It is in integral part of the ritual of public sacrifice. Its meaning seems to be purely symbolic, as the ingredients are indeed edible parts of staple foods, but not the most nutritious parts, to the contrary – irrelevant what modern health food gurus might tell about this, Hippokrates and Galen knew it was the less desirable stuff as ancient bread buyers did as well.
What made this mola salsa special was its ritual significance for once, but also that is what pre-loaded with divine significance, as it was specially prepared by the Vestal Virgins – at least in Rome proper for public sacrifices as far as we know.
The sacred focaccia was made by the Vestal Virgins for the main festivities of the Roman religion and, in particular, for the Vestalia , the Matralia , the Fornacalia , the Lupercalia and the days dedicated to Jupiter (Epulum Iovis).
The grains were to be harvested, on alternate days, in the period between the ninths and the ides of maius (from 7 to 15 May), sacred month to the goddess Maia, protector of crops and vegetation. The harvest was brought to the House of the Vestal Virgins, who proceeded to shell the ears, toast the grains and grind them finely.
The flour thus obtained was kneaded with water of perennial source and manually formed into crushed rounds to be cooked in the oven of the Temple of Vesta .
In parallel, the Vestal Virgins prepared the muries: a dressing made of salt ground in a mortar, placed in a bowl and mixed with water, always of perennial source. After having sealed it with plaster, the Vestals inserted the terrine in the sacred oven, in order to dry the excess water. The freshly baked mola was sprinkled with the muries .
It is thus can be said to have remnants in or be a combination of the bread still eaten at the Eucharist and the magic salt used in kids' magic sets.
What is mola salsa?
A mixture of spelt groats and brine that was prepared by the Vestal Virgins (e.g. Varro in Non. 223) and used as a sacrificial offering in Roman cult; in the sacra publica , it was sprinkled on the sacrificial animal by the magistrate or priest as part of the immolatio (cf., for example, Cic. Div. 2,37, Serv. Aen. 2,133 and 4,57). The spelt ears from the new harvest were presented to the Vestal Virgins between the 7th and 14th of May, then dried, pounded and ground. The ground spelt was then made into mola salsa by adding the brine during the Lupercalia and Vestalia (Vesta) as well as on the Ides of September (Serv. Ecl. 8,82).
–– Frateantonio, Christa (Gießen), “Mola salsa”, in: Brill’s New Pauly, Antiquity volumes edited by: Hubert Cancik and , Helmuth Schneider, English Edition by: Christine F. Salazar, Classical Tradition volumes edited by: Manfred Landfester, English Edition by: Francis G. Gentry. Consulted online on 12 July 2019 http://dx.doi.org/10.1163/1574-9347_bnp_e808470
The basic structure of immolatio,
They could include, for example, spelt ( far), barley-meal porridge (polenta), leavened bread, dry figs, cheeses, spelt porridge (alica), sesame, and oil. A salted flour called mola salsa, which was used in most public sacrifices, was prepared by the Vestal Virgins for the Lupercalia (February 15), the Vestalia (June 9) and the Ides of September (September 13; see C. Koch 1932). We do not know if the mola prepared by the Vestals was used in all sacrifices, or just in the public sacrifices in Rome. We know almost nothing about the particulars of public sacrifice in the colonies and municipia, since texts on this topic, describing the precise manner of the rites, are few. Therefore, the presumption that the ritual there was the same as that in Rome is pure conjecture.
After this introductory ritual, the sacrificer proceeded to the immolation (immolatio) of the victim (see Latte 1914). In the “Roman” rite, he scattered the back of the victim with salted flour (mola salsa, from which the term immolatio is derived), pouring a small amount of wine on the animal’s forehead, and, finally, passed the knife over its back. From the prayers that accompanied immolation and the comments of Roman scholars, we can conclude that this ritual signified the consecration of the victim. […]
Once this stage was completed, the victim was divided up. The parts due to the divinity (the exta, the vital organs) were set aside to cook in a pot (in the case of cattle victims) or roasted on a spit (sheep and pigs). It was for this reason that the temples always contained a kitchen area. After cooking, the sacrificer turned out the divine portion, duly sprinkled with mola salsa and wine, onto the sacrificial fire which burned on the altar. Offerings to aquatic deities were plunged in water. Those for chthonic deities (for example, the Lares) or those connected with the Underworld, were thrown onto the ground, where they were cooked on the earth or in a ditch. All of these gestures were accompanied by prayers which explicitly stated who was making the offering, who was receiving it, and who would reap the reward for the ritual; thus, in public sacrifices, the prayer always contained the formula “for the Roman people” (Paul. Fest. 59 L).
–– John Scheid: "Sacrifices for Gods and Ancestors", Jörg Rüpke (Ed): "A Companion To Roman Religion", Blackwell: Malde, Oxford, 2007.
Some preliminary definitions are necessary. Most types of sacrifice involve an offering of some kind from a visible human agent to an invisible entity usually thought of as more powerful than the offerer and capable of helping or hindering him by preternatural means. I am rather inclined to the position of Saint Thomas Aquinas who held in the Summa that while "offering" or "oblation" is the genus, sacrifice proper is a species. Some addition must be made to oblation, which determines, specifies, and reserves the sensible thing offered to the deity or power to whom it is offered. The "something done" to the offered thing Saint Thomas calls "immolation." Immolation is derived from the Latin immolare, which means to sprinkle a victim with sacrificial meal, but has come in English to assume a strong overtone destruction and even of killing, of "blood" sacrifice. But in fact immolation is according to the nature of the victim or offering. While animals may be killed, liquids may be poured out, and solids including grain and flour, burnt. In Scholastic terminology oblation can be taken as the matter (undifferentiated substance of reality or experience), immolation as the form (the arrangement of the parts of a thing that gives it its distinctive appearance) of sacrifice.
But offering something and immolating it are only two acts in the chain of acts which make up a sacrificial process.
It may involve the offering of a gift or the immolation of a victim-which may be partially or totally destroyed, consumed totally or as a special portion by officiants, or eaten by all present, often after special preparation. Prayers as well as objects are offered. Most sacrifices, whether embedded in seasonal, curative, life-crisis, divinatory, lustrational, or other kinds of rituals, or performed as isolable ritual sequences, are intended to transform the moral state of those who offer them, through the intermediacy of a victim, as Hubert and Mauss have eloquently shown.
The sacrificial process, especially when it involves the immolation of something highly valued (directly or figuratively), posits the antinomy of an unblemished self (directly and spontaneously related to other such selves) and a blemished self (or, in most non-Western contexts, multiple selves) closed or distanced from each other by conflicts and jealousies attendant upon the occupancy of positions in the social structure. Two notions of power are contrasted: power based on force, wealth, authority, status, tradition, or competitive achievement; and power released by the dissolution of systemic and structural bonds. The sacrifice of abandonment collapses hierarchical and segmentary differentiations. The first kind of power is offered and abandoned; the second, sometimes thought of as deriving from God, the gods, numina, spirits, ancestors or other types of generous "Invisibles," is tapped to purify and simplify relations among group members and the "mental sets" of individuals. The structural self is immolated to liberate the antistructural identity.
–– Victor Turner: "Sacrifice as Quintessential Process Prophylaxis or Abandonment?", History of Religions, Vol. 16, No. 3 (Feb., 1977), pp. 189-215.
More about the structure of specifically Roman sacrifices:
There is a small group of other rituals that share certain structural similarities with sacrificium, but which the Romans during the Republic and early Empire appear to have distinguished from it. Modern scholars sometimes group all of these rites under the rubric ‘sacrifice’. Furthermore, there is reason to think that the crucial moment, or perhaps the first crucial moment, in the whole ritual process of sacrificium for the Romans was the sprinkling of mola salsa onto the victim, whereas several important modern theorizations of sacrifice place the greatest emphasis on, and see the essential meaning of sacrifice in, the moment of slaughter.
As has long been recognized, sacrificare and sacrificium are compounds of the phrase sacrum facere (‘to render sacred’), and what is sacrum is anything that belongs to the gods.10 As in other cultures, Roman sacrifice was not a single act, but instead comprised a series of actions that gain importance in relationship to each other. As Scheid has reconstructed Roman public sacrifice, the ritual began with a procession that was followed by a praefatio, a preliminary offering of prayers, wine and incense. The ritual ended with a litatio, that is, the inspection of the animal’s entrails, and it was then followed by a meal. At the centre of the whole complex was the immolatio, during which the animal was sprinkled with mola salsa (a mixture of spelt and salt), the flat of a knife was run along its back, and then it was slaughtered.
Scheid’s reconstruction focuses on a living victim, and this is in keeping with the ancient sources’ own emphasis on blood sacrifice. Although there is substantial evidence for other types of sacrificial offerings in the literary sources (see below, Section III), Roman authors do not discuss them at length, preferring instead to talk about grand public sacrifices of multiple animal victims. The tendency is intensified in Christian sources, which discuss pagan sacrifice exclusively in terms of blood sacrifice, distinguishing the shameful blood of animal victims from the sacred blood of Christ. The Christian fathers’ equation of sacrifice with violence has shaped twentieth-century theorizations of sacrifice as a universal human phenomenon, most famously those of Burkert, who identities sacrificial slaughter as the ‘basic experience of the “sacred”’, and Girard, who begins his investigation into the origin of sacrifice by asserting its close kinship to murder and criminal violence.
The apparent alignment of emic (Roman) and etic (modern) perceptions of the centrality of slaughter to the Roman sacrificial process, however, is not complete. While the attention of our Roman sources is drawn most frequently to blood sacrifice, there is good reason to think that, if there was indeed a climax to the ritual, the killing of the animal was not it, at least in an early period. Admittedly the Romans often used as a metonym for the whole of sacrificium the term immolatio, the stage of the ritual that includes slaughter, suggesting the special importance of that portion of the ritual sequence. Yet to limit the consideration of immolatio to the moment of killing is to overlook the other actions (running a knife along the animal’s back, cutting a few hairs from it) that Scheid has identified as being part of that stage of sacrificium and the fact that the word immolatio itself derives from the Indo-European root *melh2− (‘to crush, to grind’): immolatio is cognate with English ‘mill’. From this same root also derives the name for the mixture sprinkled on the animal before it was killed, mola salsa. The Romans were aware of the link, as is made clear by Paul. ex. Fest. 97L: ‘Immolare est mola, id est farre molito et sale, hostiam perspersam sacrare’ (‘To immolate is to make sacred a victim sprinkled with mola, that is, with ground spelt and salt’), a passage which also suggests that the link between immolatio and mola salsa was active in the minds of Romans in the early imperial period when the ultimate source of Paulus’ redaction, the dictionary written by Verrius Flaccus, was compiled. Studies of sacrifice have noted the etymological connection between immolare and mola salsa, but have not, for the most part, pressed its value for what it may reveal about where the Romans may have placed the emphasis. Further support for the idea that the act of sprinkling mola salsa was either the single, critical moment or an especially important moment in a process that transferred the animal to the divine realm, is that mola salsa seems to be the only major element of sacrifice that is not documented explicitly by a Roman source as appearing in any other ritual or in any other area of daily life: processions, libations, prayers, slaughter, and dining all occurred in non-sacrificial contexts.
What we find is that for the Romans, to sacrifice was not simply to kill in a ritual fashion. Sacrificium is the performance of a complex of actions that presents the gods with an edible gift by the sprinkling of mola salsa and the ultimate goal of which seems to be the feeding of both gods and men. We also find that the gods were open to receiving sacrifices of vegetables, grains, liquids, and, when those were not available, miniature versions of the serveware that would normally have contained them. In this way, the native, or emic, Roman view of sacrifice is more expansive than ours. The expanded range of sacrificium suggests that meat and vegetal produce were both welcomed by the gods, and that we should not assume that meat offerings were necessarily privileged over other gifts in every circumstance. In addition, the acceptability of miniature serveware as objects of sacrificium shows the ability of the ritual to accommodate the varying social status of those performing it. All of this indicates a certain flexibility and elasticity in the ritual of sacrificium that suggests, especially if a similar flexibility could be demonstrated in other ritual forms, a need to moderate the emphasis — both ancient and modern — on the orthopractic nature of Roman religion. On a wider scale, the arguments made here about the nature of Roman sacrificium further undermine the increasingly discredited idea that sacrifice as a universal human behaviour is primarily, if not exclusively, about the violence of killing an animal victim.
–– Celia E. Schultz: "Roman Sacrifice, Inside and Out", Journal of Roman Studies, 106 (2016), pp. 58–76, 2016. DOI: 10.1017/S0075435816000319
This so far assumes the non-standard use of pabulum to refer to mola salsa exclusively. If pabulum should instead be read as in the usual translation – food – then yes, a Roman might have sacrificed anything as pabulum. But in order to do that in a public sacrifice it would have to be treated with mola salsa as well?