making ricotta cheese by ultrafiltration

Making Ricotta Cheese by Ultrafiltration

J.-L. M A U B O I S t and F. V. KOSIKOWSKI Department of Food Science

Cornell University Ithaca, N ¥ 14853

ABSTRACT

The principles of the uhraf ihrat ion process of Maubois, Mocquot, and Vassal were employed in product ion of Ricot ta cheese. Effects on cheese quality of de- gree of acidification of the cheese milk, conditions of ultrafihration, and heat t reatment of liquid pre-cheeses were studied. Cheeses produced under optimal conditions were similar to tradit ional Ricot ta cheeses. The method lends itself to continuous operation.

I N T R O D U C T I O N

Ricotta cheese is popular in Italy and Greece where often it is produced by boiling acidified cheese whey from ewe's milk. However, in the Eastern United States and Argentina, Ricot ta cheese is manufactured only from cow's milk which may be whole, partially skimmed, or whole milk mixed with whey.

The making of Ricot ta and related cheeses is still largely an art because of the complexi ty of precipitation and the critical requirements for suitable texture and flavor (7). The cheese milk is acidified to pH 5.9 to 6.0 with lactic acid starters, acid whey powder, or food grade acids. The acidified milk is heated with steam so that curd particles float to the surface. Prop- er f lotat ion is considered essential for the recovery and optimal curd texture of tradit ional Ricot ta cheese (7).

At tempts to mechanize or otherwise improve the making of Ricot ta cheese have been diverse. Schmidt et al. (13) suggested homogen- izing the milk before heating to reduce fat losses in the whey and adding CaC12 to improve protein precipitation. Pontecorvo (12)develop- ed a method for heating cheese milk with a large number of small tubes in a kettle. After

Received January 30, 1978. 1 Laboratoire de Recherches Laitieres - I.N.R.A.,

65 rue de St. Brieuc, 35042 Rennes Cedex, France.

chilling, the curd was removed from the kett le bot tom. Carswell (3) utilized a screen to drain the mixture of curd and whey, and Edwards (5) patented a method for Ricotta cheese in which skim milk is precipitated in a kettle, the whey is drained off, and cream is added to the curd. The mixture is blended and packaged cool or hot. In another plan, Balducci (1) proposed to improve protein precipitat ion by the addit ion to the cheese milk of a whey protein concentrate produced by uhrafihrat ion.

All of the above processes require a kettle, and none is continuous or mechanized. The ultrafi l trat ion process for .cheesemaking develo- ped by Maubois, Mocquot, and Vassal (M.M.V.) (10), suggested ways to design a highly mechanized and potential ly continuous Ricot ta cheese method that would not require flota- t ion of the precipitated curd. This report deals with this new process.

M A T E R I A L S A N D METHODS

Ultrafiltration of Cheese Milk

Experiments were limited to batch processes by the available ul t raf ihrat ion equipment which was pilot plant scale (Abcor UF 22S unit, with 1.23 m 2 of HFM membranes) and the amount of uhraf ihra te required for acidity adjustment (final pH 5.9). The process took two forms.

Two-stage process. From 200 to 250 kg of HTST (high temperature short t ime) chilled, pasteurized skim milk that had been pasteurized in the Cornell Dairy Plant were reheated to 54 to 55 C. Ultrafil tration was at this temperature until two-thirds of the original weight of milk was separated as permeate. The retenate was cooled to 28 C, and 2% of a commercial mesophilic lactic starter (Marlac) was added. When pH 6.0 to 5.9 was attained, the retentate was cooled to 20 C and held for further use or, alternatively, heated quickly to 55 C and ultra- f i l tered to the required protein concentrat ion (11.5 to 12.5%). Thir ty minutes before the end of ultrafihration, 15 to 16 kg of heavy cream (40% fat) were added to the recirculation vat.

1978 J Dairy Sci 61:881--884 881

882 MAUBOIS AND KOSIKOWSKI

One-stage process. From 200 to 250 kg of HTST chilled pasteurized skim milk that had been pasteurized in the Cornell Dairy Plant were heated to 28 C, and 1% of a commercial mesophilic lactic starter (Marlac) was added. Ultrafiltration was at this temperature, and through lactic acid fermentation, the optimal pH of 5.9 was obtained at the same time as the required concentration (about 4:1). Cream was added as described in the first procedure.

In one experiment, skim milk was acidified to pH 5.9 by adding 2.2% of acid whey powder (Dairy Research and Development Corp., Vernon, NY), and ultrafiltration was as above.

Manufacture of Ricotta Cheeses

"Liquid Pre-Cheeses" (LPC) obtained in above methods were heated to 80 C in a suitable steam-jacketed cooker. Precipitation oc- curred rapidly at this temperature, and after about 2 min the precipitate was stirred gently. The Ricotta cheeses were hot-packaged, sealed, cooled rapidly to 2 C, and stored at this temperature.

Alternatively, in four experiments, several 200-g samples of liquid pre-cheese were filtered into heat-stable plastic beakers and heated in a microwave oven (Litton Menumaster System 70/40).

Sensory Evaluation and Analysis

Ultrafiltered (UF) Ricotta cheese samples were evaluated by a taste panel of 13 graduate students and faculty members who used tri- angle tests in which commercial Ricotta cheeses

served as reference samples. Analytical methods were those used by

Covaeevich and Kosikowski (4) and included fat, total solids, ash, pH, and Kjeldahl protein.

RESULTS AND DISCUSSION

Ricotta Cheese Manufacture

The typical composition and maximal yield at each step during processing are shown in Table 1 and Fig. 1.

Acidification of the cheese milk to an optimum pH 5.9 could be attained either before the ultrafiltration step, during ultrafiltration, or in the 9.0 to 9.5% protein UF retentate. No differ- ences were significant in organoleptic qualities of the cheeses, and, consequently, in the pres- ent pilot scale experiments any of these ways of acidification were considered acceptable.

The pH was critical for organoleptic and tex- tural qualities (Table 2). Heating at a pH lower than optimum resulted in a lower precipitation temperature, i.e., 72 C at pH 5.7 and 56 C at pH 5.6, and an inferior cheese. Dilution of the liquid pre-cheese by adding water to a 19% protein retentate also gave low quality cheese.

Acidification of the cheese milk before ultrafiltration with acid whey powder as suggested by Kosikowski (6) led to an excellent Ricotta cheese. Additionally, acidification of the liquid pre-cheese with food grade acetic, citric, phos- phoric, tartaric, and hydrochloric acids gave good precipitation.

Cream was added to the skim milk retentate after ultrafiltration to limit the effect of the

TABLE 1. Composition of Ricotta cheeses made by the ultrafihration-high heat precipitation process (two-stage).

Total Treatment Lot solids Fat Protein Ash

(%) One-stagewith lactic starter

Two-stagewith lactic starter

1 30.55 13.5 12.5 1.45 2 33.38 14.75 13.4 1.40 3 a 33.59 14.0 13.3 1.69

4 29.06 12.75 11.7 1.24 5 30.54 13.0 11.7 1.36 6 29.71 12.5 14.8 1.19

Commercial Ricotta 1 27.92 12.5 11.5 1.11

aln lot 3 the lactic starter was replaced with acid whey powder.

Journal of Dairy Science Vol. 61, No. 7, 1978

RICOTTA CHEESE BY ULTRAFILTRATION 883

GENERAL COMPOSITION OF MILK

100 kg cheese milk 3.4% fat

3.2% protein 12.3% TS*

pH 5.9

1 ULTRAFI LTRATION

55C

26.7 kg LPC** 12.7% fat 11.6% protein 29.1% TS pH 5.9

l HEATING 80 C

1 26.7 kg Ricotta cheese 12.7% fat 11.6% protein 29.1% TS pH 5.9

73.•3 kg permeate .0% fat ~11% NPN (N X 6.38)

5.6% TS pH 5.9

*Total solids. * * Liquid pre-cheese.

FIG. 1. Typical composition and yield of Ricotta cheese from ultrafiltration-high heat precipitation method (two-stage).

milk fat on the pressure required but as in the utilization of the M.M.V. process for other types of cheese (8), it is envisioned that continuous industrial scale ultrafiltration equipment fabricated for the making of Ricotta cheese from whole or partially skimmed milk would permit the fat to be introduced directly in con- tact with the membranes.

A complete mechanized process for continuous production is envisaged as: acidification of the cheese milk to pH 5.9 with lactic starter, acid whey powder, or food grade acids; ultrafiltration at 55 to 60 C to approximately 12%

protein; heating the acidified liquid pre-cheese to 80 C in a jacket or tunnel with gentle agita- tion; and filling directly consumer containers

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884 MAUBOIS AND KOSIKOWSKI

h o t or, a l t e rna t ive ly , cool ing the resu l t ing cheese to 2 to 4 C and packaging.

In our s t udy a b o u t 40 kg of cheese mi lk per h per m 2 of m e m b r a n e were u l t r a f i l t e red a t 30 C un t i l t he r equ i red c o m p o s i t i o n for R i co t t a cheese was ob ta ined . A t 55 C th is ra te was in- c reased to a p p r o x i m a t e l y 60 kg. Such pe r fo rm- ances are a t t a inab l e in indus t r ia l -s ized equip- m e n t . No par t i cu la r c leaning and sani t iz ing p r o b l e m s were observed in u l t r a f i l t r a t ion .

P rec ip i t a t ion of l iquid pre-cheese occu r red qu ick ly a t 78 to 80 C, and the t ex tu r a l qual i ty o f the resu l t ing cheese, s imilar to t h a t o f t rad- i t iona l R i co t t a cheeses, was a t t a i n e d by gent le s t i r r ing dur ing hea t ing . The ease of precipi ta- t i on by hea t is a t t r i b u t a b l e seemingly to the c o n c e n t r a t i o n of p r o t e i n by u l t ra f i l t r a t ion . Pierre e t al. (11) c o n f i r m e d t h a t c o n c e n t r a t e d so lu t ions of mi lk p ro t e in s are m o r e hea t de- n a t u r a b l e t h a n t hose o f n o r m a l milk.

Microwave rad ia t ion p r e c i p i t a t e d p ro t e ins of t he l iquid pre-cheese rapidly . However , t e x t u r e and f lavor of t he cheeses l acked u n i f o r m i t y w i th in the sample c o n t a i n e r a n d were infer ior to those of c o m m e r c i a l cheeses or the o t h e r ex- p e r i m e n t a l cheeses. Microwave hea t ing has a p o t e n t i a l for cheesemaking , b u t more s tudy is r equ i r ed to def ine o p t i m u m layer th ickness a n d i n t ens i t y and d u r a t i o n of the rad ia t ion .

Quality and Yield

The f lavor a n d t e x t u r e of the cheeses ob- t a ined by u l t r a f i l t r a t i on and h e a t t r ea t ing the l iquid pre-cheese a t o p t i m a l pH and t empera - tu re were p re fe r red to f resh c o m m e r c i a l R i co t t a cheeses b y 70% of the tas te panel .

Shelf life was at least 9 wk at 4 C for hot - p a c k e d c o n t a i n e r s of the R i c o t t a cheese produced by u l t ra f i l t r a t ion . The new p roduc t , if p r o d u c e d c o n t i n u o u s l y , cou ld be h e a t e d in a closed, c o n t a m i n a n t - f r e e sys tem, a n d th is m i g h t lead to an even longer she l f life.

In th is m e t h o d for R i co t t a cheese, no fa t or cu rd par t ic les are lost . The on ly possible losses wou ld resul t f r o m c o n t a c t wi th the surfaces of t he ul t raf i l ter , pipes, and hea t exchangers . The yields a t t a i n e d were wi th in .1% of the t h e o r e t i - cal m a x i m u m .

REFERENCES

1 Balducci, A. 1974. Ultrafiltration of ewes' whey and use of the concentrate in the manufacture of Ricotta. Latte 471.

2 Brule, G., J.-L. Maubois, and J. Fauquant. 1974. Etude de la teneur en elements mineraux des pro- dulls obtenus Iors de l'ultrafiltration du lait sur membrane. Lait 54:600.

3 Carswell, D. R. 1973. Manufacture of Ricotta cheese. U. S. Patent No. 3,780,199.

4 Covacevieh, H. R., and F. V. Kosikowski. 1977. Skim milk concentration for cheesemaking by al- ternative ultrafiltration procedures. J. Food Sci. 42:1359.

5 Edwards, J. L. 1977. Method for manufacture of Ricotta cheese. U. S. Patent No. 4,020,186.

6 Knsikowski, F. V. 1967. Greater utilization of whey powder for human consumption and nutri- tion. J. Dairy Sci. 50:1343.

7 Kosikowski, F. V. 1977. Page 179 in Cheese and fermented milk foods. 2nd ed. Edwards Brothers, Inc., Ann Arbor, MI.

8 Mahaut, M., and J. L. Maubois. 1977. L'ultrafiltration du lait et des produits laitiers, etat actuel d'avancement des travaux. Econ. Lait. 2:29.

9 Mathur, B. N., and K. N. Shahani. 1977. Utiliza- tion of whey for the manufacture of Ricotta cheese. J. Dairy Sci. 60:Suppl 1:39.

10 Maubois, J. L., G. Mocquot, and L. Vassal. 1969. Procede de traitement du lair et des sous produits laitiers. French Patent No. 2,052,121.

11 Pierre, A., G. Brule, and J. Fauquant. 1977. In- fluence des traitements thermiques sur les proprie- tes physice-chimiques des retentats obtenus par ultrafiltration de lait de vache et de lait de chevre. Lait. (In press)

12 Pontecorvo, N. E. 1973. Process for producing Ricotta cheese. U. S. Patent No. 3,732,110.

13 Schmidt, H. G., K. G. Strauss, and W. Schmidt. 1972. Manufacture of Ricotta-type fresh cheese. Netherlands Patent Application 7,203,868.


making ricotta cheese by ultrafiltration

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