery has beenlimited to supplying bait for domes­tic fishing or frozen whole for saleon foreign markets. For centuries,squid have been used as an impor­tant and palatable source of food inthe countries bordering the Mediter-

ABSTRACT-Squid, Illex ii­iecebrosus, mantles with skin removedwere canned in oil, using quarter-poundaluminum sardine cans. The producthad a good appearance, a mild flavor,and afirm texture; however, the mantlesrequired blanching prior to canning. Tenminute blanching in 3 percent boilingbrine resulted in about 45 percentshrinkage. Addition of polyphosphate

June 1981, 43(6)

ranean Sea and in the Orient. Therehas been considerable marketresistance on the part of the U.S.consumer who has been slow to trynontraditional seafoods. The pres­ent day U.S. consumer is welloriented to processed foods and willaccept a growing variety of foods ifthey are made ready for use eitherthrough the canning or freezing pro­cess. Frozen breaded squid showspromise as a consumer item. Studiesby marketing personnel of the Na­tional Marine Fisheries Service andby personnel at the NMFS North­east Utilization Research Center in­dicate excellent acceptance of thisproduct (Ampola, 1974).

The only commercially cannedsquid product produced in theUnited States is canned with orwithout its ink in brine, in oil, andin tomato sauce and this is usedessentially in ethnic markets (Am­pola, 1974). A satisfactory cannedsquid product must be developed asfrozen foods cannot serve the needsof all merchandizing and consump­tion patterns. The canning of squidwill require considerable research todetermine portions of squid andprocessing procedures that willresult in an acceptable consumer

to the blanch water did not reduceshrinkage. Presence of citric acid inblanch water or the use of different oilsin the can did not improve the quality ofthe canned mantle strips. Frozen storagetemperature (-23 °and - 40°C) ofthe rawmaterial had no significant effect on thequality of the canned product. Squidmantle strips canned in oil had anacceptable shelf life.

product. We believe that canning ofsquid must follow the direction ofthe frozen squid industry and utilizeselected portions of the squid.

The objectives of this investiga­tion were to examine the extent ofshrinkage during thermal processingof squid mantles, to evaluate thequality of canned mantle strips, todetermine the shelf life of thecanned product, and to examine theeffect of preprocess frozen storageconditions on the quality of thecanned material.

Materials and Methods

Fresh squid, I/Iex i/Iecebrosus,were obtained from a fisherman onthe day of catch or on the secondday of catch from a processor. Atall times the squid were iced well.Frozen squid were obtained in 4.54kg (10-pound) blocks measuring 6.4x23.5x31.8 cm (2.5x9.25x12.5inches) which were blast frozen bythe processor at -34.4°C (-30°F) andstored at -20.5° to -23.3°C (_5° to-10°F) for 1 month before purchase.In the laboratory the frozen squidwere thawed for 24 hours at 7.2°C(45°F) before being taken to thepilot plant for further processing.

Commercially frozen squid wereused to determine the effect of poly­phosphate on shrinkage. The effectsof citrate and frozen storage onthe quality of the canned productwere also studied using commercial­ly frozen squid. The remainder ofthe experiments were performed us­ing fresh squid.

Cleaned squid mantles with finsand skin removed were blanched ina boiling solution of 1 and 3 percentNaCI with or without sodium tri­polyphosphate or citric acid. Themantles were cooled, cut in 1.5 cm

The authors are with the Department of FoodScience, University of Maine, Orono, ME04469. Views or opinions expressed are thoseof the authors and do not necessarily reflectthe position of the National Marine FisheriesService, NOAA.

17

T8bla 1.-Parcant ylald of anatomical parts of squid, //lex //Iacabrosus.

September 1977 October 1977 November 1977' August 1977'

Anatomical part~ Percent SO Percent SO Percent SO Percent SO

Mantle 33.1 2.0 '32.6 2.8 36.3 3.0 35.8 0.9Fins 11.4 0.6 '9.4 0.8 10.2 1.1 10.7 0.6Tentacles 22.4 2.0 22.1 2.9 20.7 2.2 25.4 2.3Head 18.1 0.6 14.7 1.7 13.6 0.6 14.1 1.4Viscera 14.1 2.1 15.3 2.1 20.1 3.6 12.5 2.0Skin 2.8 0.4Pen 0.21 0.2 0.18 0.02

Mantle length (em) 26.5 25.9 1.6 25.9 2.3 24.7 1.4Individual weight (g) 420.1 39.4 375.9 62.6 422.1 90.3 364.0 39.6Determinations 6 12 6 5

'Frozen squid.'Skinned.

wide strips, placed in rectangularaluminum cans (405 x 301 x014.5inches) and 20 ml of oil were added.The cans were sealed without vac­uum and retorted 45 minutes at115.5°C (240°F).

Shrinkage was determined onlarge samples (about 3 kg) and dryweight on several small samples(about 100 g) by weighing beforeand after blanching and retorting.Vacuum ovens at 70°C were usedfor drying.

Heat penetration was determin-edby inserting flexible thermocouplesin a squid mantle strip located inthe geometric center of the can andrecording the temperature of thedi fferent cans at 15-second inter­vals' using a Minneapolis-Honey­well' multipoint recorder (Model153 x 64PI6-X-41). Eight thermo­couples were used to monitor thecanned material and two to monitorthe retort. The cycle was repeatedat 4-minute intervals. Process timewas calculated using the heatpenetration data of the coldest canaccording to the formula method ofBall (National Canners Association,1968).

Bellows-Valvair hydraulics(Model DC-50A) equipped with a1oo-pound transducer (DaytronicCorp., Model 152A), and X-Yrecorder (Mosley, division ofHewlett-Packard, Model 135A),and a single blade shear cell (FoodTechnology Corp., Model CA-l)were used to determine texture of 6cm long mantle strips (raw and pro­cessed).

Coded samples were presented ina randomized complete block designwith three replications to a sensorypanel of six members. Appearance,odor, and flavor were evaluated ona 6-point scale with 5 representingthe best quality product and 2 or lessdenoting unacceptable samples.Texture was scored on a 5-point

'Reference to trade names or commercialfirms does not imply endorsement by the Na­tional Marine Fisheries Service, NOAA.

18

scale, with 3 representing the besttexture, 5 indicating tough tissue,and 1 indicating very soft mantles.

Results and Discussion

Yield data for various anatomicalparts of squid, IIIex iIlecebrosus, aregiven in Table 1. The edible parts,which include mantles, fins, andtentacles, represent about 66 percentof the total weight of squid. Thetotal edible portions (62 percent)reported by Schwartz (1972) as wellas individual weights (33, 9, and 20percent) of various anatomical parts(mantle, fins, and tentacles, respec­tively) compare closely with the datapresented here. Data reported byBerk (1974) were significantlyhigher for total edible parts (75 per­cent) for the same species of squidcaught off the New England coast.This difference is due to heaviermantles (47 percent) and fins (14percent), but the tentacles ac­counted for a smaller portion of thetotal weight (14 percent). Estimateof edible parts of squid excludes theweight of the head, although inpractice the consumer is known toremove the eyes, beak, and cartilagefrom the head portion, thus recover­ing additional edible meat.

Shrinkage DuringThermal Processing

Packing raw mantle strips in oiland retorting 35 minutes at 115.5°C(240°F) resulted in a 38 percentshrinkage. (Heat penetration of thispack was performed in this labora-

tory; f h = 10.0 minutes.) A similarloss in weight (31 percent) wasreported by Berk (1974) for mantlescanned in 2 percent brine using No.1 picnic cans and retorting 40 min­utes at 115°C (239°F). Since theabove product was not acceptablefor commercial markets due toexcessive shrinkage, Berk (1974)recommended a 2-minute blanch at65°C prior to canning. This investi­gator reported a 6 percent shrinkageduring blanching and an additional10 percent shrinkage during canningwith an overall loss of 15 percent ofthe total weight. Heating mantlestrips to an internal temperature of65°C for 2 minutes was observed inthe present study to result in a 33percent shrinkage, with an addi­tional weight loss of 34 percent dur­ing retorting. Such a product wasnot considered acceptable and alO-minute blanch in boiling 3 per­cent brine reported by Schwartz(1972) was adopted. This procedureresulted in a product which under­went minimal additional shrinkageduring retorting.

A lO-minute blanch in 3 percentboiling brine was reported to resultin a 37-56 percent shrinkage, de­pending on preprocess holding con­ditions (Slabyj and True, 1980). Itis important to note that duringblanching 15- 42 percent of the dryweight of tissue is lost in the blanchwater.

To evaluate the effect of poly­phosphates on weight loss duringblanching and subsequent canning,

Marine Fisheries Review

Table 2.- Effect of polyphosphate snd sslt concentra·tlon In blanch wsters on shrlnksge and loss of dryweight 01 aquld, lite. lItacabrosus, mantlas.

blanching (Table 3). Additional sof­tening of tissue upon retorting hasnot been observed, although the tex­ture of mantles in the Spanish oilpack is rather soft. The color of theraw, skinned mantle is cream-like,but becomes lighter in color duringblanching, provided the skin hasbeen removed prior to blanching.Blanching mantles with the skin on,does facilitate subsequent removalof the skin, but this procedure hasan undesirable effect in that the redpigment of the skin permeates themantle tissue.

Canning mantle strips in soybeanoil results in light, cream-coloredtissue, and a mild aroma. Prolongedholding of refrigerated, raw squidwill result in a discolored product.Bruised tissue becomes strongly dis­colored during blanching and retort­ing. Also, it becomes tough in tex­ture and develops a "dry" taste. Itwas noticed that a delay in canningblanched mantles will allow devel­opment of strong odors.

Canned squid mantle strips werefirm in texture and had a mildflavor. Because of the mild flavor ofthe canned material, it was thoughtdesirable to evaluate the quality ofthe product using various vegetableoils. Mantle strips canned in cot­tonseed, olive, and soybean oil,when examined by a panel of judgesfor appearance, texture, odor, andflavor, were noted not to be signifi-

Shrinkage due to blanching and canning ('!oj

Dry weight loss due to blanching ('!oj

51.10(5.03) 99.21 (2.17) 119.20 (1.06) 114.80 (1.16) 3

Shear force' No. of(kgl6 em determi·

strip) nations

Mantlethickness

(mm)Item

Raw 4·5Blanched 3·4Canned in oil 3·4Spanish oil pack 5·10

Table 3.-Texture of skinned squid, lite. lItacabrosus,mantles.

'Values in parentheses indicate standard deviation.

cantly different at the 5 percent level(P < 0.05). Spanish processors addcitric acid to squid tissues when can­ning it in natural juices (Schwartz,1972). To evaluate the effect ofcitric acid on the quality of the can­ned material, citric acid was addedto the blanch water at different con­centrations (0, 0.3, and 1.0 percent).Sensory evaluation of the cannedmaterial for appearance, texture,odor, and flavor revealed no signifi­cant difference among the treatmentmeans (P < 0.05).

Shelf Life of Canned Mantles

Shelf life of canned squid mantleswas studied using mantles cannedin soybean oil. The canned materialwas stored at 7.rC (45°F) for 6months, while control samples wereheld for the same period at O°C(32°F). The average sensory scorefor odor, appearance, and flavor ofcans held at 7.2°C was 4.26±0.12(SD), while control samples re­ceived an average score of 3.91 ±0.18. The average sensory scores fortexture of the two lots of cans were3.44 and 2.84, respectively. Al­though samples stored at 7.2°C re­ceived noticeably higher scores, thisdifference for individual attributes(Duncan, 1955) was statistically notsignificant (P < 0.05).

An accelerated storage study wasalso performed by incubating thecanned material at 37.8°C (100°F)for 3 months. The average sensoryscore for odor, appearance, andflavor for samples held at 37.8°Cwas 3.26±0.21, while the similarscore for control samples was3.15±0.36. Average texture scoresfor the above canned mantles were

49

41

11

32

1.0%

46

28

40

13

0.3

Polyphosphate

3 percent NaCI

47

26

48

10

o

22

24

46

39

1.0%

Shrinkage due to canning ('!oj

Shrinkage due to blanching ('!oj

25

49

26

35

0.3

Polyphosphate

1 percent NaCI

28

49

23

37

o

Quality of Canned Mantles

blanch waters contammg 1 and 3percent NaCl with 0, 0.3, and 1.0percent sodium tripolyphosphate(FREEZ GARD FP-19) were used(Table 2). There was no noticeablechange in shrinkage due to thephosphate concentration either dur­ing blanching or subsequent can­ning. However, squid mantlesblanched in 1 percent brine lost onthe average 37 percent of the totalweight as compared with thoseblanched in 3 percent brine whichlost 48 percent. The advantage inyield noticed when blanching in 1percent brine is lost during canning.Additional shrinkage during can­ning was observed to be about 23percent for mantles blanched in 1percent NaCI solution, as comparedwith 11 percent for mantlesblanched in 3 percent brine. The useof polyphosphates and differentconcentrations of salt in blanchwaters had no significant effect onthe loss of dry material duringblanching, which varied between 24and 32 percent (Table 2).

It may be of interest to indicatethat commercially frozen squid heldan additional 6 months at -23.3°C(-10°F) or -40°C (-40°F) were alsoexamined. Samples held at -23.3°Clost 48 ± 2 percent. This differencewas not significant at the 5 percentlevel.

The linear portion of the heatpenetration curve for mantle stripssealed in aluminum cans had a slopeof 17.8 minutes (I,,) for squid man­tles blanched 10 minutes in boiling 3percent brine. Using the formulamethod of Ball (National CannersAssociation, 1968) with F= 4.5 andz = 18, the process time was calcu­lated to be 40 minutes. However,since the above product was of ex­perimental nature and since Ther­mal Death Time Curves were notavailable, process time on routinebasis was set at 45 minutes.

Raw squid mantle is somewhattextured, having a rubbery-like con­sistency, but becomes soft upon

June 1981, 43(6) 19

3.08 and 3.29, respectively. Again,the statistical analysis of the data in­dicated that the judges did notdetect quality differences betweenthe treated and control lots of can­ned squid mantles (P < 0.05).

Effect of PreprocessFrozen Storage

The effect of frozen storage ofraw material on the quality of squidmantles canned in oil has been in­vestigated using squid which washeld 6 months at -23.3°C (-lOOF) and- 40°C (-40°F). The canned productwas examined by a panel of judgesfor odor, appearance, texture, andflavor. The average sensory scorefor odor, appearance, and flavorfor samples held before canning at-lo°C was 3.90±0.20, while theaverage score for samples held at-40°C was 3.68±0.31. The texturescores for the two lots were 4.13 and4.38, respectively. Statisticalanalysis of the data detected nosignificant difference (P < 0.05) be­tween the two treatments of the rawmaterial, indicating the inability of

20

the panelists to detect quality dif­ference due to preprocess frozenstorage conditions.

Acknowledgments

The authors wish to expressappreciation to Edward Logue forlaboratory assistance and ThereseWork for assisting with sensorypanels. Help received from depart­mental staff with sample prepara­tion and for serving on sensorypanels, especially John Blease andWilliam Cook, is gratefully ac­knowledged. The aluminum canswere a gift from John Gavin, Amer­ican Can Co., 217 Read St.,Portland, Maine, and the polyphos­phates were from Eugene Brotsky,Merck Chemical Div., Rahway,N.J. Robert J. Learson and VincentG. Ampola, NMFS Northeast Utili­zation Research Center, Gloucester,Mass., were very helpful in locatingfresh and frozen squid used in someof these studies.

Verification of process time by E.L. Bernier, Continental Can Co.,Paterson, N.J., and Austin Gavin,

National Food Processors Associa­tion, Washington, D.C., is grate­fully acknowledged. This investiga­tion was supported in part by theMaine Agriculture Experiment Sta­tion and NOAA, National MarineFisheries Service, Department ofCommerce, Grant #036-043-35141.

Literature Cited

Ampola, V. G. 1974. Squid - its potential andstatus as aU .S. food resource. Mar. Fish.Rev. 36(12):28-32.

Berk, Z. S. 1974. Processing squid for food.Mass. Inst. Technol. Rep. MITSG 74-13,41 p.

Duncan, D. B. 1955. New multiple range andmultiple F tests. Biometrics II: 1-42.

National Canners Association. 1968.Laboratory manual for food canners andprocessors. Vol. I. The AVI PublishingCo., Inc., Westport, Conn., 336 p.

Schwartz, J. W. 1972. Final report fromFAO fellowship to Spain, Portugal, andItaly (29.2-28.6. 1972). Polish/UNSFHighseas Fisheries Research Project,Gdynia, Poland, 58 p.

Slabyj, B. M., and R. H. True. In press.Effect of preprocess holding of squid (II­lex illecebrosus) on the quality of cannedmantles. J. Food Prot.

Takahashi, T. 1965. Squid meat and its pro­cessing. In G. Borgstrom (editor), Fish asfood, Vol. IV, p. 339-354. Acad. Press.,N.Y.

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